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FIELD GEOLOGIST'S GUIDE TO LITHOSTRATIGRAPHIC NOMENCLATURE IN AUSTRALIA

GEOLOGICAL SOCIETY OF AUSTRALIA STRATIGRAPHIC NOMENCLATURE COMMITTEE Convener: H.R.E. Staines July 1984

CONTENTS Page CHAPTER 1

INTRODUCTION

^CHAPTER 2

P R I N C I P L E S OF S T R A T I G R A P H I C C L A S S I F I C A T I O N

A. B. C. D.

General Categories of Stratigraphic Classification Distinguishing Terminologies for each Category Chronostratigraphic and Geochronologic Units

^CHAPTER 3 A. B. C. D. E. F. G. H. J. K. L. M. N.

Definitions Procedures for Establishment and Description of Stratigraphic Units Special Requirements for Establishment and Description of Subsurface Units Publication Priority Synonymy Revision or Redefinition of Previously Established Units Subdivision Change in Rank Reduction in Number of Names through Correlation Uncertainty in Assignment Abandoned Names Duplication of Names

^CHAPTER 4 A. B. C.

F. G.

L I T H O S T R A T I G R A P H I C UNITS

Purpose of Lithostratigraphic Classification Definitions Kinds of Lithostratigraphic Units Procedures for Establishing Lithostratigraphic Units Procedures for Extending Lithostratigraphic Units Lithostratigraphic Correlation Naming of Lithostratigraphic Units Revision of Lithostratigraphic Units

CHAPTER 6 I. 2.

STRATOTYPES

Definitions Stratotypes in Definition of Stratigraphic Units Requirements for Stratotypes

^CHAPTER 5 A. B. C. D. E.

DEFINITIONS AND P R O C E D U R E S

3 4 4 4 6 6 7 8 8 9 9 9 9 9 10 10 10 10 12 12 13 13 15 15 15 16 20 21 21 24

AUSTRALIAN PROCEDURES

Administrative Structure Reservation of Names for Proposed Units

25 25

Abridged (with notations added) from the International Stratigraphic Guide, with the permission of the publishers, John Wiley & Sons, New York

ii.

Page 3. 4.

A p p r o v a l of D e f i n i t i o n s of U n i t s b e f o r e P u b l i c a t i o n C e n t r a l R e g i s t e r of S t r a t i g r a p h i c N a m e s

FIGURE 1

TABLE

26 26

I l l u s t r a t i o n of d i f f e r e n c e s i n p o s i t i o n in a s t r a t i g r a p h i c s e c t i o n o f d i v i s i o n p o i n t s f o r d i f f e r e n t p r o p e r t i e s or a t t r i b u t e s of strata

(a)

U n i t - s t r a t o t y p e and b o u n d a r y - s t r a t o t y p e s f o r a lithostratigraphic unit

(b)

Boundary-stratotypes for chronostratigraphic units

S i g n i f i c a n c e of l i t h o s t r a t i g r a p h i c u n i t s i n d e c i p h e r i n g geologic history

(a)

Specimen d e f i n i t i o n card

(b)

Specimen definition card (continued)

P r o c e d u r e f o r r e s e r v i n g , d e f i n i n g and p u b l i s h i n g s t r a t i g r a p h i c names

S u m m a r y of c a t e g o r i e s and u n i t t e r m s i n s t r a t i g r a p h i c classification

Chapter One INTRODUCTION

Stratigraphic classification, including the identification, naming and definition of stratigraphic units, is an integral part of geology. In Australia, stratigraphic nomenclature has been regulated by the Australian Code of Stratigraphic Nomenclature (ACSN). The Code was published first in 1950 (Australian Journal of Science, vol. 12, pt 5, pp. 170-3), and reached a fourth edition in 1964, which was reprinted, with corrigenda and additional notes, in 1973 (Journal of the Geological Society of Australia, vol. 20, pt 1, pp. 105-112). In 1976 the I n t e r n a t i o n a l Stratigraphic Guide: A Guide to Stratigraphic Classification, Terminology and Procedure' was published for the International Subcommission on Stratigraphic C l a s s i f i c a t i o n (a subcommission of the Commission on Stratigraphy of the International Union of Geological Sciences). In August 1977 the Stratigraphic Nomenclature Committee (SNC) agreed to recommend to the Council of the Geological Society of Australia that the International Stratigraphic Guide (ISG) be adopted in toto as a replacement for the 4th edition of the Australian Code of Stratigraphic Nomenclature. Council, after considerable discussion within the Society, agreed to this recommendation at its meeting in August 1978. It also agreed to the production of a booklet incorporating chapters 2-5 of the International Stratigraphic Guide, supplemented by further chapters relating to Australian interpretations and procedures. This publication is the result. However, the chapters from the ISG are here abridged, and certain sections of the ISG are omitted. For full treatment of the subjects of these chapters the corresponding section of the ISG should be consulted. The principal purpose of a code or guide for stratigraphic nomenclature is to bring order and precision into the use of stratigraphic names. Although the ISG acknowledges that both formal and informal names in the binomial style appear in the literature, by far the best scheme is to have a single system of capitalised formal lithostratigraphic names. The Stratigraphic Nomenclature Committee maintains that to admit a second category of informal names, undefined and unsystematic, is to undermine the system that has served Australian geologists well for thirty years. Authors are urged to avoid the use of informal names that could be read as formal names, and editors of scientific journals are urged not to accept such informal names in papers submitted to them. The only special case to which this stricture is not intended to apply is the informal term '... beds' (ISG, 5 . C . 4 , p 17). New names should be proposed only when there is a clear need for them. E v e r y field geologist, before taking steps to establish and name a new unit, should carefully examine whether adding another name to the 23 000-odd Australian lithostratigraphic names already recorded will in fact improve the understanding of the geology of the area he has mapped. It should be noted that the Field Geologist's Guide deals only with lithostratigraphic nomenclature. Biostratigraphic and chronostratigraphic nomenclature are not administered by the Stratigraphic Nomenclature Committee. For these subjects chapters 6 to 8 of the International Stratigraphic Guide should be consulted. It should also be noted that the nomenclature of igneous and metamorphic rock units is excluded from this volume. Lengthy consideration has been given by the Stratigraphic Nomenclature Committee to this aspect of lithostratigraphic nomenclature, but it has proved difficult to produce a system of terminology that is widely accepted amongst Australian geologists. Consideration of the subject has also continued at international level, through the International Subcommission on Stratigraphic Classification.

Introduction

The A u s t r a l i a n C o m m i t t e e hopes t o produce a s u p p l e m e n t a r y p u b l i c a t i o n d e a l i n g w i t h igneous and m e t a m o r p h i c rock u n i t n o m e n c l a t u r e , w h i c h w i l l t a k e i n t o a c c o u n t r e c e n t i n t e r n a t i o n a l c o n t r i b u t i o n s on the subject- In the m e a n t i m e the r e c o m m e n d a t i o n s o f the present v o l u m e should be f o l l o w e d as f a r as they can be applied t o igneous and m e t a m o r p h i c r o c k units. P r o p e r observance of the provisions of the A C 5 N r e q u i r e d , and of t h e ISG r e q u i r e s , a c e n t r e w h e r e a l l published and proposed s t r a t i g r a p h i c names are r e c o r d e d f o r the use of a l l geologists. To m e e t this need the C e n t r a l R e g i s t r y of t h e B u r e a u of M i n e r a l Resources has m a i n t a i n e d since 1949 t h e C e n t r a l R e g i s t e r of S t r a t i g r a p h i c N a m e s , w h i c h is a r e g i s t e r and c a r d index of a l l published s t r a t i g r a p h i c names having the b i n o m i a l f o r m : geographic name and l i t h o l o g i c a l , or r a n k , t e r m . Since 1979 r e f e r e n c e s t o names f r o m c u r r e n t l i t e r a t u r e have been r e c o r d e d in t h e BMR's c o m p u t e r data base. P r e v i o u s l y - i n d e x e d i n f o r m a t i o n is being t r a n s f e r r e d t o the c o m p u t e r system as resources p e r m i t . The R e g i s t r y also m a i n t a i n s an index of approved d e f i n i t i o n s of s t r a t i g r a p h i c units and of names reserved p r i o r to p u b l i c a t i o n (see C h a p t e r 6). C h a p t e r s 2-5 consist of e x t r a c t s f r o m the I n t e r n a t i o n a l S t r a t i g r a p h i c G u i d e (in t h i s t y p e face) w i t h i n t e r p o l a t e d N o t e s (in i t a l i c s ) c o m p i l e d by t h e S t r a t i g r a p h i c N o m e n c l a t u r e C o m m i t t e e . The N o t e s c o n s t i t u t e a s u p p l e m e n t a r y set of g u i d e l i n e s , t o be read in c o n j u n c t i o n w i t h t h e I n t e r n a t i o n a l S t r a t i g r a p h i c Guide. They are i n t e n d e d t o assist in m a i n t a i n i n g a measure of c o n t i n u i t y of usage in the change f r o m the f o u r t h e d i t i o n of the A u s t r a l i a n Code of S t r a t i g r a p h i c N o m e n c l a t u r e to t h e I n t e r n a t i o n a l S t r a t i g r a p h i c Guide. Some of the N o t e s a m p l i f y or give a p a r t i c u l a r slant or emphasis t o s p e c i f i c p r o v i s i o n s of t h e ISG, others r e c o m m e n d dissent f r o m or m o d i f i c a t i o n of provisions of t h e ISG; some are concerned w i t h p r a c t i c e r a t h e r than p r i n c i p l e . I t is r e c o m m e n d e d t h a t w h e r e t h e r e is v a r i a n c e these Notes t a k e precedence over t h e ISG. Three sources have been d r a w n on in c o m p i l i n g the N o t e s : (i)

the

fourth

edition

the

Australian

Code

Stratigraphic

Nomenclature (ii)

the I n t e r n a t i o n a l S t r a t i g r a p h i c Guide

(iii)

decisions of the S t r a t i g r a p h i c N o m e n c l a t u r e C o m m i t t e e t o be s t i l l r e l e v a n t f o l l o w i n g the a d o p t i o n of t h e ISG.

