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Walloon Coal

SUMMARIES Maitland-Cessnock-Greta accomodation sedimentation

Chairman Vice-Chairman Honorary Secretary Honorary Treasurer Hon Assistant Treasurer Committee

Honorary Editor

Wes Nichols Bill Hayes Mark Biggs Peter Crosdale John Draper Brian Coxhead Joan Esterle Lloyd Hamilton Ken O'Reilly Ken Preston Warwick Smyth Chris Wall in Jim Beeston

Address for editorial matters: Honorary Editor Australian Coal Geology 8 Lana Street Tarragindi, Qld 4121 beest_on@bigpond.net.au Address for other matters: Mark Biggs Honorary Secretary Coal Geology Group PO Box 225 Moura, Qld 4718 mark.biggs@anglocoal.com.au Published by the Coal Geology Group, © Geological Society of Australia Inc. ISSN 0725-4938 Issued December, 2006 Price to non-members - $10.00 per issue

CONTENTS The Walloon Coal Measures - the latest coal seam gas target (B Anderson, P Crosdale, J Dingwall, G Leblang & S Scott) . . . . . . . . . . . . . . . . . . . . . . . . . .

. 1

The application of TSIM in defining intrusions, structure and lox: a case study at Commodore Mine (A Buck, W Smyth & G Parminter) . . . . . . . . . . . . . . . . . . . 9

SUMMARIES The Maitland-Cessnock-Greta Coalfield and Cranky Comer Basin - Greta Coal Measure sedimentation in a high accomodation setting (A Heeswijck) . . . . . . . . . . . . . . . . 19 Stratigraphic analysis of the Newcastle Coal Measures, Sydney Basin, Australia (M Little)20 Stratigraphic correlation of tuffs in the Newcastle Coal Measures (W Kramer) . . . . . . 21 Stratigraphic correlation of the tuffs of the Wollombi Coal Measures using geochemical fingerprinting (G Weatherall) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

POWERPOINT PRESENTATIONS (on CD) The following are reproductions of PowerPoint presentations made at various venues.

PAPER 1: Coal seam natural gas a major energy for Eastern Australia. Presented by A Lydyard at the GSA Coal Geology Group conference "CSM - is it coal or petroleum?" held in Brisbane on the 16th September, 2003. PAPER 2: Mechanisms of gas storage - Coal vs Petroleum. Presented by P Crosdale at the GSA Coal Geology Group conference "CSM - is it coal or petroleum?" held in Brisbane on the 16th September, 2003. PAPER 3: Coal seam methane: a regional perspective. Presented by J Draper at a Geological Survey of Queensland seminar "Digging Deeper into the Geological Survey of Queensland" held in Brisbane on 19th November, 2003. PAPER 4: Practical application of acoustic scanner data at German Creek Mines. Presented by M Biggs at a Bowen Basin Geologist's Group meeting held at The Curragh Coal Mine on the 15th November, 2002.

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EDITORIAL To say that it has been a while since the last volume of Australian Coal Geology would be an understatement. To say, however, that the Coal Geology Group has not provided quality geological papers during that time could be disputed. Three Bowen Basin Symposium volumes, organised by the Bowen Basin Geologists Group, and underwritten by the Coal Geology Group, have resulted in the release of 111 papers and 49 poster papers to fill the void. The Coal Geology Group was also involved in the fmal production of Geology of Australian Coal Basins published in 1995, producing 41 defmitive papers on Australia's coal geology. I recognise that a lot of papers have been 'lost' to more prestigious journals that promise recognition in a competitive world, and that is quite in order. Australian coal science is exceptional, and deserves all accolades. Australian Coal Geology fills a niche for publication between symposia, for local issues, and welcomes contentious issues. It would like to promise fast publication with minimum hassle. I return to my first statement in this editorial. Only with a sustainable supply can the journal deliver. Over to you. Dr Jim Beeston Honorary Editor Australian Coal Geology

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THE WALLOON COAL MEASURES - THE LATEST COAL SEAM GAS TARGET B Anderson, P Crosdale, J Dingwall, G Leblang & S Scott Anderson, B, Crosdale, P, Dingwall, J, Leblang, G & Scott, S, 2006: The Walloon Coal Measures - the latest coal seam gas target. Australian Coal Geology, 11 , 1- 8. Coal seam gas exploration and appraisal drilling in the Mesozoic Surat Basin has surged during the past 3 years. Prior to late 2000 only one well, a core well, ANU Southeast Teatree #1 had targeted the Late Jurassic Walloon Coal Measures to investigate its coal seam gas potential. Since late 2000 when Queensland Gas Company Limited (QGC) commenced its initial drilling program, 70 core, exploration and appraisal wells, by three different operators, have been drilled targeting the Walloon Coal Measures. Results from these wells have lead to the drilling of five pilot developments to assess the economic validity of the Walloon Coal Measures. Results of wells to date that have been made public indicate that the coals of the Walloon Coal Measures have gas contents between 1 and 12 m3/tonne and saturations between <50 and 100%. Bruce Anderson, Julie Dingwall, and Steven Scott, Queensland Gas Company Peter Crosdale, Energy Resources Consulting Garry Leblang, Integrated Exploration and Mining Services

Geology The Surat Basin is a large intracratonic basin of Mesozoic age covering approximately 300 000km2 of south-eastern Queensland and northern New South Wales (Figure 1). The basin forms part of the larger Great Australian Basin (Green & others, 1997), and interfingers westward across the Nebine Ridge with the Eromanga Basin, and eastward across the Kumbarilla Ridge with the Clarence-Moreton Basin (Exon, 1976).

Triassic to Early Cretaceous periods. The Latest Triassic to Earliest Cretaceous succession in the basin consists of five fining-upwards sedimentary cycles dominated by fluvio-lacustrine deposits (Exon, 1976; Exon & Burger, 1981 ; Day & others, 1983). The lower part of each cycle typically comprises coarse-grained mature sandstone, grading up into more labile sandstone and siltstone, with mostly siltstone, mudstone and coal in the upper part. In the Cretaceous, inundation of the land through an increase in sea level led to deposition of predominantly coastal plain and shallow marine sediments in two cycles.

Basement blocks.consisting of the Central West Fold Belt and the New England Fold Belt limit the basin to the south, while in the north the basin has been eroded and unconformably overlies Triassic and Permian The Middle Jurassic Walloon Coal Measures sediments of the Bowen Basin. form part of the Injune Creek Group and are developed throughout the Surat Basin (Figure 2). It ranges in thickness from less The Surat Basin contains up to 2500m of sedimentary rocks deposited during the Latest than 50m to greater than 450m (Figure 3).

