Issuu

CONTENTS

Regional studies of carbonate minerals in the Baralaba and Rangal Coal Measures (JH Patterson, JF Corcoran & KM Kinealy) ...................................................... ..... 3

Australian Coal

Paleomagnetic evidence for the age of the Lapstone Monocline, NSW (PW Schmidt, MA Lackie & JC Anderson) ...................................................... ..... 13 HIGHER DEGREE THESES IN GEOLOGY

Master of Science theses

. ...

•.

..,

::: .

...

: <

·'

,,.,'!'-i ~ d

...

.·

. . ►

,._

APRl t. 19 ISSN 0725

.,.

•

Chairman: . . . . . Vice Chairman & Hon Secretary: Hon Treasurer Committee: Hon Editor:

LHamilton .. C Wallin . C Pattison . KO'Reilly S Matheson BCoxhead . J Beeston

Address for editorial matters: Honorary Editor, Australian Coal Geology 8 Lana Street, Tarragindi, Brisbane, 4121 Address for other matters: Honorary Secretary Coal Geology Group c\- Energy Minerals Pty Ltd 62 Yallamurra Street, The Gap Queensland, 4061 Published by the Coal Geology Group, © Geological Society of Australia Inc ISSN 0725-4938 Issued April, 1995 Price to non-members - $10.00 per issue

CONTENTS

Regional studies of carbonate minerals in the Baralaba and Rangal Coal Measures (JH Patterson, JF Corcoran & KM Kinealy) ............. ......... ....................... ...... ........ 3 Paleornagnetic evidence for the age of the Lapstone Monocline, NSW (PW Schmidt, MA Lackie & JC Anderson) ... . . ... ........ ... ........... .... ........ .............. ... 13 HIGHER DEGREE THESES IN GEOLOGY Doctor of Philosophy theses ....................................................................... 23 Master of Science theses ....... ....................... .. .... ... ................................... 34 Bachelor of Science (Honours) theses .................. ....... .. .. ..... ... ............... .. ......... 42

AUSTRALIAN COAL GEOLOGY

EDITORIAL

Back in 1987 (Volume 7) I introduced the publishing of a number of theses abstracts with themes related to coal geology, and followed up in 1992 (Volume 8) with a further selection. This edition I am pleased to continue the process. I would like to thank the University of Queensland (St Lucia), James Cook University of North Queensland, Queensland University of Technology, University of New South Wales, University of Newcastle, University of Wollongong, and Monash University, for permission to publish the abstracts, and for sending me the copies. Too often, the results of hard work and diligence represented in post-graduate theses are literally 'left on the shelf' without the exposure that they deserve . Sometimes they represent the last concerted and concentrated piece of intense original research by the individual, prior to a career outside or inside the industry, where unfortunately the requirements of 'making money' tend to become dominant. I therefore offer you the opportunity to gain some insight into the thoughts and knowledge available to you when you next visit your local University, to find out the puzzle you have been milling over has already been answered .

AUSTRALIAN COAL GEOLOGY

REGIONAL STUDIES OF CARBONATE MINERALS IN THE BARALABA AND RANGAL COAL MEASURES JH PATTERSON, JF CORCORAN & KM KINEAL Y PATTERSON, J.H., CORCORAN, J.F. & KINEALY, K.M., 1995: Regional studies of carbonate minerals in the Baralaba and Rangal Coal Measures. Australian Coal Geology, 10, 4-13. The amount and chemical composition of carbonate minerals strongly influence ash behaviour during coal utilisation in conventional power plants and slagging gasifiers. Scanning electron microscope and electron microprobe analyses have been made of carbonate minerals found in the stratigraphically equivalent Baralaba and Rangal Coal Measures of the Bowen Basin. The chemical compositions and associations of these phases have been examined for the coal seams intersected in boreholes along strike from Baralaba to Theodore South and in the Blackwater district respectively. Five main modes of occurrence of carbonates were observed: calcite infilling in coal, ankerite infilling in coal, siderite/magnesian siderite nodules in coal, siderite nodules in claystone and magnesian or calcian siderite infilling in coal. Regional variability in the type and amount of these carbonates reflect local conditions during diagenesis and maturation of the coal and influence the suitability of the coal for use in conventional and advanced power generation processes. JH Patterson and JF Corcoran, CSIRO Division of Coal and Energy Technology KM Kinealy, CSIRO Division of Exploration and Mining PO Box 136, NORTH RYDE NSW 2113

The coal-based electricity industry worldwide faces increasing pressures to reduce emissions of greenhouse gases, sulphur and nitrogen oxides, and particulates from coal-fired power stations. This has led to development of a number of integrated gasification-combined cycle (IGCC) processes which are at the demonstration phase (Gainey, 1994). Many of these processes include slagging gasifiers and it has therefore become important to assess the suitability of Australian bituminous coals for use in such processes. Under the high operating temperatures prevailing in slagging gasifiers, ash fusion temperatures, ash composition and the viscosity and flow characteristics of the molten slag become of prime importance. For Australian bituminous coals, carbonate minerals are the main precursors of the natural fluxing components in the coal ash and account for variability in ash fusion temperatures (Kent & Champion, 1964), in ash composition (Shibaoka, 1970) and in slag viscosity (Patterson & Hurst, 1994). Carbonate minerals have also been associated with slagging in conventional pulverised fuel power stations (Kent & Champion, 1964; Wibberley & Wall, 1982). Carbonate minerals in Australian coals have therefore been chemically characterised in recent years (Patterson & others, 1992; 1994a,b) using scanning electron microscopy and electron microprobe techniques. This work revealed unexpected variability in the composition of ankeritic and sideritic carbonates and raised the possibility that the four compositional types of siderite observed might be indicators of depositional environment. It is generally considered that siderite nodules are syngenetic and formed very early in diagenesis whereas calcite and ankerite cleat and vein in-

fillings are epigenetic and only formed after coal compaction and much later in maturation (Kemezys & Taylor, 1964, Ward, 1978; 1986). A series of reference boreholes along the southeastern boundary of the Bowen Basin, from Baralaba to Theodore South, provide the opportunity to examine carbonate minerals in a number of seams and localities within the Baralaba Coal Measures. A geochemical study of the inorganic constituents in these same boreholes is available (Shibaoka, 1970) and seam correlations throughout the area are well established (Svenson & others 1975). The CSIRO had also examined a series of reference boreholes in the stratigraphically equivalent Rangal Coal Measures of the Blackwater District (reported in CSIRO Location Reports). Seam correlations and geology of the district have been described by Staines (1972) and Johnson & others (1975) respectively. This paper reports the results of scanning electron microscopy and microprobe studies of carbonate minerals found in equivalent coal seams along the south-eastern and western boundaries of the Bowen Basin. EXPERIMENT AL PROCEDURES

The carbonate minerals occurring in coal and claystone particles were studied using scanning electron microscopy and electron microprobe analyses as previously described (Patterson & others, 1992). Samples were selected on the basis of the petrographic analyses of the various core sections, as reported in CSIRO Location Reports. Polished grain samples used in these original studies were repolished to provide fresh surfaces for analysis. This enabled an effective coverage of

AUSTRALIAN COAL GEOLOGY

4 BLACKWATER

Capricorn Highway

NS24

• Baralaba

•NS93 eNS94

eNS88 • NS95 • NS106R eNS86 •NS96 • NS101 • NS97 • NS102R

• NS100

• Boreholes

5km

• BHP28

Figure 2. Locations of boreholes examined in the Rangal Coal Measures. CARBONATE MINERAL ASSOCIATIONS AND GENESIS

Baralaba coal measures

• Boreholes □

Townships O 5 10km

I I Figure 1. Locations of boreholes examined in the Baralaba Coal Measures .

the main carbonate minerals present in each of the selected boreholes. The locations of the boreholes examined in the Baralaba Coal Measures are shown in Figure 1. A total of 67 samples from 6 localities provided a good coverage of the major coal seams from Baralaba to Theodore South. The locations of the boreholes examined in the Rangal Coal Measures are shown in Figure 2. A total of 40 samples from 12 localities was examined, along strike from north to south for a distance of about 25km. Individual ply samples and / or composite samples were examined for each borehole. The Aries, Castor and Pollux seams were examined in BHP28 and the Main Lower seam was examined in the other boreholes. However, the Main Lower seam comprises various combinations of the Castor, Pollux and Orion seams in different localities (Staines, 1972).

The scanning electron microscope and microprobe examinations revealed the same five compositional types of carbonates in both the Baralaba and Rangal Coal Measures. These carbonate types were: calcite, ankerite, siderite, magnesian siderite and calcian siderite. In addition a number of common forms and associations were observed (Figure 3). Compositional ranges for the above carbonates are shown for the Baraiaba and Rangal Coal Measures in Figures 4 and 5 respectively. Results are comparable and moreover they are very similar to those previously reported for Queensland and New South Wales coals (Patterson & others, 1994a), excepting that ankerite is less variable in composition. As a result, calcite and ankerite have essentially fixed compositions wherever they occur, and only vary in amount throughout the Baralaba and Rangal Coal Measures examined here. The composition of sideritic type carbonates is more variable (Figures 4 and 5) and differs at the various locations. Variability in the composition of sideritic carbonates observed in selected boreholes is shown in Figures 6 and 7. The five carbonate types and their forms and associations are discussed in turn below.

AUSTRALIAN COAL GEOLOGY

.,. (a) Calcite cleats (bright) in coal

(b) Atikerite cleats (bright) in coal

(d)

Siderite nodules (bright, porous) and Ca-siderite grains (bright, non porous) in coal

~~ •

(e) Ca-siderite cleat infilling

· ·, . •

:'. -~t

.....

(f) Mg-siderite infilling in coal

Figure 3. Scanning electron microscope photographs of carbonate associations.

AUSTRALIAN COAL GEOLOGY

Ca Calcite

Ankerite

Siderites

Mg----------------~-~-~~--~Fe Figure 4. Compositions of carbonates in the Baralaba Coal Measures.

Ca Calcite

Ankerite

Siderites

+ +

Figure 5. Composition of carbonates in the Rangal Coal Measures.

AUSTRALIAN COAL GEOLOGY

(a)

Ca(S0)

Ca(S0) (d)

NS24

NS45

BARALABA

NIPAN

Mg(50)

Ca(50)

Ca(S0)

(e)

(b)

No 1294

NS27,47R

MOURA

THEODORE

Mg(50)

Ca(50)

Fe (f)

(c)

Ca(50)

NS33

NS14

MOURA

HEODORE SOUT

Mg(50)

Figure 6. Compositions of siderites at different locations in the Baralaba Coal Measures.

AUSTRALIAN COAL GEOLOGY

Ca)

Ca(50)

Cc)

NS93

Ca(50)

NSJ00

+ + +

Fe Mg(50)

Mg(50) (b)

Ca(50) (d)

Ca(50)

BHP28 NS101 NS97 NS102R +

Mg(50)

Figure 7. Compositions of siderites at different locations in the Rangal Coal Measures. Calcite Cleat Infillings Calcium carbonate was observed in many samples in all localities and seams examined in both the Baralaba and Rangal Coal Measures (excepting for borehole No. 1294, Figure 1). As discussed later calcite was generally more abundant in the upper coal seams from Baralaba to Theodore South. In the Blackwater district it was particularly abundant in boreholes north of NS106R and in the Castor seam, borehole BHP28 (Figure 2). As found for other Australian coals, calcite occurred predominantly as cleat infillings in coal (Figure 3a) and was essentially pure calcium carbonate with only minor substitution of calcium by mainly iron (Figures 4 and 5) . Rare calcite infills were observed in coal (probably in inertinite) . Thus in all cases calcite is considered to be epigenetic in origin and it is considered to have formed by precipitation from percolating waters, after the coal has been compacted and undergone most of

its maturation (Kemezys & Taylor, 1964; Shibaoka, 1970). Ankerite Cleat Infillings Cleat infillings by ankerite were rare in the Baralaba Coal Measures and a minor component in the Rangal Coal Measures, where ankerite generally occurred in cleats and veins in the coal (Figure 3b). Ankerite is therefore also considered to be epigenetic and to have formed later in coal maturation. As previously mentioned, the chemical composition (Figures 4 and 5) was similar throughout and appears to be less variable than for some other Australian bituminous coals (Patterson & others, 1992, 1994a). Because of limited occurrences ankerite is of lesser importance than calcite and sideritic carbonates in relation to coal utilisation.

AUSTRALIAN COAL GEOLOGY

coal rather than claystone. Chemical compositions were, in this case, more variable from location to location (Table 2).

Table 1. Structural formulae for primary siderites in the Baralaba Coal Measures. Locality

Structural Formula

Baralaba Moura (No. 1294) Moura (NS33) Nipan Theodore Theodore South

Feo.ss Cao.06 Mgo.06 Mno.03 CO3 Feo.91 Cao.03 Mgo.01 Mno.os CO3 Feo.s7 Cao.07 Mgo.03 Mno.03 CO3 Feo.91 Cao.as Mgo.03 Mno.01 CO3 Feo.89 Cao.as Mgo.02 Mno.02 CO3 Feo.ss Cao.04 Mgo.06 Mno.02 CO3

Siderite was observed in boreholes NS86 and BHP28, calcian siderite in borehole NS93 and magnesian siderite in boreholes NS97, 100, 101 and 102R. However, levels of substitution of calcium and magnesium for iron, are generally low in the range 8-15 % (Table 2) . Thus again this may simply reflect differences in pore fluid composition at the various locations examined. Magnesian Siderite Infillings in Coal

Sideritic Nodules in Coal and Claystone Siderite nodules (>87-90 % FeCO3 with <8 % MgCO3 or CaCO3) were observed at all localities in the Baralaba Coal Measures (Figure 6) and the average compositions determined by microprobe analyses for the different localities are given in Table 1. The SEM and microprobe results showed that the nodules crystallised in both claystone or coal bands. Bedding planes are often clearly deformed around the pre-existing siderite nodules as shown in Figures 3c and 3d respectively. As such, siderite nodules are syngenetic in origin and formed early in diagenesis, as previously reported by Kemezys & Taylor (1964). There are only subtle differences in chemical composition (Table 1 and Figure 6) and these are considered to reflect variability in pore fluid composition at the time and location of crystallisation. Primary sideritic nodules (porous nodules in Figure 3d) were also observed throughout the Rangal Coal Measures, generally associated with

Occurrences of magnesian siderite infilling were mainly observed in boreholes NS24 at Baralaba and NS14 south of Theodore (Figure 1). Minor amounts were observed as cell wall replacements associated with cell infilling by calcian siderite in the Rangal Coal Measures (Patterson & others, 1994b). A scanning electron photomicrograph of magnesian siderite infilling in coal is shown in Figure 3f and a massive magnesian siderite band was observed within the Dawson seam at Baralaba. These occurrences are thought to be epigenetic in origin and to reflect crystallisation later in coal maturation. This may account for the variability in composition of these magnesian siderites as shown in Figures 6a, 6e and 6f. Calcian Siderite Infillings and Grains in Coal Infillings were mainly observed in the Rangal Coal Measures as cell replacements and cleats in coal particles (Figure 3e). Calcian siderite infilling was only observed in one sample from borehole NS14 in the Baralaba Coal Measures (Figure 6f).

Table 2. Structural formulae for siderites in the Rangal Coal Measures. Borehole

Origin

NS93 NS93

Primary Secondary

Feo.ss Feo.84

Mgo.01 Mgo.02

Cao.09 Cao.11

Mno.02 Mno.03

co3 CO3

NS86

Primary

Feo.93

Mgo.04

Cao.01

Mno.02

CO3

NS101

Primary

Feo.s4

Mgo.11

Cao.03

Mno.02

co3

NS97 NS97

Primary Secondary

Feo.s6 Feo.76

Mgo.10 Mgo.os

Cao.03 Cao.17

Mno.01 Mno.01

co3 CO3

NS102R NS102R

Primary Secondary

Feo.ss Feo.7s

Mgo.10 Mgo.os

Cao.03 Cao.17

Mno.02 Mno.02

CO3 co3

NSlO0

Primary

Feo.so

Mgo.1s

Cao.04

Mno.01

CO3

NSl00

Secondary

Feo.72

Mgo.10

Cao.17

Mno.01

CO3

BHP28

Primary

Feo.s9

Mgo.02

Cao.o7

Mno.02

co3

BHP28

Secondary

Feo.73

Mgo.os

Cao.is

Mno.04

CO3

Structural Formulae

AUSTRALIAN COAL GEOLOGY

Table 3. Analyses of seam composite samplel, Theodore South borehole NS14. Air dry, wt%

AFT*

Ash Composition, wt%

Silica

Ash

CO2

·c

SiO2

AhO3

Fe2O3

CaO

MgO

Ratio+

Nipan 4,5

6.1

1.24

1310

35.6

25.1

10.8

20.0

1.64

Nipan 6

5.7

0.50

1350

46.9

26.4

9.8

10.0

1.17

Nipan 7

9.6

0.72

1310

49.9

23.2

14.7

3.5

1.58

Nipan 8

5.1

0.35

1350

49.4

24.0

20.1

0.8

1.93

Nipan 9

6.8

0.08

1450

67.7

18.1

6.7

1.8

1.41

Nipan 10 (tops)

15.6

0.04

1590

60.1

26.7

3.9

0.3

1.12

Nipan 10 12.9 0.26 1430 69.4 (bottoms) ~ Data from CSIRO Location Reports ,. Ash flow temperature (reducing conditions) + Silica Ratio= 100 SiOi/SiO 2 + Fe 203 + CaO + MgO

15.2

5.2

1.6

1.53

Suc_h occurrences are also considered to be epigenetic and to have formed much later in coal maturation, perhaps at the same time as calcite cleat infilling. This is supported by the observation that calcium siderite infilling was generally found at localities which were also subject to calcite cleat infilling (i.e. boreholes north of NS106R and the Castor seam in borehole BHP 28, Figure 2).

variations in the total amount of carbonate minerals.

Seam

The origin of calcian siderite grains in the Rangal Coal Measures is more uncertain. These grains are less porous than the primary sideritic nodules obs~rved in the same coal particles (Figure 3d), possibly reflecting greater consolidation of the sediments prior to crystallisation. The coexistence of sideritic nodules and calcian siderite grains was observed in most of the boreholes examined generally towards the base of the Main Lower Seam. Microprobe analyses for the nodules and grains are shown in Table 2 and the clear differences in composition between the two types are shown in Figures 7b, 7c and 7d. The similarity in composition to the calcian siderite cell and cleat in~illings discussed earlier, suggests a similar genesis. Thus, the calcian siderite grains are also thought to be epigenetic in origin and possibly formed at about the same time, due to percolation of calcium rich solutions through the coal seams. REGIONAL VARIABILITY IN CARBONATES

As already discussed , the amount of calcite and ankerite and the type and amount of sideritic carbonates are variable from location to location (Figu res 6 and 7). The original analyses of composite coal seam samples from the various boreholes are available in CSIRO Location Reports and provide the opportunity to examine regional

Shibaoka (1970) has demonstrated that the majority of calcium, magnesium and iron is associated with carbonate minerals in the Baralaba Coal Measures. The present SEM investigations show that this is also true for the coal sections examined from the Rangal Coal Measures. Relevant data are compiled in Tables 3 and 4 for some of the Baralaba and Rangal Coal Measure boreholes respectively. From Baralaba to Theodore South, differences relate ma inly to variations in the amount of secondary calcite and magnesian siderite infilling relative to sideritic nodules. As discussed later, variations in calcite content are more related to stratigraphic depth. However, secondary magnesian and calcian siderites were only observed at Baralaba and south of Theodore. The chemical composition of the primary siderite is essentially constant throughout the region (Table 2) suggesting that a similar depositional environment prevailed throughout the various cycles of coal seam formation and early in diagenesis. The chemical analyses given in the original CSIRO Location Reports, from the Baralaba and Rangal Measures reveal large variations in inorganic carbon content due to variability in the amounts of carbonate minerals. Shibaoka (1970) examined trends in total carbonate minerals with stratigraphy for most of the boreholes included in the present study of the Baralaba Coal Measures. A good correlation was demonstrated between the total iron, calcium and magnesium in the ash, and the inorganic carbon content of the coal. The majority of these elements in the coal are present as carbonates.

AUSTRALIAN COAL GEOLOGY

Table 4. Analyses of borehole composite coal samplel, Rangal Coal Measures. Air dry, wt%

AFT*

Ash composition, wt%

Silica

·c

SiO2

AhO3

Fe2O3

CaO

MgO

Ratio +

14.9 NS93 2.72 1200 NS94 13.6 2.06 1230 12.9 NS88 2.75 1190 12.9 NS95 1.81 1260 NS106R 10.4 0.45 1340 NS86 10.0 0.24 1520 NS96 14 .6 1.74 1220 NS101 9.4 0.05 >1600 NS97 9.4 0.06 1600 NS102R 9.2 0.28 1530 NS100 0.52 10.5 1480 BHP28 16.1 2.30 1230 12.1 BHP28 2.32 1240 BHP28 14 .2 2.18 1200 f ,. , and + Footnotes see Table 3

38.2 42.1 32.8 37.9 48 .6 53.0 46 .4 54 .3 53 .6 48.3 57.4 46.2 44.9 39 .1

17.3 18 .7 17.1 20.0 25 .6 28 .2 19 .7 30.0 30.3 29.6 25 .0 16.9 16.6 18 .0

18.7 18.7 20.7 15.9 12.0 9.0 13.8 5.1 3.3 8.4 9.4 17.9 7.7 27.9

13.2 9.35 17.5 14.9 5.4 2.2 8.8 2.5 4.1 3.9 1.3 9.4 20.9 7.1

2.9 1.9 2.1 1.8 0.8 0.7 2.5 0.5 0.5 0.8 1.6 3.0 2.4 1.7

52 58 45 54 73 82 65 87 87 79 82 60 59 52

Borehole Ash

CO2

It was also demonstrated that in the Moura-Theodore district, the coal seams immediately below the Rewan Formation or the Kia-Ora conglomerate were richer in inorganic carbon (and hence carbon.ites), with the exception of seams intersected in borehole NS33 (Shibaoka, 1970). Moreover, when the inorganic carbon content of the top seams is high, the ash has a higher CaO content and lower MgO and Fe2O3 contents. Thus calcite infilling is generally greater in the upper seams, strongly suggesting that calcium containing solutions percolated down from the overlying rocks. Analyses for Nipan seams 4 to 10 in borehole NS14 are given as an example of the above trends in Table 3. Increasing total carbonate content in the coal leads to ashes with lower silica ratios (l00SiO2/SiO2+CaO+MgO+ Fe2O3) and generally lower ash fusion temperatures. A silica ratio of <70 and a flow temperature <1400 °C (reducing conditions) are considered as desirable for coal use in slagging gasifiers (Patterson & Hurst, 1994). Thus the carbonate rich upper seams would appear most prospective for usage in IGCC power plants. It could even be feasible to market seams immediately below the Rewan Formation for IGCC and the other coal seams for conventional power generation. Ash contents also tend to be somewhat lower in the upper Nipan seams (Table 3), another advantage for use in slagging gasifiers. Chemical analyses of seam composite samples from the Blackwater district also reveal large variations in inorganic carbon (CO2) content and in ash composition due to variability in the amounts of carbonate minerals in the coal (Table 4). From Table 4 it can again be seen that when the inorganic carbon content in high, the ash has higher CaO, Fe2O3 and MgO contents which reflects in low Silica Ratios and relatively low ash fusion temperatures. Thus the carbonate rich areas from

borehole NS106R north to the Capricorn Highway (Figure 2), would appear most prospective for usage in IGCC power plants. On the other hand, the same coal seams from boreholes NS101 to NSl00 contain less carbonates, have high Silica Ratios, and ash fusion temperatures and are more suited to use in conventional power stations. Thus mines in different localities of the Blackwater district could produce coals for either IGCC or conventional power generation use, depending upon the concentration of carbonate minerals. CONCLUSIONS

Similar carbonate minerals have been observed in the stratigraphically equivalent Baralaba and Rangal Coal Measures, on the south-east and western perimeters of the Bowen Basin. A number of links have been demonstrated between carbonate type and depositional environment during diagenesis and maturation of the coals. Regional and stratigraphic variability in the amount of carbonate minerals impact on coal utilisation. 1. Nodular siderite in coal and claystone may reflect conditions early in diagenesis. It is syngenetic in origin and occurs in variable amounts throughout the sections examined. Minor compositional variations between siderite nodules probably reflect the composition of pore fluids at the particular location and time of crystallisation. 2. Magnesian siderite and calcian siderite commonly occur as infillings and replacements in the coal. They are considered to be epigenetic in origin and formed at a later stage during maturation of the coal. 3. Ankerite is a minor component and occurs as epigenetic cleat and vein infillings in the coal.