considered

A b b r e v i a t i o n s in the t e x t are as f o l l o w s : GSA

G e o l o g i c a l Society of A u s t r a l i a

ACSN

A u s t r a l i a n Code of S t r a t i g r a p h i c N o m e n c l a t u r e

SNC

Stratigraphic Nomenclature Committee

ISG

I n t e r n a t i o n a l S t r a t i g r a p h i c Guide

^ e c f e r e n c e s such as '5.C,4» r e f e r I n t e r n a t i o n a l S t r a t i g r a p h i c Guide.

to c h a p t e r , s e c t i o n ,

and s u b - s e c t i o n

the

n -i , P ? ™ i 8 S l o n c h 8 S b e e n g i v e n b y t h e Publishers of t h e I n t e r n a t i o n a l S t r a t i g r a p h i c Guide, John Wiley & Sons, to r e p r o d u c e e x t r a c t s f r o m C h a p t e r s 2-5 of t h a t p u b l i c a t i o n on p a y m e n t of a s m a l l r o y a l t y . T h a t permission is g r a t e f u l l y a c k n o w l e d g e d . We are 'also indebted to the past and present C h a i r m e n of t h e I n t e r n a t i o n a l S u b c o m m i s s i o n on S t r a t i g r a p h i c C l a s s i f i c a t i o n (ISSC), H . D . Hedberg and A . Salvador, f o r m a k i n g t ^ n e T e s s a r v y ne a r r a n g e m e n t s w i t h the publishers of t h e ISG. cessary As t h i s Guide is put i n t o use in A u s t r a l i a , i t w i l l u n d o u b t e d l y b e c o m e a p p a r e n t hat i m p r o v e m e n t s are r e q u i r e d . C o m m e n t s and suggestions w i l l be w e l c o m e d , and should be f o r w a r d e d to the Convener of the S t r a t i g r a p h i c N o m e n c l a t u r e C o m m i t t e e

Chapter Two PRINCIPLES OF STRATIGRAPHIC CLASSIFICATION

GENERAL

T h e w h o l e E a r t h is s t r a t i f i e d , in a broad sense, so t h a t a l l rocks and a l l classes of r o c k s - s e d i m e n t a r y , igneous, and m e t a m o r p h i c - f a l l w i t h i n the scope of s t r a t i g r a p h y and of stratigraphic classification. R o c k s t r a t a have many d i f f e r e n t p r o p e r t i e s . I t is possible t o classify s t r a t i f i e d r o c k s a c c o r d i n g t o any of t h e i r p r o p e r t i e s : l i t h o l o g y , fossil c o n t e n t , m a g n e t i c p o l a r i t y , e l e c t r i c a l p r o p e r t i e s , s e i s m i c response, c h e m i c a l or m i n e r a l o g i c a l c o m p o s i t i o n , and many o t h e r s . R o c k s t r a t a can also be c l a s s i f i e d a c c o r d i n g t o such a t t r i b u t e s as t h e i r t i m e of o r i g i n or t h e i r e n v i r o n m e n t of genesis. T h e s t r a t i g r a p h i c p o s i t i o n of change f o r any one p r o p e r t y or a t t r i b u t e does not n e c e s s a r i l y c o i n c i d e w i t h t h a t f o r any o t h e r . C o n s e q u e n t l y , u n i t s based on one p r o p e r t y do n o t g e n e r a l l y c o i n c i d e w i t h units based on a n o t h e r , and t h e i r boundaries not u n c o m m o n l y c u t across each o t h e r . T h e r e f o r e , i t is not possible to express w i t h a single kind of s t r a t i g r a p h i c u n i t the s t r a t i g r a p h i c changes i n all d i f f e r e n t p r o p e r t i e s or a t t r i b u t e s ; a d i f f e r e n t set of u n i t s is needed f o r each (see F i g u r e 1).

BIOSTRATIGRAPHIC UNITS

Foraminifers Mollusks

0) JO

E D 0) c £

<o E d <D LoL. XI

GEOPHYSICAL UNITS Spores and Pollen Zone S

Magnetic Reversals 0)

03 CO UJ cc 111 CO 9)

tf>

o E

LoL o

E 00

o 1j_ < c o C O

(/> UJ CC

(/)

« <0

oL U

F i g u r e 1. I l l u s t r a t i o n of d i f f e r e n c e s in p o s i t i o n in a s t r a t i g r a p h i c s e c t i o n of d i v i s i o n p o i n t s f o r d i f f e r e n t p r o p e r t i e s or a t t r i b u t e s of s t r a t a .

Principles of Stratigraphic Classification

CATEGORIES OF STRATIGRAPHIC CLASSIFICATION

Rock strata may be classified into many d i f f e r e n t categories, each of which needs its own distinctive units. The units of the following three categories are the best known and the most widely used: 1.

Lithostratigraphy - that element of stratigraphy which is concerned with the organization of strata into units based on their lithologic character.

Biostratigraphy - that element of stratigraphy which is concerned organization of strata into units based on their fossil content.

Chronostratigraphy - that element of stratigraphy which is concerned with the organization of strata into units based on their age relations.

DISTINGUISHING TERMINOLOGIES FOR E A C H C A T E G O R Y

with

the

For lithostratigraphy and chronostratigraphy the numerous terms represent d i f f e r e n t hierarchical ranks; for biostratigraphic units they result from the recognition of various kinds of biozones. For the units of newer or less used categories, only very simple terminologies (commonly zones of certain kinds) have been used thus far, but it may be expected that more elaborate schemes for some of these (e.g., magnetic polarity) may be developed before long. Table 1 gives terms here recommended for various stratigraphic categories. D.

CHRONOSTRATIGRAPHIC A N D G E O C H R O N O L O G I C UNITS

Each interval of stratified rocks represents a certain interval of geologic time. Accordingly, each chronostratigraphic unit (interval of rock strata) has a corresponding geochronologic unit (interval of geologic time). Table 1 summarizes these units. Because geochronologic units are units of geologic time - an intangible property - while stratigraphic units are tangible material units composed of rock strata, geochronologic units are not in themselves stratigraphic units. To illustrate the d i f f e r e n c e , a chronostratigraphic unit can be likened to the sand that flows through an hourglass during a certain interval of time, while the corresponding geochronologic unit can be compared to the interval of time during which the sand flows. It may be said that the duration of the sand flow measures a certain interval of time - an hour, for instance - but the sand itself cannot be said to be an hour. Note I. Geochronologic and chronostratigraphic terms. 'Early1, 'Middle', and 'Late' are used to describe epochs in the Palaeozoic and Mesozoic Eras. fLower', 'Middle', and 'Upper' describe the corresponding series. The Stratigraphic Nomenclature Committee recommended in 1972 that 'Early', 'Middle', and 'Late' be used for time (geochronologic) terms rather than 'Lower', 'Middle', and 'Upper'. It was intended that the latter group of terms be used in referring to time-rock (chronostratigraphic) units. The Committee also recommended that all of these terms be formalised by capitalisation of the initial letter. Subsequent discussion indicated, however, that because of the difficulties of global correlation, it is not possible to unequivocally apply formal chronostratigraphic terms to Australian sequences. Informal usage, i.e. with lower case initial letters, is therefore allowable for such references (and is in fact preferable where exact correspondence of units cannot be demonstrated). Care should be taken, however, to avoid inadvertent formalisation, which may occur (i) when the name is typed completely with capitals, or (ii) in written reporting of an oral presentation. Note 2. Abbreviation of 'lower1. The abbreviation 'L' or T for 'lower' should not be used because the letter can also stand for 'late'. In some contexts it may not be possible for the reader to determine which is meant.

Summary of categories and unit t e r m s

T a b l e 1. S u m m a r y of c a t e g o r i e s and u n i t t e r m s in stratigraphic classification*

Stratigraphic Categories

Principal Stratigraphic Unit-Terms

Lithostratigraphic

Group Formation Member Bed(s)

Biostratigraphic

Biozones Assemblage zones Range zones (various kinds) Acme-zones I n t e r v a l zones O t h e r kinds of , biozones

Chronostratigraphic

Other stratigraphic categories (mineralogic, e n v i r o n m e n t a l , seismic, magnetic, etc) *

Eonothem Erathem System Series Stage Chronozone

Equivalent Geochronologic Units Eon Era Period Epoch Age Chron

Zone ( w i t h appropriate prefix)

If a d d i t i o n a l ranks are needed, p r e f i x e s Sub and Super may be used w i t h u n i t - t e r m s when a p p r o p r i a t e , although r e s t r a i n t is r e c o m m e n d e d t o avoid c o m p l i c a t i n g the n o m e n c l a t u r e unnecessarily.