Australian Coal Geology

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The formation attains its maximum thickness in the eastern central region of the basin (Scott & Crosdale, 2000). It thins to the south-west where it on-laps the Walgett Shelf (Green, Carmichael & others, 1997). In the western basin, the environment of deposition of the Walloon Coal Measures changed with the formation becoming coarser, the total sand percentage increasing and the coal volume decreasing to near zero. This change is transitional but by the boundary between the Surat and Eromanga Basins, the Nebine Ridge, the difference is enough for the formation to be renamed the Birkhead Formation (Scott & Crosdale, 2000). In the north-east Surat Basin, the formation was raised to Subgroup status by Jones & Patrick (1981) and, in stratigraphic order, was divided into the Taroom Coal Measures,

Figure 2: Depth to top of Walloon Coal Measures

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Tangalooma Sandstone and Juandah Coal Measures. Green, Hoffmann & others (1997) argued that this division could not be sustained across the entire basin, and, on these grounds, rejected this subdivision. Drilling by QGC confirms Jones and Patrick' s subdivision, at least in the north-eastern Surat Basin. QGC has devised a modified sub-division based on Jones and Patrick' s work (Figure 4). In ascending stratigraphic order, the Walloon Coal Measures have been divided into the Durabilla formation, the Taroom coal interval, Tangalooma sandstone and Juandah coal interval. The main coal bearing units are the Juandah and Taroom coal intervals but the Tangalooma sandstone and Durabilla formation both contain minor coal seams that have not been correlated. There is a difference in seam architecture between seams in the Juandah coal interval. Due to this difference, QGC has also subdivided the Juandah coal interval into upper and lower units dependent on the coal development and composition.

Figure 3: Walloon Coal Measures - thickness

The upper Juandah coal interval is generally composed of thicker and cleaner coal plies, making them a greater target for coal explorers and gas explorers who are intending to utilise horizontal well completions. The lower Juandah and Taroom coal intervals are composed of numerous, thinner coal plies interspersed with soft tuffaceous mudstone, carbonaceous mudstone and siltstone.

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To add confusion to attempts at discriminating the coal-bearing formations in the eastern Surat basin, the overlying Late Jurassic Springbok Sandstone and Westboume Formation also contain, at times, thick, fine-grained, coal-bearing intervals. 300m These coal intervals are not as well developed as those in the underlying Walloon Coal Measures and are generally only well Figure 4: Walloon Coal Measures stratigraphy developed in the north-eastern basin.

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Overall the Walloon Coal Measures comprise very-fine to medium grained, labile, argillaceous sandstone, siltstone, mudstone and coal with minor calcareous sandstone, impure limestone and ironstone. This sedimentology carries through each of the formation' s subdivisions. The formation comprises a series of fining pwards sequences, beginning with a medium to fine grained cross-bedded sandstone, which then fines up into a complex carbonaceous mudstone, mudstone and coal interval; the coal seam.

As mentioned above, the subdivisions of the Walloon Coal Measures are similar to each other, and it was only during Taroom and Juandah coal interval time that the coal systems were stable enough to deposit thick, continuous coal seams. From work carried out so far, no marker beds have been identified, which does compound the difficulty of seam identification. Apart from the thicker coal development within the Macalister Seam, the similarity between each of the subdivisions makes correlation difficult but not insurmountable.

Figure 5: Walloon Coal Measures - net coal thickness

seams and the Taroom coal seams, seam correlation from shallow coal exploration wells is very difficult and mis-correlation between these wells was very common.

Coal geology As mentioned above, coal thickness varies across the basin from east to west. Scott & Crosdale (2000) showed that the thickest deposition of coal was in the north-eastern and central eastern basin. Work carried out by QGC since 2000 has confirmed this. Net coal thickness in the upper and lower Walloon Coal Measures varies from <1 5m to >40m (Figure 5). Seam correlations have been carried out across the entire eastern Surat Basin, using the fully cored and exploration wells drilled by QGC as well as the geophysical logs of petroleum exploration wells and a number of deep coal exploration and stratigraphic wells. Because of the architectural similarity between many of the lower Juandah coal

Many of the coal intervals thicken and thin over very short distances and correlation between widely spaced CSG exploration wells was initially a very inaccurate science. The Juandah coal interval generally comprises six named coal groups or seams. In descending stratigraphic order these are the Kogan, Macalister, Nangram, Wambo, Iona and Argyle seams. The Macalister Seam can occur as two distinctive intervals which have been informally referred to as the Macalister Upper, and Macalister Lower intervals by QGC. The upper Juandah coal interval comprises the Kogan, Macalister Upper and Lower seams, the lower Juandah coal interval comprises the Nangram, Wambo, Iona and

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Figure 6b: Walloon Coal Measures - Inertinite %

Argyle seams. The lower Juandah and Taroom coal intervals are composed of numerous, thinner coal plies interspersed with soft tuffaceous mudstone, carbonaceous mudstone and siltstone.

the thicker Macalister Seam intervals so most analytical work undertaken was of this seam.

From work undertaken by QGC, the coals of the Walloon Coal Measures are composed of predominately vitrinite (77%) with In many areas, erosion by the overlying subordinate amounts of liptinite (19%) and Springbok Sandstone has removed the Kogan only minor amounts of inertinite (4%). Coals Seam. of the upper Juandah interval have marginally less vitrinite (75%) and liptinite (15%) but greater amounts of inertinite ( 10%). The Taroom coal interval generally comprises three named coal groups or seams. In descending stratigraphic order these are The coals of the lower Juandah and Taroom the Auburn, Bulwer and Condamine seams. coal intervals have marginally higher vitrinite (79%) and liptinite (19%) composition with only trace amounts of inertinite (Figures 6a & As mentioned above the coal seams within 6b). the Juandah and Taroom coal intervals have been correlated and named by QGC during its extensive exploration and appraisal program. From a coal seam gas potential the upper Seam nomenclature was devised using local Juandah coals have a marginally greater names and by building on the work capacity to hold gas than the lower Juandah undertaken by Marathon Petroleum and Taroom coals but in many cases these (Australia) Pty Ltd during its shallow lower Juandah and Taroom coals are gas underground coal exploration undertaken saturated or very close to it while the upper during the early 1980s. Juandah coals can be undersaturated. Petrographically the Walloon Coal Measures composition has been known since the early coal exploration era. Swarbrick (1973) described the Walloon Coal Measures coals as perhydrous, typically black, exhibiting a greasy lustre, conchoidal or subconchoidal fracture and a poorly developed cleat. Most of the coal exploration work concentrated on

Coal seam gas potential QGC has drilled 13 fully cored wells to investigate the coal seam gas potential of the Walloon Coal Measures in the eastern Surat Basin. The coal seams intersected by these wells were sampled on a full seam rather than

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Figure 7: Walloon Coal Measures - Gas Content (m /t)

selective basis. Full seam desorption took approximately 80 days.

of CO 2, indicating that late stage desorption of CO 2 is not an issue. The area of interest in the Surat Basin has not been the subject of volcanic activity, and so is not considered prone to CO 2 generation caused by volcanic activity.