AUSTRALIAN COAL GEOLOGY

12 Epigenetic calcite, in cleats and veins in 4. the coal, was observed in all localities to varying extents. It is enriched in coal seams immediately below the Rewan Formation or Kia-Ora conglomerate, in the Baralaba Coal Measures, and in area s just south of the Capricorn Highway near Blackwater. This is considered to refl ect percolation of calcium-containin g solution s from the rocks above, much later in diagenesis after the coal ha s been compacted and u ndergo ne mos t of its maturation . Coals rich in ca rbonate minerals appear 5. well su ited fo r u se in slagging ga si fi ers and hence, in ad vanced integrated gasificati on-combined cycle processes which are currently at the d emonstrati on phase. Coals low in carbonates are better suited 6. for use in conventio nal power generation . The possibility of selective mining (by seam or by area), to meet both new IGCC and conventional thermal coal markets is suggested. ACKNOWLEDGE MENTS

We thank Mr P. Marvig for the preparation of p olished blocks and Dr D.H . French fo r the u se of his data plo tting program . REFERENCES GA INEY, B.W., 1994: Status a nd pros pects fo r integrated coal gasi fi cation combined cycle (IGCC) in Energy fo r Life Foru m, Pacific Power, Sydney. JOHNSON, M.W ., SVENSON, D. & STAI NES, H .R.E., 1975: Blackwater d istrict . In Traves, D.M. & King, D. (editors): Economic geology of Au stralia and Papua New Guinea, 2 - Coal. The A ustralasian In stitute of Mining and M etallurgy , Monog raph Series, 6, 118-130.

KEMEZYS, M . & TAYLOR, G.H ., 1964: Occurrence and distribution of minerals in some Au stralian coals. Journal of the In stitute of Fuel, 37, 389-397. KENT, C.R. & CHAMPION, A.O., 1964: The in fl uence of carbonate mineral s on the ash fusion characteristics of coals. Proceedings of a Sym posium on the In organic Constitue nts of Fuel,

Instit ute of Fuel (Au stralian Membership), 83-99.

PATTERSON, J.H., CORCORAN, J.F. & KINEALY, K.M ., 1992: Scanning electron microscope and microprobe studies of the carbonate minerals in Australian bituminous coals. Proceedings of the 5th A ustralian Coal Science Conference, Melbourne, 358-365 . PATTERSON, J.H ., CORCORAN, J.F. & KINEALY, K.M ., 1994a: Chemistry and mineralogy of carbonates in Australian bituminous and sub-bituminous coals. Fuel, 73, 1735-1745. PATTERSON, J.H ., CORCORAN, J.F. & KINEALY, K.M ., 1994b: Variability of carbonate minerals in coals from the Blackwater district. Proceedings of the

6th

A ustralian

Coal

Science

Conference,

Newcastle, 332-340 . PATTERSON,J.H . & HURST, H.J., 1994: Effects of Ash and Slag Characteristics on the Utilisation of Australian Coals in IGCC Power Generation. Australian Combustion Technology Centre (ACIRL Ltd) Practical Workshop on : Impact of Coal Quality on Power Plant Performance, 15-18 May, Brisbane, Queensland. SHIBAOKA, M., 1970: A geochemical study of the inorganic constituents of the Bowen Basin and other Queensland coals. Proceedings of the 2nd Bo wen Basin Symposium. Geological Survey of Queensland, Report, 62, 49-60. ST AINES, H .R.E., 1972: Blackwater coalfield Correlation of Seams in the Rangal Coal Meas ures. Geological Survey of Queensland, Report, 70 .

SVENSON, D., CHIU CHONG, E.S. & TAYLOR, D.A., 1975: Theodore-Baralaba District. In Traves, D.M. & King, D. (Editors) : Economic geology of Australia and Papua New Guinea, 2 - Coal. The A ustralasian Institute of Mining and Metallurgy, Monograph , 6, 108-118.

WARD, C.R., 1978: Mineral matter in Australian bituminous coals. Proceedings of the Australasian In stitute of Mining and Metallurgy, 267, 7-25. WARD, C.R., 1986: Review of mineral matter in coal. A ustralian Coal Geology, 6, 87-110. WIBBERLEY, L.J . & WALL, T.F., 1982: Ash chemistry, fu sion and deposits during coal firing . The University of Newcastle, Institute of Coal Research, Report No . ICR82/l.

AUSTRALIAN COAL GEOLOGY

PALAEOMAGNETIC EVIDENCE FOR THE AGE OF THE LAPSTONE MONOCLINE, NSW PW SCHMIDT, MA LACKIE & JC ANDERSON SCHMIDT, P.W., LACKIE, M.A. & ANDERSON, J.C., 1995: Palaeomagnetic evidence for the age of the Lapstone Monocline, NSW. Australian Coal Geology, 10, 14-19. Estimates of the age of the Lapstone Monocline range from Triassic to Cretaceous/Tertiary. Magnetic overprints, which are ubiquitous throughout the Permo-Triassic Sydney Basin sediments and the Jurassic breccia diatremes, have been deflected by movement on the monocline. From other palaeomagnetic investigations the age of the magnetic overprinting is thought to be ~ 90Ma, which is supported by fission-track ages of apatites and K-Ar ages on illites. This indicates that most of the movement on the Lapstone Monocline occurred after -90Ma. PW SCHMIDT, CSIRO Exploration and Mining, North Ryde, 2113 MA LACKIE, School of Earth Sciences, Macquarie University, 2109 JC ANDERSON, Kembla Coal and Coke, Wollongong, NSW, 2500

The Lapstone Monocline runs north-south for over 100km to the west of Sydney and forms an escarpment adjacent to the Blue Mountains plateau about 1000m ASL (Figure 1). Branagan & Pedram (1990) have described the form of the structure in some detail. They use the name "Lapstone Structural Complex" to include in it related folds and faults, such as the Nepean Fault at the southern end of the monocline. Estimates of the age of the monocline, based on a variety of evidence, range from Triassic to Cretaceous/Tertiary. David (1897) considered undifferentiated gravels that drape, and appear to pre-date the monocline, to be Cretaceous or possibly Tertiary in age. This would seem to indicate a late Cretaceous or younger age, at least for the main phase of the folding. However, there is also evidence that the structure was active during the Triassic sedimentation since sequences thin significantly to the west of the monocline . Moreover, as Pickett & Bishop (1992) observe, there is over 490m difference in elevation of the uppermost strata, the Wianamatta Shale, across the monocline, indicating that whilst some movement may have occurred during deposition, a major phase of movement continued after deposition. Pickett & Bishop (1992) suggest, from the lack of evidence of faulting in a diatreme outcropping at Nortons Basin, that major movement had ceased by the Early Jurassic . This study presents palaeomagnetic evidence that suggests that the major tilting of the Hawkesbury Sandstone along the Lapstone Monocline occurred after a period of pervasive magnetic overprinting throughout the Sydney Basin, which is thought to be -90Ma in age (i.e. Mid-Cretaceous; Schmidt & Embleton, 1981).

OVERPRINT MAGNETISATIONS IN ROCKS OF THE SYDNEY BASIN

Evidence for overprinting in the Sydney Basin has been found in rocks that are stratigraphically older than the Early Tertiary (Table 1). These rocks are either partially or completely remagnetised, while rocks of Early Tertiary or younger ages (mainly basaltic rocks) are not affected (Schmidt & Embleton, 1981; Schmidt, 1982). The direction of the overprint remagnetisation is very consistent and, on the basis of palaeomagnetic measurements from dated rock units, corresponds to the mid-Cretaceous direction for the Sydney Basin. This magnetisation has been used by the coal industry to orient fractures and cleat directions in bore core (Schmidt & Anderson, 1990, Lackie & Schmidt, 1992a and b). The magnetisation history of any particular rock unit depends not only on the thermal conditions to which it has been subjected, but also on lithology and diagenesis. Thus, coarse grained permeable sandstones of the Hawkesbury Sandstone carry a late Tertiary remanence dating from late Tertiary weathering associated with the breakdown of siderite and the formation of haematite and maghaemite. It is noteworthy that these weathering magnetisations are roughly divided between normal and reversed polarity, with little bias to the present "normal" polarity (Hunt, 1985). This indicates quite a long history of weathering (>>lMa) and the ability of these rocks to retain such a record . However, some less permeable rocks are not so prone to Tertiary weathering and carry more ancient remanences. These include many igneous rocks including diatreme breccias, and finer grained sediments. Fine grained rocks of the Narrabeen Group (Late Permian to Early Triassic) from the rock platform at Coal Cliff and from the drift at the Tahmoor Colliery (Figure 1) are magnetised uniformally in

AUSTRALIAN COAL GEOLOGY

FORRESTERS BEACH NORTH

20km

SCALE

HAWKESBURY LOOKOUT

IC 0

8..:i' •

Park

Figure 1. Locality map showing the Lapstone Monocline and site locations (closed squares) discussed in the text.

AUSTRAL IAN COAL GEOLOGY

Table 1. Stratigraphic Column. Age

Stratigraphy

Tectonic/Depositi onal Event

Late Tertiary

undifferentiated gravels and volcanics

fluvial deposition and volcanism coal measures reach maximum level of coalifica tion main uplift of Blue Mountains overprint palaeomagnetic directions set in Sydney Basin rocks

Mid-Cretaceous (-90Ma)

breccia diatremes

intrusive (and extrusive?) volcanism continued sedimentation but later eroded

Jurassic Wianamatta Group Triassic

Permian

Sydney

Hawkesbury Sandstpne Narrabeen Group

I red claystones

Illawarra Coal Measures

I Bulli Coal

Gerringong Volcanics a direction similar to the overprints established in younger rock units, such as the overlying Triassic red beds and the Jurassic diatremes (Figures 2 and 3). In only a few samples of the Narrabeen Group is there any relict of an older magnetisation, and this is only shown up after high alternating field demagnetisation (>600 Oersted) and because the relict magnetisation has reversed polarity. It is not possible to recognise unequivocally older magnetisations of normal polarity in the Narrabeen Group. The rock units which best display partial remagnetisation are the Milton Monzonite, the Hornsby Breccia and the red claystones of the Narrabeen Group. Palaeomagnetism of the Hornsby Breccia samples display two well separated components after step-wise thermal demagnetisation (Schmidt & Embleton, 1981). Red claystone samples from the Patonga Claystone near The Entrance (Figure 1) typically reveal steep normal components overprinting original Early Triassic magnetisations. Embleton & McDonnell (1980) have shown that the Early Triassic magnetisations may be either of normal or reversed polarity. As they did not publish stereo projections of directions of the components, stereonets are reproduced here for comparison (Figure 2). The overprint components from the Patonga Claystone are identical to those found in the Narrabeen Group at Tahmoor and Coalcliff, and in the breccia pipes at Hornsby, Dundas, Marsden Park and St Marys. Details of results from the breccia pipe localities are reported in Schmidt & Embleton (1981) and Schmidt (1982). Clearly the overprint event had a wide-

Basin

sedimentation extrusive (and intrusive?) volcanism spread effect on magnetisations of Sydney Basin rocks. The mean directions of the overprint are listed in Table 2. RESULTS FROM LAPS TONE MONOCLINE AND T AHMOOR 600 PANEL MONOCLINE

The amplitude of the Lapstone Monocline decreases to the south where it merges with the Nepean Fault. The fault cuts across the eastern portion of the Tahmoor mining lease and is an effective barrier to mining. The Nepean Fault generally strikes NNW but over the 10km interval from Picton to the southern edge of the Tahmoor lease it shows some minor local changes in direction, or lateral off-sets. Seismic lines show that the fault zone is about 500m wide with a down-throw of a few tens of metres to the east. The boundaries of the fault zone have been taken as the limits of good quality seismic reflections from the Bulli coal. The boundaries are not sharp and it is possible that smaller scale faulting occurs alongside the main fault. A number of seismic lines that cross the fault zone north of Tahmoor have been interpreted to show high angle reverse faulting dipping down to the west (Herbert, 1989). In detail there appears to be a complex system of reverse faults and sub-ordinate normal faults with individual fault planes dipping either to the east or west. In plan, individual faults are laterally discontinuous and are arranged in an en echelon pattern. Herbert (1989) further concludes that the Nepean

AUSTRALIAN COAL GEOLOGY

Magnetic Overprint Directions 1n Sediments N

Norah Head

Toowoon Bay

+ 0

o&O

<Je

a+-

0 0.

-9

Forresters Beach North

Otford 0

Coalcliff

Tahmoor Drift

o t o 0

B:>~ +

'Bo<9

~<o~ 0

+ 0

00 0

•

~ 9cI>

0 0

Figure 2. Upper hemisphere equal-area stereonets of magnetic overprint directions in Narrabeen Group sediments throughout the Sydney Basin. Sediments sampled at Norah Head, Toowoon Bay, Forresters Beach (North) and Otford are red claystones, while the sediments at Coalcliff and Tahmoor are drab coloured shales and sandstones.

A USTRALI A N COAL GEOLOGY

Magnetic Overprint Directions 1n Breccia Diatremes

Hornsby

Dundas

6' Cb 0

+ 8

& 0 0

+ E

9:>o

(i)

-f)

Marsden Park

St Marys

+ 0

+ E

Figure 3. Upper hemisphere equal-area stereonets of magnetic overprint directions in breccia diatremes throughout the Sydney Basin.

AUSTRALIAN COAL GEOLOGY

Table 2. Mean Directions of Sydney Basin Overprint Magnetisations. Locality

Dec(') Inc(')

(X95(')

Norah Hd

17.0

-80.3

94.1

3.8

Toowoon

6.4

-74.8 183

1.8

ForesterN

17.9

-77.5

83.9

2.6

Otford

0.8

-79 .1

41.4

5.8

Coalcliff

355.2

-74.4

60.9

3.7

Tahmoor

131

6.0

-76.4

60.6

1.6

Hornsby

5.5

-77.5

65.3

2.1

Dundas

349.7

-75 .7

22.9

8.8

Marsden

43.5

-78 .0 165

1.9

24 358.1 -81.8 133 2.6 St Marys N: number of samples, Dec: declination, Inc: inclination, k: precision parameter, a9s: 95 % confidence radius. Fault generally has a compressive origin but with a degree of wrenching. This interpretation may be equally applicable in the Tahmoor lease, particularly at the stratigraphic level of the Bulli coal. A monocline located near the southern boundary of the Tahmoor mining lease was first encountered in a mine roadway (600 Panel) driven to ventilate the southern end of a series of northsouth oriented longwall blocks, and is referred to here as the 600 Panel Monocline. The monocline represents the northern tip of the westernmost en echelon fault of the Nepean Fault zone. Its strike is NNW and bedding dips to the WSW by as much as 40 • with an overall displacement of Sm. Figure 4 is a photo mosaic of the monocline looking towards the north-west. The monocline attenuates to the north. At an intersection 200m north of 600 Panel, the displacement is only 0.Sm and further north it disappears altogether. The 600 Panel Monocline is located 500m to the west of the Nepean Fault Zone. This proximity and the similarity in strike and tectonic style suggest that it is an integral part of the zone. There are other structures close to, and parallel with, the Nepean Fault Zone but the monocline is the largest in the Tahmoor Mine workings. In the immediate vicinity of the Nepean Fa ult Zone, faults parallel and antithetical to the Nepean Fault coupled with high lateral stress have resulted in severe mining problems (I. Stone, personal communication, 1993 ).

Table 3. Mean Directions from Lapstone Monocline. N

Oh(') Ih( ')

(X95( ')

Db(') lb')

(X95( ')

286.3 -66.6

3.9

68.4 -74.1

4.1

63.3 -56.5

4.3 352.4 -80.3

4.3

50.4 -46.0

5.5 334.9 -60.7

5.5

4 104 37.1 -67.2 7.8 16.9 -73.8 5.7 Key, 1 - 600 Panel (*variable dips), 2 - Lapstone, 3 Hawkesbury Lookout, 4 - All data. N: number of samples, D: declination, I: inclination, h: with respect to present horizontal, b: corrected for bedding, a 9s: 95% confidence radius. To investigate the effects of the monocline on the overprint directions samples were collected from 600 Panel (Figure 4). The samples were taken from basal Narrabeen Group sediments forming the roof of the Bulli Coal. Strata showing a variety of dips were sampled and directions of magnetisation were found to show concomitant amounts of deflection, when compared with the mean direction observed in flat-lying strata (cf. Figures 2 and 5). Underground samples were oriented using a combination of magnetic compass and survey data but accuracy was affected by the presence of roof-straps and rib-mesh (clearly evident in Figure 4). Since underground orientations were not as accurate as can be achieved above ground, further samples were collected from recent roadworks at both Lapstone and the Hawkesbury Lookout, where major roads cross the Lapstone Monocline (Figure 1). The samples were all from grey shales near the top of the Hawkesbury Sandstone. The strata sampled at Lapstone are dipping 32' to the east, while the strata at Hawkesbury Lookout dip so· to the east. Directions from these samples are plotted in Figure 5 and listed in Table 3. It is clear from these data that the directions of remanence from sediments at Lapstone and Hawkesbury show a deflection which is consistent with the sense of dip at each locality. Some directions, particularly from Hawkesbury Lookout samples appear to be over-corrected which might imply magnetisation in some intermediate attitude, or some partial remagnetisation in the present geomagnetic field. These possibilities will require further sampling to test. The point we wish to convey in this report is that the monocline has affected the directions of the overprint magnetisation by a considerable amount.

AUSTRALIAN COAL GEOLOGY

Figure 4. Photo mosaic of the underground 600 Panel Monocline at Tahmoor Colliery.

Magnetic Overprint Directions 1n Monocline Sediments N

Tahmoor 600 Panel

Lapstone Cutting oBoo

~~o89 ~

l 9J<:P

0 '{8

~• <900e0

~OQ

o~o 8° o 0 oo o

•

•8 +

+ 000

0 0

+ 0

oo i

<D O 0

<Y 0

80 E

Hawkesbury Cutting +

+ 0 0

Q:>

0 6) 00,o + O

o'O

o (} <D i o0oooo -o O a>

oOoo

~'f:F)

<Jo

All In Situ

All Unfolded

Figure 5. Upper hemisphere equal-area stereonets of magnetic overprint directions in Narrabeen Group (at Tahmoor) and Hawkesbury Sandstone (at Lapstone and Hawkesbury Lookout), showing in situ directions and tilt corrected directions. The main phase of tilting of the monocline appears to post-dates the magnetization age which is about 90Ma.

AUSTRALIAN COAL GEOLOGY

21 DISCUSSION

There is now overwhelming evidence from a variety of techniques that the Sydney Basin has been subjected to low temperature metamorphism during the Mid-Cretaceous, particularly in the southeast. Evidence has been derived from palaeomagnetism (Schmidt & Embleton, 1981, Schmidt, 1982), fission-track dating (Morley & others, 1980), vitrinite reflectance (Middleton & Schmidt, 1982), fluid inclusion data and Kl Ar dating (Bai & others, 1993). These last two avenues of research support the inference based on palaeomagnetic data that a thermal event occurred at about 90Ma involving uplift and supracrustal cooling from elevated temperatures. Fluid inclusions in quartz overgrowths in Narrabeen Group samples from only a few hundred metres depth reveal minimum homogenisation temperatures of up to 100°C requiring some considerable overburden, may be coincident with an enhanced geothermal gradient. K/ Ar dates of fine authigenic illite reveal a consistent eastward decrease towards the coast from 146Ma to 91Ma, closely paralleling iso-reflectance contours (P.J . Hamilton, personal communication, 1994). Modelling of vitrinite reflectance values indicates palaeotemperatures of 130°C to 180°C and requires burial depths of 1500m to 2100m in the midJurassic (Bai & others, 1993). This modelling is independent of that used by Middleton & Schmidt (1982) which arrived at similar conclusions. Overprinting, or complete remagnetisa tion, related to the Mid-Cretaceous thermal event have been recognised in many different rock-types throughout the Sydney Basin, including red, grey and green fine sandstol)eS, siltstones, claystones, Permian and Early-Mid Jurassic igneous rocks, such as the Gerringong Volcanics, the Milton Monzonite and the breccia diatremes. In sedimentary strata or intruded igneous rocks that have not been tilted, the Cretaceous overprint magnetisations are consistently directed northward, albeit steeply upwards. This property has afforded the coal industry a valuable orientation tool. The deflection of Cretaceous overprint directions by the Lapstone Monocline, and related structures, indicates that these tectonic structures post-date the Mid-Cretaceous, viz. ~90Ma. This in turn implies that the major movement along the Lapstone Monocline post-dates ~90Ma and was probably related to precursor events leading to rifting in the Tasman Sea. Other models for the age of the Lapstone Monodine include those which support its early development (Early Mesozoic; Pickett & Bishop, 1992) and its later development (Cretaceous-Tertiary; David, 1897). The evidence tendered by Pickett & Bishop (1992) is contingent on the magnitude of the Glenbrook Fault at its southern extremity. If this fault actually peters out north of Nortons Basin then their observation, that the breccia out-

cropping there shows no signs of faulting, is of little consequence. The southern extremity of the Glenbrook Fault is not well defined as Pickett & Bishop (1992, page 22) clearly recognise. The palaeomagnetic evidence shows that although sedimentary units thin to the west of the Lapstone Monocline indicating that the structure was active during sedimentation, the major tilting along the monocline was at least as young as the mid-Cretaceous. An earlier palaeomagnetic study of Hawkesbury Sandstone folded by the monodine by Bishop & others (1982) concluded that movement had ceased before the Late Tertiary on the basis that weathered sandstones yielded palaeomagnetic pole positions consistent with an age of 15±7Ma irrespective of structural position . Movement may have ceased long before this time. CONCLUSIONS

The deflection of palaeomagnetic overprint directions associated with a mid-Cretaceous thermal event indicates that major movement on the Lapstone Monocline post-dates ~90Ma. The palaeomagnetic evidence therefore strongly supports a Cretaceous-Tertiary development of the Lapstone Monocline. ACKNOWLEDGEMENTS

The authors acknowledge funding by ACARP Project C1615 and helpful discussions with Ian Stone (KCC), and Joe Hamilton and Peter Eadington (both CSIRO Petroleum Resources) and David Titheridge (KCC) for comments and suggestions on an earlier version of the paper. REFERENCES BAI, G.P., EADINGTON, P.J. & HAMILTON, P.J., 1993: Fluid history investigation of Permo-Triassic sandstones in the Sydney Basin. CSIRO Division of Exploration Geoscience, North Ryde, Restricted Report 417R. BISHOP, P., HUNT, P. & SCHMIDT, P.W., 1982: Limits to the age of the Lapstone monocline, NSW - a palaeomagnetic study. Journal of the Geological Society of Australia, 29, 319-326. BRANAGAN, D.F. & PEDRAM, H., 1990: The Lapstone Structural Complex, New South Wales. Australian Journal of Earth Sciences, 37, 23-36. DAVID, T.W.E., 1897: Anniversary address. Summary of our present knowledge of the structure and origin of the Blue Mountains of New South Wales. Journal and Proceedings of the Royal Society of NSW Bulletin, 30, 33-69. EMBLETON, B.J.J. & MCDONNELL, K.L., 1980: Magnetostratigraphy in the Sydney Basin, Southeastern Australia. Journal of Geomagnetism and Geoelectricity, 32(III), 1-10.

AUSTRALIAN COAL GEOLOGY

HERBERT, C., 1989: The Lapstone Monocline-Nepean Fault - A high angle reverse fault system. Twenty Third Newcastle Symposium, Department of Geology, University of New castle, Newcastle, 179-186.

MORLEY, M.E., GLEADOW, A.J.W., & LOVERING, J .F., 1980: Evolution of the Tasman rift: Apatite fission track dating from the southeastern Australian continental margin. Proceedings of the Vth Gondwana Symposium, 289-293.

HUNT, P.A ., 1985: The mobility of silicon and iron in the near surface zone: a re-evaluation of the concept of duricrust in central and eastern New South Wales. Ph.D. thesis, School of Earth Sciences, Macquarie University, NSW .

PICKETT, J.W. & BISHOP, P., 1992: Aspects of landscape evolution in the Lapstone Monocline area, New South Wales. Australian Journal of Earth Sciences, 39, 21-28.