Chapter

Three

D E F I N I T I O N S A N D PROCEDURES

DEFINITIONS

1. Stratigraphy, from the Latin stratum and the Greek graphia, is literally the descriptive science of strata and is used here simply as the science of rock strata. All classes of rocks - igneous and metamorphic as well as sedimentary, unconsolidated as well as consolidated - fall within the general scope of stratigraphy and stratigraphic classification. Some nonstratiform rock bodies are considered under stratigraphy because of their association with or close relation to rock strata. 2. Stratum. A geologic stratum is a layer (a generally tabular body) of rock characterized by certain unifying characters, properties, or attributes that distinguish it from adjacent layers. 3. Stratigraphic Classification is the systematic organization of the Earth's rock strata, as they are found in their original sequence, into units with reference to any of the characters, properties, or attributes that rocks may possess. 4. Stratigraphic Unit. A stratigraphic unit is a stratum or assemblage of adjacent strata recognized as a unit (distinct entity) in the classification of the Earth's rock sequence, with respect to any of the many characters, properties, or attributes that rocks possess. Stratigraphic units based on one character will not necessarily coincide with those based on another; it is therefore essential that different terms be used for each so that their named units can be distinguished from each other. 5. Stratigraphic Terminology deals with the unit terms used in stratigraphic classification, such as formation, stage, biozone. It can be either formal or informal. Note 3. Formal and informal lithostratigraphic units. The ISG distinguishes between formal and informal lithostratigraphic units (3.A.5, p. 6; 5.C.1, p. 16; and 5.C.S, p. 19), but most of the examples of informal units constitute such casual usage that they do not fall within the definition of 'stratigraphic nomenclaturef as defined in 3.A.6 (p. 7). However, the second paragraph of 5.C.8 (p. 19) appears to acknowledge that the binomial form of a stratigraphic name may be used informally, in which case the lithologic term is not capitalised. The Stratigraphic Nomenclature Committee considers that there is no place in the geological literature for a dual system of lithostratigraphic nomenclature (one formal and the other informal), and strongly urges authors not to establish informal units with the binomial form of a geographic name followed by an urtcapitalised lithological term. There are five reasons: (i) If a unit merits a name it merits proper definition and description. Adequate definition and description imposes a discipline on a worker that reduces the risk of unsound units being created, leading to confusion in the literature. Provided a definition is approved by the relevant Stratigraphic Nomenclature Subcommittee (see Chapter 6) it is possible to have the definition published in most States even if the editor of the journal in which the name first appears is not prepared to publish space-consuming definitions.

Definitions

(ii)

(iii) (iv)

(v)

If informal names with uncapitalised lithological terms are published, inevitably sooner or later they will be republished with a capital initial letter, and thus the intent of the original author will be lost. Use of geographic names for informal names renders those names unavailable for formal lithostratigraphic units. Informal names, not having been reserved prior to publication, may usurp already reserved but unpublished names. Further, as informal names are likely to be used more lightly and after less research into the availability of the names than are formal names, they may duplicate published names. In conversations and oral presentations, it is not possible to determine if a unit term is being capitalised or not.

6. Stratigraphic Nomenclature deals with the proper names given to specific stratigraphic units, for example, Trenton Formation, Jurassic System, Dibunophyllum Range-zone. 7. Stratotypes. Many kinds of stratigraphic units are best defined by reference to a designated type in a specific sequence of rock strata. A stratotype is the original, or subsequently designated, type representative of a named stratigraphic unit or of a stratigraphic boundary, identified as a specific interval or as a specific point in a specific sequence of rock strata, and constituting the standard for the definition and recognition of that stratigraphic unit or boundary (see Chapter 4 on Stratotypes). 8. Zone. The term zone is commonly used for a minor stratigraphic interval in any category of stratigraphic classfication. Thus there are many kinds of zones depending on the stratigraphic characters under consideration - lithozones, biozones, chronozones, mineral zones, metamorphic zones, zones of reversed magnetic polarity, and so on. 9. Interval. A stratigraphic interval is the body of strata between two stratigraphic markers. A geochronologic interval is the time span between two geologic events. 10. Horizon. A stratigraphic horizon is an interface indicative of a particular position in a stratigraphic sequence. In practice it is commonly a distinctive, very thin bed. 11. Correlation. To correlate, in a stratigraphic sense, is to show correspondence in character and in stratigraphic position. There are different kinds of correlation depending on the feature to be emphasised. Lithologic correlation demonstrates correspondence in lithologic character and lithostratigraphic positions. 12. Geochronology is the science of dating and determining the time sequence of events in the history of the Earth. 13. A Geochronologic Unit is a subdivision of geological time (time determined by geologic methods). It is therefore not a stratigraphic unit, although it may correspond to the time span of a stratigraphic unit (see Section 2D). 14. Geochronometry is that branch of geochronology that deals with the quantitative measurement of geologic time (usually in years). B.

P R O C E D U R E S F O R ESTABLISHMENT A N D DESCRIPTION O F S T R A T I G R A P H I C UNITS

(These are described for lithostratigraphic units in Chapter 5. Procedures for Australian nomenclature are described in Chapter 6).

Definitions and Procedures

8. C.

SPECIAL REQUIREMENTS FOR ESTABLISHMENT AND DESCRIPTION OF STRATIGRAPHIC UNITS

The same general rules of procedure used for outcrop sections apply, to subsurface units defined on the basis of exposures in mines or tunnels or f r o m sections penetrated in wells.

Note 4. Sub-surface units. It is desirable that formal names not be given to formations which are identified in only one borehole. Borehole evidence may be helpful in defining a unit, but if well-exposed surface sections are available they should be preferred to subsurface sections. (ACSN, Art 28)

PUBLICATION

Establishment of a f o r m a l stratigraphic unit requires t h a t an adequate description of the unit be published in a recognized s c i e n t i f i c medium. I t is d i f f i c u l t to define s t r i c t l y what constitutes "a recognized s c i e n t i f i c medium" but the chief qualifications are s c i e n t i f i c purpose and availability to the s c i e n t i f i c public on request by purchase or through an accessible library. Regularly issued s c i e n t i f i c journals meet this requirement. Many independent or i r r e g u l a r l y issued publications also meet i t , although in such cases some notice of the proposal should also appear in a widely c i r c u l a t e d regularly issued s c i e n t i f i c journal. Names proposed in i n f o r m a l or r e s t r i c t e d media such as l e t t e r s , company reports unavailable to the public, unpublished addresses, theses or dissertations, newspapers, and c o m m e r c i a l and trde journals do not q u a l i f y . P u b l i c a t i o n of new stratigraphic names in abstracts issued in advance of complete reports usually does not establish these names, because the essential conciseness of abstracts does not p e r m i t adequate description. Casual mention or i n f o r m a l reference, such as " t h e f o r m a t i o n at Jonesville schoolhouse 11 or "the limestones cropping out near San Francisco de C a r a , " does not establish a new f o r m a l unit, hor does mere use in a table or columnar section or on a map. To be valid a new unit must by duly proposed and duly described.

Note 5. Publications. The definition of a 'publication' is also considered in ACSN, Art. 12. The following are not regarded as publications for stratigraphic nomenclature purposes (i.e., priority is not established for names appearing in them): (i) Any source which may be quoted from only by permission of the issuing body (e.g. Bureau of Mineral Resources Record). Names appearing in such documents are not recorded in the Central Register of Stratigraphic Names. (ii) Preliminary edition maps of BMR (and similar maps). Such maps are unedited and names have not always been cleared; but names appearing on such maps are regarded as reserved for the authors' use in a later publication. (iii) Reports and abstracts of addresses delivered to scientific meetings. Stratigraphic names appearing therein are not recorded in the Central Register of Stratigraphic Names. (iv) GSA Specialist Group Newsletters, and similar issues. ("The Australian Geologist" is regarded as a publication). Quotation, in a publication, of a previously unpublished name renders the name 'published'. Even if quotation marks are used, their likely omission would render such a name indistinguishable from a normal published name. All binomial stratigraphic names, including those in quotation marks, are recorded in the Central Register of Stratigraphic Names. Authors intending to quote unpublished names which they wish to perpetuate should follow the normal procedures for reservation of the name and publication of the definition of the unit.

Change in Rank

Note 6. Recording of published names of units which are not adequately described or defined. It is normal practice to record in the Central Register of Stratigraphic Names all names that consist of a geographic name and a lithological or stratigraphic term (formation, group, member), and are published in a recognised scientific or technical journal (see Note 5, p. 8), whether the unit is valid and validly named or not. It is considered that publication of a formal name, even if not validly established, pre-empts the use of that name for any other stratigraphic unit, therefore every use (or misuse) of a published name must be recorded. Recording of a stratigraphic name in the Central Register is consequently not evidence that the named unit has been validly established. Nor does reservation of a name by an intending author, through the Central Registry, give priority if the name is subsequently published by someone else before the author who reserved the name does so. E.