Gas content across the seams is very inconsistent. Selective sampling of the seams could provide an incorrect view of the gas content and saturation of the coal measures. After desorption was completed, ply samples Sampling by QGC has shown that the gas were combined to produce composite samples ranges Measures Coal Walloon the content of 3 of the main coal seams. These composite from 1 to 12m /tonne (Figure 7). samples were then analysed for methane adsorption. As well, the intra-seam sediments also contribute and desorb will contain gas, which to the gas resources of the project area. While Overall the upper Juandah coal seams have the highest methane adsorption followed by this gas volume is small when compared to the lower Juandah coal seams and then the that contained within the coal, the thick and Taroom coal seams (Figure 8). This mudstone carbonaceous sequences of difference in the coals' ability to adsorb mudstone that make up the coal intervals coal methane is difficult to explain, as the coals' Taroom and Juandah the both within composition is very similar. As mentioned intervals will contribute significant volumes the of above the vitrinite composition ranges from resources gas overall the of gas to 75 - 80% and this slight variation does not Walloon Coal Measures. explain the large range seen in the gas content. Gas composition of sample taken from the least at Walloon Coal Measures averages Most literature on the subject infers that gas 95% C~, and the balance mostly 2 and is proportional to vitrinite content. content . H C and minor amounts of CO2 2 6 Compositional analysis of gas samples taken This does not seem to be true with coals of the Walloon Coal Measures. If anything, the from late stage desorption and residual gas higher inertinite content of the upper Juandah analysis have not shown substantial amount

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Figure 8: Walloon Coal Measures - Gas adsorption

coal interval seams appear to hold the higher gas content. Another factor influencing the coal seam gas potential of the Walloon Coal Measures is the gas saturation of these coals. The early QGC cores targeted the shallow upper Juandah coal interval seams, mostly seams less than 300m in depth. These coals exhibited low to moderate gas saturations. This low saturation has been attributed to a number of factors including relative proximity to the outcrop, outcrop elevation and the erosive nature of the overlying aquifer.

content and lower gas saturation. These results were obtained from relatively deep wells, which by rights should have had the highest gas contents and saturations of any well drilled up to that time.

Coal composition was not markedly different to any other area of the basin and an explanation for the results is not yet fully understood.

On the other hand, results from wells drilled and cored in the central eastern basin have This decrease in gas saturation of the thicker demonstrated high gas contents and saturations. The coals in this region, which is upper Juandah seams was, initially, a centred on a structural feature called the discouraging revelation. Subsequently the Undulla Nose, are generally higher in gas lower Juandah seams were cored and content and saturation than corresponding demonstrated that an increase in depth, in coals in other parts of the eastern Surat Basin. many cases, lead to an increase in gas saturation. Unfortunately there always seems These coals also exhibit high permeability to be an exception to the rule, and wells cored and have shown to have some free gas in the south-eastern basin not only exhibited trapped within the coal cleats and/or fractures. lower net coal thickness but also lower gas

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Wells within this region have flowed at rates REFERENCES up to 3 000m3/day. Again the coals within the Undulla ose have a composition that is not DAY, R.W. , WHITAKER, W.G., MURRAY, C.G., WILSON, I.H. & GRIMES, K.G., markedly different to any other region of the 1983: Queensland Geology. Geological eastern basin and while net coal thickness is of Queensland Publication, 383. Survey greater than the south-eastern basin, it is not as thick as the north-eastern basin. EXO , .F., 1976: Geology of the Surat Basin, Queensland. Bureau ofMineral Resources, Geology and Geophysics, Across the entire eastern basin, the overlying Bulletin, 166. Springbok Sandstone has irregularly eroded EXO , .F. & BURGER, D., 1981: down into the Walloon Coal Measures, in Sedimentary cycles in the Surat Basin and places eroding down to the top of the global changes of sea level. BMR Journal Macalister Upper Seam and in other areas it ofAustralian Geology and Geophysics, 6, is at least 10 to 15m above the top of the 153- 159. Kogan Seam. GREE , P.M., CARMICHAEL, D.C., BRAIN, T.J., MURRAY, C.G., MCKELLAR, J.L. , BEESTO , J.W. & This is also true on the Undulla ose, wells GRAY, A.R.G., 1997: Lithostratigraphic as close as 500m have shown the removal of units in the Bowen and Surat Basins, up to 15m of section but here the overlying Queensland. In Green, P.M. (Editor): The Springbok Sandstone aquifer does not appear Surat and Bowen Basins, south-east Queensland. Queensland Minerals and to have greatly effected the gas content and Energy Review Series, 41-108. saturation of the upper Juandah coal interval seams. GREE , P.M., HOFFMANN, K.L., BRAIN, T.J. & GRAY, A.R.G., 1997: Project aims and activities, exploration history and geological investigations in the Bowen CONCLUSION and overlying Surat Basins, Queensland. In , Green, P.M. (Editor): The Surat and Bowen Basins, south-east Queensland. Work undertaken by QGC over the past three Queensland Minerals and Energy Review Series, 1-11. years has shown that the Middle Jurassic Walloon Coal Measures contain significant JONES, G.D. & PATRICK, R.B. , 1981: resources of coal seam gas. These resources Stratigraphy and coal exploration geology are contained within up to nine coal intervals of the northeast Surat Basin. Coal within the upper and lower coal measures. Geology, 1 (4), 153-163. SCOTT, S.G. & CROSDALE, P., 2000: The Walloon Coal Measures - The next coal This work has also shown that when wells are seam gas target? APPEA Journal, 40 (1), drilled into these coals, they can produce 86--94. daily gas volumes that can be economically feasible. Permeability testing from wells SWARBRICK, C.F.J., 1973: Stratigraphy and shows that in areas within the eastern basin, economic potential of the Injune Creek fracture stimulation is not necessary to Group in the Surat Basin. Geological Survey of Queensland, Report 79. achieve economic flow rates.