LACKIE, M.A. & SCHMIDT, P.W., 1992a: Some examples of drill core orientation using palaeomagnetism in the South Sydney Basin . CSJRO Division of Exploration Geoscience, North Ryde, Restricted Report 300R. LACKIE, M.A. & SCHMIDT, P.W., 1992b: Preliminary study of drillcore orientation using palaeomagnetism, German Creek Colliery. CSIRO Division of Exploration Geoscience, North Ryde, Restricted Report 345R. MIDDLETON, M.F. & SCHMIDT, P.W., 1982: Paleothermometry of the Sydney Basin. Journal of Geophysical Research, 87, 5351-5359.

SCHMIDT, P.W ., 1992: Linearity spectrum analysis of multi-component magnetizations and its application to some igneous rocks from south-eastern Australia. Geophysical Journal of the Royal Astronomical Society, 70, 647-665. SCHMIDT, P.W. & ANDERSON, J.C., 1990: Feasibility of using palaeomagnetism to orient drill core from the Tahmoor Colliery. CSIRO Division of Exploration Geoscience, North Ryde, Restricted Report 177R. SCHMIDT, P.W. & EMBLETON, B.J.J., 1981: Magnetic overprinting in southeastern Australia and the thermal history of its rifted margin. Journal of Geophysical Research, 86, 3998-4008.

AUSTRALIAN COAL GEOLOGY

DOCTOR OF PHILOSOPHY THESES ABSTRACTS (Abstracts have been reproduced here roughly as they appear in their respective thesis documents, with minimal editing. Ed.) THE GEOLOGY OF AN AREA AROUND LIMEKILNS, BATHURST DISTRICT, NSW I.J. Stone, University of Wollongong, 1973.

Rocks of Devonian age outcrop around Limekilns, approximately 28km NNE of Bathurst, NSW. The oldest rocks mapped are the Lower Devonian Merrions Tuff, a massive pyroclastic rock. This unit is overlain conformably by the Lower Devonian Limekilns Group, which consists of three conformable formations: the basal Rosedale Shale (300m thick); the middle Jesse Limestone (40m thick); and the Limekilns Creek Shale (450m thick). Fossil evidence indicates that the Rosedale Shale has a Lower Emsian age, whereas the top of the Jesse Limestone is Late Emsian. The limestones, of the Limekilns Group, consist of two types; a bedded detrital unit with basal conglomerates which outcrops in the west of the area mapped; and a more massive type that is brecciated in places. An apparent unconformity separates the Limekilns Group from the overlying Winburn Tuff, a pyroclastic unit, similar to the Merrions Tuff. Occurrence of limestone is representative of geosynclinal shelf deposits on the Capertee Geanticline. Cessation of geosynclinal conditions, caused by uplift during the Tabberabberan Orogeny, has resulted in an angular unconformity between the Lower and Middle Devonian rocks and the overlying Upper Devonian Lambie Group which occurs to the east of the area mapped. Andesite and dolerite dykes occur as a swarm in the area and may be related to a phase of the Tabberabberan Orogeny. The structure of the area consists of three main folds - the Pembrook Anticline, the Alice Dale Syncline, and the Wyoming Anticline. Numerous small folds are superimposed onto the three larger fold structures. Fold styles vary from open to overturned isoclinal structures. All folds trend north-south although the plunge sense and direction may change. ORGANIC PETROLOGY OF OIL SHALES

A.C. Hutton, University of Wollongong, 1982.

Oil shales are a diverse group of rocks that may become an important source of liquid fuel and chemical feedstocks. The bulk of the organic matter in oil shales is generally exinite derived from a variety of organisms ranging from terrestrial higher plants to freshwater and marine algae. In this study reflected light and fluorescence mode petrography provide data not readily available

through chemical, transmitted light and palynological studies. The petrographic studies elucidate the mode of preservation and mineral-maceral relationships usually destroyed during mineralisation and pyrolysis. Previous petrographic terminology for algal components is revised and two new terms, lamalginite and telaginite, are defined. Type of exinite is used to classify oil shales into three primary and six secondary groups. OIL SHALE

Tcrtcial

/11,ine

Cannel Coal Torbanite

)1~

Lamosite Tasmanite Marinite Kukersite

Telalginite derived from Reinschia and Pila, both related to the extant green alga Botryococcus braunii, is the major exinite in torbanite which is formed in shallow lakes associated with coal forming swamps. The reflectance of vitrinite in torbanite decreases as the alginite content increases. Lamosites are freshwater, laminated oil shales and are divided into Rundle type and Green River type. Australian Tertiary lamosites belong to the Rundle type and contain discrete lamalginite derived in part from the colonial green alga Pediastrum, the freshwater dinoflagellate Septodinium, and the acritarch Cleistosphaeridium. Botryococcus telalginite and humite are minor constituents. Green River lamosite contains layered lamalginite with minor bitumen and huminite. Differences between the two forms of lamalginite in the Rundle and Green River type lamosites indicate that the environments of deposition were not the same for both. Australian Tertiary lamosites were deposited in fresh to brackish water, probably nearshore lakes. Recognition of phytoplankton algae, but not benthonic or mat-forming algae, suggests that the bulk of the exinite in these lamosites was derived from planktonic precursors. The Rundle-Stuart and Byfield deposits have a brown coal unit overlying the lamosite units. In the Condor and Byfield deposits a brown coal unit underlies the lamosite units. The boundaries between the coal and lamosite units represent significant changes in the environments of deposition. The Duaringa deposit has brown·coal interbedded with lamosite (as occurs in several of the RundleStuart lamosite units) in a lower unit that is over-

AUSTRALIAN COAL GEOLOGY

lain by a younger lamosite unit containing a different assemblage of alginite to the older unit. Within the lamosite units of Australian Tertiary deposits the abundance of lamalginite changes vertically (but is not related to depth) but type does not. Lateral variation in the type of lamalginite was not observed in any deposit. Cannel coal contains abundant exinite derived from higher plants. Tasmanite, contains abundant telalginite derived from Tasmanites punctatus and related algae that have affinities with Pachysphaera pelagica. Lamalginite, derived from dinoflagellates, acritarchs and other algae, or bituminite is the dominant exinite in marinite. Marinite also contains tasmanitid telalginite and in some specimens, vitrinite-like organic m a tter of probable algal origin. Kukersite is composed of telalgite derived from Gloeocapsomorpha prisca, an alga that is closely related to Botryococcus. The classification and characterisation of oil shales provides much-needed data from which a framework for further studies can develop. More meaningful comparisons of the chemical properties of kerogen and shale oil can be attempted and the behaviour of the oil shale during retorting can be more readily understood. THE RELATIONSHIP BETWEEN COALS AND DISPERSED ORGANIC MATTER IN ASSOCIATED SEDIMENTS IN FOUR BASINS IN CENTRAL AUSTRALIA

M. Smyth, Universi.ty of Wollongong, 1985.

The major oil and gas fields in Australia produce from coal measure sediments, in contrast to the giant oil fields of the Northern Hemisphere which are associated with the marine rocks. The organic matter in the Australian fields is present both as coal seams and fragments of coaly material dispersed through the adjacent sediments. The purpose of the study is to determine whether the organic matter in the coal seams and as dispersed fragments is the same, different or systematically related. The type of organic matter in each may indicate that one is better, or the same, as a source for hydrocarbons. The sedimentary sequences examined are those of the Permian- Triassic Cooper Basin, the Permian Pedirka Basin, the Triassic Simpson Desert Basin, and the Jurassic-Cretaceous Eromanga Basin, all of which are located in central Australia. In addition, the relationship of organic matter type to the depositional environment for the Permian sequence in the Cooper Basin was investigated.

All of the studies were carried out using reflected and transmitted light microscopic techniques for analyses of the organic matter. Relationships have been found between the maceral types of the dispersed organic matter (DOM) and the maceral and microlithotype compositions of the associated coals. Exinite (sporinite) DOM correlates with vitrinite and sporinite in the associated coals in the Cooper and Eromanga Basins. Exinite (cutinite) DOM correlates negatively with cutinite in the coal in the Simpson Desert Basin. Sporinite DOM correlates with vitrite plus clarite and intermediate microlithotypes (duroclarite, clarodurite and vitrinertite) in the coals of the Cooper Basin. Vitrinite DOM correlates with vitrinite and the intermediate microlithotypes in associated coal in the Cooper Basin, and with resinite in the coal of the Eromanga Basin. Inertinite DOM, mostly inertodetrinite, correlates with inertodetrinite and durite plus inertite in the associated coals in the Cooper Basin. The microlithotype compositions of coals formed in association with a large lake environment are distinctly different from the microlithotype compositions of coals formed on the lower coastal plain and in areas dominated by coal swamps in the Permian of the Cooper Basin. Channel belt coals are also distinct in type from those of the lower coastal plain, upper coastal plain and areas dominated by coal swamps. Lower coastal plain coals can be differentiated from upper coastal plain coals on the basis of their microlithotype compositions. Those coals with the highest vitrinite plus clarite contents have formed in channel belt and associated with large lakes. Coals with the highest durite plus inertite contents have formed in the areas dominated by coal swamps. Given that exinite is the coal maceral richest in hydrogen, and therefore the best material for genera ting hydrocarbons, the best source rocks in the Permian of the Cooper Basin are those which have formed in the large lake and channel belt environments. If inertinite has the least potential as a source for hydrocarbons, then the sequences in areas dominated by coal swamps have the lowest potential as source rocks for hydrocarbons. THE SEDIMENTOLOGY OF THE RUNDLE OIL SHALE DEPOSIT

Lee Coshell, University of New South Wales, 1986.

The Rundle deposit is a major oil shale resource located in The Narrows Graben, near Gladstone, central Queensland, Australia. It contains an estimated 2.65 billion barrels of oil in situ and is considered generally to have good prospects for commercial viability. The Tertiary infill of the graben, The Narrows Beds, consists predominantly

AUSTRALIAN COAL GEOLOGY

25 of intercalated claystone and oil shale, lesser lignite and sporadic dolomite, with a composite thickness in excess of 1000 metres. In this study the sedimentology of the deposit at Rundle is investigated, specifically the uppermost 400 metre thick section of the oil shale-rich Rundle Formation which is analysed in terms of facies with a view to interpreting the environment of deposition .

repetitive elements with specific properties, and thus providing a means by which the deposit may be mapped, characterised and rock mechanical behaviour predicted using a minimal number of variables.

Eight repetitively occurring facies are recognisable in the Rundle Formation and each member of the formation comprises all or some of these, uniquely distributed in correlatable cycles. Of the eight facies, five consist of oil shale, each characterised by distinctive composition, colour, density, texture and sedimentary structures. The remaining three correspond to claystone, lignite and dolomite and are designated 6, 7,and 8 respectively. Inherent in all these facies is a predictable oil-producing potential. Application of the statistical method of Markov chain analysis to the facies sequence indicates strong preference for certain facies (and subfacies) transitions, and a common pattern of cyclic behaviour appears prevalent throughout the succession. A model cycle is proposed .

H.K. Mishra, University of Wollongong, 1986.

Montmorillonite is by far the most abundant mineral phase present and with quartz and minor amounts of illite, kaolinite, feldspar and carbonates it constitutes an assemblage that accounts for nearly 90% of the sediments. These minerals almost certainly reflect provenance and diagenetic processes generally have played a somewhat subordinate role in sediment development. Dolomite concentrations ascribable to facies 8 are apparently penecontemporaneously formed secondary features. Rare analcime is considered indicative of saline/alkaline conditions in the Telegraph Creek Member. The almost ubiquitous organic matter is primarily derived from algae although in places higher plants also have contributed significantly. The sediments are considered to have formed within the framework of a shallow, fresh-water, lacustrine environment of deposition. This environment fluctuated between open-water, limnic marsh (or swamp), variably anoxic mudflat and pedogenic subenvironments, the latter probably saline/ alkaline at times. Structures attributable to subaerial desiccation are almost ubiquitous. Ordered repetition and interaction of these subenvironments over time (probably through climatic variations) has resulted in the cyclic deposition of a limited number of characteristic facies and subfacies. The closest modern analogue to the Rundle depositional environment appears to be, in general terms, a plankton-rich, shallow tropical lake situated in a predominantly closed drainage basin, and showing periodic changes in water level that at times lead to dryness. The results of this study appear to have considerable practical application, resolving the oil shale resource at Rundle into a limited number of

A COMPARATIVE STUDY OF THE PETROLOGY OF PERMIAN COALS OF INDIA AND WESTERN AUSTRALIA

Investigations on coal type and rank in Indian basins (Damodar Valley, Son-Mahanadi Valley and Pench-Kanhan Valley Basins) and western Australian basins (Collie, Perth and Canning Basins) indicate that the Permian coals of India and western Australia are petrologically broadly similar. The Indian and western Australian basins therefore probably had closely related depositional environments and were probably deposited in adjacent areas. Comparisons of these coals with some other Gondwana coals also show broad similarity of petrological characteristics. Coals from other ages (Carboniferous, Triassic, Jurassic, Cretaceous and Tertiary) all have distinctive and in many cases characteristically different petrological properties. These variations of coal composition through time are a systematic response to changing floras and changing climates. In India, outcrops of bituminous rank coals are restricted to the Damodar Valley basins. In this area vertical rank gradients are higher and uplift and removal of cover have occurred to a greater extent than in other Gondwana basins of India. Coals of the other Gondwana basins occur at shallow depths and are sub-bituminous rank. Coals examined from the Collie and Canning Basins are sub-bituminous in rank and do not vary significantly in rank laterally or with depth. Coals examined from the Beagle Ridge area of the Perth Basin are very high in rank compared with other Permian sequences in the basin. The maturation history of the Jharia Basin of India implies that the Permian section of the basin has suffered a major Permian to Triassic thermal event. During this time a tensional regime probably prevailed in India possibly centred on the Jharia Basin . This regime caused extensive subsidence and consequently a thicker sedimentary sequence (>3km) was deposited in the Jharia Basin than in other Gondwana basins of India . A similar situation also existed in the Beagle Ridge . area of the Perth Basin but there a much thinner Permian sequence has resulted. In other parts of the Perth Basin the major control of heat flow is the depth to basement. In these areas isoreflectance surfaces are depressed in the 'cool' deep troughs and are elevated and more closely spaced over basement highs. Regional uplift exerts significant local control of rank trends. The overall low temperature gradient in the Perth Basin is probably related to an attenuating post-break up thermal event.

AUSTRALIAN COAL GEOLOGY

The Canning Basin has suffered significant preJurassic coalification which was interrupted by widespread uplift and erosion in the Triassic. Mesozoic and Tertiary coalification is generally weak, resulting in a pattern of rank distribution relatively unfavourable for generation and reservoiring of major hydrocarbon occurrences. Potential hydrocarbon source rocks occur throughout the Perth Basin. Organic matter in the Perth Basin is mainly humic with the exception of Kockatea Shale Formation. The Perth Basin, nevertheless, has good source potential for oil and gas . Rank, type and temperature data indicate that Permian sediments of the Damodar Valley basins also have good source po tential for hydrocarbon generation whereas the Kidson Sub-basin, Lennard Shelf and Fitzroy Graben of the Canning Basin have moderate source potential. This study has demonstrated that coal petrological data can be used to interpret coal properties, petroleum source potential, depositional characteristics, burial and thermal histories, and to interpret relationships between the histories of continental masses. ASPECTS OF SOURCE ROCK AND RESERVOIR POTENTIAL OF THE PORT CAMPBELL AREA, OTWA Y BASIN, VICTORIA

H. Panggabean, University of Wollongong, 1986.

Sedimentary sequences in th e Port Campbell area range from the Early Cretaceous to Pliocene in age. Two major groups are distinguished in the Cretaceous sequences. The Otway Group was deposited in a braided river fluviatile environment which is unconformably overlain by the fluviodeltaic to shallow marine sequences of the Sherbrook Group. The Tertiary sequences are divided into Wangerrip Group (paralic to deltaic and shallow marine), Nirrandra Subgroup and Heytesbury Group (both marine environments). The present study of organic p etrology gives an assessment of organic matter type and abundance, and the rank of possible petroleum source rocks in the Port Campbell area . Organic matter in the Early Cretaceous- Tertiary sequences of the area is predominantly in a dispersed form but some thin coal seams also occur in the sequence. Inertinite is the dominant maceral in the dispersed organic matter (d.o .m. ) but the liptinite . and vitrinite which are present in the sequences probably have the most significant generation potential. The Eumeralla Formation is considered as the most effective source of hydrocarbons as the formation contains intervals with abundant organic matter and lies in the principal zone of oil generation (0.7% - 0.9 % Rvmax). The next most effective sources of hydrocarbons are the Waarre Formation and the Belfast Mudstone; both are marginally mature (0.5 % Rvmax ).

Rank data, together with information from palaoethermal models suggest that an early and relatively rapid phase of coalification began during the Cretaceous and post-Cretaceous. The largest hydrocarbon accumulation found to date has been in the Waarre Formation. Thin section petrographic, SEM and cathodoluminescence studies show that secondary intergranular and intra-cement pore textures are common in this unit. Thus, the formation has good reservoir potential. The petrography of one hundred and ten samples of fine- to coarse-grained sandstones showed that the detrital components of sandstones in the Port Campbell area comprise variable amounts of quartz, feldspar and volcanic rock fragments. The main sandstone groups are quartzarenite, sublithareni te, volcarenite, litharenite and feldspathic litharenite. The fine-grained rocks include carbonaceous mudstone, glauconitic mudstone, chloritic mudstone, siltstone and marl. X-ray diffraction analyses indicate that kaolinite is more abundant than illite, chlorite, sericite, montmorillonite and mixed-layer clays in most of the samples examined. In some samples from the Eumeralla Formation chlorite is more abundant than kaolinite. A CLASSIFICATION AND PETROLOGICAL ASSESSMENT OF ORGANIC FACIES IN THE DENISON TROUGH, BOWEN BASIN, QUEENSLAND

James William Beeston, University of Queensland, 1987.

The Permian Denison Trough, located along the western edge of the Bowen Basin, Queensland, is a graben complex containing a sedimentary sequence in which a range of terrestrial, nearshore and marine deposystems is recognised. Distribution of organic matter within the deposystems is varied, most accumulations being associated with meandering stream, fluvio-deltaic and deltaic/back barrier systems. Deposition of organic matter in the Denison Trough was controlled largely by plant types, palaeoclimate, and palaeogeography. Plant matter was derived from glossopterids, sphenophytes, ferns and colonial algae, with lesser contributions from lycophytes, unicellular algae, conifers, fungi and bacteria. Differential distribution of organic matter and variations in plant tissue types and their associated palynofloras, as observed in the sediments, is attributed chiefly to pre-depositional variations in sites of growth along with variable proximity to sites of deposition and avenues of transport. Climatic changes affected the accumulation and preservation of organic matter through variations in water influx, while changes in external tectonic setting and internal depositional environment chiefly influenced elastic sediment input.

AUSTRALIAN COAL GEOLOGY

The petrological classification of coals and carbonaceous mudstones in the Denison Trough is based on such characteristics as plant origin, gelification, oxidation, particle reworking, particle size, and particle segregation. Five coal facies, the Detrital, Leaf, Wood, Herbaceous and Gel Coal Facies are defined. Various combinations of these facies can be distinguished in coal seams, banded coals and carbonaceous mudstones, leading to the recognition of seven coal facies assemblages. The classification of disseminated organic matter (DOM) relies on variations in quantity, physical degradation, and oxidation, and in general cannot be related to the more detailed criteria that distinguish coal facies. Six DOM suites, the Channel, Overbank, Swamp, Nearshore, Shoreline, and Offshore suites, are described. Those macerals showing greatest potential for oil generation are low reflecting, highly fluorescing liptinites. They occur in trace proportions, as remnants of organic matter that was abundant prior to the generation stage, at which stage it was converted to oil. SOURCE ROCK AND MATURATION CHARACTERISTICS OF THE SEDIMENTARY SEQUENCE OF THE OTWAY BASIN, AUSTRALIA H.J.M. Struckmeyer, University of Wollongong, 1988.

The Otway Basin is one of several extensional basins along the southern margin of Australia. These basins developed in the Late Jurassic to Early Cretaceous before the breakup of eastern Gondwanaland. The Otway Basin is located to the west of the Gippsland Basin which contains large reserves of hydrocarbons. In the Otway Basin, only three small commercial gas accumulations have been discovered to date, in spite of extensive exploration. Organic petrological methods yield information on abundance, composition and maturity of organic matter in sedimentary rocks . This information enables assessment of hydrocarbon source potential. The Otway Basin contains a succession of Mesozoic to Tertiary sedimentary rocks up to 10km thick comprising a ?Late Jurassic to Early Cretaceous synrift sequence and a Late Cretaceous to Tertiary post-breakup sequence. Three distinct organic facies are present in the Otway Basin sequence: a fluvial to lacustrine facies (?Late Jurassic to Early Cretaceous), a deltaic to restricted marine facies (Late Cretaceous to Early Tertiary) and a shallow marine facies (Midto Late Tertiary). The fluvial to lacustrine facies is characterised by abundant coaly organic matter, where the lower unit of the Eumeralla Formation contains the largest amounts of organic matter. The organic matter is commonly rich in vitrinite and liptinite although, locally, inertinite-rich coals are present. Alginite-rich oil shale occurs in

the Casterton Formation. The deltaic to restricted marine facies is characterised by inertinite-rich dispersed organic matter and vitrinite-rich coals. These coals are mostly confined to the upper part of the Sherbrook Group and to the Wangerrip Group. The shallow marine facies is characterised by rare vitrinite-poor dispersed organic matter. Assessments of source potential in the Otway Basin are based on several concepts, some of which have been developed during the course of this study: coal is an efficient generator of liquid hydrocarbons at low maturation levels; all three maceral groups have the capacity of generating liquid hydrocarbons; the specific generative potential of the maceral groups is dependant on their hydrogen content; the generation of oil versus gas is probably related to rank only, where the different maceral groups and macerals have varying thresholds for the onset of oil generation. A hydrocarbon generation score (Score A) employing maceral composition is used to evaluate source potential. Three major source rock sequences are present: the Casterton Formation, the lower unit of the Eumeralla Formation and the Wangerrip Group. They occur juxtaposed against suitable reservoir and cap rocks. The patterns of rank variation in the Otway Basin suggest that age, burial depth and depth to basement are the major factors controlling the maturity of organic matter. In areas where Late Cretaceous sediments are thin or absent, Early Cretaceous source rocks are immature to mature and reached the oil window mostly in the Tertiary. In Late Cretaceous burial centres, Early Cretaceous source rocks are mature to post-mature and reached the oil window early in their burial history. Early generation was probably enhanced by high palaeotemperatures and the predominantly coaly nature of the source rocks. The Tertiary Wangerrip Group is immature over most of the basin but locally reaches oil maturity. A major departure from the regional maturation pattern exists in the Otway Ranges where high maturation levels occur at shallow depths. The timing of hydrocarbon generation is probably the major factor controlling the development and preservation of oil accumulations in the Otway Basin. Optimum prospects for oil discoveries exist in areas where source rocks reached oil maturity in the Tertiary when fault-related closures were fully developed. These associations exist in the Robe-Penola Trough, the Portland Trough, the Crayfish Platform and the margins of the platform abutting the western Voluta Trough. Commercial gas fields have been discovered in the Otway Basin and the pre-conditions exist for the occurrence of commercial oil fields.

AUSTRALIAN COAL GEOLOGY

28 STRATIGRAPHY AND SEDIMENTOLOGY OF THE LATE PERMIAN ILLAWARRA COAL MEASURES, SOUTHERN SYDNEY BASIN, NSW W.J. Bamberry, University of Wollongong, 1991.