PRIORITY

P r i o r i t y i n p u b l i c a t i o n of a p r o p e r l y proposed, named, and defined u n i t should be r e s p e c t e d . H o w e v e r , t h e c r i t i c a l f a c t o r s should always be the usefulness of the u n i t , t h e adequacy of i t s d e s c r i p t i o n , f r e e d o m f r o m a m b i g u i t y , and s u i t a b i l i t y f o r widespread a p p l i c a t i o n . P r i o r i t y alone does not j u s t i f y displacing a w e l l - e s t a b l i s h e d name by one n o t w e l l k n o w n or only o c c a s i o n a l l y used; nor should an inadequately established name be p r e s e r v e d m e r e l y on a c c o u n t of p r i o r i t y . F.

SYNONYMY

B e f o r e a t t e m p t i n g to establish a new f o r m a l s t r a t i g r a p h i c u n i t , authors should r e f e r t o n a t i o n a l , s t a t e , or p r o v i n c i a l records of s t r a t i g r a p h i c names t o d e t e r m i n e w h e t h e r a n a m e has been p r e v i o u s l y used. The many volumes of the IUGS Lexique Stratigraphique I n t e r n a t i o n a l and o t h e r a p p r o p r i a t e n a t i o n a l or regional lexicons c o n s t i t u t e valuable r e f e r e n c e sources f o r most c o u n t r i e s . G.

R E V I S I O N O R R E D E F I N I T I O N O F P R E V I O U S L Y ESTABLISHED U N I T S

R e v i s i o n or r e d e f i n i t i o n of an adequately established u n i t w i t h o u t changing i t s n a m e r e q u i r e s as m u c h j u s t i f i c a t i o n and the same kind of i n f o r m a t i o n as f o r establishing a new u n i t , and g e n e r a l l y requires the same procedures. Names of long standing and c o m m o n usage may be preserved l e g i t i m a t e l y i f they are adequately defined even though t h e i r n o m e n c l a t u r e may not c o n f o r m t o m o d e r n usage (see Section 5.F.3, p. 24). H.

SUBDIVISION

When a u n i t is d i v i d e d i n t o t w o or more units, the o r i g i n a l name should not be e m p l o y e d f o r any of t h e subdivisions. The r e t e n t i o n of the old name f o r one of t h e subdivisions w o u l d not only risk confusion but would also preclude use of the name in a t e r m of h i g h e r r a n k . J.

CHANGE IN RANK

Change i n rank of a s t r a t i g r a p h i c u n i t does not r e q u i r e r e d e f i n i t i o n of the u n i t or i t s b o u n d a r i e s , or a l t e r a t i o n of i t s proper name. Thus a stage may be raised to series rank or r e d u c e d t o a substage, or a f o r m a t i o n may be raised t o a group or reduced to a m e m b e r , w i t h o u t c h a n g i n g i t s name. The rank of any s t r a t i g r a p h i c u n i t should be changed only f o r s u b s t a n t i a l reasons and a f t e r c a r e f u l c o n s i d e r a t i o n .

Definitions and Procedures

10. K.

R E D U C T I O N I N NUMBER OF NAMES T H R O U G H C O R R E L A T I O N

If c o r r e l a t i o n has established the i d e n t i t y of t w o named s t r a t i g r a p h i c units, the later name should be replaced by the e a r l i e r , other considerations being equal, in the interests of s i m p l i c i t y in nomenclature. L.

U N C E R T A I N T Y I N ASSIGNMENT

If there is uncertainty w i t h respect to the assignment of s t r a t a to one or the other of t w o named units, i t is always b e t t e r to express this doubt rather than to make an a r b i t r a r y assignment. The f o l l o w i n g conventions may be used: Devonian? Macoa? F o r m a t i o n Peroc-Macoa F o r m a t i o n

Silurian-Devonian Silurian or Devonian Silurian and Devonian (undifferentiated)

doubtfully Devonian doubtfully Macoa F o r m a t i o n s t r a t a i n t e r m e d i a t e in position (horizontally or v e r t i c a l l y ) between beds assuredly assigned t o either of the two formations, which partake of the characters of both but which cannot be assigned decisively to either one and may eventually be made into a new f o r m a t i o n one part Silurian and one part Devonian questionably either Silurian or Devonian both Silurian and Devonian but no d i s t i n c t i o n yet possible between the two.

The name of the older or lower unit, if this d i s t i n c t i o n can be made, should always come f i r s t when t w o units are hyphenated. Note 7• Hyphenation of two unit names to describe strata that cannot be certainly assigned to either. This practice has not been followed in Australia in the past and it is strongly recommended that it should still be avoided. M.

A B A N D O N E D NAMES

A name for a stratigraphic unit, once applied and then abandoned, preferably should not be revived except in its original sense. When i t seems useful to r e f e r to an obsolete or abandoned f o r m a l name, its status should be made clear by using such a phrase as "Mornas Sandstone of Hebert (1874)." N.

D U P L I C A T I O N OF NAMES

Duplication of names should be avoided. A name previously applied to any unit should not later be applied to another unless geographic separation precludes confusion. Note 8. Duplication of names. Owing to the scarcity of officially recognised geographic names in many parts of Australia, some duplication of names may be acceptable. The test is whether confusion could possibly arise from the duplication. The following principles apply: (i) The same geographic name should not be used for two units (even completely different in age and lithology) in the same State or Territory. Use of the same name in contiguous States or Territories is to be avoided, because one unit may extend into the State or Territory in which the other occurs. (ii) The same geographic name should not be used for two units of approximately the same age. (iii) The same geographic name should not be used for two units of similar (or containing similar) rock types.

Duplication of Names

Advice will be given on request by the Convener of the Stratigraphic Nomenclature Committee whether duplication of a particular geographic name is acceptable. Officers of the Central Registry of Stratigraphic Names advise only whether a name has been published before and not whether duplication is acceptable. Geographic names already used for mainland or Tasmanian units may be used for units in Australian Antarctic Territory or Australian ocean territories, although duplication of names of well-known units should be avoided.

11.

Chapter Four STRATOTYPES

DEFINITIONS

1. Stratotype (Type Section) - the original or subsequently designated type of a named stratigraphic unit or of a stratigraphic boundary, identified as a specific interval or a specific point in a specific sequence of rock strata, and constituting the standard for the definition and recognition of the stratigraphic unit or boundary. 2. Unit-Stratotype - The type section of strata serving as the standard for the definition and recognition of a stratigraphic unit. The upper and lower limits of a unitstratotype are its boundary-stratotypes (see Figure 2a). 3. Boundary-Stratotype - a specific point in a specific sequence of rock strata that serves as the standard for definition and recognition of a stratigraphic boundary (see Figure 2b).

Figure 2. (a) Unit-stratotype and boundary-stratotypes for a lithostratiqraphio unit (f ormation I J), (b) Boundary-straUitypoo lor chronoatraUrjraphic uml<; (Upnor buwnlnrv of 7 Stage A is lower boundary of Stage B).

Requirements for Stratotypes

13.

4. Composite-Stratotype - a u n i t - s t r a t o t y p e f o r m e d by the c o m b i n a t i o n s e v e r a l s p e c i f i e d t y p e i n t e r v a l s of s t r a t a k n o w n as component-stratotypes.

5. Type Locality and Type Area. The type locality of a s t r a t i g r a p h i c unit, b o u n d a r y , or other f e a t u r e is the s p e c i f i c g e o g r a p h i c locality in w h i c h its stratotype is s i t u a t e d , or l a c k i n g a d e s i g n a t e d s t r a t o t y p e , the locality where it w a s originally defined or named. T h e type area (or type region) is the g e o g r a p h i c territory surrounding the type locality. A t y p e l o c a l i t y or type a r e a d i f f e r s f r o m a s t r a t o t y p e (type section) in that it r e f e r s to a g e o g r a p h i c l o c a l i t y or area rather than to a s p e c i f i c profile or s t r a t i g r a p h i c section. In principle, s t r a t o t y p e s should not be altered or amended. H o w e v e r , if an e s t a b l i s h e d s t r a t o t y p e is p e r m a n e n t l y destroyed, or if it has been found to have been e s t a b l i s h e d in v i o l a t i o n of a c c e p t e d s t r a t i g r a p h i c principles, a new s t r a t o t y p e m a y be e s t a b l i s h e d , p r e f e r a b l y in the type area. There m a y be more than one typical s e c t i o n but only one type s e c t i o n or s t r a t o t y p e .

STRATOTYPES IN DEFINITION OF STRATIGRAPHIC UNITS

Standard Definitions

S t r a t i g r a p h y m a k e s use of n u m e r o u s named divisions of the s t r a t i g r a p h i c c o l u m n b e l o n g i n g to v a r i o u s s t r a t i g r a p h i c c a t e g o r i e s - lithostratigraphic units, b i o s t r a t i g r a p h i c units, c h r o n o s t r a t i g r a p h i c units, and so on. It is essential that these named units, and their b o u n d a r i e s , be c l e a r l y defined so that all who use them will start w i t h the s a m e basic u n d e r s t a n d i n g of their m e a n i n g and so that there will be a c o m m o n standard for their r e c o g n i t i o n a w a y f r o m their places of origin. F o r many such units a designated s t r a t o t y p e p r o v i d e s an e s s e n t i a l or at least useful aid to definition.