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THE APPLICATION OF TSIM IN DEFINING INTRUSIONS, STRUCTURE AND LOX: A CASE STUDY AT COMMODORE MINE A. Buck, W. Smyth & G. Parminter Buck, A, Smyth, W & Parminter, G, 2006: The application ofTSIM in defining intrusions, structure and LOX: a case study at Commodore Mine, Australian Coal Geology 11, 9- 17. The Thiel Surface Impedance Method (TSIM) has been successfully used in the Walloon Coal Measures in the Moreton Basin for fault location, subcrop location and dyke location at the Commodore Coal Mine. TSIM has been most successful in defining the subcrop or Line of Oxidation (LOX). Accurate delineation of the LOX has resulted in cost savings in exploration drilling. Relatively large resistivity contrasts exist where coal subcrops at the LOX between coal and surrounding sediments. The TSIM measures electric and magnetic fields induced by VLF (very low frequency) radio waves to detect changes in the earth's electrical conductivity. The TSIM method is used to map near surface geological structures. Electrical conductivity changes can be interpreted simply and rapidly, providing a simple means of accurately targeting boreholes. The TSIM method is able to be straightforwardly operated by a single person and consequently is a low cost geophysical exploration tool for LOX definition. It has been used successfully at Commodore Coal Mine to locate coal subcrop LOX, faulting and dykes in the Commodore Seam in the C-Pit and B-Pit.

Adrian Buck, Warwick Smyth, GeoConsult Pty Ltd Graham Parrninter, Roche Mining Pty Ltd

Introduction Geophysical methods have proven to be useful and cost effective in coal exploration. VLF geophysical techniques have developed slowly over several decades (Biggs, 1990), despite repeated success in the coal industry (Thiel, 1990; Nichols, 1995; Nichols, 1996; Nichols & Wilson, 2000). The Thiel Surface Impedance Method (TSIM), developed by Professor David Thiel (Griffith University, Brisbane), is one such technique. At very low frequencies, the surface impedance can be determined by quantitatively measuring the horizontal

electric and magnetic field components. The Thiel Surface Impedance Meter (TSIM), originally described by Thiel ( 1979) for electric wave tilt measurements, measures the horizontal magnetic field using a shielded ferrite cored, multi-tum loop antenna and the horizontal electric field using a centre-fed insulated dipole antenna lying on the surface of the earth. This antenna has been shown to have an input impedance independent of the earth at VLF (Thiel, 1979). Traditionally, horizontal electric field measurements have been made using the staked dipole antenna configuration (Wait, 1997). There has been much discussion in the

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• It can be utilized to minimize drilling literature on how to best measure the costs by better defining targets. 1989; Thiel, & (Wu field electric horizontal Wait, 1989; Thiel & Mittra, 1997; Wait, • It is cheap in comparison to other 1999) with the conclusion being that both the exploration geophysical techniques. staked dipole and the insulated dipole of measurements reliable yield configurations A general renewal of interest by GeoConsult the horizontal electric field. in the technique led to its inclusion for the first time as part of the 2005 exploration The susceptibility to electromagnetic noise, program at Commodore Mine (Figure 1). the reliability of making repeatable measurements, the influence of a strong vertical electric field component and the reliance on a high-input impedance detector system are all important considerations in attempting horizontal electric field measurements at VLF (Wilson & others, 2000). The TSIM 89 model was developed by Energy Control International Pty Ltd under agreement with Griffith University as part of the 1988 NERDDP grant 'Coal seam and strata condition prediction using electromagnetic surface impedance', of which CCPL was a sponsor. The TSIM 91 model was developed in-house by the Radio Science Laboratory of Griffith University with particular application to ice depth profiling (Thiel & eall, 1989; Thiel & others, 1996). TSIM 91 Model is a cheap and seldom utilised instrument outside of Anglos Callide Mine for defining intrusions, structure and LOX during near surface coal exploration programs. Several key feah rres make TSIM an efficient and attractive geophysical technique for coal exploration, resource definition and mine planning: • The method is very afe.

Figure l: Commodore Mine location plan (from Queensland Department of Mines and Energy)

The goal of the Commodore Mine TSIM survey was to reduce drilling costs by limiting the holes required to accurately define the location of the LOX and faulting. In addition to this, the difficult task of delineating several thin in-pit dykes beyond the highwall was attempted. The survey was highly successful, with the LOX, faulting and dykes locations delineated.

TSIM Technique

• It is essentially passive, mea uring the ground' s response to radio wave sources thousands of kilometres away.

TSIM is an electromagnetic geophysical method which employs surface impedance theory. Surface impedance is a localised • Field acquisition can be handled by one measurement of the earth's resistance to the flow of an oscillating current. The resistivity person with completely portable at a point is determined as the ratio of the equipment.

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horizontal electric field to the perpendicular horizontal magnetic field. VLF radio wave transmitters, such as Northwest Cape communication signal, are an ideal source of electromagnetic energy for surface impedance surveys as they represent a powerful uniform signal which penetrates relatively deep into the ground.

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The propagating VLF radio waves have two component parts, electric field (Ex) and magnetic field (Hy) that fluctuate at right angles to each other (Gharibi & Pedersen, 1999). The magnetic component of the source induces a secondary electromagnetic field (Ez and Hz) or eddy current in conductive earth materials (Wilson & others, 2000). The strength of these induced eddy currents in the Earth is a result of lateral resistivity variations (Wilson & others, 2000; Figure 2).

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Surveys comprise lines spaced typically 50m to 100m apart orientated in a direction parallel the VLF transmitter (generally east-west). The TSIM instrument with trailing antenna is traversed taking passive apparent resistivity measurements at a set spacing typically 5m (Figure 4).

Figure 2. Surface impedance (Zs) is a relationship between the electric and magnetic fields induced by VLF radio waves. It is calculated using the above formula. Figure adapted from Gharibi & Pedersen (1999).

Fundamentally, the TSIM measures near surface geologic response to VLF radio waves. Abrupt changes in geology such as intrusions, faults, and LOX produce distinct electromagnetic anomalies that are easily identified using TSIM (Figure 3).

Figure 4. Typical TSIM operation. The TSIM instrument with trailing antenna is traversed taking passive apparent resistivity measurements at a set spacing.

One person can easily manage the field operation of the lightweight battery-powered equipment, making it a very cost-effective and very safe method for surface exploration work.