This thesis reports on a study of the stratigraphy, depositional settings and petrography of the Late Permian Illawarra Coal Measures in the southern Sydney Basin of New South Wales, eastern Australia. The depositional settings of the Sydney Subgroup, the upper of the two subgroups in the coal measures, are detailed as it contains the economic coal seams of the region. Thirteen modifications to the currently-accepted stratigraphic nomenclature are recommended in this study. These include changes to the definitions or status of some previously-defined units and the naming of several new units. Six depositional systems have been recognised using an hierarchical approach to facies analysis. The lowermost depositional unit, Del taic System A, comprises the Pheasants Nest Formation and records a continuation of a regressive trend in the upper part of the marine Shoalhaven Group. This system is represented by widespread deltaic facies which grade up-dip into alluvial fan and braidplain facies, flanking the "Gerringong Volca -

nics". The upper part of Deltaic System A was reworked during a transgression which resulted in the deposition of extensive, sandy, subtidal to middle shelf facies in the Shallow Marine System (Erins Vale Formation and Kulnura Marine Tongue). A regressive phase of sedimentation is recorded in the overlying Flu vial/Shore-zone System in the east and the Braided Pluvial System in the west. Upper shoreface to beach deposits of the Pluvial/Shore-zone System were deposited along a storm-dominated, south-west-north-east trending shore-line. This was periodically charged with sediment from meandering rivers (lower Wilton Formation) and was located in the eastern part of the basin. At a similar tim e , alluvial fan, braidplain and fan-delta facies of the craton-derived Marrangaroo Conglomerate (Braided Fluvial System) were deposited along the western margin of the basin. The distribution of the overlying Woonona seam above a wide range of depositional units suggests the synchronous development of the Marrangaroo Conglomerate and lower Wilton Formation, and indicates a period of tectonic stability. Several delta systems are identified in Deltaic System B. They record deposition of widespread interdeltaic facies constructed around a thin framework of distributary channels . The delta systems in the west passed up-dip into an extensive braidplain represented by the Blackmans Flat Conglomerate (Braided Pluvial System). The

abandonment of these delta systems is reflected in the blanket geometry of the overlying Tongarra seam. Progradation of a complex delta-system, Deltaic System C, resulted from expansion of the New England Orogen. The lower half of the system records deposition on a lower deltaic plain. This includes the prodelta, delta front and interdeltaic sequences of the Bargo Claystone, Darkes Forest Sandstone and Allans Creek Formation respectively. Upper deltaic plain sedimentation is recorded in the very lithic Kembla Sandstone which was deposited by a complex network of distributaries that flowed directly across the basin. The thick Wongawilli Coal formed on abandonment of this fluvial system and passes up-sequence into interdistributary lake-fill deposits in the lower Eckersley Formation. Sandstone is the dominant component of the upper Eckersley Formation and records deposition by meandering rivers in extensive fluvial tracts. The coal seams associated with these fluvial sequences (Balgownie and Bulli seams) are laterally extensive and exhibit little evidence for contemporaneous fluvial sedimentation. Sandstone in the Sydney Subgroup can be categorised into two petrographic suites. The Quartz Suite rocks are characterised by quartz to rock fragment ratios greater than 0.5 whereas the same ratio is less than 0.5 for Lithic Suite rocks. The Quartz and Lithic Suites were derived from the Lachlan Fold Belt, and from the New England Orogen and "Gerringong Volcanics", respectively. Tuffaceous units in the Illawarra Coal Measures of the southern Sydney Basin have been recognised on the basis of petrographic criteria. GENETIC STRATIGRAPHY, DEPOSITIONAL SYSTEMS, SANDSTONE PETROGRAPHY AND DIAGENESIS OF THE TRIASSIC IN THE GUNNEDAH BASIN, NSW, AUSTRALIA Feng Xu Jian, University of New South Wales, 1991.

Based on detailed study of drill cores and geophysical logs from more than 50 fully cored boreholes, the genetic stratigraphic framework and depositional systems have been established for the Triassic sequence in the Gunnedah Basin, the middle portion of the Sydney-Gunnedah-Bowen Foreland Basin system along the eastern margin of Australia. The petrography and diagenesis of the sandstones and the clay mineralogy of the claystones have been studied in thin section and by XRD and SEM, and the tectonic controls on sedimentation patterns have also been investigated . Unconformities, disconformities and regional lacustrine flooding surfaces, as well as surfaces indicated by major changes in mineralogical composition of the sediments, have been identi-

AUSTRALIAN COAL GEOLOGY

fied as important within the Triassic succession. The Triassic sequence in the Gunnedah Basin is divided into a basal Digby Genetic Stratigraphic Sequence and an overlying Napperby Genetic Stratigraphic Sequence, with the boundary represented by a basin-wide palaeosol horizon that is a major disconformity surface on the top of the Digby Sequence and by a regional lacustrine flooding surface at the base of the Napperby Sequence. The Digby Sequence is di vided into the Conglomerate Interval in the lower part and the Sandy Interval in the upper part, with the latter further separated into the Quartz-Lithic Sandstone Unit and the Quartz Sandstone Unit. The Napperby Sequence is divided into five intervals, referred to as Intervals A,B,C,D and E. The lower part of the Digby Sequence was formed by a south-westerly prograding alluvial fan system derived from the New England Fold Belt that provided volcano-lithic detritus to the basin. In the later stages of its development, however, deposition became dominated by a southeasterly flowing fluvial system emanating from the Lachlan Fold Belt that provided Quartzose sediments. The Napperby Sequence was constructed by lacustrine deltaic and fluvial systems. The establishment of an extensive lacustrine in the Gunnedah Basin at the beginning of its deposition appears to have coincided with a major reversal of palaeocurrent trend in the adjacent Sydney Basin, after which the Hawkesbury Sandstone was deposited by a north-easterly flowing braidplain system. The fluvial-dominated deltaic systems of the Napperby Sequence evolved from a lobate, coalesced sandy fan delta complex with dominantly bed-friction processes in its mouth bars and low to high density underflows in the prodelta and distal delta front areas to an elongate of digitate deltaic system with inertia-dominated processes in the mouth bars and turbidites formed by slumping process in the prodelta and distal delta front. Pluvial systems were dominant in the late stage of the Napperby depositional episode, and formed the sediments at the top of the Napperby Sequence. The deltas and the axes of the alluvial fan and fluvial systems appear to have formed in areas with more rapid subsidence rates, while the interdeltaic, inter-fluvial or inter-alluvial system areas tended to occupy sectors of the basin with slow subsidence rates. Sediment entry points for the Triassic succession often occupied structural and topographically stable areas, but the amount, composition and grain size of the sediment supplied from the different entry points appears to have varied dramatically due to geological variations in the source areas.

Major palaeogeographic reorganisation often involved changes in sediment provenance, together with an increase or decrease in number or perhaps shifting of the sediment entry points and fluvial drainage axes, and changes in mineralogical composition of the sediments. The contrasting geometries and internal facies distribution patterns of the fluvial-dominated lacustrine deltas in the Napperby Sequence are considered to have been caused mainly by differences in sediment input to the delta systems. Existing delta classification schemes cannot accommodate variations in the nature and facies pattern of deltas caused by such differences in the sediment input, and a new scheme for delta characterisation and description was developed, based on the results of the present study together with a review of available information on delta sedimentology. This scheme considers six different attributes, and should prove to be a useful tool for studying ancient deltaic sequences. Changes in sediment source rocks caused by changes in provenance or tectonic activity, combined with changes in weathering intensity in the source areas (controlled by climate and weathering duration), have been recognised as the major controls on the mineralogical composition of the sandstones and claystones of the Triassic sequence. The gentle slopes of source areas apparently outweighed climate effects in controlling this weathering intensity. The sandstones of the Digby Sequence change gradually upwards from volcano -lithic in the Conglomerate Interval to quartzose in the Quartz Sandstone Unit, due to a change in provenance from the New England to the Lachlan Fold Belt. The lithic sandstones of the Napperby Sequence generally decrease upwards in detri tal quartz content, and the lithic fragments in them change from mainly silicified volcanics and chert in Intervals A and B to mafic volcanic fragments in Intervals C and D. The change in this case is thought to have been caused by more prolonged weathering of the source rocks for Interval A, and by volcanic activity in the New England Fold Belt during deposition of Intervals C and D. The claystones of the Quartz Sandstone Unit are richer in kaolinite, and the claystones of the Conglomerate Interval contain more smectite and illi te, again related to changes in sediment provenance. The Napperby Sequence claystones decrease upwards in kaolinite content but increase in chlorite and smectite. As with the associated sandstones, this also resulted from more strongly weathered source rocks for Interval A, and from volcanic activity in the New England Fold Belt with deposition of Intervals C and D. The texturally immature but mineralogically mature quartz sandstones and associated flint clays in the Quartz Sandstones Unit appears to have been formed by prolonged weathering under a

AUSTRALIAN COAL GEOLOGY

30 cool-temperate climate. This contradicts previous views that quartz sandstones and flint clays were formed under a warm humid setting, and again suggests that longer weathering related to gentle slopes in the source area may outweigh climatic effects. Detrital mineralogy has been found to be the primary control on sandstone diagenesis, with the depositional systems and genetic facies being the secondary controls. The proportion of secondary quartz in the sandstones is proportional to the detrital quartz content. The clay minerals in the sandstones of the Digby Sequence are dominated by kaolinite, with more coarse grained dickite appearing in the Quartz Sandstone Unit. Kaolinite generally decreases upwards in the sandstones of the Napperby Sequence, but smectite and chlorite increase upwards. The depositional systems in the Gunnedah Basin have also controlled the distribution of diagenetic minerals such as calcite and dawsonite. Calcite mainly occurs in the organic-rich Napperby lacustrine-deltaic sequence, and dawsonite occurs only in the Digby Sequence. Genetic facies control the distribution of detrital clays and hence the initial porosities and permeabilities of the sandstones. The sandstones with high proportions of detrital clays are low in secondary quartz and authigenic kaolinite, but are high in illite. The Gunnedah Basin has been shown to have foreland basin characteristics which largely control the Permian and Triassic sedimentation patterns. It is suggested that the flexural response of the lithosphere beneath the basin to thrust-loading by the New England Fold Belt was associated with the westward progradation of alluvial fan or deltaic systems derived from the New England Fold Belt and the introduction of lithic detritus into the basin. The long-term relaxation response to the stress induced by thrust-loading caused further basin subsidence and also the uplift of a forebulge involving the Lachlan Fold Belt. This relaxation phase is believed to be the cause of uplift in the Lachlan Fold Belt and the associated introduction of quartoze detritus for the basin by the fluvial systems derived from the uplifted area. The attainment of isostatic equilibrium by the relaxation process is indicated by the basin-wide palaosol horizon, and in the Permian by extensive coal seams or by maximum marine flooding surfaces. Sedimentation cycles made up of a thrust-loading phase, a relaxation phase and finally an equilibrium phase have therefore been identified not only in the Triassic but in the complete permoTriassic basin fill.

TERTIARY SOURCE ROCKS, COALS AND RESERVOIR POTENTIAL IN THE ASEM ASEM AND BARITO BASINS, SOUTHEASTERN KALIMANT AN, INDONESIA H. Panggabean, University of Wollongong, 1991.

The Asem Asem and Barito Basins, in southeastern Kalimantan, are likely areas for coal exploitation and have good potential for hydrocarbon accumulation. Therefore, an understanding of the development of the basins, the coal and source rock potential within the sedimentary sequence, together with the physical properties of the rocks, will provide valuable information for the economic assessment and development of the region. Rifting occurred on the southeastern margin of the Sundaland continent during the Late Palaeocene-Early Eocene. This formed a large, initially contiguous basin, comprising the Barito, Asem Asem and Kutei Basins, in the south-east and east Kalimantan areas. The Meratus Uplift commenced in Late Miocene and continued during the Plio-Pleistocene causing the subdivision of the large basin into the present Basito, Asem Asem and Kutei Basins. The Barito and Asem Asem Basins were filled with Tertiary and Quarternary sedimentary sequences. Deposition of the Tanjung Formation commenced in the Eocene from a meandering river system which gave way to a fluvial-dominated delta and shallow marine systems. The Tanjung Formation was succeeded by the peak of the Late Eocene transgressive phase, represented by the carbonate-dominated facies of the Berai Formation. The overlying unit is the regressive lower delta plain and ·fluviatile succession of the Miocene Warukin Formation. The sequence ends with the Plio-Pleistocene Dahor Formation which unconformably covers the earlier units. Both the Tanjung and Warukin Formations have abundant sandstone units which consist largely of quartzarenite and sublitharenite, whilst feldspathic litharenite and subarkose are minor constituents. The Berai Formation is composed mainly of wackestone, packstone and grainstone with subordinate carbonate mudstone. The Dahor Formation is composed of conglomerate, sandstone, siltstone and mudstone. The elastic rocks of the Tanjung and Warukin Formations were transported southwards from a recycled orogen source, which probably included the Kuching High, part of the Mangkalihat Ridge and the Sundaland continent or Schwaner Block. Organic petrology shows that vitrinite and liptinite are the dominant macerals within both fine-grained elastic rocks and coal in the Tanjung, Warukin and Dahor Formations, Inertinite is a minor maceral in these units, but it is slightly more prominent in the Berai Formation.

AUSTRALIAN COAL GEOLOGY

The Eocene and Miocene coals do not differ greatly in terms of macerals group composition. However, the Eocene coal contains more liptinite than the Miocene coal. The rank of the Eocene coal ranges between sub-bitumino.!:!_s and where the average vitrinite reflectance (Rvmax) is 0.43 %. The Miocene coal contains Jess mineral matter than the Eocene coal. Mineral matter comprises mainly kaolinite, quartz, p yrite, ca·'- - -:iate and small amounts of chlorite.

Both the Tanjung and Warukin Formations have very good hydrocarbon generation potential. The Berai Formation has less significant source potential as this unit contains little organic matter. The vitrinite reflectance data indicates that the onset of oil generation occurs below 1600m depth throughout both basins. In most parts of the basins the Tanjung Formation entered the oil window zone during the Miocene. In the deeper parts of the basins the Berai Formation and, locally, the lower and middle parts of the Warukin Formation also lie within the oil window. The oil generation zone does not extend up into the Dahor Formation. The results of maturation modelling and burial history indicate that relatively rapid, early coalification of the section of Eocene age occurred over most of both the Asem Asem and Barito Basins. A second, more rapid, phase of coalification affected the lower part of the Miocene succession. A late Miocene-Pliocene history of constant or falling temperature resulted in a lowered thermal drive for maturation and migration. Microscopic features indicating hydrocarbon generation occur in many samples from the Tanjung and Warukin Formations, but they are most prominent within coal samples. These features comprise migrabitumen, oil droplets, oil cuts, oil haze and dead oil. Organic geochemical analyses show that the Warukin Formation has produced some oil in the Barito Basin. A minor quantity of oil from the Tanjung Formation may have migrated into reservoir rocks in the Warukin Formation. The study showed that the oil is mainly of terrestrial higher plant origin . Sandstone beds in the Tanjung and Warukin formations have good to very good potential as petroleum reservoir rocks. The Berai Formation is considered to be marginally favourable as a reservoir rock for hydrocarbon accumulation. Diagenetic regimes (eodiagenesis and mesodiagenesis) have controlled the enhancement of secondary porosity after reducing primary porosity within the reservoir rocks. The most economically viable areas for coal are on the eastern flank of the Senakin Peninsula, and in the Kintap, Bunati and Gunung Kukusan areas. For petroleum exploration, the eastern and southern Barito Basin, and south of Pulau Laut and the A-1 and A-2 wells in the Asem Asem Basin, probably have the highest potential for hydrocarbon discovery.

OIL SHALES

N.R. Sherwood, University of Wollongong, 1991.

The main petrological factors that control occurrences and properties of oil shales are depositional environments, organic sources, diagenesis and maturation . The present studies on organic petrography, organic geochemistry and their interrelationships provide insights into these controls and lead to improved methods of characterisation and classification of oil shales and other organic matter-rich rocks. The classification developed relates the petrological factors to deposit sizes, deposit grades, retort yields and oil quality. this information is critical for planning and developing research activities, exploration programs and exploitation projects for oil shales; it is also important for systematic work on source rocks for petroleum. Although the classification developed employs the pre-existing concepts of using maceral composition as a basis for terminology, the divisions proposed involve a systematic approach similar to that developed for coal microlithotype categories. A set of ternary diagrams provide unequivocal assignment of oil shale types according to their maceral compositions. In addition to the use of maceral as a basis for the classification, validity of the categories is confirmed by chemical analyses. Macera! compositions determined from reflected light microscopy of whole-rock samples enables division of oil shales into basic categories. Three main types of oil shale are deposited in nonmarine settings. Cannels contain dominant liptinite derived from higher-plants, torbanites have dominant Botryococcus-related alginite and lacosites contain dominant lamellar alginite (lamalginite). Four major types of oil shale are deposited in marine environments. The main maceral of bitosites is bituminite, of marosites is dinoflagellateand acritarch-derived lamalginite, of tasmanites is tasmanitid-derived alginite and the main maceral of kukersites is Gloeocapsomorpha-related alginite. Bituminite has probable algal precursors and has characteristics intermediate to those of vitrini te and liptinite macerals such as sporinite. Tertiary oil shales from the Rundle deposit in Australia, the Green River Formation in USA and the Mae Scott Basin in Thailand are 'type' examples of lacosites. The present study indicates that these oil shales were deposited in lakes that had highly variable water levels and highly variable physico-chemical regimes. The oil shale deposit of the Cretaceous Toolebuc Formation of north-eastern Australia is a ' type' example of a bitosite occurrence. These oil shales contain micrinite and alginite along with the dominant bituminite. The micrinite is an alteration product of the bituminite and probably formed mostly during maturation. Organic and inorganic petrological data indicated that the

AUSTRALIAN COAL GEOLOGY

32 bitosites were deposited in hemipelagic facies of a shallow, 'open' epicontinental sea. According to the present work, stratified water columns with anoxic bottom waters are not necessarily prerequisites for the deposition of organic matter-rich rocks. High organic productivities, high sedimentation rates, resistance of the precursor organic matter to decay as well as environmental stress are controlling factors for oil shale deposition. The amount of maturation for most oil shale deposits is low. Vitrinite reflectance data however provide an underestimate of their true rank and some deposits have generated considerable amounts of hydrocarbons. Because of the loss of heteroatoms and consequent increase in oil yield with small amounts of maturation, 'early oil mature' oil shales are the most attractive targets for exploitation. Statistical analyses of geochemical and petrographic variates show that elemental composition of demineralised oil shales, elemental composition of retort oils and parameters from pyrolysis studies are largely related to maceral composition . The amount and type of organic matter determine the yields of shale oil and its characteristics. Alginite-rich rocks give high yields of good quality retort oil, bituminite-rich rocks give moderate yields of fair quality oil and coaly rocks give low yields of poor quality oil. Subdivisions of the basic oil shale categories are refined as a result of the correlation studies. THE ORIGIN OF UNBURNT COMBUSTIBLES IN COAL

J.G. Bailey, University of Newcastle, 1992.

The two principal focuses of this study are the prediction of coal combustion efficiency using coal, char and combustion parameters, and the identification of the char types originating from the various coal macerals and microlithotypes, in order to establish the origins of unbumt combustibles in fly ash. Measurements of coal bum-off at industrial, pilot and laboratory scales show that rank parameters such as vitrinite reflectance are important in estimating the combustion performance of a range of coals. However, for coals of similar rank, the levels of unbumt carbon remaining at high temperature also vary in accordance with petrographic composition. Unbumt carbon levels measured at 900°C at laboratory scale provide good estimates of unbumt carbon at higher temperatures. Alternatives to combustion testing, which combine rank and petrographic information, such as coal fuel ratio, aromaticity and Petrofactor (reactives/vitrinite random reflectance) may be used to estimate relative combustion performance of both whole coals separate lithotypes.

Microscopic examination of power station fly ash and residues from combustion testing at laboratory scale reveals that the nature of the unburnt carbonaceous material varies with the rank and type of the feed coal. A char classification system was developed, based on macroporosity, pore size distribution and char wall thickness, and incorporating terms from the literature and char morphotypes regularly observed in fly ash, combustion and pyrolysis residue. Chars produced by pyrolysis are found to be the most intact and indentifiable particles for classification. The proportion of dense (less than 50% macroporosity) and thick-walled (greater than Sµm) chars produced by pyrolysis at 1500 ·c is found to provide a good estimate of the unbumt carbon levels of a range of whole coals at 1300°C. According to the classification system, dense char types such as inertoid and solid (less than 50% macroporosity) contribute over half the mass of unburnt carbon in fly ash and high temperature combustion residue for the bituminous coals studied. Correlation between char morphotypes and the coal microlithotypes from which they are produced reveals that dense and mixed char types are derived from inertinite-rich coal. However, coal rich in low-reflecting inertinite may produce char of moderate to high porosity at high temperature in oxidising conditions. In addition, the dominant char types produced from vitrinite-rich coal vary with coal rank, increasing their wall thickness and optically anisotropic texture as rank increases to the medium volatile bituminous coals. There is an overlap between the char types produced by vitrinite-rich and semifusinite-rich precursors for the bituminous coals. Inertinite is not implicated as the sole contributor to unburnt carbon. Some high vitrinite coals produce unbumt carbon levels which far exceed those which would be expected from their inertinite contents. Fused, optically anisotrophic, thick-walled chars produced by vitrinite (crassispheres and mesospheres) are suspected of being detrimental to efficient bum-off. The reasons suggested for this are limited access to their internal surface area, possible size increase due to swelling or agglomeration, and reduced chemical reactivity as a result of the enhanced crystallinity indicated by anisotrophic char texture. Modelling of combustion, assuming that coal has two components of different reactivity, generates predicted bum-off curves which fit the experimental data points far more accurately than single reactivity models. Although the optimum proportion of the low reactivity component is not yet based on actual coal properties, the coal components which most closely correlate with the model values for the low reactivity material for a range of coals are the proportions of infusible, fusible and partly fusible inertinite, calculated from the full coal reflectogram according to the equations of Diessel (1986) for reactivity cut-off levels in carbonisation.

AUSTRALIAN COAL GEOLOGY

33 Since, for some coals, only the completely infusible (high-reflecting) inertinite reports in the low reactivity component, it may be concluded that generally more of the inertinite in coal is reactive in combustion than in carbonisation, and in no coal studied should all the inertinite be regarded as unreactive. Coal users should thus be aware that the use of total inertinite content as an index of combustion efficiency for Australian coals is inaccurate, and disadvantages both buyer and seller in the international marketplace. ORGANIC PETROLOGY AND GEOCHEMISTRY OF THE TERTIARY FORMATIONS AT MEULABOH AREA, WEST ACEH BASIN, SUMATRA, INDONESIA

Hadiyanto, University of Wollongong, 1992. The West Aceh Basin is one of several Indonesian Tertiary forearc basins which contain a thick sedimentary succession of coal-bearing rocks that were deposited during the Oligocene to Pliocene. The continued subduction of the Inda-Australian Plate under continental Sundaland was responsible for the development of this asymmetrical, tectonically-active forearc basin which is located along the west coast of the Aceh region of northwestern Sumatra. Significant petroleum discoveries have not been found in any Indonesian forearc basin and this study was initiated to assess the hydrocarbon generation potential of the West Aceh Basin and to formulate a model to aid future exploration in this and other forearc basins. The type, abundance and maturity of organic matter in the Tertiary sequence was determined using optical microscopy and geochemical techniques. The organic matter in both coals and elastic rocks is derived from land plants with a minor algal component in some of the claystones and shales. The coals, ranging in age from Oligocene to Pliocene, are dominated by vitrinite with lesser liptinite and only very minor inertinite. A distinctive feature of the coals is the abundance of exsudatinite, resinite, suberinite and cutinite. Using optical properties and textural features, exsudatinite can be divided into two groups and much of this secondary maceral is derived from resinite and suberinite. The significance of ex-

sudatinite as an indicator of petroleum generation is discussed. Dispersed organic matter (DOM) in the elastic rocks comprises mostly liptinite with lesser vitrinite and only minor inertinite. The rocks contain small but significant quantities of bitumen which indicate migration of hydrocarbons through the rocks or in situ generation of hydrocarbons. The coal and elastic rocks are potential source rocks but most are immature and have not produced significant liquid hydrocarbons. Use of a modified petrographic scoring system shows that of the elastic rocks, the Tangla Formation shales and to a lesser extent, the Kueh Formation, are.the best source rocks. The Oligocene coal, and possibly the Miocene coal, have very good hydrocarbon generation potential. The onshore vitrinite reflectance gradients are greater than those offshore and thus the oil window is predicted to be shallower in the onshore areas. Geochemical data confirms the source rock potential of the rocks although the organic matter is mostly Type III or transitional Type II/III using the 1984 classification of Tissot and Welte. The shale contain 1 to 5% Total Organic Carbon (TOC) and Rock Eval data show that the organic matter in the shale and coal is oil to gas prone with Hydrogen Indices (HI) of less than 200 to 465. S2 values are highest in the Tangla FormaJion but lowest in the Tutut Formation. Samples from the Tangla Formation contain the highest extractable hydrocarbons (mgHC/gTOC) although petrographic data suggest that this is due to bitumen impregnation. Pyrolysis-CC traces of these Oligocene and Miocene coals are characterised by a high abundance of normal alkane hydrocarbons. In many respects, the pyrograms are similar to those of the Talang Akar coal which are known source rocks. Future exploration should be directed towards the onshore areas or those offshore areas where the sequence is thick and the potential for intersecting the oil window is greater. Areas of greatest interest would be those which contain coal and carbonaceous shale as these lithologies have the greatest source rock potential.