Reference to a Specific Rock Section

T h e c o n c e p t of a s t r a t i g r a p h i c unit is usually based on f e a t u r e s or attributes of the r o c k s t r a t a - l i t h o l o g y , fossil content, age or time span, and so on - w h i c h are observable or v e r i f i a b l e in the r o c k s t r a t a and m a y be related in advance of n a m i n g to a s p e c i f i c i n t e r v a l of r o c k s t r a t a . The s t r a t o t y p e of such a unit, therefore, constitutes the standard of r e f e r e n c e on w h i c h the c o n c e p t of the unit is uniquely based.

REQUIREMENTS FOR STRATOTYPES

Expression of Concept

T h e m o s t i m p o r t a n t requisite of a s t r a t o t y p e is that it adequately represents the e s s e n t i a l s of the c o n c e p t s for w h i c h it is the m a t e r i a l type. A complete exposure of all s t r a t a in the unit f r o m b o t t o m to top and throughout its entire lateral extent would be the ideal s t r a t o t y p e . H o w e v e r , because it is impossible to find or establish such a c o m p r e h e n s i v e s t r a t o t y p e , reliance is usually placed on a single section, as complete and well e x p o s e d as possible. L a c k of continuous exposures or the presence of s t r u c t u r a l c o m p l i c a t i o n s m a y m a k e it impossible to find even such a single continuous s e c t i o n through an e n t i r e s t r a t i g r a p h i c unit. It m a y then be necessary to resort to a c o m p o s i t e - s t r a t o t y p e or to s u p p l e m e n t a r y and r e f e r e n c e s e c t i o n (parastratotypes and hypostratotypes), or to express the u n i t - s t r a t o t y p e s i m p l y as the s t r a t i g r a p h i c interval between a designated b o u n d a r y s t r a t o t y p e m a r k i n g the base of the unit and another designated b o u n d a r y - s t r a t o t y p e m a r k i n g the top of the unit.

Description

T h e d e s c r i p t i o n of a s t r a t o t y p e should be both geographic and geologic. The • e o q r a p h i c d e s c r i p t i o n should enable anyone to find the stratotype readily in the field. It s h o u l d include a detailed m a p s h o w i n g l o c a t i o n and means of access to the type locality. It

Stratotypes

14.

would also be desirable to include air photographs and other photographs at an appropriate scale to show the geographic e x t e n t of the unit in the type area and the geographic position of its boundaries. The geologic description should cover thickness, l i t h o l o g y , paleontology, mineralogy, s t r u c t u r e , geomorphic expression, and other geologic f e a t u r e s of the type section. "The boundaries and relations w i t h adjacent units p a r t i c u l a r l y should be described in d e t a i l , and reasons f o r choice of boundaries should be given. The d e s c r i p t i o n should be accompanied by graphic profiles, columnar sections, s t r u c t u r e sections, and photographs. 3*

Identification and Marking

A n essential requirement of a s t r a t o t y p e is t h a t i t be c l e a r l y marked. A b o u n d a r y - s t r a t o t y p e should be based on a single point in a designated sequence of rock s t r a t a , serving to indicate the position of the boundary horizon at one place. A u n i t s t r a t o t y p e desirably should be clearly d e l i m i t e d by boundary-stratotypes f o r i t s base and for its top. P r e f e r a b l y , a boundary-stratotype or the l i m i t s of a u n i t - s t r a t o t y p e should be indicated by a permanent a r t i f i c i a l m a r k e r , but in any case boundary points should be described geographically and geologically in such d e t a i l t h a t there can be no doubt as to t h e i r exact l o c a t i o n . 4.

Accessibility

If the s t r a t o t y p e is to f u l f i l l the role of a standard, i t should be s i t u a t e d in an area geographically accessible to all who are interested, regardless of p o l i t i c a l or other circumstances.

Chapter Five LITHOSTRATIGRAPHIC UNITS

PURPOSE OF LITHOSTRATIGRAPHIC CLASSIFICATION

The purpose of l i t h o s t r a t i g r a p h i c c l a s s i f i c a t i o n is t o o r g a n i z e s y s t e m a t i c a l l y r o c k s t r a t a o f t h e E a r t h i n t o named u n i t s t h a t w i l l r e p r e s e n t t h e p r i n c i p a l v a r i a t i o n s of these r o c k s i n l i t h o l o g i c c h a r a c t e r . A l l s t r a t i g r a p h i c u n i t s are composed of r o c k and thus have " r o c k c h a r a c t e r 1 1 , b u t only l i t h o s t r a t i g r a p h i c units are d i f f e r e n t i a t e d on t h e basis of k i n d of r o c k ( l i t h o l o g i c c h a r a c t e r ) ; l i m e s t o n e , sandstone, sand, t u f f , c l a y s t o n e , b a s a l t , m a r b l e , and so on. L i t h o s t r a t i g r a p h i c c l a s s i f i c a t i o n is usually a f i r s t approach i n s t r a t i g r a p h i c w o r k i n any new area. H o w e v e r i t also c o n t i n u e s always t o be an essential e l e m e n t of t h e s t r a t i g r a p h y o f t h e area. L i k e w i s e i t is always an i m p o r t a n t key t o g e o l o g i c a l h i s t o r y . F o r i n s t a n c e , m u c h c a n be deduced w i t h c e r t a i n t y about t h e g e o l o g i c a l events t h a t have t a k e n p l a c e i n t h e area of F i g u r e 3, even though no ages are a v a i l a b l e f r o m e i t h e r fossils or i s o t o p i c age d e t e r m i n a t i o n s .

METAMORPHICS

SANDSTONE

| SHALE

JEVAPORITES

| IGNEOUS

I CON GLOMERATE

LIMESTONE

COAL BEDS

F i g u r e 3. S i g n i f i c a n c e of l i t h o s t r a t i g r a p h i c units in d e c i p h e r i n g geologic h i s t o r y .

DEFINITIONS

1. Lithostratigraphy - t h e e l e m e n t of s t r a t i g r a p h y t h a t deals w i t h the l i t h o l o g y o f s t r a t a and w i t h t h e i r o r g a n i z a t i o n i n t o u n i t s based on l i t h o l o g i c c h a r a c t e r . 2.

L i t h o s t r a t i g r a p h i c classification - t h e o r g a n i z a t i o n of r o c k s t r a t a i n t o u n i t s

on t h e basis o f t h e i r l i t h o l o g i c c h a r a c t e r . 3. Lithostratigraphic unit - a body o f r o c k s t r a t a t h a t is u n i f i e d by c o n s i s t i n g d o m i n a n t l y o f a c e r t a i n l i t h o l o g i c t y p e or c o m b i n a t i o n of l i t h o l o g i c types, or by possessing o t h e r i m p r e s s i v e and u n i f y i n g l i t h o l o g i c f e a t u r e s . A l i t h o s t r a t i g r a p h i c u n i t may consist of s e d i m e n t a r y , or igneous, or m e t a m o r p h i c r o c k s , or of an a s s o c i a t i o n of t w o or m o r e of these.

Lithostratigraphic Units

16.

The c r i t i c a l requirement of the unit is a substantial degree of overall lithologic homogeneity. (Diversity in detail may in itself constitute a f o r m of overall lithologic unity). Lithostratigraphic units are recognized and defined by observable physical features and not by inferred geologic history or mode of genesis. The geographic extent of lithostratigraphic units is controlled entirely by the continuity and extent of their diagnostic lithologic features. Only major lithologic features readily recognisable in the field should serve as the basis for lithologic units. C.

KINDS OF LITHOSTRATIGRAPHIC UNITS

Hierarchy of Formal Lithostratigraphic Units

Formal lithostratigraphic units are those that are defined and named in accordance w i t h an explicitly established or conventionally agreed scheme of classification and nomenclature (see Table 1, p. 5; and Section 3.A.5, p. 6). The conventional hierarchy of f o r m a l lithostratigraphic terms is as follows: Group - two or more formations Formation - primary unit of lithostratigraphy Member - named lithologic entity w i t h i n a f o r m a t i o n Bed - named distinctive layer in a member or f o r m a t i o n 2.

Formation

The formation is the primary formal unit of lithostratigraphic classification; it is a body of rock strata of intermediate rank in the hierarchy of lithostratigraphic units. Formations are the only formal lithostratigraphic units into which the stratigraphic column everywhere should be divided completely on the basis of lithology. The degree of change in lithology required to j u s t i f y the establishment of distinct formations (or other lithostratigraphic units) is not amenable to s t r i c t and uniform rules. It may vary w i t h the complexity of the geology of a region and the detail needed to portray satisfactorily its rock framework and to work out its geologic history. The thickness of units of formation rank follows no standard and may range from less than a meter to several thousand meters, depending on the size of units locally required to express best the lithologic development of a region. Practicability of mapping and delineation on cross sections is an important consideration in the establishment of formations. Formations may be composed of sedimentary rocks, or extrusive or intrusive igneous rocks, or metamorphic rocks, or under some circumstances associations of two or more of these types of rock. 3.

Member

A member is the formal lithostratigraphic unit next in rank below a formation and is always a part of a formation. It is recognized as a named entity w i t h i n the formation because it possesses lithologic characters distinguishing i t f r o m adjacent parts of the formation. No fixed standard is required for the extent or thickness of a member. A formation need not be divided into members unless a useful purpose is thus served. Some formations may be completely divided into members; others may have only certain parts designated as members; s t i l l others may have no members. A member may extend f r o m one formation to another. .

Kinds of Lithostratigraphic Units

17.