The TSIM instrument simultaneously measures the electric field (Ex), the Magnetic field (Hy) and the phase difference between the primary transmitter wave and the induced secondary wave.

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From these measurements the surface impedance is calculated and variation identified.

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Qualitative interpretations of geologic features and their locations are made on the curve shape of the apparent resistivity and phase angle. Detailed quantitative modelling of coal depth, thickness and fault orientation is also achievable (Wilson & others, 2000; Gharibi & Pedersen, 1999).

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Commodore Mine The Commodore Mine, 200km west of Brisbane in south-east Queensland is located within 10km of the town of Millmerran (Figure 1). The mine is the sole source of coal to the adjacent Millmerran Power Station. Roche Mining provides a total mine service under contract to the mine owners, Millmerran Power Partners, and are responsible for the management and operation of the mine, including exploration activities. The mine is situated at the western edge of the Moreton basin, in the Cecil Plains sub-basin. The deposit forms part of the Early Jurassic Walloon Coal measures.

At Commodore the coal seam sequence is made up of three main intervals, in descending order (Figure 5):

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Figure 5: Typical stratigraphy of the Commodore Deposit. The target mining horizon is the Commodore Seam (M).

The relatively low dip of the coal seams and the gently sloping topography are responsible for wide zones of coal seam oxidation. The TSIM survey layout was designed with three separate objectives;

1. To define the LOX, 2. To delineate a known structure, 1. The upper group of seams; Domeville (D), 3. To trace several thin dykes from the open pit Gore (G), Koorangarra (K) into the current mine design. 2. The Commodore Seam (M) 3. The Bottom Seam (B).

The upper group of seams (D, G and K) vary from a few thin bands of coal to a banded sequence some metres thick. The Commodore Seam is the main target mining horizon and is composed of 21 coal and stone plies which can be traced across the deposit with confidence.

The location of the survey is illustrated in Figure 6 below. Lines 1-7 were planned in an E-W direction north of Pit C to delineate the LOX with 1-3 lines extended slightly to the west of Pit C to delineate a known fault. Lines 8-11 , 200m in length were planned in an E-W direction north of Pit B to delineate the dykes and devolatilised coal zones.

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Figure 6: Layout of the Commodore Mine and TSIM survey

Results - LOX Survey

Results - fault survey

Several TSIM lines were used at Commodore Mine's C-Pit to refine previous LOX line interpretation and design limits for open cut pit mine planning. The area had been drilled during earlier exploration programs.

Exploration drilling of the area to the west of C-Pit had previously identified a steepening in the base of coal contours. Three TSIM lines were extended to cover this area with the goal of better defining the structure. All three lines over the zone revealed pronounced fault signatures. The location of the fault was well constrained and a minor conjugate fault recognised to the south.

The drilling program established the depth to coal, the base of weathering at a depth of approximately fifteen metres, approximate LOX and structure locations. Each TSIM line across the sparse drill hole defined LOX showed a distinct surface impedance anomaly and allowed for closer definition on the location of the LOX. Figure 7 shows geophysical traces that were used to delineate the LOX line north of C-Pit at Commodore Mine. Interpretation of the geological features was based on phase angle and apparent resistivity anomalies observed along the TSIM traverses.

Results - dyke survey The Commodore deposit is generally free from intrusion, however several less then 1m thick basalt dykes have been encountered across the site, with the greatest concentration occurring in the B-Pit. The zone of devolatilisation extends to approximately lm on either side of the dykes. The dykes are near vertical and intrude all the coal seam. The strike of the dykes in the current strip varies slightly from 300° to 330° magnetic. The dykes had proven difficult to trace on the

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LINE 7 PLOTS PhaseAr,gle 100 Low variable phase angle indicates absence of conductive layer (e.g. Weathered , thin or deep seam)

Ill

Cl)

Consistent trend of increasing phase angle values suggest seam dipping gently east

::I Ill

nl 1/1

CII-

== t

E ns

in c

Phase angle minimum corresponding to offset in apparent resistivity trend, implies

discontinuous coat seam

1- ·-

et 0

Apparent Resistivity

Cl)

300

"011'1 Cl)-

250

> '0 "' -~ Cl)

Cl)

"0 "0

200

"' "0

u Cl)

150

Cl)

100

... -o ...

u "'

..."' "'

t-0

Offset in apparent resistivity trend,

327500

implies discontinuous coal seam such as strong seam oxidation

327550

327600

327650

327700

327750

327850

327800

LINE 7 SECTION G-Seam

Diagrammatic geological cross-section along TSIM Line 7

327500

327550

327600

327650

327700

327850

327800

327750

PL N C,

-..j

N 0 0

New LOX line location from TSIM survey results as much as 40 metres to the west

co 0

-..j

...... c.,,

-..j

......

~q_V /

/ /

0 0

co 0

LINE 6

/ Previous LOX line location based on early drilling

327500

327550

327600

327650

327700

Figure 7. TSIM delineation of Commodore Mine LOX line

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327750

327800

327850

LINE 8 PLOTS Phase Angle

120 100

!II

i:41

...::I 41

!II

ftl !II

41-

--t

E"' :I:

rtJ C 1--

Phase angle displays minimal variation to thin vertical conductive intrusives

E~ 41

Apparent Resistivity

1600

,= E

,:,

.,,

Two typical apparent resistivity dyke features. The dyke is located in a trough between two peaks. The amplitude and width indicate the western dyke is slightty thicker.

400

QI ftl .:!:

'-,:,

1200

'0,:, ftl ... ftl u

1000

QI 41

-o

Strong positive anomaly may indicate edge of large intrusiva body or sill

800

,:, 41 41 ...

u ftl

..,... ftl

1-0

-'1

Low conductivity region

200

"328420

328400

328460

' • 328440

328480

328520

328500

328540

328560

LINE 8 SECTION Diagrammatic geological cross-section along TSIM Line 8 Base of Weathering •••••• ~ ••••••••••... • .• .•••••••••••••• Dyke;

i;s~·tl~;n·.;~ th~ • . .

·················~~---··~---·

observed in highwall no outcrop beyond • due towe

328460

328440

328480

328500

328520

328540

a, <D 0 -..J -..J

'?-~

q_V

~~/

Validation drillhole missed dyke but intersected heat affected coal

LINE 8

a, <D 0 -..J -..J 0 0

328560

./.

a, <D 0 -..J

Dykes less than 1m thick accurately / delineated using TSIM

a, O> 0

a, <D 0 -..J

LINE 9

a, a,

a, <D 0 -..J

ighwall o to the sout

a, ~

/ 328400

328420

328440

328460

'LINE 10 328480

328500

Figure 8. TSIM mapping of Commodore Mine Dyke

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328520

328540

328560

surface and were virtually undetected by exploration drilling. Several TSIM lines were set out to map the direction and extent of two dykes observed in the B-Pit highwall and thought to be striking near perpendicular to the highwall.

drilling. The TSIM technique is easy to administer and provides cheap geophysical data for the identification of near surface shallow geological anomalies.