AUSTRALIAN COAL GEOLOGY

,,. 34

MASTER OF SCIENCE THESES ABSTRACTS COAL RANK VARIATION IN THE BOWEN BASIN James W. Beeston, University of Queensland, 1980.

Isoreflectance maps on selected stratigraphic horizons within the Bowen Basin show regular rank trends, with parallelism between horizons and structural trends in the Basin. These similarities imply coalification due to depth of burial. Depth/reflectance profiles calculated through the various coal bearing horizons in various areas across the Basin indicate increasing reflectance with depth and increasing re flec tance gradient with increasing reflectance. Comparisons of reflectance values between horizons in the north Bowen Basin indicate two distinct regions based on rank histories. The major distinction is attributed to different histories of subsidence. These regions are the Nebo Synclinorium and the Collinsville Shelf/Comet Ridge. The reflectance comparisons delineated within these regions are suggested as a means of rank interpretation during exploration. Coal rank in the Bowen Basin is interpreted to be due to increasing temperature of burial under conditions of high geothermal gradient over a short period of time. As coking coals are confined within definable rank limits, rank trends within the Basin can be used to delineate the available resources. LITHOFACIES ASSEMBLAGES AND BOUNDARY RELATIONSHIPS OF THE TERTIARY LATROBE VALLEY GROUP AND OVERLYING STRATA IN THE LATROBE VALLEY, VICTORIA P.F. Bolger, Monash University, 1984.

Interbedded lignites, elastic sediments and basalts comprising the Palaeocene to Miocene Latrobe Valley Group, are overlain by an extensive sheet of coarse to fine grained terrigenous sediments known as the Haunted Hill Formation in the Latrobe Valley of Victoria, and on highland areas surrounding the Valley. This study shows that a marked contrast on both the structural history and depositional environments is evident in these units in many areas and that the nature of the boundary between them is variable. In the Latrobe Valley, NE-SW trending basement structures controlled Latrobe Valley Group sedimentation, with accumulation of thick elastic sediments and coals on structural lows, and thick coals and minor elastic sediments on structural highs. Late Miocene movements along the major structures deformed the Latrobe Valley Group producing anticlinal structures on the basement highs. Erosion of more than 100m of Latrobe Valley Group coals and sediments from these areas

prior to deposition of the Haunted Hill Formation has produced an angular unconformity between flat-lying Haunted Hill Formation and folded Latrobe Valley Group. The unconformity surface is characterised by erosional channels and weathering profiles in the coals at the interface, and is further modified by deep fireholes from which coal has been burnt, in some cases after deposition of the Haunted Hill Formation. No angular unconformity is recognisable at the top of the Latrobe Valley Group in structural lows where the uppermost Yallourn coal seam is overlain by younger Latrobe Valley Group elastic sediments. However in one area, post-Yallourn seam sediments are deeply weathered at the interface with the overlying Haunted Hill Formation. Thick basalts and subordinate, often coarse grained, elastic sediments equivalent to the lower parts of the Latrobe Valley sequence occur in the highland areas. They are overlain by the Haunted Hill Formation in the highlands north of the valley with the boundary showing evidence of erosion of the Latrobe Valley Group. The Haunted Hill Formation is absent from the Strzelecki Ranges to the south of the valley. The unconformity surface is more or less planar on a regional scale, although in the Latrobe Valley it has been uplifted across major structures by post-Haunted Hill Formation tectonic movements. It is highest where recognised in the highland areas north of the Latrobe Valley, and around the margins of the valley. The Latrobe Valley Group accumulated in predominantly low energy swamp/marsh, lacustrine and meandering river environments. The haunted Hill Formation, apart from a locally developed clay unit at its base, was deposited by higher energy multiple channel "braided" rivers. The increase in runoff and bedload causing this alteration to the drainage system arose from late Miocene tectonic activity accompanied by a change from a humid equable climate to a cooler, more seasonal climate. Reducing conditions prevailing during Latrobe Valley Group sedimentation allowed accumulation of coals, preservation of carbonaceous matter producing brownish-grey colours in elastic sediments, and the formation of authigenic siderite and pyrite. The Haunted Hill Formation was deposited under oxidising conditions, and contains ferruginous palaeosols and locally abundant haematite cements and the sediments possess reddish-yellow colours. Although not always definitive, these contrasts are useful criteria for recognition of the boundary between the two units in areas of the Latrobe Valley where the angular unconformity is not recognised.

AUSTRALIAN COAL GEOLOGY

Apart from the diagenetic mineralogy, sediments above and below the unconformity are texturally and compositionally similar. Coarse terrigenous detritus consists dominantly of common quartz, with minor feldspar, micas, sedimentary and rare volcanic rock fragments and the heavy minerals zircon and tourmaline. Kaolinite, with subordinate illite and mixed layer illite/montmorillonite, is the major clay mineral. The detrital mineralogy indicates granitic and sedimentary source rocks for both the Latrobe Valley Group and Haunted Hill Formation. Highland areas north and north-west of the Latrobe Valley, consisting mainly of Palaeozoic sediments and granites, were elevated throughout most of the Tertiary, and were a likely source of epiclastic detritus . However, available palaeogeographic data suggests that the Latrobe Valley Group sedim~nts were derived from the south, west and north-west of the Valley, while the northern parts of the basin were cut off from a supply of coarse sediments from the elevated areas to the north. The Strzelecki Ranges, consisting of Lower Cretaceous Strzelecki Group sediments and thin Tertiary deposits, now form the southern boundary of the Latrobe Valley. As there is no evidence to suggest that they were elevated during the main phase of Latrobe Valley Group sedimentation, Palaeozoic granites and sediments exposed in the Wilsons Promontory area are a further possible source area. Sediments forming the Haunted Hill Formation were derived from all the highland areas surrounding the valley, including the Strzelecki Ranges, which were sufficiently elevated during the early Miocene to provide Strzelecki Group detritus to the Haunted Hill Formation. THE VARIATION OF MOISTURE WITH LITHOTYPE AND OF NITROGEN AND CERTAIN INORGANICS WITH PETROGRAPHY IN YALLOURN SEAM BROWN COAL

R.J. Gaulton, University of Wollongong, 1985.

A tendency for darker lithotypes in Latrobe Valley brown coals to possess a higher bed moisture content than adjacent lighter lithotype coal has for some time been noted. Although the range of moisture values relating to this is generally limited to only a few per cent by weight, evidence exists to suggest that such apparently minor differences in bed moisture can and do exert a disproportionally large effect on the net output of large brown coal-fuelled thermal power stations. Samples taken over an 18 metre length of coal core obtained in Yallourn Open Cut show a correlation between moisture and lithotype, with the darker lithotypes tending to have the highest moisture and pale lithotypes the lowest. A high degree of correlation is also evident between nitrogen and the amount of residual woody mate-

rial present and between nitrogen and the concentration of calcium, magnesium and iron as soluble cationic species in the coal. As a result, it is shown that the small scale distribution of certain inorganic constituents is influenced by petrographic structure. THE EFFECT OF FINISHING TEMPERATURE AND SOAKING OF THE COKE IN THE OVEN UPON THE MICROSTRUCTURE AND STRENGTH OF METALLURGICAL COKE

W.R. Gadsden, University of Wollongong, 1988.

Large modern blast furnaces, such as No . 5 unit at Port Kembla which produces 7000 tonnes per day of iron, demand high quality feed materials. The blending of coals to yield coke of the required cold strength was resolved by the mid seventies and in the last decade infurnace properties have been studied critically. Japanese technologists have claimed improvement by the practice of soaking the coke in the ovens at the finishing carbonisation temperature. Researchers have shown that the microstructure and degree of ordering of the coke substance may be altered by heat treatment over a temperature range exceeding that practical in industrial ovens. The finishing temperature in such ovens is poorly defined and often variable within and between ovens. There is scope to improve thermal regimes and this investigation examines the relationship of finishing temperature to microstrength of the coke, the ordering of the microstructure as indicated by bireflectance and changes in crystallite dimension over the temperature range that may exist, (900 ·c - 1070 °C). Three series of tests with different coals, carbonised in a laboratory furnace, showed common trends to higher values, without evidence of a plateau level. Limited attempts to correlate microstrength from laboratory coke with commercial product raise doubts as to whether changes of the magnitude reported exist in practice, and it is doubted that the benefit from soaking would compensate for the sacrifice in coke size that would result from the faster coking rate required to maintain tonnage output. It is evident that fundamental coke properties are still being influenced by variation in the finishing temperature within the range occurring in industrial operations. These should be considered in the defining of the finishing carbonisation temperature. OPTIMISATION OF DRILLING PATTERNS IN MINERALS EXPLORATION AND EXPLOITATION IN LONG NARROW AREAS

Barry Stuart Tasker, Queensland University of Technology, 1989.

In this work, the solution is presented for a mathematical problem arising from a geological

AUSTRALIAN COAL GEOLOGY

co!ltext,_involving th~ design of a regular drilling gnd which has to be imposed on a very long strip of ground. The drill holes in the grid are considered to form the centres of circular areas of influ~nce. It is necessary that the total area of the strip 1s completely covered by these circles of influence; but the most efficient grid will be such that the overlap is a minimum, and hence the total number of drill holes required for a given length of the strip will also be a minimum. The geological applications of the theory developed apply to a variety of different contexts, whenever a long narrow area is to be drilled for exploration or the proving of reserves of coal or other stratiform mineral deposits. Long narrow areas are regarded as strips which have lengths so much greater than their width that they can be co_nsidered infinite. This situation arises naturally with some mineral deposits which by their nature are very elongated, but the particular application ~hich gave rise to the present study was the proving of reserves in the economically exploitable segment of an inclined coal seam. The geometric requirements have been translated into algebraic terms, and the standard methods of algebra and analysis have been applied as appropriate. Additionally, certain specialised mathematical techniques have been developed specifically for the rather unusual types of problem encountered. These techniques involve the determination of required geometrical properties of polynomials in 1 and 2 variables from the algebraic relationships between their coefficients. Some of these problems have been associated with the large matrices with very large integer entries which have arisen in the investigation of properties of polynomials in 2 variables, which act as the determinators of the properties of the various grids. In most cases it has been possible to reduce consideration of the polynomial concerned to a semi-finite strip, as a subset of its domain of definition. A series of techniques for dealing with such a strip has been developed, and listed (with proofs) in Appendix lB. For the problem as posed above, all regular geometric possibilities have been canvassed, and those which are less than optimal have been systematically eliminated. Finally, it has been shown that the most efficient grid comprises obtuse-angled isosceles triangles, constructed as follows. CONSTRUCTION:

(a) Let H be the width of the strip, and let R be the chosen radius of influence; H

put h= R' [This effectively measures the strip-width using the radius of influence as the unit of measure.] (b) It is now necessary to split the total strip into N bands of equal width. It is shown in the

thesis that the optimal choice may be found from the condition b(N - 1) ~ h < b(N),

where

✓3N2 + 8N+4 bN=

[

2(N + 1)

2 ✓ 3N + 2N - 1 sothatb(N-1)= 2N .

A table is provided in the concluding chapter to facilitate this choice (when the strip is not immoderately wide). (c) Let w =~and W = Rw; this allows for W to be the width of each of the N equal bands.

Also let V=21R+ ✓R 2 -W 2 this is shown to be the length of the base of each isosceles triangle formed by the construction below. (d) The strip of width H should be split into N bands, each of width W. The parallel edges of these bands should be marked off into intervals of length V, staggered for alternate edges so that the vertices marked form isosceles triangles of vertical height W and with base of length V. It will be found that such triangles have an obtuse angle at the vertex. In the concluding chapter of the thesis following, a table is provided for the simplification of step (b) in which the optimal number of bands is chosen. Prior to this, it is proved in detail that the cons!ruction above gives the most efficient grid possible under the circumstances outlined for this problem. A GEOTECHNICAL STUDY OF OVERBURDEN EXCAVATABILITY AND PARTINGS REMOVAL BY RIPPER EQUIPPED BULLDOZERS

Mark W. Van Schoten, University of New South Wales, 1989.

This project report summarises the results of an investigation into removal of overburden, in surface coal mines, by very heavy duty ripper equipped bulldozers. Work was funded by a research grant from the Australian Coal Industry Research Laboratory, and as such, forms part of ongoing research at the University of New South Wales into the effect of engineering geology on excavatability. The aim of this project was to determine the effects of geotechnical factors, including seismic and ultrasonic velocity, on overburden excavatability within the Hunter Val-

AUSTRALIAN COAL GEOLOGY

37 ley No.1 mine. Bulk overburden removal, using face shovels, and partings removal, using ripper equipped bulldozers, were initially studied. But the majority of the research effort was di rected towards ripping as this material was unblasted and consequently productivity was dependant on the rock mass condition and rock properties. The major objectives of the study were to: 1) Obtain quantitative data demonstrating correlation between overburden and/ or partings excavatability, and the discontinuities/fractures in the rock mass, either natural or blast induced . 2) Obtain a ~orrelation between excavation rate (bank m /hr) of bulldozers (and shovels) with geotechnical factors. 3) Examine the relationships between seismic velocity and rock mass fracturing, using the Velocity Reduction Ratio and its relationship with the geomechanical characteristics of the rock mass, as well as the relationship between geotechnical properties of intact rock. 4) Observe and film ripping and digging processes to provide qualitative information on the effect of the rock mass on overburden excavation mechanisms. IGNEOUS INTRUSIONS IN THE BOWEN BASIN Christopher Ian Pattison, Queensland University of Technology, 1990.

Igneous intrusions, in the form of stocks, sills and dykes are abundant in the Bowen Basin. They are predominantly Early Cretaceous in age, exclusively epizonal in origin and range in composition from dolerite to granodiorite/ dacite. All rock units within the basin, up to and including the Clematis Group, are intruded to some degree. This study assesses the distribution, form, petrology and mode of emplacement of plutons, igneous sills and dykes occurring in the Bowen Basin, and considers their relationship to the prevailing structure. The tectonic implications of the findings are then assessed. Igneous sills occur in two geographically distinct domains, one in the northern Bowen Basin and the other in the central Bowen Basin. The sills emanated from pre-existing, north to north-northwest trending reverse faults, and preferentially intruded coal seams. The boundaries to sill intrusion are marked by major north-east trending basement structures. These basement structures occur at regular intervals throughout the basin, and correspond with the localisation of plutonic and dyke activity, anomalous structural disturbance, and changes in the gross structure of the basin. They are interpreted as transfer faults that

were inherited from an Early Permian, basinforming extensional episode. Petrological evidence indicated that the plutons and sills occurring in the northern Bowen Basin are petrogenetically related, and that a progressive variation in their chemistry occurs across the axis of the basin from east to west. Intrusions in the east belong to the calc-alkaline rock suite, while those in the west belong to the syenitic suite. This transition in interpreted in terms of increased crustal contamination as the magma migrated from a source under the basin. This detachment was inherited from the above mentioned extensional phase and is intimately linked to structures that penetrate up-section through the basin succession. Reactivation of the transfer faults during the Early Cretaceous initiated the emplacement of dykes, and the synchronous development of north-east trending normal and wrench-style faults. The dykes exhibit characteristics that indicate they were self-propagating, and can be regarded as good palaeostress indicators. This phase corresponded with a major compressional event that involved the reactivation of pre-existing thrust structures, deformation of the Folded Zone and eastern margins of the Nebo Synclinorium and Mimosa Syncline, and the rapid preferential uplift of the central Bowen Basin region. GEOMECHANICAL PROPERTIES OF THE GREAT NORTHERN SEAM, NEWCASTLE COAL DISTRICT; A GEOLOGICAL PERSPECTIVE L.M. Sawyer, University of New South Wales, 1990.

The Great Northern Seam is a major steam coal producing seam of the Newcastle Coal Measures. It is a Permian coal deposited as a member of an upper deltaic plain facies in a foredeep marginal basin syngenetic with the uplift of the New England Fold Belt. The major structure associated with the Great Northern Seam is the Macquarie Syncline, which is axial to the minor basin in which the coal has formed. Faulting and dykes as well as two joint and cleat sets are common and have a similar strong NW-SE and a minor NE-SW orientation. Interlaminations and bedding parallel stratification are also a common feature of the seam. Regional stress is variable due to the faulting and intrusions in the coal but is generally dominated by a principle horizontal N-S maximum principal stress. Ash content of the seam is high to moderate but varies with proximity to dirt bands and the floor or roof of the seam. Such variation can be attributed to palaeo-environment facies changes. The mineralogy of the ash is constant throughout the seam. The density of the coal is proportional to the ash content of the coal. Moisture content of the different lithotypes is varied but that of the coal is

AUSTRALIAN COAL GEOLOGY

38 relatively constant. Depth of overburden and seam thickness are related to the basin geomorphology and palaeo-environmen t. The coal of the Great Northern Seam is a hard brittle and tough coal. The unconfined compressive strength is generally high fo r coal but varies across the plies and sample sites. This is attributed to coal rank, type and ash content variations within the seam. Tensile strength is very low and it does not greatly influence the strength of the coal. The point load strength index for the coal is low and the corresponding ratio to UCS is high. The coal is relatively inelastic . This is d ependent on coal type, rank and ash content of the seam sample. The shear strength of the coal is related to the coal lithotype and coal ash content. Shear strength is widely variable and always much less than the compressive strength of the coal. Joint strength is low and the residual stiffness, and cohesion, of the joints is also low. Coal shear strength, cohesion and joint stiffness cause shearing modes of failure to dominate. This effect is enhanced by stress differentials across the inter-layer boundaries and petrographic stratification within the seam. THE APPLICATION OF TUBE WAVE ENERGY ON BOREHOLE NO. 35256 PEAK DOWN COAL MINE, QUEENSLAND, AUSTRALIA Budi Sulistijo, Ir, University of New South Wales, 1990.

Vertical seismic profiling has been carried out in the past based mostly on the first arrival time of direct arrival time P and S waves in order to calculate the velocities of these waves. The result is satisfactory to delineate the stratigraphy from a borehole, but it is unsatisfactory to delineate fracture location or relative permeability of layers. Tube wave has a low frequency and based on the relationship of tube wave and P wave, the tube wave velocity generally falls within the range of 1100m/s to 1450m/s for fresh rock. The noise can be suppressed by applying the bandpass filtering around above number. The attenuation of the tube wave energy was used to detect the location of fractures or relative permeability of layers. Energy was calculated based on the mean and sum square method . To determine transit energy between two hydrophones, delta mean square and delta sum square were applied. Tube wave energy attenuation was determined on borehole to show location of fracture or relative permeability of layer based on the fixed sparker system and the fixed sparker-hydropho ne distance system at Peak Down Coal Mine which is situation on the Western edge of coal bearing Bowen Basin.

OBSERVATIONS ON MODES OF SULPHUR IN COALS AND COAL BEARING STRATA FOUR (4) MINE SITES ALONG A GEOTRA VERSE IN THE BOWEN BASIN OF QUEENSLAND G.D. Hokin, University of Wollongong, 1991.

Sulphur in coals can and does cause environmental problems. Much of the world's coal contains relatively high percentages of sulphur and is therefore environmentally undesirable. Australian coals have attained a dominant position in the world market by being able to provide low sulphur coals. To maintain this position it is necessary to maximise sulphur removal from mine product to meet the increasing demand for sulphur free coal throughout the world. Observations of modes and levels of sulphur occurrence in coals and coal bearing strata along a geotraverse in the North Bowen Basin of Queensland indicate that the modes of occurrence of sulphur are sufficiently distinct to indicate plant material as the principle source of sulphur in these coals, and to indicate sedimentary/ climatic factors as playing an important role in the percentage level and modes of occurrence of sulphur present. The sulphur inherent within the surrounding strata of these coal seams does not have a direct and significant effect on the percentage level or modes of occurrence of sulphur within the coal seams. GEOLOGICAL FACTORS OF IMPORTANCE IN THE PREDICTION OF ROCK RIPP ABILITY AND RIPPING PRODUCTIVITY B.M. Whitehead, University of New South Wales, 1991.

Many workers have tried to predict the best method of excavating rock. These methods are based on either the seismic velocity of the rock mass or its geological characteristics or both. Caterpillar (1988) advocate the use of seismic velocity but point out that the only certain way to ascertain the rippability of the rocks at a particular excavation is to carry out field trials. This study has been carried out to look at the geological factors which influence rippability, in an attempt to predict rippability more accurately, without the need for expensive field trials. A GEOTECHNICAL PERSPECTIVE OF THE ABANDONED RHONNDA COLLIERY, NSW Peter Wiseman, University of New South Wales, 1991.

The project involved the investigation of an abandoned room and pillar mine that had been burning for 20 years. The lease area contained

AUSTRALIAN COAL GEOLOGY

39 severe subsidence within the gullies due to increased in situ stresses and a reduction in strength of the roof strata through wetting and drying. These areas are dominated by major structural weaknesses (jointing) and reduced thickness of the strata. The formation of the structural discontinuities has leri •') block development within the conglomerate uutcrops. These discontinuities control subsidence on the site. The highly fractured gullies has meant that only during severe rain storms is there sufficient volume of water entering the burning workings for excess water to build up in the mine. Based on the information supplied by Coal and Allied it appears the water is either being lost in steam or leaking into neighbouring workings. The volume of effluent which is being discharged into the mine is insufficient to cool the mine. Thus to extinguish the fire within the Great Northern Seam of the Rhondda Colliery there needs to be a . ub~tantial increase in the volume of water entering the mine.

FLOOR HEAVE AT COORANBONG AND NEWV ALE NO2 COLLIERIES Dieter Bruggemann, University of New South Wales, 1992.

Cooranbong and Newvale No2 collieries are both located within the Permian Newcastle Coal Measures. In both collieries the Great Northern Seam is currently worked, with the Fassifern Seam lying 3 metres beneath which is not worked . The seams are separated by the Awaba Tuff claystone which is extensive across the Newcastle Coal Measures. The claystone is extremely susceptible to volume expansion in especially underground situations when roadways are opened in collieries. This is termed 'floor heave'. The expansion is due to mainly its inherent mineralogy where up to 100% swelling smectite content have been recorded. Other important contributing factors are water influx, time, thickness of the claystone and certain geomechanical failure mechanisms resulting in a re-distribution of stress fields surrounding opened roadways. This causes floor heave of roadways where it has been attempted to categorise the heave potential into low, medium and high of all areas of both collieries using various laboratory tests and in particular the slaking/ dispersion test which have been done on all grab and core samples.

DEPOSITIONAL ENVIRONMENT OF THE BULL! COAL AND ITS EFFECT ON QUALITY CHARACTERISTICS B.R. Clark, University of Wollongong, 1992.

The Bulli Coal is the uppermost coal in the Illawarra Coal Measures of the Southern Coalfield of the Sydney Basin. This thesis examines the influence of depositional environment and tectonism on coal quality and seam occurrence, geometry and splitting of the Bulli Coal. Deposited in an upper delta plain/fluvial environment the Bulli Coal was strongly influenced by basement structure. Block faulting in the basement east of the cratonic Lachlan Fold Belt produced structural effects and rapid subsidence of the northern part of the Southern Coalfield allowing sediment incursion into the Bulli Coal peat swamp. Established on a floodplain topography peat accumulation progressed under a lowering watertable until the later stage of the peat swamp when the water-table rose, eventually drowning the swamp and halting peat accumulation. Water movement in and around the peat swamp and the control on the water-table level by subsidence are reflected in the Bulli Coal properties thickness, ash content, vitrinite content (and maceral composition), phosphorus content and silica/alumina ratio . Sulphur was derived entirely from the organic matter and not influenced significantly by water movement or water-table level. A STUDY OF MINE WATER INFLOW INTO LONGWALL PANELS 6, 7 AND 8 AT COORANBONG COLLIERY John Conrick, University of New South Wales, 1992.