Bed

A bed is the smallest f o r m a l unit in the hierarchy of l i t h o s t r a t i g r a p h i c units. It is a u n i t layer in a s t r a t i f i e d sequence of rocks which is l i t h o l o g i c a l l y distinguishable f r o m other layers above and below, for example, the Baker Coal Bed. Several contiguous beds of s i m i l a r l i t h o l o g y may also together constitute a f o r m a l unit, for example, the Marcus L i m e s t o n e Beds. The t e r m "bed" is applied customarily to layers a c e n t i m e t e r to a few meters in thickness. Those of less thickness are called laminae. S t r a t i f i c a t i o n is not necessarily i d e n t i c a l w i t h s p l i t t i n g properties and the two should not be confused. A single named bed or named sequence of beds may constitute a member or a f o r m a t i o n , and in such a case, the unit t e r m bed (or beds) is replaced by member or f o r m a t i o n , f o r example, "Bracklesham Beds" = Bracklesham F o r m a t i o n , "DrusbergSchichten" = Drusberg F o r m a t i o n . A specific bed conceivably may pass f r o m one member or f o r m a t i o n to another and s t i l l r e t a i n the same name. C u s t o m a r i l y only d i s t i n c t i v e beds (commonly known as marker beds) p a r t i c u l a r l y useful f o r s t r a t i g r a p h i c purposes, like correlation or reference, are given proper names and considered f o r m a l l i t h o s t r a t i g r a p h i c units. Intervening beds are l e f t unnamed. In r e l a t i v e l y unexplored country where only rapid reconnaissance can be carried out, a f o r m a l and properly surveyed hierarchy of formations and groups cannot always be established i n i t i a l l y . In such cases, the use of a geographic name coupled w i t h "beds" (uncapitalized) w i l l be accepted as a temporary i n f o r m a l designation.

Note 9. Use of 'Group' or 'beds' for poorly identified sequences. The provision in the ISG (5.C.5, below) that groups need not consist entirely of defined formations reduces the need to use 'beds' for poorly identified rock sequences. However 'Group1 should be used only where the upper and lower limits of the unit can be identified and specified. A unit should be named and designated as '... beds' only when it is essential for stratigraphic classification or descriptive purposes (see Note 3, p. 6). Note 10. Status of former "Beds" units. The term "Beds" has been used under the provisions of the Australian Code (Article 27) for a sequence of poorly known strata, but in the ISG "Beds" has a very different connotation. In future references to such units, the term "Beds" should be changed to the informal term "beds", and the unit should be regarded as an informal unit until further work is carried out. Later work may enable the unit to be redefined as a formation (ISG, 5.C.2, p. 16) or as a group (ISG, 5.C.4, above). 5.

Group

A group is the f o r m a l l i t h o s t r a t i g r a p h i c unit next in rank above a f o r m a t i o n . The t e r m is applied most commonly to a sequence of two or more contiguous associated f o r m a t i o n s w i t h significant unifying lithologic features in common. The type or reference sections of a group are the type or reference sections of its component formations. The proposal for r e c o g n i t i o n of a group should outline clearly the unifying characteristics on which i t is based and the formations of which it is composed. Formations need not be aqqregated into groups, but the t e r m group is generally used for an assemblage of f o r m a t i o n s except t h a t i t may also be used for a stratigraphic sequence of any kind of rocks t h a t w i l l probably be divided in whole or in part into formations in the f u t u r e .

Lithostratigraphie Units

18.

Note 11. Establishment of a unit at group level without constituent formations when it is expected that formations will later be established. . . It is recommended that stratigraphers should avoid establishing groups without constituent formations in anticipation of the possible action of future field workers. It is considered preferable to establish the unit as a formation and allow future workers 10 subdivide it, establish constituent formations, and change the rank of the original formation to group. Thickness of a sequence is not a valid reason for defining a unit as a group rather than a formation (ISG, 5.C.2, p.

16).

The aggregation of f o r m a t i o n s into groups provides a useful means of s i m p l i f y i n g and generalizing s t r a t i g r a p h i c c l a s s i f i c a t i o n for those who may not need, or may wish to avoid, the o f t e n complex d e t a i l of f o r m a t i o n a l subdivision in c e r t a i n regions or c e r t a i n intervals. The name of a group should p r e f e r a b l y be derived f r o m an appropriate geographic f e a t u r e near the type areas of its component f o r m a t i o n s , f o r example, Sucre Group, N e w a r k Group, Garhwal Group. Generally, i t is not possible t o c h a r a c t e r i z e the l i t h o l o g y of a group in its name.

Note 12. Lithologic term in name of group. In the special circumstance where a group consists of formations of the same or similar lithology, an appropriate lithologic term may be included in the name of the group if it is desired to indicate the character of the whole group. The component f o r m a t i o n s of a group are not necessarily e v e r y w h e r e the same. For example, in parts of western Iran the Fars Group comprises simply the Gach Saran and Agha J a r i F o r m a t i o n s ; in parts of the province of Fars in southern Iran the group consists of the Razak, Mishan, and Agha J a r i F o r m a t i o n s . A f o r m a t i o n may e x t e n d l a t e r a l l y f r o m one group to another. The wedging-out of a component f o r m a t i o n or f o r m a t i o n s may j u s t i f y the r e d u c t i o n of a group to f o r m a t i o n rank, r e t a i n i n g the same name. A group may be extended l a t e r a l l y beyond the area where i t is divided i n t o f o r m a t i o n s , if i t seems probable t h a t the equivalent i n t e r v a l w i l l eventually be divided i n t o f o r m a t i o n s . O t h e r w i s e , the group becomes, in e f f e c t , a single f o r m a t i o n and should be known as such.

Note 13. Reduction in rank from group to formation in lateral extension of a unit without constituent formations. It is recommended that the rank of group be retained, rather than the unit be permitted to carry the name of Group' and '... Formation Less confusion is likely to arise if any named unit carries only one rank. 6.

Subgroup and Supergroup

A group may on occasion be divided i n t o subgroups. The t e r m supergroup may be used f o r several associated groups, or f o r associated f o r m a t i o n s and groups w i t h s i g n i f i c a n t f e a t u r e s in common.

Complex

A complex is a l i t h o s t r a t i g r a p h i e unit composed of diverse types of any class or classes of rock (sedimentary, igneous, m e t a m o r p h i c ) and c h a r a c t e r i z e d by highly c o m p l i c a t e d s t r u c t u r e to the e x t e n t t h a t the o r i g i n a l sequence of the component rocks may be obscured. The t e r m may be used as a part of a f o r m a l name in the place of a l i t h o l o g i c or rank t e r m , f o r example, A k k a j a u r e C o m p l e x , L e w i s i a n C o m p l e x .

Kinds of L i t h o s t r a t i g r a p h i c U n i t s

19.

N o t e 14. Complex It is desirable to confine the term 'Complex' t o a large mass of diverse rocks (ACSN, A r t i c l e 33). Such a mass is unlikely to have the rank of formation or member; rather it is likely to consist of sequences which, if mappable, wouid constitute a group, supergroup or number of groups. 8.

I n f o r m a l Lithostratigraphic Units

I n f o r m a l l i t h o s t r a t i g r a p h i c units include l i t h o l o g i c bodies t o w h i c h casual r e f e r e n c e is made but f o r w h i c h t h e r e is i n s u f f i c i e n t need, i n s u f f i c i e n t i n f o r m a t i o n , or i n a p p r o p r i a t e basis t o j u s t i f y designation as a f o r m a l u n i t . These may be r e f e r r e d t o i n f o r m a l l y as l i t h o z o n e s (e.g., shaly zones, c o a l - b e a r i n g zones) or as beds or m e m b e r s ( l o w e r case) of one s o r t or another (e.g. sandy beds, the pebbly bed, the shaly m e m b e r ) . The t e r m " m e a s u r e s " has been used i n f o r m a l l y f o r a sequence of coal beds (e.g. t h e M a r a c o a l measures). Note 15. Coal measures. Australian practice has been to accept 'Coal Measures' as a formal unit name equivalent in rank to group, subgroup, or formation (ACSN, Article 35). It is not proposed to discontinue this practice, although it differs from the provisions of the ISG. The term 'seam' is an informal term and does not fall within the definition of formal stratigraphic nomenclature. Where individual coal seams are named with a geographic component they should be defined as formations or members, and named accordingly, e.g. Bulli Coal, Balgownie Coal Member. When i n f o r m a l u n i t s such as those m e n t i o n e d above are given geographic names, t h e u n i t - t e r m should not be c a p i t a l i z e d (unless some p r o b l e m arises because of the languages i n v o l v e d ) . G e o g r a p h i c names should be combined w i t h the t e r m s " F o r m a t i o n " and " G r o u p " only i n f o r m a l n o m e n c l a t u r e (see N o t e 3, p. 6). C e r t a i n o t h e r r o c k bodies r e l a t e d to or cloqely associated w i t h l i t h o s t r a t i g r a p h i c u n i t s are not t r u e l i t h o s t r a t i g r a p h i c units because they emphasize mode of o r i g i n , or shape, of some c h a r a c t e r o t h e r t h a n l i t h o l o g y f o r i d e n t i f i c a t i o n ; others are not s t r a t i g r a p h i c units at a l l . A m o n g these t w o types are slides and slumps, mud f l o w s , o l i s t o s t r o m e s , o l i s t o l i t h s , d i a p i r s , s a l t plugs and w a l l s , veins, b a t h o l i t h s , c y c l o t h e m s , and such. These may be given i n f o r m a l names. 9.