LIMITATIONS

ACKNOWLEDGMENTS

The TSIM VLF survey method is limited to shallow and near surface deposits. It is estimated that in normal and favourable conditions the technique will detect geological features up to 50m depth of cover.

The authors would like to acknowledge Roche Mining Pty. Ltd. and Millmerran Power Partners for granting permission to publish this paper. The authors would also like to acknowledge the assistance provided by the staff of Commodore Mine during the survey data acquisition and Professor David Thiel for his expertise during the data interpretation.

Despite the spectrum of advanced geophysical techniques currently available Surface impedance proved to be an ideal tool for coal exploration, a number of simple yet for tracing dykes at Commodore Mine. Each effective methods are still being overlooked. The TSIM surface impedance method is line revealed a characteristic and readily continually developing and improving. identifiable signature over the intrusions. Natural radio signals such as lightning are Figure 8 shows the apparent resistivity and being looked at as alternate VLF sources and phase angle anomalies. advanced electrical and magmatic sensing technology is now becoming available. The TSIM interpretation of one 50cm thick These improvements along with enhanced on dyke was confirmed by subsequent validation site data manipulation is making TSIM a drilling. The hole did not intersect the dyke reliable technique for real time identification but, did intersect the heat affected margin of near surface geology. around it.

Investigation of utilising a portable transmitter with variable wave magnitude is underway. This will investigate using the technique to define deeper structures and optimise the orientation of the survey to the geological feature to be defined.

CONCLUSIONS This paper has outlined a case study for a successful and positive interpretation of coal subcrop and LOX, faulting and dykes at Commodore Coal Mine in the Walloon Coal Measures using the TSIM geophysical technique. The TSIM method has again proved to be a significant cost saver in determining target drilling and locating and interpreting concealed intrnsions and structure. In this case the interpretation of the fault and dykes has been confirmed by

REFERENCES BIGGS, M., 1990: Results From Trials of the TSIM Surface Impedance Geophysical technique at Callide Coalfields. In, Bowen Basin Symposium Proceedings, Geological Society of Australia, 181-184. GHARIBI, M. & PEDERSON, L., 1999: Transformation of VLF Data into Apparent Resistivity and Phases. Geophysics, 64(5), 1393-1402. NICHOLS, W., 1995: Location of Coal Subcrop at Callide Coalfields using the TSIM Geophysical Method. In, Bowen Basin

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Symposium Proceedings, Geological Society of Australia, 257-264. NICHOLS, W., 1996: Geophysical trials for Fault Location at Callide Coalfields' Trap Gully Mine, Callide Basin, East Central Queensland. In, Mesozoic Geology of Eastern Australia Plate (Extended Abstracts), Geological Society of Australia, 414-423. NICHOLS, W. & WILSON, G., 2000: Applications of Multiple Geophysical Techniques for the Identification of a Suspected Intrusion at Callide Coalfields. In, Bowen Basin Symposium Proceedings, Geological Society of Australia, 335-342. THIEL, D., 1979: Relative Wave Tilt Measurements at VLF, Geoexploration, 17, 285-292. THIEL, D., 1990: Surface Impedance Changes in the Vicinity of an Abrupt Lateral Boundary at the Earth's Surface. IEEE Transactions on Geoscience and Remote Sensing, 28(4), 500-502. THIEL, D., JAMES, D. & JOHNSON, P., 1996: VLF Surface-Impedance Measurements for Ice-Depth Mapping-An Assessment of some Commonly Encountered Interference Effects. Journal of Glaciology, 42(140), 33- 36. THIEL, D. & MITTRA, R., 1997: Surface Impedance Modelling Using the

Finite-Difference Time-Domain Method. IEEE Transaction on Geoscience and Remote Sensing, 35(5), 1350-1356. THIEL, D. & NEALL, F., 1989: VLF Surface Measurements for Ice Depth Mapping in the Antarctic, Journal of Glaciology, 35(120), 197-200. WILSON, G., THIEL, D. & O'KEEFE, S., 2000: VLF Surface Impedance Modelling Techniques for Coal Exploration. In, Bowen Basin Symposium Proceedings, Geological Society of Australia, 347- 353. WAIT, J.R., 1989: Comments, with reply, on ' electrical field sensors in electromagnetic sounding' by Wu Xiu Wa & and David Thiel. IEEE Transactions on geoscience and remote sensing, 27(6), 789-792. WAIT, J.R., 1997: Horizontal magnetic dipole over an inhomogeneous Earth model with exponential variation in Earth conductivity; discussion and reply, Pure and Applied Geophysics, 149 (4), 793-799. WAIT, J.R. , 1999: Antennas in the geophysical environment, Lecture Notes in Earth Sciences, 83, 10-18. WU, X. & THIEL, D., 1989: Electric Field Sensors in Electromagnetic Soundung, IEEE Transactions on Geoscience and Remote Sensing, 27(1), 24-27.

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THESIS SUMMARIES (Abstracts have been produced here roughly as they appear in their respective theses documents, with minimal editing. Ed.)

MASTER OF SCIENCE

and defined by the Standing Committee on Coalfield Geology ofNSW (1994). A stratigraphic study of the Greta Coal Measures in the Cranky Comer Basin outlier was undertaken by Booker (1950) and Slee (1968).