Mine water inflows are one of the most serious problems confronting underground coal mines working at shallow depths of cover. Such inflows are capable of severely affecting production rates, sterilising coal reserves, damaging machinery and even causing the loss of lives. Longwall mining operations are particularly susceptible to water ingress due to the large scale rock fracturing which tends to occur as a result of the high tensile strains induced during panel extraction. The effect of rock fracturing in allowing the flow of water from surface water bodies or aquifers into the underlying workings is further compounded by the presence of discontinuities such as faults, shear zones, joints and dykes, and the nature of the overlying stratigraphy, especially the percentage of sandstones compared to mudstones, claystones and shales. Cooranbong Colliery is currently preparing to extract its 6th, 7th and 8th longwall blocks from an area of ground with very shallow depths of

AUSTRALIAN COAL GEOLOGY

40 cover (40 - 90 metres) which underlies swampy ground of the Jigadee Creek floodplain. This low lying swampy flood plain is known to consist of 7 to 15 metres of alluvium, much of which is aquiferous sand and/ or gravel deposits. As a consequence of these factors there is a perceived risk of major mine water inflows affecting the longwall operations in Panels 6, 7 & 8. The colliery's previous longwall experience has been at depths of cover in excess of 100 metres where workings underlied topographical higher and better drained ground than that of the Jigadee Creek floodplain. Bearing in mind the above factors, the management of Cooranbong Colliery need to know the extent of mine water inflow that can be expected to enter the longwall voids during the extraction of Panels 6, 7 and 8. In particular they require a prediction of the likely mine water ingress into Longwall 6 so that it can be decided as to whether Longwalls 7 and 8 are economically viable, given the lower perceived risk of mine water inflow into Longwall 6 than Longwalls 7 and 8. D.J. Douglas and Partners have prepared a report which analyses the potential for mine water inflow into Longwalls 6, 7 and 8, while ACIRL have undertaken a literature survey with particular emphasis on aspects of caving and its effect on mine water ingress. Both of these reports will therefore be extensively consulted and reviewed in undertaking the study at hand. In order to address the problem of predicting mine water inflows in to Longwalls 6, 7 and 8 it is envisaged that a number of different factors will need to be taken into consideration. Firstly, the precise nature of the problem needs to be defined and this placed into context by comparison with case histories of mine water inflows for other similar coal mines. Secondly, the local geology of the study area requires analysis, with particular emphasis being placed on the hydrogeology of the area immediately above the longwall panels themselves. Thirdly, potential water transporting discontinuities such as faults and dykes, which are known to exist in the areas, need to be delineated, with magnetic and resistivity geophysical techniques considered to be the most appropriate and cost-effective means of achieving this aim. Fourthly, subsidence parameters for Longwalls 6, 7 and 8 need to be determined and caving height predicted based on previous studies from other mines. Based on the information obtained from an examination of the above factors, it will subsequently be possible to carry out an analysis of mine water inflow so that the likely extent of water ingress into Longwalls 6, 7 and 8 can be ascertained. It should however be cautioned that these predictions will be approximate estimates only as accurate predictions are impossible due to the fact that a number of mine water inflow parameters cannot be properly quantified. Much more accurate estimates of mine water inflows into Longwalls 6, 7 and 8 will only be possible

after extraction of Longwall 6 has begun and preliminary inflow rates have been measured. In this respect the extent of mine water inflow into Longwall 6 can be used in order to obtain more accurate predictions of inflows for Longwalls 7 and 8, which will subsequently allow much more efficient and cost effective mine planning of these longwall extractions to be undertaken. STRESS, STRUCTURE AND COAL MINING CONDITIONS IN AUTHORISATION 278, MITTAGONG AREA; WITH APPLICATION TO THE WONGAWILLI SEAM John Whitehouse, University of New South Wales, 1992.

This thesis will discuss the effect of stress, geological structure and intrusive activity on coal mining conditions of the Wongawilli Seam within Authorisation 278 near Mittagong in the southwestern part of the Southern Coalfield. The seam ranges in thickness from 1.5 to 5.0 metres and averages 2.6 metres and contains medium to high ash thermal quality coal of substantially diminished coking potential. The Wongawilli Seam is amenable to underground mining only and occurs at depths ranging from less than 100 metres to the south-west to over 300 metres towards the northeast and averages 260 metres. Igneous intrusions in the form of sills and laccolithic intrusions are expected to exert the main influence on strata behaviour during underground mining of the Wongawilli Seam. Because of the considerable difficulty in establishing their nature and distribution, sills and laccolithic intrusions are considered to be synonymous during the course of this thesis. Intrusions are extensively emplaced in the Wongawilli Coal and affect coal seam mineability by reducing both the quantity and quality of the coal resource, and forming geomechanically unsatisfactory roof and floor rocks. Due to the erratic distribution of intrusions within the Wongawilli Coal, mining is likely to be restricted to bord and pillar extraction methods. In situ stress is imperfectly understood. In general, it appears to be extremely weak. With the possible exception of the north-eastern part of Authorisation 278, in situ stress is not expected to constitute a significant restraint on underground coal mining operations. The influence of local and regional structure behaviour is not clear. Apart from a number of normal and ring faults associated with large intrusions emplaced at Mount Flora and Mount Jellore, major faults have yet to be defined elsewhere in Authorisation 278. However, extensive lineaments are comparatively widespread. They appear to have a spatial relationship to the several large intrusions emplaced at a number of localities including Mount Jellore and Mount Flora to the south and Nattai Tableland to the north. By way of comparison, no

AUSTRALIAN COAL GEOLOGY

41 relationship between geological structure and intrusive activity has so far been defined within the central and eastern parts of Authorisation 278. INVESTIGATION OF MINE WORKINGS FIRE, RHONDDA COLLIERY, TERALBA, NSW Peter Sinclair, University of New South Wales, 1993 . ..

Rhondda colliery, Lake Macquarie, NSW, is the site of an underground fire that has spread throughout the Great Northern seam workings of the abandoned mine. The burning seam occurs at depths of 10 to 30 metres beneath massive sandstone overburden . Underlying Fassifern seam workings are flooded and therefore unaffected. Surface expressions include fissures open to 300mm width, block subsidence up to lha in area, rock slope collapse, ground scorching and emission of fumes and steam. The fire which began in March 1971 and now covers over 160ha of the lease, has been in various stages of activity for the last 22 years. Attempts to extinguish the fire by sealing the mine, CO2 injection, and later by local flooding with sewerage effluent, have had limited success. To develop effective control techniques for underground fires requires an understanding of the fire' s extent, behaviour and its degree of activity. Thermal imagery from Thematic Mapper data sets for 1987, 1989 and 1991 were trialled, through the help of the leaseholder Coal & Allied Pty Ltd. The data was processed and the area mapped according to its spectral reflectance. Broad fire regions were delineated from the images, but unfortunately pixel resolution (120m) limited the amount of detail that could be extracted. Comparison of the three data sets revealed variations of fire activity over time. More detailed field mapping followed, locating the individual hotspots and related subsidence features on a 1 :4000 field map. These included open subsidence fractures and collapses, scorched soils and dead vegetation, and hot moist fire gases issuing from ventholes and fractures. An assessment of each active fire area was based on the intensity bf these features. A more objective technique delineating fire regions using a thermal emissivity gun was trialled . Traverses across hotspots graphing temperature against distance located the extent and intensity of a hotspot. Unfortunately due to low thermal conductivities of rock and soil this was found to be no more effective in delineating fire regions than conventional mapping. The behaviour of the fire was also studied by tracing the fire movement from historical records. An anticlinal roll structure, the crest of which is known as the Rotorua Region, was once a very active hotspot. It is thought the structure influ-

enced the quick spread of the fire up dip to this area, consuming much of the fuel. Rotorua Region still vents steam and fire gases, although it is believed the main fire centres are now elsewhere in the mine, the Rotorua Region behaving as a 'chimney' for the fire. Structural detail also reveals an ancient washout feature cutting the Great Northern seam along the fire within the lease in these areas. A plan was constructed detailing areas where the fire may escape through the present barriers, spreading to adjoining leases. It is these areas that are recommended for closer monitoring and investigation into barrier pillar integrity and viable fire control techniques, including trenching, grouting or blind flushing, and localised effluent infusion. SUBSIDENCE MONITORING ABOVE APPIN COLLIERY- LONGWALLS 21B AND 22B SOUTHERN COALFIELD - NSW Peter Willey, University of New South Wales, 1993.

This report details the findings of an intensive surface subsidence monitoring program above Longwalls 21b and 22b at Appin Colliery, in the Southern Coalfield of NSW. Information from earlier longwalls has been included when relevant. The results obtained to date are from the extraction of two longwalls only. The work was done as part of ACIRL' s research project entitled "Improved Methods of Subsidence Engineering" . The project was funded by NERD DP. During this project ACIRL has concentrated on achieving a better understanding of the surface deformation that result from subsidence in relation to surface structures. The Water Board and BHP Collieries were planning a monitoring program at the site involving the use of bay lengths of less than 20m which is the typical baylength used in the area. Integration of this program with ACIRL's work was an opportunity to pool resources. Subsidence data was collected over a larger area and over a variety of bay lengths. The ground movements observed during the program may be used to design subsidence tolerant water supply and treatment works for new suburbs. The Water Board contributed funds and surveying services towards the monitoring program. BHP Collieries provided advice and surveying services. The extraction thickness over Longwalls 21b and 22b ranges between 470m and 505m and the average thickness of the Bulli Seam is 2.25m. The overburden is dominated by 180m massive Hawkesbury Sandstone and 168m of Bulgo Sandstone. The remainder consists of claystones, mudstones and siltstones . The surface geology consists of clay soils derived from the Wianammatta Group shales. In the lower part of

AUSTRALIAN COAL GEOLOGY

42 the site, closer to Myrtle Gully, the Hawkesbury Sandstone outcrops. The extraction width for each longwall is 205m and they are separated by 33m wide chain pillars. A variety of survey grid layouts were installed at several localities over the longwall to sample surface deformations over different bay lengths. The different bay lengths were chosen to determine the variation in the magnitude and orientation of deformations over different distances. Bay lengths ranged between 2.Sm and 20m. Measurement accuracy proved to be adequate although more precision was necessary for the shorter bay lengths. Levels were determined by precise levelling techniques. Distances were determined using two different methods: conventional chaining using a steel band for the 8 to 20m bay lengths; and a tape extensometer for the 2.Sm and Sm bay lengths. In addition, pegs in the Main Grid were surveyed in three d imensions using a GPS method. Little subsidence occurred in the area until Longwall 21b had passed the site. Maximum subsidence at the completion of Longwall 21b was 179mm. At the completion of Longwall 22b maximum subsidence had increased to 687mm. Over the 20m bay lengths the maximum compressive strain after the extraction of Longwalls 21b and 22b was lOmm/m and occurred in Myrtle Gully. Compressive strains were generally much lower being around 2 to 3mm/m. The maximum tensile strain was 2.4mm/m. Over the 20m bay lengths the maximum tilt was

5.3mm/m. The tightest curvatures recorded over the 20m bay lengths were associated with the bump in the profile near pegs B380 and B400. The tightest concave curvature was 0.28km- 1 (3.6km). The tightest convex curvature was 0.16km- 1 (6.3km) . Larger deformations were recorded over shorter bay lengths. Longer bay lengths tend to "smooth" measured deformations. Bay lengths chosen should reflect the structure/ ground interaction and take into account the size of the structure rather than just the depth of cover. Several "humps" in the subsidence trough occurred over the longwall panels. These were often associated with the underlying chain pillars and/ or surface creeks. Similar occurrences at Tahmoor Colliery have been in flat terrain a long way from any creek. Their origin is unknown but the frequency of their occurrence means that they can no longer be considered "anomalies". Their occurrence can be treated statistically. The humps were associated with high local strains, tilts and curvatures. The angle of draw in NSW is currently based on a cut-off criteria of 20mm vertical subsidence. If it is differential ground deformations that do damage to surface structures then it would be logical to use different values of these for the cut-off criteria. Using these criteria the practical angle of draw could be substantially reduced. Continuing the monitoring at the site would ensure that the full development of the subsidence trough was recorded . Further monitoring will depend on the availability of funds.

BACHELOR OF SCIENCE (HONOURS) THESES ABSTRACTS THE GEOLOGY OF THE BROKE - MT. THORLEY AREA

J. Bailey, University of Newcastle, 1981. The stratigraphic sequence outcropping in the Broke-Mt. Thorley Area includes the Permian marine Maitland Group, the Wittingham and Wollombi Coal Measures of the Singleton SuperGroup and the Triassic Narrabeen Group. McKellar's (1969) stratigraphy of the Maitland Group has been accepted in the main, but relatively extensive modifications to Britten's (1972) stratigraphy of the Singleton Super-Group have been suggested by the author. The Archerfield Sandstone and Bulga Formation have been combined as the Archerfield/Bulga Formation. The Burnamwood, Mt. Ogilvie and Malagar Formations of the Jerry' s Plains Sub-Group have been replaced by the "Upper Formation" and "Lower Formation". The Whynot Coal Member is considered to be an upper split of the Blakefield Coal Member. the Fairfield Claystone has been

recorrelated to a horizon in the Piercefield Coal Member of the Type Bore. The claystone between the Blakefield and Glen Munro Coal Members is referred to as the Saxonvale Claystone. Within the Wollombi Coal Measures, the Apple Tree Flat and Horseshoe Creek Sub-Groups have been combined. Coal seams of the Wollombi Coal Measures have been relegated to the status of member. Formations within the Wollombi Coal Measures defined as being bounded by two coal seams and without further distinguishing features, have not been recognised. The elastic sediments comprise a generally regressive marine, trough-filling sequence. They progress from marine sediments of the basal Maitland Group to lower delta plain deposits interfingered with coal within the Foybrook Formation. The Archerfield/Bulga Formation represents a marine transgression and barrier bar sand. The "Lower Formation" and "Upper Formation" evolve stratigraphically upward from bays and high-sinuosity streams, to coarse elastics of

AUSTRALIAN COAL GEOLOGY

braided stream and piedmont depositional facies. Palaeocurrent data indicate that the Loder Anticline was active syndepositionally with the Wittingham Coal Measures. The anticline is believed to have been a source of elastic detritus in the rudites of the "Upper Formation". The New England Fold Belt to the north-east was a source of acid volcanics and low-grade metamorphic material. The claystones of the Wittingham Coal Measures chiefly occur within or adjacent to coal seams and may be defined as tonsteins according to the classification of Schuller and Hoehne. The claystones of the Wollombi Coal Measures are altered vitric and crystal tuffs and are considered to have been deposited by volcanic vent explosions and by "nuee ardente" turbulent ash clouds. The coal seams of the Wittingham Coal Measures reflect the increasingly terrestrial depositional environments of the elastic sediments stratigraphically upward through the sequence, according to facies diagrams of Hacquebard and Donaldson (1969). Only the Vaux and Mt. Arthur Coal Members follow Markovian cyclicity, and the dominant cycle appears to represent increasing water depth in the coal swamp and a vegetative cycle. The dominant mudstone seat rocks of the coal seams appear to be flood deposits. The abundance of Vertebraria root systems in the sediments of the Wittingham Coal Measures indicates that the associated coal seams are autochthonous . The Bayswater Coal Member represents a distinctive horizon of durain-rich coal and is considered to be largely allochthonous. The Fordwich Sill is a differentiated teschenitic sill of Tertiary age with a tabular form. Structural deformation is dominated by the asymmetrical Loder Anticline which has an arcuate north-north-westerly trending axis and steep dips on its western flank. Evidence from sedimentology, coal seam disposition, coal rank studies, palaeocurrent trends and the nature of deformation indicates that the Loder Anticline was active during deposition of the Wittingham Coal Measures. Activity on the anticline is considered to be due to movement on a basement step-fault. Faulting is chiefly tensional and is almost totally restricted to a narrow zone on the western flank of the Loder Anticline. Major joint sets appear to represent shear joints associated with the anticline. Jointing is most intense high on the western flank and crest of the Loder Anticline.

low or green fluorescing alginite B and lamellae and lenses of corpohumite interbedded with mineral matter. With increasing retorting temperature, huminite/vitrinite reflectance increases and alginite fluorescence changes from medium green or yellow to dull brown. Green fluorescing oil seeps from Mahogany Zone samples retorted at 410 °C and 450 °C and from Kerosene Creek samples retorted at 450°C. Destructive distillation of alginite occurs in Mahogany Zone oil shale retorted 450°C and 500°C and in Kerosene Creek oil shale retorted at 500 °C. A major difference between the two shales is that the alginite in the Mahogany Zone shale forms three types of carbonaceous residues during retorting (pyrobitumen, coke-like material and material similar to carbon black), whereas no carbonaceous residues can be found in samples of fully retorted Kerosene Creek shale. Retort oils were obtained from the oil shales using the modified Fischer assay procedure and were analysed by open column chromatography, gas chromatography and mass spectrometry. More than 500 compounds were identified in each retort oil. They included homologous series of alkanes, alkenes, nitriles, ketones, amides and substituted cycloalkanes, cycloalkanes, benzenes, napthalenes, phenanthrenes, thiophenes, carbazoles and pyridines. The Mahogany Zone retort oil has a high isoprenoid and low n-alkane content compared to the Kerosene Creek retort oil and typical paraffinic crude oils. Reasons for these differences include the possibility that organic matter in the Mahogany Zone oil shale was biodegraded, and the significant difference in the maturation levels of the two oil shales. THE GEOLOGY SOUTH OF MAULES CREEK

P.J. Crosdale, University of Newcastle, 1982.

During geological mapping of 140km2 south of Maules Creek rocks of the Late Carboniferous and Early Permian were encountered. These rocks are divided into the Currabubula Formation of Carboniferous age and the Boggabri Volcanics, Leard Formation and Maules Creek Formation of Permian age. The Currabubula Formation is composed of cobble conglomerates, sandstones, siltstones and shales of fluvial and glacial origin . These sediments are punctuated by ignimbrites and tuffs that have undergone penecontemporaneous erosion.

COMPARISON OF THE KEROSENE CREEK AND MAHOGANY ZONE OIL SHALES AND THEIR RETORT OILS

The Boggabri Volcanics were found to consist of devitrified, glassy rhyolitic flows and flow breccias. Minor interbedded basalt was also recorded.

I.L. Ingram, University of Wollongong, 1981.

Rocks of the Leard Formation have a contentious origin but appear to be a redistributed weathering profile formed on the Boggabri Volcanics.

The organic petrology and chemistry of oil shales from the Kerosene Creek seam, Rundle and the Mahogany Zone, Green River Formation are compared. Both oil shales consist chiefly of yel-

The Maules Creek Formation is dominantly a coarse elastic sequence with interbedded coal

AUSTRALIAN COAL GEOLOGY

44 seams. These rocks have been derived from the Currabubula Formation and deposited in a piedmont, braided-stream environment. The coal has been formed in areas between alluvial fans and has been deposited under progressively drier conditions. Parts of the Maules Creek Formation have been intruded by igneous rocks of possible Tertiary age. Structurally, the area is dominated by the 10"W trending Hunter-Mooki Fault. Outcrop patterns to the east of this fault are typical of those of dome-and basin-type terrains, which may have resulted from two deformations. To the west of the Hunter-Mooki fault, faulting occurs in two prominent directions which are at approximately 45° to the Hunter-Mooki Fault. THE GEOLOGY OF THE WARKWORTH AREA, NEW SOUTH WALES

Graham M. Ingram, University of Newcastle, 1983. "The Geology of the Warkworth Area" is a stratigraphically based study that presents a revised nomenclature system for the Whittingham Coal Measures. The formally accepted system of Britten (1972) is shown to be inconsistent while the suggested modifications of Bailey (1981, 1983) are not considered as applicable to the Warkworth Area . The Jerrys Plains Formation and the Warkworth Coal Member are proposed for inclusion within the Whittingham Coal Measure Group. Correlation across company boundaries has allowed the nomination of equivalent units within the respective company nomenclatures. The wealth of geological information made available from extensive coal exploration has been compiled, and proposed as an important contribution to the Geology of the Warkworth Area. THE GEOLOGY OF THE JERRY'S PLAINS AREA

E. McHugh, University of Newcastle, 1984. The Jerry's Plains area, situated twenty-five kilometres southwest of Muswellbrook SW, comprises strata of Permian age, represented by the Wittingham and Wollombi Coal Measures of the Singleton Super-Group. The sedimentary sequence includes terrestrial coal-bearing units (Foybrook Formation, Jerry's Plains Sub-Group and Wollombi Coal Measures), together with two marine transgressive/regressive facies (Archerfield Sandstone/Bulga Formation and Watts Sandstone/Denman Formation). These latter units are considered to be representative of beach and barrier-bar /near-shore deposits. Coal seams within the area are considered to have formed under predominantly telmatic forest

moor conditions. Coalification has largely postdated tectonic activity associated with the development of the Muswellbrook Anticline. Strata of the Jerry's Plains Sub-Group has been intruded by two igneous bodies of probable Tertiary age. These intrusions, the Carrington and Plashett sills, represent differentiated, largely concordant bodies of alkali olivine basalt type. The area is structurally dominated by the Muswellbrook Anticline, being located on the western flank of this feature. Normal faulting associated with this structure is believed to have provided a conduit for the injection of the Carrington sill. GEOLOGY OF THE SOUTHERNMOST CALLIDE BASIN, EAST-CENTRAL QUEENSLAND

Robert Arthur Behets, University of Queensland, 1987. The upper Triassic Callide Coal Measures comprise up to 150m of coal-bearing sediments that have accumulated in humid alluvial fan plain environments within the fault-controlled intermontane Callide Basin, east-central Queensland. Detailed mapping, measurement of vertical sections, petrographic analysis of core and outcrop samples and utilisation of subsurface information, provided an insight into the geology of the Callide Basin sequence and the associated basement rocks. Sedimentological studies of the Callide Coal Measures reveal an upward trend towards lower energy conditions. The Basal Callide Coal Measures accumulated in alluvial fan environments characterised by hyperconcentrated flood flow deposits whereas alluvial plain envjronments including nonmeandering, low sinuosity channels, floodbasins and peat-forming swamps were the sites of accumulation of the Upper Callide Coal Measures. Mesoscopic and microscopic examination of coal of the Callide seam has recognised five coal facies ranging from well laminated, vitrinite rich, low ash types through to the dominant homogeneous, inertinite rich, high ash types. The coal facies represent accumulation of peats in subaqueous to subaerially expo~ed subenvironments of the peat swamp. Tonstein bands present in coal seams of the Callide Coal Measures represent the accumulation and subsequent diagenetic alteration of distal fallout tephras. Areas of thick coal coincident with thickest development of the Callide Coal Measures, and the preferential occurrence of thick sandstone bodies above thick coal plies suggests that structural and compactional controlled subsidence, with contemporaneous channel activity were the major

AUSTRALIAN COAL GEOLOGY

45 controls on sediment accumulation patterns during the Callide Seam interval.

should pinpoint where variation from ideal fragmentation can be expected.

THE EFFECT OF STRUCTURE ON BLAST INDUCED FRAGMENTATION AT DRAYTON COLLIERY, NSW

PERMIAN STRATIGRAPHY AND SEDIMENTOLOGY OF THE MOURA-BANANA DISTRICT, SOUTHEAST BOWEN BASIN, CENTRAL QUEENSLAND

David N. Donehue, University of New South Wales, 1987.

Variable fragmentation of the Ayrdale Sandstone Member is a major engineering problem at the Drayton open-cut coal mine, situated in the Upper Hunter Valley region of NSW. The major aims of this study were: 1.

to undertake a structural analysis of the mine area, specifically of the major joint directions and joint spacings throughout the mine, and to identify the factors that control the variable fragmentation of the Ayrdale Sandstone Member from an analysis of three overburden blasts on this unit.

The principal joint sets in the mine area are 035°-045 and 120°-130° (strike directions) and are cross-fold joints related to the Muswellbrook Anticline. Secondary joint sets trending 360°- 010 ° and 90°-100° are also present, and are interpreted as a-c joints, also related to the Muswellbrook Anticline. Joint spacing for the principal joint set is fairly constant throughout the mine, although fluctuations from 0.9 to 1.8m are noted in fault blocks of the western area . Generally mean spacings of 1.10-1.20m for the 035 °-045 • strike direction and 1.70-2.00m for the 120 °-130 ° strike direction are noted. Three overburden blasts were monitored, two in the eastern area (EN0l and ES0l strips) and one in the western area (SW0l strip). Bed spacing is the primary control on fragment size with over 80% of all fragments containing one or more bedding planes. Jointing is a secondary control with over 50% of rock fragments measured containing one or more joint planes. The variable fragmentation in the rock of the Ayrdale Sandstone Member does not appear to be caused by changes in joint spac;ing for the principal joint trends. Mean joint spacings for the three blasts were consistent (1.2m for the 035 °-045 • strike direction and 1.7- 2.0m for the 120°-130 ° strike direction). A more likely cause of the variable fragmentation is the changing nature of the joint planes from tight (minimal separation) to cemented. The cemented joint planes are thought to cause reflection of the stress waves from the blast hole, and hence the production of oversized blocks. Further research into the extent of weathering in the Ayrdale Sandstone Member within the mine lease

Cameron Iain Edgar, University of Queensland, 1987.