Some Special Aspects of Igneous Rocks

Igneous r o c k bodies of more or less t a b u l a r f o r m , c o n f o r m i n g t o the general s t r a t i f i c a t i o n of t h e r o c k s e c t i o n , may c o n s t i t u t e t h e basis f o r l i t h o s t r a t i g r a p h i c units, e i t h e r i n t h e m s e l v e s or in c o m b i n a t i o n w i t h adjacent interbedded s e d i m e n t a r y s t r a t a of e s s e n t i a l l y t h e same age or much older. Igneous r o c k s , h o w e v e r , present some special problems in l i t h o s t r a t i g r a p h y . For e x a m p l e , m a n y igneous rocks occur as dikes or other bodies i n j e c t e d across the d o m i n a n t s t r a t i f i c a t i o n of the s e c t i o n . M o r e o v e r , sills, f l o w s , and other more or less a c c o r d a n t l y i n t e r s t r a t i f i e d i n t r u s i v e or e x t r u s i v e igneous rock bodies may have been emplaced in the s t r a t i g r a p h i c s e c t i o n at a l e v e l f a r above t h a t at w h i c h t h e i r parent m a g m a o r i g i n a t e d , y e t t h e y m a y s t i l l be c o n n e c t e d w i t h the source body across i n t e r v e n i n g s t r a t i g r a p h i c units by necks pipes, or dikes of the same rock m a t e r i a l . These c r o s s - c u t t i n g igneous bodies do not in t h e m s e l v e s c o n s t i t u t e s t r a t i g r a p h i c units but they are, of course, an i m p o r t a n t p a r t of the l i t h o l o g i c p i c t u r e . They may c o n v e n i e n t l y be r e f e r r e d t o as "associated" w i t h the s t r a t a of t h e l i t h o s t r a t i g r a p h i c u n i t s t h a t they t r a n s e c t .

Lithostratigraphie Units

20.

Note 16. Names of cross-cutting igneous bodies. Such bodies are normally quite distinct from the surrounding rock unity and if named have names of the same style as stratigraphic units, i.e. geographic name followed by lithological term. For stratigraphic nomenclature purposes they should therefore be treated as stratigraphic units and should be named as far as possible according to the principles in 5.F, (p. 21). D.

PROCEDURES F O R ESTABLISHING L I T H O S T R A T I G R A P H I C U N I T S

Stratotypes as Standards of Definition

Each named l i t h o s t r a t i g r a p h i e unit of whatever rank should have a clear and precise standard d e f i n i t i o n based on the f u l l e s t possible knowledge of its l a t e r a l and v e r t i c a l variations. The designation of a type section ( u n i t - s t r a t o t y p e ) is essential i n the d e f i n i t i o n of a l i t h o s t r a t i g r a p h i e unit. The s t r a t o t y p e of a l i t h o s t r a t i g r a p h i e unit is the s p e c i f i c a l l y designated sequence of rock s t r a t a on which the standard d e f i n i t i o n of the l i t h o l o g i c c h a r a c t e r of the unit is based. I t is designated at a specific geographic l o c a l i t y , p r e f e r a b l y t h a t f r o m which the name of the unit is derived. The stratotypes of l i t h o s t r a t i g r a p h i e units of f o r m a t i o n or lesser rank are commonly simple u n i t - s t r a t o t y p e s . The stratotypes of l i t h o s t r a t i g r a p h i e units larger than a f o r m a t i o n (e.g. groups) are commonly composite-stratotypes, t h a t is, a composite of the stratotypes of the component f o r m a t i o n s of the group. Where s t r a t a are nearly horizontal or poorly exposed and a c o m p l e t e section of a unit does not crop out in a reasonably l i m i t e d area, i t may not always be p r a c t i c a b l e to designate any one specific complete and continuous section as the u n i t - s t r a t o t y p e . Only a type area or a type l o c a l i t y , rather than a type section, can be indicated. In such cases i t is essential to i d e n t i f y e x p l i c i t l y t h e lower and upper boundary-stratotypes at specified sections where the change to underlying and overlying units can be seen. The equivalent of the u n i t - s t r a t o t y p e is t h e r e f o r e c o n s t i t u t e d by the ensemble of exposures in the type l o c a l i t y or type area lying s t r a t i g r a p h i c a l l y between the lower and upper boundarystratotypes. Although the s t r a t o t y p e of a l i t h o s t r a t i g r a p h i e unit is a specific i n t e r v a l of s t r a t a in a specific section or area, the u n i t , as recognized elsewhere, may c o n t a i n a greater or lesser thickness of s t r a t a than in the s t r a t o t y p e , and may span a greater or lesser t i m e i n t e r v a l than the s t r a t o t y p e . The only c r i t i c a l requirement of the unit as i d e n t i f i e d elsewhere is t h a t i t has essentially the same lithology and r e l a t i v e s t r a t i g r a p h i c position as in the s t r a t o t y p e . 2.

Reference Sections (Hypostratotypes)

The d e f i n i t i o n of a l i t h o s t r a t i g r a p h i e unit based on the designation of a units t r a t o t y p e section (holostratotype) is o f t e n usefully supplemented by designating in other geographic areas one or more auxiliary reference sections (hypostratotypes), sometimes b e t t e r exposed or more accessible than the o r i g i n a l u n i t - s t r a t o t y p e . These reference sections, however, must always be considered as subsidiary to the h o l o s t r a t o t y p e . 3.

Boundaries

Boundaries of l i t h o s t r a t i g r a p h i e units are placed at positions of l i t h o l o g i c change. They are usually designated at sharp l i t h o l o g i c contacts, but also may be placed a r b i t r a r i l y w i t h i n zones of l i t h o l o g i c gradation. They should be drawn to express most usefully l i t h o s t r a t i g r a p h i e development. Boundaries of l i t h o s t r a t i g r a p h i e units commonly c u t across t i m e horizons, across the l i m i t s of fossil ranges and across the boundaries of any other kind of s t r a t i g r a p h i c u n i t .

Naming of Lithostratigraphic Units

21.

Unconformities and Hiatuses

A sequence of rocks of closely similar lithology but including a local or minor hiatus, disconformity, or unconformity should not be separated into more than one lithostratigraphic unit merely because these types of sedimentary breaks occur, unless there is a nthologic distinction adequate to define a boundary. However, the union of adjacent strata separated by regional unconformities or major hiatuses into a single lithostratigraphic unit should preferably be avoided even if no more than minor lithologic differences can be found to justify the separation. E.

PROCEDURES FOR EXTENDING LITHOSTRATIGRAPHIC UNITS LITHOSTRATIGRAPHIC CORRELATION

A lithostratigraphic unit and its boundaries should be extended away from the type locality only as far as the definitive lithologic features on which the unit was based in its type section are known certainly to exist or through indirect evidence are presumed with assurance to continue. F.

NAMING OF LITHOSTRATIGRAPHIC UNITS

The name of a lithostratigraphic unit should be formed from the name of an appropriate local geographic feature, combined with the appropriate term for its rank (group, formation, member, bed), or with the name of the dominant rock type of which the unit is composed, or with both (e.g. Gafsa Formation, Spiti Shale, Sables de Cuise, Taylor Coal Member). Descriptive adjectives should not be included in the name of a lithostratigraphic unit. Note 17. Geographic component of name.

Authors have the option of using the full geographic name, consisting of both proper name and feature term (e.g. Mount Bowen, Turpentine Creek), or using only the proper name (Bowen, Turpentine) providing no confusion can arise; however the essential part of the geographic name is regarded as the proper name. Consequently use of a proper name in any form (e.g. Fitzroy River, Mount Fitzroy, Cape Fitzroy, Little Fitzroy Creek) normally pre-empts its use in any other form. Authors are encouraged to use the proper name only; short concise names are better than long compound names. Note 18. Abbreviation of formal name after first reference.

Experience has shown that unit names are often used incorrectly by later authors; e.g. Kombolgie Formation appears as Kombolgie Sandstone, or the incorrect rank is used. This type of error is minimised if workers are accustomed to using the full name, and seeing it in print. Conversely, the number of incorrect usages recorded in the Central Register of Stratigraphic Names can be expected to increase sharply if abbreviated forms of the names are accepted. It is therefore strongly recommended that the full stratigraphic name be used at all times. Note 19. Change of lithological term for local or regional variation in a unit.

For the reason given in Note 8 and having regard for the general tenor of the ISG, it is considered undesirable that, to use the example qiven in the ISG, a dolomitic phase of the Galena Limestone be referred to as Galena Dolomite. For regional changes a change of name is desirable; for example, Compton Shale, where metamorphosed to a schist, could become the Millikan Schist, as cited For less extensive changes the form used in the fourth edition of the Australian Code (Article 20) is preferred - Bell Shale (slate phase), or Galena Limestone (dolomite phase).

Lithostratigraphic Units

22.