The Maitland-Cessnock-Greta This present study aims to produce a regional Coalfield and Cranky Corner Basin stratigraphic synthesis of the Greta Coal - Greta Coal Measure sedimentation Measures and its bounding formations. The in a high accommodation setting. study area is confined to the MaitlandBy Aldo Van Heeswijck, University of Newcastle, 1999 The Early Permian Greta Coal Measures contain two fluvial, coarse elastic depositional episodes that formed as a result of extension in the northern Sydney Basin. The coal measures extend along the periphery of the northern Sydney Basin, a sub-basin of the Sydney- Bowen Basin. Clastic sedimentation developed on a broad shelf undergoing thermal subsidence on the margin of a rift flank in the Southern New England Fold Belt (SNEFB). Time equivalents are the Leard Formation and Maules Creek Formation in the Gunnedah Basin, the upper Clyde Coal Measures in the southern Sydney Basin and the intracratonic Ashford Coal Measures in the Ashford Basin. In the Bowen Basin the Reids Dome beds are earlier in age and the Collinsville Coal Measures are later in age. The Markwell Coal Measures in the Myall Syncline are possibly time equivalent (Harrington & others, 1989). Since T.W. Edgeworth David' s (1907) definitive mapping of the Hunter River Coal Measures, academic and commercial study of the Greta Coal Measures and bounding formations has been predominantly confined to the South Maitland Coalfield area. The outcrop of the Greta Coal Measures in the Hunter Coalfield has been recently studied

Cessnock-Greta Coalfield (Jones, 1939) and the Cranky Comer Basin. These regions are currently defined as part of the Newcastle Coalfield in the northern Sydney Basin. The area of study contains proximal to distal sedimentation facies derived from a SNEFB source. A framework of outcrop and borehole data was analysed using sequence stratigraphic principles including parasequence sets and stacking patterns. The pattern of facies development was studied to determine the relationship between sediment supply and accommodation during the development of the Greta Coal Measures and bounding formations . This information leads to the conclusion that the Greta Coal Measures developed after a fall in relative base level exposed a broad marine shelf. A large sediment supply and close proximity to the hinterland saw braidplain fans prograde in two events over this coastal plain. In regions of low fluvial deposition between fan lobes, peat swamps in a high accommodation rate setting developed thin, isolated coal seams. As relative base level rose, the accommodation overfilled and a transgressive surface developed. An areally extensive peat swamp formed a relatively thick coal seam. A continued rise in relative sea level produced a backstepping estuarine shoreline facies and subsequent cessation of sub aerial deposition.

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Palaeontological, palynological and radiometric dating was compiled to constrain the time of events. Due to a lack of suitable material within the Greta Coal Measures in the study area the time span of deposition is subjective. Radiometric dates infer a hiatus at the Dalwood Group and Greta Coal Measures boundary. A diachronous interval occurs at the top of the flu vial Greta Coal Measure sediments between Cessnock and Muswellbrook. This diachronism is supported by palynological stage ages for the Greta Coal Measures in the Newcastle Coalfield and the Hunter Coalfield.

BScHONOURS

was first necessary to conduct an accurate regional correlation of the complete Newcastle Coal Measure strata, and then to refine the existing stratigraphic terminology. Stratigraphic revision of the Newcastle Coal Measures has been conducted by the correlation of coal and tuff horizons across a framework grid of 13 7 stations (boreholes and outcrop) over 1000km2 . A new stratigraphy is proposed using six regional tuffs as formation boundaries and formations. The regional tuffs are the only lithology that divides the coal seams on a regional basis and no elastic units divide the coals over the entire study area.

These formation status tuffs divide the intervening coal, conglomerate, sandstone and shale into an additional seven formations, dividing the Newcastle Coal Measures into a total of thirteen formations. All the coal Murray Paul Little, University of Newcastle, between each tuff is named as a single member. Thirty-eight conglomerate/ 1998 sandstone members have been identified with nine of these, from the newly named The non-marine Newcastle Coal Measures Tulootaba and Bunya Bunya Formations, not (up to 400m thick) formed during the Late previously recognised in older stratigraphic Permian Sydney Basin, a tectonically active divisions. foreland basin. The Newcastle Coal Measures consist of a succession of coal, conglomerate, sandstone, shale and numerous tuffs. The The Newcastle Coal Measures formed in an presence of regional tuffs, in addition to alluvial environment where fluvial systems thinner tuffs that occur within coal seams, (conglomerate, sandstone & shale) and peat provided a means to conduct high resolution mires (coal) accumulated contemporaneously. lithostratigraphic and chronostratigraphic The coeval relationship between fluvial regional correlation. systems and peat mires resulted in a complex splitting pattern of the coal seams. The fluvial These correlations also provided the basis for conglomerate/sandstone units are an excellent opportunity to compare the value multi-channel, vertically and laterally amalgamated channel systems up to 109m of lithostratigraphy to that of sequence stratigraphy in proximal non-marine foreland thick and 16km wide, and show minimal basin strata. The study also aimed to provide erosion of underlying coal seams. a depositional model for entire Newcastle Coal Measures based on architectural element Fluvial styles changed from dominantly analysis, coal characteristics, provenance sandy-meandering and sandy-braided analysis and the regional correlations. systems, in the lower Newcastle Coal Measures, to coarse-grained braided river To enable a detailed sequence stratigraphic systems in the middle to upper Newcastle analysis of the Newcastle Coal Measures it Coal Measures. The change in fluvial style is

Stratigraphic analysis of the Newcastle Coal Measures, Sydney Basin, Australia

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associated with an upward increase in mean maximum clast size, proportion of gravelly facies and decrease in shaly facies. The coeval relationship between fluvial systems and peat mires is significant for sequence stratigraphic interpretation, as this relationship indicates that the thick conglomerate/sandstone units are not incised-valley systems, and therefore the base of these units are not sequence boundaries.

The high accommodation rate and overwhelming sediment supply resulted from the proximity of thrust fronts in the New England Fold Belt and the Offshore Uplift. In such a high accommodation setting sequence stratigraphy does not offer an alternative method of stratal correlation for the Newcastle Coal Measures. Lithostratigraphic control provided by tuff markers permits the most effectjve method of correlation and interpretation in the Newcastle Coal Measures.