The Moura-Banana district, located east of the Mimosa Syncline in the southeast Bowen Basin, received approximately 3000m of Permian sediments during several transgressive and regressive phases. Depositional environments ranged from marine shelf to alluvial plain. In ascending order, the Permian units exposed in the study area comprise: the mainly continental Camboon Volcanics (thickness, 200m+), marine Buffel Formation (10- 90m), nearshore Mt Ox Subgroup (60-lO0m), muddy Barfield Formation (500-750m), shallow-marine Flat Top Formation (550-600m), continental Gy randa Formation (<750m) and the economically important Baralaba Coal Measures (<500m). Data used in the Moura mine sedimentological study in the B-D interval of the Middle Permian Baralaba Coal Measures were derived from highwall mapping, subsurface data and detailed examination of representative core material. Palaeocurrent data, fades associations, absence of marine fossils, moderate thickness of coal, finingupward cycles, sequence position and lateral relationships all suggest that the B-D interseam interval accumulated in a northward-draining alluvial plain setting with 35m deep, long-lived, sinuous, laterally migrating channel, levee, flood basin and extensive peat-forming environments. Laterally accreted channel sequences at Moura display enormous scale epsilon cross-bedding and are among the largest in the geological record . Underground operations at Moura are hampered by north-west-trending, low-angle thrust faults that ramp through the sandstone dominated sequence. These post-depositional structures propagated through weaker intervals near coal seams and are strongly influenced by pre-existing lithologies. Depositional maps and fade s analysis indicate that margins of palaeo-river meander belts include areas of thinly bedded, slickensided material that are zones of potential massive roof fall. The seven fades recognised in the B-D interval, in combination with computer generated isopach maps, allow confident prediction of depositional environments. As a consequence of this sedimentological study it may be possible to predict zones of roof failure and areas prone to thrust-associated structures.

AUSTRALIAN COAL GEOLOGY

46 IMAGING AND MIGRATION: AN APPLICATION TO DOWNHOLECROSSHOLE SEISMIC METHODS IN COAL BEARING STRATA Francis Ientile, University of New South Wales, 1987.

Very high resolution downhole-crosshole seismic techniques are capable of resolving geological features of l.0m or less. Currently these methods have been employed to locate and map coal geological structures. As seismic images are geometrically distorted when complex structure is encountered, migration is required. The theoretical background for a migration method for the generalised Yo-Yo method has been developed. The first step in this process was the development of forward modelling to produce seismic images of typical coal geological structures using the half Yo-Yo geometry. The seismic images obtained were 90° rotated mirror images of the actual images obtained where stratigraphic models imaged as continuous reflection events while structural models imaged as discontinuous reflection/ diffraction events. A selected range of these models was used as input to the migration process. The migration was based on the principles of ellipse geometry. The migrated images obtained for single common source gather inversion have good vertical but poor lateral resolution. Stacking several migrated common source gathers from a variety of source depths improves lateral resolution. The results of this study have outlined the procedure for further work. The generalised Yo-Yo method will require a migration process which extracts, migrates and stacks each common source gather contained within a generalised data set individually. THE GEOLOGY OF THE WAKEFIELD BRUNKERVILLE AREA, NSW M.J. Roach, University of Newcastle, 1987.

The geology of an area of 84 square kilometres, located approximately 20 kilometres southwest of the City of Newcastle, was investigated. The Muibring Siltstone, Tomago Coal Measures, Newcastle Coal Measures and lower Narrabeen Group occur in outcrop within the study area. Deposition of the study section occurred during a basin wide marine regression with minor transgressions superimposed. Sedimentation patterns were controlled by the interplay between elastic sediment supply and basin subsidence. Differential subsidence, related to movements of the Lochinvar Anticline to the west of the study area, also has a considerable influence on the type and distribution of elastic and organic sediment. Investigations into the lateral and vertical variations in sediment distribution were conducted, including vertical profile analysis, the generation of isopach and lithofacies maps and measurement

of palaeocurren t directions. Additional studies were conducted in structural geology, coal geology, igneous petrology and Magnetics. Considerable resources of both energy and coking coal occur within the study area. This thesis highlights some of the problems which will need to be addressed by any company attempting the efficient and economic extraction and utilisation of these resources. FACIES AND DEPOSITIONAL ENVIRONMENTS AT ATP271P, THE EROMANGA BASIN, QUEENSLAND C. Turvey, University of Newcastle, 1987.

ATP 271P lies in the north-eastern portion of the Eromanga Basin, Queensland, which comprises sediments of Jurassic and Cretaceous age. Depositional patterns in the study sequence result from both taphrogenesis and eustatic sealevel change. The predominant structural feature in the area is the Maneroo Platform which significantly influenced deposition patterns. Compressive tectonism during the Late-Cretaceous-Early Tertiary resulted in the reversal of pre-existing normal faults and formation of low amplitude folding and concomitant Cretaceous crestal faulting. Cycles of high and low energy deposition occur throughout the study sequence. Initial deposition occurred in restricted areas of lacustrine deposits forming the evergreen Formation. The Hutton Sandstone was deposited in an alluvial fanbraided stream environment; Birkhead Formation in fluvial meandering streams with minor lacustrine and deltaic deposition; Adori Sandstone in braided streams; Westbourne Formation initially comprises a long period of lacustrine conditions, with sub-lacustrine fans, shoreface, and overlying fluvial meandering stream deposits; Lower and Upper Hooray Sandstone Units deposited by braided streams whilst the middle portion formed by meandering streams; Cadna-Owie Formation represents the beginning of a widespread marine transgression, being deposited in a restricted marginal marine environment overlain by beach, barrier-bar, and deltaic distributary channel sands of the Wyandra Sandstone Member. Extremely good hydrocarbon potential is envisaged for structurally favourable areas of Hutton and Adori Sandstone pinchout against basement. The absence of the Hutton Sandstone over much of the western portion of the permit has a significant effect on the prospectivity of the area. The Hutton, Adori, Hooray, and to a lesser extent the Wyandra Sandstone have excellent reservoir potential. Aranaceous sediments of the Birkhead, Westbourne, and Cadna-Owie Formations have a secondary reservoir potential. Heavy mineral provenance of basal sand units in four recent exploration wells indicates a proximal

AUSTRALIAN COAL GEOLOGY

47 basement derived source close to the base of the study sequence, decreasing in influence with decreasing depth. Basement samples reveal both high-energy chemical and diagenetically derived surface textures. Detrital grains generally reveal mechanically derived surface textures with a diagenetic overprint.

A HYDROGEOLOGICAL STUDY OF CONTAMINANT TRANSPORT FROM THE WON GA WILLI COAL WASTE EMPLACEMENT

( - · ,_;LOGY OF THE NORTHWESTERN CALLIDE BASIN, EAST CENTRAL QUEENSLAND

This report details a study on the hydrological impact of the Wongawilli coal waste emplacement. The site is located 14km to the south-west of Wollongong on the eastern coast of NSW and is owned and operated by BHP Steel Pty Ltd. The main objective of the study was to quantify the impact of the emplacement on local groundwaters.

Derek William Waterfield, University of Queensland, 1988.

The Late Triassic Callide Coal Measures are contained by the fault controlled intermontane Callide Basin of east-central Queensland. An alluvial fan and alluvial plain environment was the setting for deposition in which at least 180m of sediments were laid down. An unconformable relationship between the Early Permian Youlambie Conglomerate (basement) and the Callide Coal Measures exists to the north of the Boundary Hill Mine. The Galloway Plains Tonalite to the west of the mine, is closely associated with the Callide Basin and was the source for much of the basal sediments of the Coal Measures. Field mapping, measured sections, borehole and outcrop sample examinations, pit observations, and subsurface modelling allowed for a better understanding of the Boundary Hill Mine area and the surrounding region. Lower and upper associations were recognised in the Callide Coal Measures. The lower is dominated by conglomerates originating from hyperconcentrated flood flows in an alluvial fan environment, whereas the upper association is a heterolithic sequence of sandstone, siltstone, claystone tuff, and coal deposited on an alluvial plain. Deposits related to channels, floodbasins, prograding minor deltas, and peat swamps are recognised within the sequence. Detailed study of the coal (Callide seam) on macroscopic and microscopic scales revealed six coal fades which are dominated by macerals of the inertinite and vitrinite groups. The study revealed the presence of two vitrinite types (A and B). Based on this, the vitrinite content of the coal is considered not as low as previously noted, and that the inertinite-rich (vitrinite-poor) classification of the coal is incorrect. The environment of deposition is interpreted as a wet forest moor situated in the distal regions of a floodbasin on an alluvial plain. A Model for the Distribution of Coal Quality, Type and Breakage Character in the Katoomba Seam, Illawarra Coal Measures, Sydney Basin, Australia.

Steven E. Phillips, University of New South Wales, 1989.

To determine the present composition of the aquifer an extensive borewater sampling and purging programme was undertaken. The results confirmed previous data on the site, showing a relatively high background salinity zone trending down the centre of the site. The dominant constituents of the groundwaters are chlorides and sulphates which at certain locations show concentrations that are above class P water quality standards for the area. The study identified sulphate concentrations of over 400mg/L in a bore located close to the dump. Average background sulphate concentration ranges from 30- 70mg/L. This result is therefore believed to represent leachate affected groundwater. Chemical changes in groundwater produced by stagnation within the bores were not detected in the study. To laterally complement groundwater quality information from bores, resistivity and electromagnetic methods were used. These methods were found reasonable successful in determining subsurface structure, but were unable to resolve resistivity contrasts caused by groundwater conductivity changes of up to 3000µS/cm. this was mainly due to the larger resistivity effects of lithology variations. Groundwater modelling was performed over the site using a two dimensional computer fluid flow and contaminant transport program. Background aquifer sulphate and chloride conditions were first modelled and then future simulations performed incorporating the presence of leachates from the emplacement. Chloride and sulphate mass influxes from the coal wash waste were determined from a leachate column study. Modelling and sampling results indicate that chlorides leaching out of the emplacement will have a minimal affect on the aquifer. In contrast the modelled effect of sulphate is more noticeable, with values close to the site rising from background conditions of 20-30mg/L up to 60mg/L. It is thought that the long term model for sulphate is probably an underestimate of future conditions due to the anomalous concentrations exhibited at BH12A.

AUSTRALIAN COAL GEOLOGY

48 THEHYDROGEOLOGYOFU DERGROUND MINE INFLOWS AT LIDDELL COLLIERY Utzon Reed, University of New South Wales, 1989.

Major groundwater inflows into the Liddell workings enter via an extensive network of joints, fractures and bedding surfaces. At the two study locations, different geologic controls were responsible for the occurrence of these fractures. Over the longwall panels, water flowed from a surface stream down subsidence induced cracks in the substrata and into the overlying goaf. At the barrier pillar separating Liddell Colliery from the abandoned Hazeldene Colliery, water entered through a pre-existing set of natural fissures and joints that were intensified by goaf retreat of the latter mine. Geotechnical modelling of the barrier pillar and Liddell workings under the increased stress of water pressure buildup and flow through these joints indicated a link between heading roof and wall stability and the head of water in the adjacent abandoned workings. SEDIMENTOLOGY AND STRATIGRAPHY OF THE RANGAL COAL MEASURES, BLACKWATER AREA, CENTRAL QUEENSLAND Steven Geoffrey Scott, University of Queensland, 1989.

Within the Blackwater area Late Permian to ?Early Triassic sediments of the Blackwater and Rewan Groups are exposed on the eastern flank of the Comet Anticline. The Comet Anticline is one of eight structural elements comprising the Permo-Triassic Bowen Basin. Regionally, Palaeozoic and Mesozoic formations exposed at Blackwater dip gently towards the east at approximately s·. Locally, faulting may increase this dip. Formations exposed at Blackwater, from oldest to youngest, are the Fair Hill and Burngrove Formations, Rangal Coal Measures, Sagittarius Sandstone and possibly Arcadia Formation. All these units offer little topographical relief and only a thick Tertiary sandstone, developed in the southwestern quarter of the study area, provides any positive relief. A number of water courses running through the area have incised into surficial Cainozoic material producing some pre-Cainozoic exposure, but it was not until the development of the Blackwater coal mine that large, continuous exposure of the Rangal Coal Measures were available for study. Facies analysis of the Rangal Coal Measures has allowed rationalisation into six lithofacies which were deposited in environments ranging from channel through levee and overbank to peat

swamp, in an alluvial plain setting. Palaeocurrent data collected from within the mine area suggests that Rangal Coal Measures stream systems flowed towards the south. This is a marked divergence from interpretations of some previous researchers who suggested a northward direction of sediment transport. The type section of the Rangal Coal Measures has been critically assessed. Because of mining operations the section has been effectively destroyed and a lectotype, the fully cored Queensland Department of Mines borehole Blackwater NS 83, is proposed. This cored hole is retained in the Government Core Library and provides a full section of the coal measures including the boundaries with enclosing units. Four sites where coked coal and indurated sedimentary rocks are exposed were investigated. Sedimentary rocks at these sites were mostly brick red and in places were admixed with a very hard, vesicular clinker. The sedimentary rocks were heavily fractured and dipped approximately to the west. This is nearly the reverse of the regional dip. From the similarity of the cream claystone bands found overlying the coked seam to the characteristic tuffaceous claystone bands found near the top of the Burngrove Formation it is proposed that the seam which was naturally ignited is either the uppermost seam of the Burngrove Formation (Virgo seam) or a combination of the Virgo and the lowermost seam of the Rangal Coal Measures (Pisces seam). THE GEOLOGY AND MINERALOGY OF THE WAKEFIELD AREA, SYDNEY BASIN, NSW M.B. Wilson, University of New South Wales, 1989.

The study examines the geology of an area covering some 70 square kilometres, centred around the village of Wakefield in the Newcastle Coalfield, New South Wales. The sediments of the Newcastle Coal Measures in this area are studied in detail, along with those of the Narrabeen Group that also crop out in the study area. Reference has also been made to the nature of the underlying Tomago Coal Measures, Maitland Group, Greta Coal Measures and the Dalwood Group which make up the other units of the Newcastle Coalfield region. The sediments cropping out in the study area are predominantly fine grained, though numerous localised and more regionally distributed conglomerate units also occur. The conglomerates usually contain clasts of granule to pebble size. The Permian-Triassic boundary is difficult to identify in the study area due to the absence of the recognised marker horizon, the Vales Point seam at the top of the Newcastle Coal Measures, and to the lithological similarity between the uppermost Permian units of the Newcastle Coal Measures

AUSTRALIAN COAL GEOLOGY

and the lowermost units of the Triassic Narrabeen Group.

GEOLOGYOFTHEGLAD STONETO T ARGINIE AREA

A near complete exposure of the Newcastle Coal Measures is found in the study area. All units from the Montrose/Wave Hill seam are exposed, though the units of the Boolaroo and Moon Island Beach Subgroups cover the majority of the area. The units show a general thinning to the west, due to pinchout approaching the Lochinvar Anticline, to the west of the study area. The units are also affected by the Macquarie Syncline immediately to the east of the study area.

Anita Kay Finegan, University of Queensland, 1990.

The sediments within the Newcastle Coal Measures in the Wakefield area are also very similar mineralogically. The bulk of the materials analysed consist of quartz, kaolinite, feldspar and montmorillonite or a montmorillonite/illite regular mixed layer clay. Claystones that occur within coal seams tend to be either kaolinite or montmorillonite rich, however, with very Ii ttle quartzfeldspar rocks in the study area. The coarser grained rocks of the sequence tend to have slightly more feldspar, but this does not always hold. The claystones between the coal seams are generally feldspar free, particularly in the Adamstown Subgroup of the Newcastle Coal Measures. The Low temperature (oxygen-plasma) ashes of coal samples from the Australasian seam, Montrose/Wave Hill seam, Upper Pilot seam and Fassifern seam contain quartz, kaolinite, montmorillonite and feldspar whilst ashes from the Great Northern seam contain quartz, kaolinite and montmorillonite. The kaolinite is well crystallised in the Australasian and Montrose/Wave Hill seams, but is poorly crystallised in the coal seams, such as the Great Northern, in the upper Newcastle Coal Measures. The major geologically based engineering problems in the area are subsidence effects and slope or foundation failure due to claystone behaviour. Subsidence in the area is due to underground mining of the major seams at West Wallsend, Newstan and Stockton Borehole Collieries. It is particularly noticeable over the shallow workings at Newstan. The abundance of claystones in the area is of concern, as well as their mineralogical properties, particularly in the construction of the F3 Freeway extension. The claystones form layers of weakness and are possibly capable of resulting in slope failure in road cutting walls. There is also the possibility of liquification of certain claystone bands under pressure in the road bed.

Extensional tectonics in the late Cretaceous to Early Tertiary resulted in the formation of rifted basins along the Queensland coast. These were associated with the opening of the Coral and Tasman Seas. The Narrows Basin was created in Middle Devonian to Early Carboniferous rocks of the Curtis Island Group, which formed as subducting abyssal plain deposits on a convergent margin. Geological mapping of the Gladstone to Targinie Area resulted in the recognition of seven stratigraphic units, three of which are newly defined. Subsurface correlation of seven drill holes allowed the recognition of another two formations. The structure of the Narrows Basin has been reinterpreted and is now proposed to be that of a half-graben. Consequently, the name of the basin has been changed from Narrows Graben to Narrows Basin. Detailed sedimentological studies of subsurface stratigraphic sections enabled the determination of a new scheme of lithofacies for the Middle to Late Eocene aged Worthington and Rundle Formations. The scheme comprises five lithofacies subdivided into fifteen subfacies. Three lithofacies and four subfacies accumulated on an internally drained alluvial plain (Worthington Formation) and the remaining in an hydrologically drained perennial lake (Rundle Formation). Late Tertiary to Recent sedimentation patterns reflect changes from alluvial plain to a modern day coastal plain. Characteristic features of the two regimes have been presented . AN ENVIRONMENTAL RECONSTRUCTION OF THE AYRDALE SANDSTONE OF THE GRETA COAL MEASURES IN THE MUSWELLBROOK DISTRICT Flanagan, S.J., University of Newcastle, 1990.

The Ayrdale Sandstone Member is the most persistent non-coal horizon of the Greta Coal Measures in the Muswellbrook district. In the region of the Savoy Trig. Station south of the township of Muswellbrook NSW, the Ayrdale Sandstone immediately overlies the economically significant Balmoral Coal Member and forms a competent bed usually 9-25 metres thick. The Ayrdale Sandstone Member is characteristically arenite dominated with subordinate fine grained sequences of inter-bedded siltstone and sandstone. It is most unusual in that with its thick vertical development and lateral consistency, it records the occurrence of well sorted, equiant arenite grains but only minor weakly defined cross-bedding.

AUSTRALIAN COAL GEOLOGY

50 Of conspicuous origin, the Ayrdale Sandstone has been interpreted by Robinson (1963) as having a deltaic origin and by Tobin (1980) as of estuarine origin. An inter-distributary bay environment was postulated by Hamilton (1984) and a transgressive beach origin by Diessel (1990, unpublished). A study of field and laboratory data collected in the region of lease A173 owned by the Drayton Coal Company, the present author postulated that the Ayrdale Sandstone Member formed as the resulted from the infilling of a substantial lagoon established during the time of peat accumulation of the most upper Balmoral coal splits, namely the Bl seam. Depositional mechanisms include those of tidal regimes coupled with the more 'dynamic' processes of washover fans toestablish substantial tidal flats in the Savoy Trig. Station region. Further to the north, infilling of the lagoon was by fluvial conditions which prograded south to eventually be established in the study area during late Ayrdale Sandstone deposition time. THE GEOLOGY OF THE NORTHEASTERN PART OF THE SYDNEY BASIN Albert Migliucci, University of New South Wales, 1990.

channel structures were found to correspond with conglomerate bodies in geological cross-sections of the area, and with observed roof conditions in mines within the study area. Seam Rolls were delineated in the roof of the Great Northern Seam. It soon became apparent that these features represented longitudinal bars, deposited under waning flow conditions of a powerful palaeocurrent. Outcrop mapping indicated a definite channel margin between Catherine Hill Bay and Flat Rocks. The Gelification Index and Tissue Preservation Index of samples of coal from within the Moon Island Beach Subgroup, were found to be very similar to braidplain coals. Thus the area is thought to be the result of a braided stream, migrating laterally across an area of peat accumulation, to produce a series of complexly split coal seams, and conglomeratic palaeochannels. STRATIGRAPHY AND SEDIMENTOLOGY OF SOUTHEAST BRISBANE Angelique Cutovinos, University of Queensland, 1991.

An analysis of the geology of the northeastern part of the Sydney Basin (New South Wales) has been undertaken incorporating Thematic Mapper satellite imagery, field measurements and seismic data. The area forms part of the Hunter Valley Dome Belt along the northern margin of the basin.

The study area is located in southeast Brisbane encompassing suburbs: Bulimba, Balmoral and Hawthorne to the west and Wynnum, Manly and Lota to the east. The northern side is bounded by the Brisbane River.

Foreland-style tectonism during the Permian appears to have influenced the style of sedimentation in the Sydney Basin. Four coarsening upward depositional cycles are recognised. It is proposed that these cycles are responses to an episodic SENW convergence of the craton with an oceanic plate further to the east.

Southeast Brisbane is part of the Ipswich Basin, which is interpreted as intermontane. Maximum development of this basin occurs to the west of Ipswich and thins out to the east. Palaeocurrent readings suggest sediment flow to the east, towards the present shoreline, indicating a smaller, separate basin which is connected to the major Ipswich Basin.

The Hunter Fault is a NW trending fracture that developed oblique to the principal compressive stress, resulting in both loading and uplift to the north of the Hunter Valley with sediments being shed from these highs into a subsiding trough. A close correlation between the orientation of joint and fracture patterns, and the lineament trends interpreted from satellite imagery is evident. These lineaments are believed to be surface expressions of basement structures, structural pattern and geological history. PALAEOCHANNEL DEVELOPMENT IN THE MOON ISLAND BEACH SUBGROUP, NEWCASTLE COAL MEASURES, NSW Weekes, J.W., University of Newcastle, 1990.

A sand/shale ratio data stripping program was devised, and computer modelling of this data produced recognisable channel structures. These

Neranleigh-Fernvale beds constitute the Palaeozoic basement rocks and are the main source of sediment to the Ipswich Coal Measures. Unnamed sediments lie unconformably above the basement rocks, and are correlated to the Kholo Sub-Group. Middle to late Triassic volcanism interrupted sediment activity. The Tingalpa Formation, part of the Brassal SubGroup is the formation representing ~he Ipswic~ Coal Measures in the study area. Sed1mentolog1cal and Stratigraphic studies reveal the accumulation of sediments of the Tingalpa Formation was one of fluvial, floodplain and peat mire environments with laterally migrating moderate to high sinuosity channels. Interseam sequences of the Tingalpa Formation occur in point bar, levee and floodplain environments. Trough cross-bedded sandstones and planar cross-bedded sandstones are laterally accreted channel sequence, deposited on point

AUSTRALIAN COAL GEOLOGY

51 bars by migrating sinuous crested dunes and migrating transverse bars respectively. Carbonaceous mudstones and thin crevasse -splay deposits accumulated in flood plains. Interbedded sandstone and mudstone accumulated on levees near channels.

seam in the Greta Coal Measures in the Muswellbrook district, whilst the Ayrdale Sandstone Member is a thick sequence of quartz-lithic sandstone occurring in a localised area south of Muswellbrook. The majority of data was gathered during mapping in Bayswater No.2 Colliery.

The Tingalpa Formation is correlated to the Tivoli Formation.

The study was intended to find the sedimentological cause for seam splitting by examination of the kaolinite-rich pelletoidal claystone that occurs in the non-coal partings of the Balmoral Coal Member.