Preliminary non-marine sequence stratigraphic models predicted that systematic Stratigraphic correlation of tuffs in changes in the arrangement of fluvial the Newcastle Coal Measures channels, provenance, and coal seam distribution would enable the identification of Wendy Kramer, Newcastle University, 1999 sequences and systems tracts in non-marine strata. Four widespread tuffs of the Newcastle Coal Measures (NCM) have been studied extensively in order to determine whether However, such systematic changes do not each had a geochemical signature useful for occur in the Newcastle Coal Measures and regional correlation. An economic aspect to therefore these preliminary non-marine the study is the more efficient identification sequence stratigraphic models are not appropriate for the Newcastle Coal Measures. of the coal seams associated with the tuffs. In the quest to correlate the tuffs, the source of Variation in the proportion of epiclastic sediment in coal seams is the best indicator of Late Permian volcanism, pyroclastic depositional processes and environment of accommodation changes in the Newcastle Coal Measures. Changes in the proportion of deposition of the ash were studied. Alteration of tuffs to clays and the implications of epiclastic sediment in coal seams indicates diagenetic and environmental conditions were that the Newcastle Coal Measures formed a also investigated. broadly and slowly varying trend from first stable, then increasing to high, and then later Tuffs used to geochemically correlate the decreasing accommodation conditions. NCM have been altered to bentonites of mixed layer illite-smectite composition. Alteration has been identified by core The Newcastle Coal Measures represent a sequence stratigraphic end member example logging, thin section examination, scanning electron microprobe studies and confirmed by where sequence boundaries, incised-valleys, and major flooding surfaces have not formed. X-ray diffraction. Diagenesis has resulted in the production of interlayered illite-smectite The lack of sequence boundaries is with illite concentrations of 62- 78%. interpreted as the result of the Alteration is initiated by an increase in accommodation rate always being positive, and the rate of sediment supply being always temperature in the early diagenetic zone. greater than the rate of accommodation The thick interseam tuffs of the NCM were increase, resulting in the absence of major sampled from four cores and have been flooding surfaces. In addition, the high correlated over a distance of 47km. Trace and subsidence rate was able to counter any major element concentrations determined by eustatic falls.

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X-ray fluorescence were subjected to step-wise discriminant analysis. The elements that serve as the best discriminators of chemical composition between tuffs are Y, Cl, Cr, S, P, Ga, Ti, Zn, Hi, V. The geochemical signature improved once the altered samples were removed from the data set and separation of the four tuffs on territorial maps becomes clearer. It is noted how the immobile elements Ti02, Y and Ga feature highly when chemically correlating the altered tuffs. This directly reflects other elements being mobilized during alteration and indicates that geochemical correlation of the tuffs of the NCM is successful regardless of extent of alteration.

The tuffs were deposited in a lower delta plain environment. The most widespread facies in this environment are the interdistributary bays. Most deposition occurred here and the fact that the interdistributary bay deposits often have peat swamps associated with them helps explain why there is a coal-tuff association in the NCM.

Major and trace element data acquired by X-ray fluorescence and neutron activation analysis have been applied to various magmatic discrimination models. The elemental data suggest the tuffs are of rhyodacitic to dacitic composition and of calc-alkaline magmatic affinity. Immobile element ratios have constrained the Late Permian volcanism to that of a volcanic arc setting possibly associated with an active continental margin.

Limited work has been carried out on the Wollombi Coal Measures (WCM) and as such there is little knowledge on the lateral continuity of the tuffs and coal layers within the sequence.

Stratigraphic correlation of the tuffs of the Wollombi Coal Measures using geochemical fingerprinting Glyn D. Weatherall, University of Newcastle, 1999

There are many similarities between the stratigraphy of the WCM and that of the Newcastle Coal Measures, and as such the WCM are believed to be the northern extent of the Newcastle Coalfields.

Geochemical studies were carried out to determine if the tuffs of the WCM carried unique and identifiable geochemical fingerprints, thus enabling correlation not only within the Hunter coalfield but south into the Newcastle coalfields and potentially the Western coalfields. The determination of a geochemical fingerprint wi 11 lead to a better understanding of the WCM and its lateral continuity and allow more accurate The tuffs in this study have been deposited by assessment of its coal reserves, as well as ash fall and ash-cloud mechanisms associated employing a new me~ns of exploration for with a pyroclastic flow. Mesoscopic and thin not only coal, but potentially other section analysis of the tuff rules out earlier economically significant reserves. thoughts that deposition was by ash fall alone. Other pyroclastic depositional Determination of depositional environment, processes were possibly involved but settling potential source region and magma affinities in water and resedimentation may have were used to complement the geochemical removed vital structures indicative of flows fingerprint obtained. Magnetic susceptibility or surges. studies were carried out to ascertain if a The source of volcanism has not been constrained with no clear evidence of late Permian 'root zones ' in the southern New England Fold Belt. The Offshore Uplift, east of the present coastline, is still a possible source with fallen tree trunks and volcanic ash thicknesses indicative of a source to the east.

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magnetic signature could be paired with the geochemical signatures obtained and since very weak signatures were received, no further magnetic studies were carried out. Samples from tuffs of four cores from the Wollombi Coal Measures, DMB2, DMB4R, DMDCKl O and DMDCKll, were collected and analysed for major and trace elements by X-ray fluorescence. These were subjected to stepwise, discriminant analysis to determine the most powerful grouping of elements which would allow the differences in chemistry to be identified. The discriminant analysis revealed that for the WCM, V, Th, Fe, U, Zn, Pb, Cr and Ca listed in order of their relative strength to discriminate amongst the tuffs as a group account for all but 1% of the variance existing within the tuffs. Territorial maps indicate the discriminant model is very effective in correlating between the tuffs in the WCM and the NCM and that tuffs of the late Permian Wollombi Coal Measures (WCM) of the Hunter Coalfields can be correlated with the Awaba, Wamers Bay, Mt Button and Nobbys tuffs in the Newcastle Coal Measures (NCM). Both petrographic and geochemical data indicate that the tuffs are calc-alkaline, have dacitic-rhyodactic compositions and are derived from a normal continental arc setting. Subduction-related attributes of the tuffs include enrichment in the light rare earth elements (LREE) and moderate depletion of the heavy rare earth elements (HREE) and increases in the high field strength elements (HFSE) (Nb, Ta, Zr, Hf and Ti).

The similar REE and trace element data obtained from tuffs indicate that they were sourced from the same region which appears to be off the present coastline, not the New England Fold Belt as previously thought. The source is considered to be the Offshore/Northumberland Ridge. Palaeoenvironment reconstruction based on maceral, core-logging and vertical profile analysis reveals that the tuffs were deposited in intermittently, dry, forested swamps. Examination of depositional structures and features in core and petrographic evidence, shows that the tuffs were transported primarily by surge mechanisms. The results of this study indicate that the tuffs of the WCM are correlatable, not only across the Hunter Coalfield but also into the Newcastle Coalfield, and potentially the Western Coalfields. The geochemistry, magnetic, petrographic and palaeoenviron ment studies indicate that the tuffs of the WCM are more closely related to their correlatives in the NCM than previously thought, and the results will lead to a better understanding of the formation of the coalfield, by understanding of stratigraphy, deposition and environmental factors. The results demonstrate the presence of a unique and identifiable geochemical fingerprint of the tuffs for the WCM, and provide an additional tool for the correlation of tuffaceous bands in coalfield and tracking and understanding the evolution and relationships of other igneous derived bodies.

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NOTES

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NOTES

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NOTES

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