THE GEOLOGY OF THE LOWER SYDNEY BASIN, WESTERN COALFIELD NSW

R. Feldtmann, University of Wollongong, 1991.

This thesis describes the stratigraphy and depositional setting of the Shoalhaven Group, the Nile Subgroup and Cullen Bullen Subgroup of the Permian Sydney Basin in the Western Coalfield, NSW. Seven modifications to the current stratigraphic nomenclature are recommended in this study. These include changes to the definitions of previously-defined units and minor boundary modifications. The Shoalhaven Group was deposited in a transgressive marine environment and consists of basal debris flow and shoreface conglomerates, that were unconformably deposited on an irregular Palaeozoic basement. The conglomerates grade upward to near shore sandstones, which are overlain by shelf-deposited siltstones. Sporadic dropstones occur in the upper part of the sequence. Storm-influenced beds towards the top indicate that a marine regression occurred towards the end of the Shoalhaven depositional event. The Cullen Bullen Subgroup was deposited in a high energy flu vial environment, characterised by alluvial fans and distributary braidplains, with sequences of coal occurring in the interfan and distal reaches of the system. Interfingering of the flu vial units with coal seams is a result of contemporaneous deposition of these units. It is evident that the structure of the basement is influenced by the palaeogeography, that was dominated by basement highs near the present basin margin. These formed sea cliffs in the EarlyPermian transgressive period and were eroded to supply sediment for the alluvial fans of the Cullen Bullen Subgroup. SEDIMENTOLOGY OF THE LOWER GRETA COAL MEASURES ON THE MUSWELLBROOK ANTICLINE, NEW SOUTH WALES

Paul Richard Salmon, University of New South Wales, 1991.

Sedimentological and petrological analysis was undertaken on the Balmoral Coal Member and the overlying Ayrdale Sandstone Member. The Balmoral Coal Member is the lowest and thickest coal

Seam splitting in the Greta Coal Measures has been modelled to be a product of the alluvial environment in which the coal was produced. The alluvial model, in which the pelletoidal claystone was deposited during flood stages in the backswamp area of an alluvial plain (overbank deposits), was derived from the overall study in the area with detailed study of Bayswater No.2 Colliery, and reflects the way in which flooding brought in successive waves of pelletoidal claystone, which when deposited, caused breaks sequence of peat. The occurrence of a large amount of organic material in the AS2 sandstone unit has been the most important factor in adopting the lacustrine-deltaic model as the likely sedimentary environment existing at the time of formation of the Ayrdale Sandstone Member. This unit reflects the way in which lacustrine-deltaic conditions followed the formation of the Balmoral Coal Member and caused the infilling of the "Balmoral" swamp. THE EFFECT OF MARINE INFLUENCES ON COAL COMPOSITION, GRETA COAL MEASURES, UPPER HUNTER VALLEY, NSW

C. Jeffery, University of Newcastle, 1992.

The Greta Coal Measures in the Upper Hunter Valley represent terrestrial sedimentation in the Early Permian, between the underlying Gyarran Volcanics and the overlying Maitland Group. Sedimentological and petrological analyses were undertaken on the Balmoral Coal Member and the Ayredale Sandstone Member and results show that the Balmoral coal is an inertinite-rich coal containing abundant syngenetic pyrite. The Ayredale Sandstone Member is a unit that contains approximately 50% quartz in a fine mix of kaolinite and some carbonate. It ranges from 22 metres on the crest of the anticline and thins away from this to 12- 16 metres. The sandstone is found in the Drayton/Bayswater Coal Mine area (Frontispiece supplied by Drayton Coal Mine). The Balmoral Coal Member is the lowermost unit of the Rowan Formation and has a coal thickness of 10-12 metres excluding partings. This study was completed to determine the effect of marine influences on the composition of the Balmoral Coal Member and to interpret the enigmatic Ayredale Sandstone Member.

AUSTRALIAN COAL GEOLOGY

52 Seam splitting within the Bal moral Coal Member is intimately related to the amount of tectonic subsidence that occurred during the formation of the Muswellbrook Anticline. The Balmoral Coal Member is thought to have been formed in a backswamp in close proximity to the Permian Sea. The most likely palaeo-environment for the localised deposition of the Ayredale Sandstone member is a washover fan from a shoreline barrier. This is evidenced by the petrographic composition of the coal, the total sulphur and sulphur isotopic composition of the coal and the sedimentary structures observed within the Ayredale Sandstone and the interseam sediments of the Balmoral Coal Member. CLEAT IN RELATION TO FAULTING AND INFILL AT THE GREGORY AND NEWLANDS COAL MINES AND THE STRUCTURAL GRAIN AT THE GREGORY MINE, QUEENSLAND Hesham Mansour, James Cook University of North Queensland, 1992

The Gregory mine is situated on the western edge of the Bowen Basin, Queensland, on a gently plunging Middle Triassic anticlinorium which contains mine scale NNW trending reverse and normal faults, NE thrust faults, NE normal faults and monoclines. The predominant structures formed during the Middle and Middle to Late Triassic crustal shortening events which produced SSE plunging folds, SSW and SE monoclines, NW trending reverse and NE antithetic normal faults. The Early and late Cretaceous to Early Tertiary crustal extension formed the mine scale NW trending normal faults. The east-southeast to east-west mine scale joints, cleat and irregular cleat formed syn-burial with the roof joints occurring earlier to cleat and irregular cleat. The penetrative NE-SSW and NW-SE joints overprint the early Permian syn-burial ESE-EW joints and are due to the Cretaceous or Ter tiary unloading. The roof sequence is dominated by penetrative NE-SSW joints in almost all units with orthogonal, less penetrative NW-SE joint which overprints the NNE-SSW and ESE-EW joints, with the SE-NW joints forming orthogonal to it. The occurrence of the joint sets varies across the mine. Both joint height and spacing was predominantly between 0.1 to two metres. Cleat and coal seam joints displayed no pattern or proportional relationship regarding cleat frequency. The predominant coalseam joint direction is NE and SE. The obvious diagnostic features of faults in the Lilyvale Seam includes an increase in intermediate joint frequency, tonstein shearing, gouge material and brecciated coal. Faulting increased the cleat and coalseam joint frequency on all but the seam penetrative joint scale in the fault zone and the adjacent metre. The non-seam penetrative, metre to centimetre scale joints are the most responsive joint scale to faulting and results in a

substantial joint frequency increase. The ensuing two metres adjacent to faults displayed reductions in cleat and coalseam joint frequency with respect to background levels. The fault type, orientation and throw had a negligible effect on cleat and coalseam joint frequency and morphology. Microfractures were only detected in fault zones. The microfractures at Gregory varied from subvertical to horizontal in orientation indicating ductile movement following their formation whereas New lands displayed uniform 45 • dipping microfractures which are likely to have undergone negligible re-orientation following formation. At Newlands the porosity increased from 2-5% to 15-20% at 10 metres away and within the fault zone, whereas Gregory showed negligible porosity dilation. The increase in porosity is due to the stress concentrations around the dull band fragments exceeding the confining stresses keeping them in contact. A linear relationship could not be deduced with respect to bright band thickness and cleat frequency although it is quite clear that a reduction in bright band thickness results in an increase cleat frequency. The predominant infill at Gregory consisted of pyrite, marcasite, kaolinite, illite, smectite and interlayered combinations of the latter three. The syn- and post-coalification cleat and coal seam joints contained distinct mineralogical, crystallographic and trace element signatures. The syncoalification infill, including the contact and tonstein infill, both contain cubic pyrite crystals with contact infill being tightly packed possibly due to burial compression. The post-coalification infill incorporates the large to small scale joints and mostly contain octahedral pyrite with a thin layer on the surface containing mainly kaolinite, smectite and illite and interlayered equivalents. Similar clay mineralogies are also present in the syn-coalification infill as dispersed fragments. The syn- and post-coalification infill both contained As, Co, Cu, Ni and Zn. The post-coalification infill contains greater i and Co, whereas both contained As, Co, Ni, Te, Zn and both lacked Cd and Hg with respect to post-coalifica tion infill . There were at least four infill mineralisation phases at Gregory and included the early Late Permian pyrite infill in the contact between the bright and dull bands and tonstein, possibly in a swampy to early burial environment. The next stage saw the occurrence of irregular cleat kaolinite infill via hydraulic fracturing, following cleat formation in the early Late Permian. The postcoalification infill contains pyrite, illite and smectite minerals which form in alkali, reducing conditions and marcasite and kaolinite occur under acidic, oxidising conditions and therefore indicates the likelihood of at least two distinct post-coalification fluid migration phases.

AUSTRALIAN COAL GEOLOGY

The irregular cleat infill contained mostly kaolini te with minor illite and interlayed illite/smectite. The presence of Mg and Fe trace elements are most likely associated with smectite as kaolinite is very pure. GEOLOGY OF THE SOUTHERN MOURA MINE AND MALAKOFF RANGE, SOUTHEAST BOWEN BASIN, CENTRAL QUEENSLAND

Deborah Elizabeth Miller, University of Queensland, 1992. This thesis presents a comprehensive study of the Malakoff Range and the surrounding open-cut pits of the southern BHP A.C. Moura Mine. The Late Permian strata of the Blackwater Group are well exposed throughout the area, allowing detailed mapping of the Gyranda Formation, the Kaloola Formation, and the Baralaba Coal Measures. The Triassic Rew an Formation, and Tertiary and Quaternary sediments were also mapped. Well defined lithological units of the Kaloola Formation and their similarity to the type section has resulted in the upgrading of the previous Kaloola Member to Kaloola Formation. The identification of bioturbated horizons supports the evidence for lateral equivalence of the Gyranda Formation with the Burngrove Formation. Petrological work concluded that the origin of dominantly volcanolithic clasts was from a fresh volcanic source. This is consistent with the interpreted evolution of the Bowen Basin as a retro-arc foreland basin by Fielding (1990), positioned to west of the hinterland . Palaeocurrent data for the Gyranda Formation, the Kaloola Formation and the Baralaba Coal Measures indicated a dominant palaeodrainage supplying medium to coarse grained sediments, from the east.

data, borehole log information, and mapping of existing and pre-existing highwall has resulted in the production of palaeoreconstructions for each interseam interval. These reconstructions along with the observed geotechnical relationship with the defined lithofacies, aid in the prediction of large-scale inclined strata, down-dip from present mining operations. A preliminary study of geotechnical parameters was conducted in order to predict stand-up times for unsupported roof strata after mining.

A COMPARISON OF THE TOT AL METHANE GAS MAKES OF THE ADJACENT LONGWALLS NO 9 AND NO 10 AT TERALBA COLLIERY, LAKE MACQUARIE, NSW

G.J. Noon, University of Newcastle, 1992. The occurrence of methane gas (CH4) in the coal mine atmosphere is extremely hazardous. Permissible CH4 concentrations in air are governed by government statutory regulations for the NSW underground coal mining industry. Teralba Colliery operates in the lower portion of a multi-seam environment within the Newcastle Coal Measures. A post-extraction methane drainage system is used to remove up to 60% of the total methane gas released mainly from adjacent seams in the overburden from the floor sequence and the Young Wallsend Seam. At Teralba Colliery the freed gas can be diluted and removed sufficiently fast by conventional ventilation methods.

Structural elements of the local geology are consistent with regional tectonic elements. Coinciding joint and cleat orientations formed as a result of post-compressional de-stressing events in the Bowen Basin. Carbon/Oxygen isotope results conclude a direct relationship between isotopic signatures and the stratigraphic relationship of fault positions.

The methane degassing patterns of the adjacent Longwall No. 9 and Longwall No . 10 Panels indicate the formation of anomalous methane gas make domains during extraction. Those domains are not related to variations in production tonnage output.

Sedimentological studies indicate that the depositional setting of the Baralaba Coal Measures was an alluvial plain, continually crossed by extensive (sinuous) meandering rivers. Large-scale inclined strata common to Moura Mine highwalls represent the preservation of laterally accreting point bars as the river migrated across the plain. An analysis of the palaeoenvironmental setting of the Baralaba Coal Measures identified eight lithofacies, four representing various types of channel fill, three representing floodbasinal environments and one representing an arborescent mire setting. A direct relationship exists between the defined lithofacies and the identified macrofossil assemblage. Integration of geometries, palaeocurrent

Investigation by the present author and a review of existing data indicate that thickness variations of the Charlestown Conglomerate Member, variations in the amount of coaly material of coal seams within the roof and floor strata relative to the extracted seam, the presence of a normal fault adjacent to the south-west side of L.W. No. 10 and the presence of a reverse fault trending obliquely across the study area are the main factors affecting the degassing patterns of L.W. No. 9 and L.W. No. 10 panels. The domains have been defined and delineated and it has been shown that there are zones where the factors noted above can act either individually or in combination to markedly alter the measured methane gas flows.

AUSTRALIAN COAL GEOLOGY

54 THE GEOLOGY AND ENGINEERING GEOLOGY OF THE LITHGOW DISTRICT WESTERN COALFIELD NEW SOUTH WALES

Marie Tungka, University of New South Wales, 1992.

The Lithgow district is located in the region of the Western Coalfield, approximately 105km west of Sydney. The stratigraphic sequence, most of the structure, and the features associated with abandoned underground coal mining activity in the area have been mapped from surface studies at a scale of 1 :10,000. The stratigraphic sequence within the Lithgow district consists of the marine Shoalhaven Group, the overlying Illawarra Coal Measures and the Narrabeen Group. The detailed stratigraphy of the area has also been determined by examination of boreholes sunk by various companies for coal exploration. Subsidence features such as troughs, sinkholes, cracks and cliff failures are present above abandoned workings, especially above shallow workings, in the thesis area. Water analysis also indicates a small increase in concentration of the major ions in the creeks in the vicinity of the abandoned underground coal mining areas. THE GEOLOGY OF THE ELONG ELONG AREA, CENTRAL-WEST NEW SOUTH WALES

Donna Frater, University of New South Wales, 1993.

The Elong Elong area contains a Permian to Jurassic fluvial sedimentary sequence that has been deposited against a basement high. These sediments were deposited in the Coonamble Embayment, unconformably ove rl ying the SilurianDevonian meta-sediments of the Hill End Trough. Structural and palaeocurrent data indicates that Permian and Triassic sediments were deposited from the south and east, while the Jurassic sediments came from the west and south-west. The basement rocks consists of phyllitic schists, slates and volcanics with minor limestone lenses, and are referred to as the Gollan beds. Unconformably overlying this material is the Permian Dunedoo Formation, containing shale, coal and claystone and overlying that is the Triassic Wollar Sandstone. These units are difficult to differentiate in outcrop since both contain braided-stream sandstone deposits. They are overlain by a shaly Triassic succession referred to as the Napperby Formation, and then by the Jurassic Purlawaugh Formation. The Purlawaugh Formation includes the coal-bearing Ukebung Member and above that the sideritic Digilah Member. At the top of the sedimentary sequence is the extensive Pilliga Sandstone unit. Petrographic analysis indicates that the Permian sediments were derived from the rocks of the Hill

End Trough, with the coal and claystone forming in abandoned channels and localised protected areas. The Wollar Sandstone contains large angular fragments, indicating a relatively short distance from its own sediment source . The Napperby Formation contains few sandstones, but those that do occur indicate deposition from the east and north-east. The Jurassic sediments are less mature than the Late Triassic, and have been deposited from the west and south-west in very large volumes. The coal and claystones of the Jurassic Ukebung Member form larger deposits than the Permians' coal of the area but surface outcrop is very poor to quantify the extent of the resources. The Jurassic Pilliga Sandstone forms plateaus that extends northwards. Isolated areas of coal and kaolinite clayrock were identified in both the Dunedoo Formation and the Ukebung Member in the area, but they are not of the quantity nor quality required to make them a commercial interest. A plug of continental alkaline basalt, probably of Tertiary age, intrudes the Napperby Formation near the south-western corner of the study area. THE GEOLOGY OF THE BALLIMORE AREA, NEAR DUBBO, CENTRAL NEW SOUTH WALES

Shane Schofield, University of New South Wales, 1993.

The Ballimore area is situated 35km east of Dubbo and contains a veneer of Early Permian to Late Jurassic fluvial sediments of the Great Australian (Artesian) Basin which rest upon Palaeozoic strata of the Lachlan Orogen . The sedimentary succession rests unconformably upon the Molong Anticlinorium and has a gentle north-north-westerly dip. Permian and Triassic sediments are related to deposition within the Sydney-Gunnedah Basin. Early Jurassic sedimentation began with the onset of regional downwarping of the northeastern Lachlan Orogen to form the Coonamble Embayment of the Surat Basin. Throughout the region Tertiary basalts intrude and have effused over this sedimentary veneer. Airphoto interpretation and systematic traverses have been used to carry out detailed outcrop and float mapping. Subsurface information from geophysics (magnetic and seismic data), lithological logging of core from two drill holes, and evaluation of the logs of several other holes has aided this field mapping, especially in areas of poor exposure. Integration of these techniques has identified several small, though significant, errors in current geological maps of the Ballimore area. Three features of particular geological significance have been uncovered from this study of the Ballimore area;

AUSTRALIAN COAL GEOLOGY

55 (1) An Early Permian breccia which is at least 190m thick was partially penetrated by drilling in Denison Soda DDH3. This breccia does not crop out in the Ballimore area, nor has it been reported in adjacent areas. It probably represents an alluvial fan or talus accumulation at the foot of a latest Carboniferous to earliest Permian half-graben.

(2) At Spicer's Rocks in the south-western corner of the area coal of Permian age, with reported Glossopteris fossils, was mined at the turn of the century. Mapping of the area failed to locate any coal exposure, but a Triassic plant fossil, which has been tentatively identified as Dichroidium, was found in a shaley interbed of the Wollar Sandstone. The Wollar Sandstone crops out in the creek-bed, below the level from which Permian coal was won. The coal probably represents either an inlier of the Permian Dunedoo Formation which has been onlapped by Triassic sediments or a channel, infilled by Triassic sediments, that has been cut into Late Permian strata. (3) XRD analysis indicated that sample BH 10 (a claystone sample from the eastern face of Ballimore Hill) contains dominantly mullite and cristobalite. This suggests that this rock has been subject to elevated temperatures. The heat source which provided impetus for this alteration is probably the burning of a coal seam. Sodium bicarbonate (NaHCO3) rich ground water has been reported from relatively few areas around the world; the Gulf Coast Plain (Foster, 1950), the Otway Basin (Blake, 1989) and the eastern margin of the Great Artesian Basin (Herczeg et al, 1991). NaHCO3 water has been sampled and analysed from five bores in the Ballimore area. A series of weathering and dissolution reactions are proposed to explain the origin of these waters. THE PALAEO-ENVIRONMENTAL DEVELOPMENT OF THE WITTINGHAM COAL MEASURES IN THE MUSWELLBROOK REGION, NSW

S.P. Tamplin, University of Newcastle, 1993. The stratigraphic sequence subcropping in the Muswellbrook area, incorporates the middle to lower portions of the Late Permian, Wittingham Coal Measures of the Singleton Super-Group. This strata is characterised by two constructive coalbearing episodes (Foybrook Formation & Jerrys Plain Sub-Group) which are separated by a significant transgressive event (Archerfield Sandstone). The depositional environments of the Foybrook Formation are considered to evolve stratigraphically upwards from a lower delta plain, characterised by interdistributary bays and distributary channels, to an upper delta plain dominated by highly sinuous meandering rivers. The Archerfield Sandstone represents a prograding beach complex which was deposited during the

regression that followed a brief and almost basin wide marine incursion. The Jerrys Plain SubGroup is a terrestrial succession deposited in a river dominated upper delta plain . The character of the fluvial systems changed from braided channels at the base of the Jerrys Plain Sub-Group to meandering varieties in its middle portions. The elastic sediments of the Foybrook Formation are considered to represent an overall progradational coal-bearing succession, which were deposited as part of a high stand systems tract. Peat accumulation on the coastal plain was favoured during intermittent base-level rises that interrupted the Foybrook Formation's overall progradational development. This relationship is explained in terms of increasing accommodation space. The Archerfield Sandstone together with the Wynn Seam are considered to have been deposited during, and immediately following the maximum flooding event of a transgressive systems tract. Consequently, a systems boundary is inferred to exist in an undefined area below the Wynn Seam. The influx of saline waters associated with the marine incursion resulted in a strong marine signature in the roof of the Upper Wynn Seam, which is interpreted to be almost entirely post-depositional in origin. Due to the presence of either a fresh-water bulge or a high natural levee system, these marine waters had little effect on the sulphur content of the Wynn Seam, immediately beyond the incursion's maximum flooding surface. Following the regression of marine conditions, the Bayswater Seam formed on the broad coastal plain that subsequently developed. Optical analysis suggest that the lower portions of this seam developed under a progressively lowering water table, whereas the upper portions were drowned by a lacustrine transgression. These trends are considered to reflect the development of the Bayswater Seam under initially regressive, and later, transgressive conditions. The role of differential compaction in controlling changes in depositional architecture, depositional environmental and coal bed geometry is also discussed . These influences are especially pronounced in the lower portions of the Foybrook Formation, where S-Z splitting patterns are observed. A MODEL FOR THE DISTRIBUTION OF COAL QUALITY, TYPE AND BREAKAGE CHARACTER IN THE KA TOOMBA SEAM, ILLAWARRA COAL MEASURES, SYDNEY BASIN, AUSTRALIA

L.M. Walsh, Queensland University of Technology, 1993. Increasing demands to optimise production in the coal industry has created interest into controls on coal quality and coal type distribution through a coal seam. Depositional models for the origin of

AUSTRALIAN COAL GEOLOGY

56 coal seams help to explain and often predict this distribution. This study was undertaken to determine the original depositional model fo r the Katoomba seam to explain the variation in coal type and quality seen between two collieries, Clarence and Canyon, which mine this particular seam in the western coalfields of the Sydney Basin. Of concern to both mines was the aspect of coal breakage and fines generation during mining, handling and processing. Therefore a subsidiary study using a single particle breakage test was undertaken to study the breakage characteristics of coal type occurring within the seam. Breakage testing verified that the basal ply of this seam which was a dull high ash coal, was harder to break and produced fewer fine particles as represented by lower T10 values. This differed to the lower ash content, dull banded and dull minor coal type of the main seam ply, which was found to be easier to break. o particular dependence on the orientation of the coal block ie. perpendicular or parallel to the i put energy could be determined from the inpu t energies used in this study. However further work undertaken outside of this study has indicated that with higher energy, the orientation of impact affects coal breakage for different coal types. Fines generation and also breakage characteristics of this particular seam have also been researched involving a petrographic analysis of the fines taken from within the preparation plant, and further along the preparation circuit at the wet and dry filter cake stages. This has determined the fines to be compositionally primarily inertiniterich with some vitrinite. A depositional model for this seam has been proposed as a ombrotrophic bog in a temperate climate. This is supported by the geometry of the deposit and the distribution of ash and coal type. The peat deposit is suggested to have begun in an elongate thin channel and progressively built into a raised bog peat deposit. Clastic influx into this system, which is seen by the presence of claystone bands throughout the seam, decrease up section . The overburden sequence is interpreted to represent a series of overbank or possible crevasse splay deposits in a lower de! ta p lain environment.

THE GEOLOGY OF THE MEANDU COAL DEPOSIT AND THE CENTRAL TAR ONG BASIN, SOUTHEAST QUEENSLAND

Bernadette Michelle Williams, University of Queensland, 1993.

The geology of the central Tarong Basin and the Meandu Coal Mine is presented within this thesis. The Tarong Basin is Carnian in age and formed during the final stage of the Hunter- Bowen Orogeny. The formation of this basin is still presently open to question. The Tarong Beds are the sedimentary units deposited within this basin, and are bounded unconformably by the Boondooma Igneous Complex (west), and to the east by the Maronghi Creek Beds. These three formations are, in part, unconformably overlain by the Main Range Volcanics. The Tarong Beds dominantly consist of coarse conglomerates and sandstones, with minor occurrences of siltstone, claystone, and coal. The sedimentology and stratigraphic studies reveal that the Tarong Beds were deposited within fluviatile and adjacent floodplain environments. A revised facies scheme, composed of eight facies types, was introduced within this thesis. Within these Tarong Beds, Facies 8: Coal and interbedded elastics, was chosen for further study. This study was conducted within the Northwest pit of the Meandu Coal Mine. Lithotypes and macerals were described for samples taken throughout the pit and were found to be highly variably, even within short intervals. The Queen seam (North-west pit) contains mainly thin (to thick), claystone to sandstone partings. One such parting, the E-stone, was logged and described in detail at six locations around the pit. The E-stone is composed of six different lithologies and ranges from less than one metre to greater than seven metres in thickness. Sedimentological and structural data collected during this thesis provide an insight into the apparent formation of the Tarong Basin. Previous models have depicted the basin as forming by downwarp with no faults, or by dextral, strikeslip, pull-apart, faulting. Within this thesis, however, the basin has been reinterpreted as a half-graben, with the fault lying along the eastern margin of the basin.

AUSTRALIAN COAL GEOLOGY