Geographic Component of Name

a. Source. The geographic name should be the name of a natural or a r t i f i c i a l feature at or near which the lithostratigraphic unit is typically developed (see Note 17, p. 21). Names derived f r o m such impermanent sources as farms, churches, schools, crossroads, and small communities are not entirely satisfactory but are acceptable if no others are available. Names for formations or other important rock units may be selected f r o m those that can be found on state, provincial, county, forest service, topographic, hydrographic, or comparable maps. If a name that does not meet this test must be used, the place f r o m which the name is derived should be described and identified precisely and shown on a map accompanying the description of the new unit. A unit should not be named from the source of its components: for example, a t i l l deposit, supposedly derived from the Keewantin glaciation center, should not be called " K e e w a t i n Till.11, The name of a highranking unit may appropriately, though not necessarily, be derived f r o m a more extensive geographic feature or area than the names of its lower ranking components.

Note 20. Scarcity of geographic names• In some States the names of landholdings, parishes and counties given on cadastral maps are a fruitful source of names for stratigraphic units. Should there be no available geographic name that is suitable for stratigraphic purposes a submission may be made to the SurveyorGeneral of the State or Territory concerned proposing a name for an unnamed feature, or proposing that a locally used name be officially adopted. b. Duplication. Duplication of geographic names should be avoided (see Section 3.N p. 10; also Note 8, p. 10, Note 17, p. 21, and Note 20, above). c. Names for Parts of Units. The same name should not be applied both to the unit as a whole and to a part of i t . For example, the Astoria Group should not contain an Astoria Sandstone, nor the Germav Formation a Germav Shale Member. In formal lithostratigraphic nomenclature the same geographic name should not be used for lithologically d i f f e r e n t parts of members of a unit. The application of identical geographic names to several minor units in one v e r t i c a l sequence is considered informal nomenclature (lower Mount Savage coal, Mount Savage fireclay, upper Mount Savage coal, Mount Savage rider coal, and Mount Savage sandstone). The application of identical geographic names to the several lithologic units constituting a cycle of sedimentation is likewise considered informal. The terms lower, middle, end upper should not be used for f o r m a l subdivisions of a lithostratigraphic unit. d. Spelling. Spelling of the geographic component of a lithostratigraphic name should conform to the usage of the country that contains the type l o c a l i t y . However, a stratigraphic name repeatedly published w i t h a spelling d i f f e r e n t f r o m that of its geographic source should nevertheless be retained. For example, Bennett Shale, uniformly used for more than 30 years, should not be altered to Bennet Shale on the grounds that the town is named Bennet. Stratigraphic names that have been spelled variously should be made uniform by adopting the spelling used by the most authoritative local geographical and geological sources. e. Changes in Geographic Names. Change in the name of a geographic feature does not entail change of the corresponding name of a stratigraphic unit. The original name of the unit should be maintained} e.g., Mauch Chunk Shale should not be changed to Jim Thorpe Shale because the former town of Mauch Chunk is now called Jim Thorpe.

Naming of Lithostratigraphic Units

23.

D i s a p p e a r a n c e of a geographic f e a t u r e does not require the elimination of the corresponding name of a s t r a t i g r a p h i c unit. For example, Thurman Sandstone, named from a f o r m e r village in Pittsburgh County, Oklahoma, does not require renaming. f. Inappropriate Names. A name t h a t suggests some well-known locality, region, or political division should not, in general, be applied to a unit typically developed in another less well-known locality of the same name. For example, it would not be advisable to use the n a m e "Chicago Formation" for a unit in California, or the "London Formation" for a unit in Wales, even though localities with these names do exist in California and in Wales. g. Names of Offshore Lithostratigraphic Units. Offshore drilling in many areas p r e s e n t s problems in applying formal geographic names to the units penetrated in the wells. In some cases, the lithostratigraphic units penetrated in the wells cannot be correlated with the s u r f a c e units in the bordering region, and it may be very difficult to find locality names for new f o r m a t i o n s . If the offshore well in which a new lithostratigraphic unit has been p e n e t r a t e d has been given a name taken from coastal, oceanographic, or other f e a t u r e s , this n a m e can be used for a subsurface unit providing that the requirements of Section 3.C are followed. 2.

Lithologic Component of Name

Where a lithologic term is used in the name of a lithostratigraphic unit, the simplest generally acceptable term is recommended (e.g., limestone, sandstone, shale, t u f f , g r a n i t e , q u a r t z i t e , serpentinite). However, a compound term such as "shale-sandstone" or a descriptive a d j e c t i v e , if part of the lithologic term, may be used in special cases where a more detailed indication of composition would be particularly helpful without making the name awkward or misleading in scope. Lithogenetic terms such as "turbidite" or "flysch" should be avoided for formally named lithostratigraphic units.

Note 21. Use of 'Volcanics' and 'Metamorphics1 as the lithological term of stratigraphic names. The Australian Code (Articles 31 and 32) sanctions the use of these terms, and they have proved to be useful. It is therefore proposed to continue their use, although the practice is not sanctioned by the ISG and differs from usage in other countries. These terms will be used as formation terms only. For intrusive igneous rocks, the lithologic term should express the name of the dominant rock type, for example, Dido Granodiorite. "Dike", "stock", "pluton", "batholith", and other similar names, or more general terms such as "intrusion", are neither lithologic nor s t r a t i g r a p h i c terms; accordingly, the names of such intrusive igneous bodies as the Idaho batholith or the Ordubad pluton should not be considered stratigraphic terms.

Note 22. Use of the same geographic name for a stratigraphic unit and a structural or form feature (e.g. fault, batholith, dyke). This usage is allowable provided there is no likelihood of confusion. The stratigraphic name and the form name should apply to precisely the same rock mass. A series of laterally discontinuous bodies having approximately the same lithologic c h a r a c t e r , stratigraphic position, and age may be named as a single unit. An example is the Gila Conglomerate, which is a series of valley beds distributed in disconnected areas along the gorges of the upper Gila River. Similarly, a series of disconnected reef limestones or of coal lentils lying at approximately the same stratigraphic position may all be included in the same named unit if their size and separation is not s u f f i c i e n t to w a r r a n t naming each one individually. Examples might be the Permian patchr e e f s of West Texas or the Leduc r e e f s of Canada.

Lithostratigraphic Units

24.

Preservation of Traditional Names

A l t h o u g h i t is strongly urged t h a t a l l new l i t h o s t r a t i g r a p h i c units be named in accordance w i t h the recommendations of this chapter, i t is realized t h a t there are many well-established and t r a d i t i o n a l l y used, l i t h o s t r a t i g r a p h i c units of long h i s t o r i c a l standing for which exception should be made. Examples are M i l l s t o n e G r i t , K u p f e r s c h i f e r , Teagreen Marl, C a l c a i r e Grossier, and such. Such units should not be abandoned m e r e l y because they lack geographic names. G.

REVISION OF L I T H O S T R A T I G R A P H I C UNITS

Change in Lithologic Designation

A change in the l i t h o l o g i c t e r m applied to a l i t h o s t r a t i g r a p h i c unit does not necessarily require a new geographic t e r m . P r i o r i t y should not i n h i b i t more exact lithologic designation if the original designation is not everywhere applicable; f o r example, i f the t e r m " L i m e s t o n e " in such names as Galena Limestone and Bahram Limestone were locally inapplicable, i t could be changed to " D o l o m i t e " even though the t y p e section may have been c o r r e c t l y named (see N o t e 19, p. 21). If the l i t h o l o g i c v a r i a t i o n w a r r a n t s neither name, the t e r m " F o r m a t i o n " may be preferable. 2.

Change in Rank

Change in rank of a l i t h o s t r a t i g r a p h i c unit does not require a l t e r a t i o n of the geographic part of its name. It is possible f o r a member to become a f o r m a t i o n , or vice versa, and for a f o r m a t i o n to become a group or vice versa. When a previously established f o r m a t i o n is broken down into t w o or more components units that are f o r m a l l y given f o r m a t i o n rank, the o r i g i n a l f o r m a t i o n , w i t h its o r i g i n a l geographic name, should be either raised to group status or abandoned. The old name should not be retained for any of the divisions of the original u n i t .

Chapter AUSTRALIAN

Six

PROCEDURES

Administrative structure

The machinery set up to provide orderly use of stratigraphic nomenclature in A u s t r a l i a , p a r t i c u l a r l y to avoid duplication of names and to help authors define or redefine units adequately, consists o f : (i) The Stratigraphic Nomenclature Committee of the Geological Society of Australia, w h i c h consists of all members of the respective Divisional Subcommittees. Its Convener provides a continuing point of reference for matters r e l a t i n g to stratigraphic n o m e n c l a t u r e , including i n t e r p r e t a t i o n of the International Stratigraphic Guide and the Field Geologist's Guide to S t r a t i g r a p h i c Nomenclature. (ii) Divisional Stratigraphic Nomenclature Subcommittees, which are responsible f o r s t r a t i g r a p h i c nomenclature m a t t e r s w i t h i n their own Divisions, and p a r t i c u l a r l y f o r advising on and approving definitions and redefinitions of l i t h o s t r a t i g r a p h i c units. (iii) The Central Register of Stratigraphic Names, which is maintained by the Bureau of M i n e r a l Resources, Canberra. The C e n t r a l Registry s t a f f searches all publications received in the Bureau of Mineral Resources Library and maintains a record of all r e f e r e n c e s to l i t h o s t r a t i g r a p h i c names w i t h the binomial f o r m , regardless of whether the unit named has been defined, described, named only, or only r e f e r r e d to, and whether capitals have been used for the l i t h o l o g i c a l or rank t e r m . The cards for definitions of s t r a t i g r a p h i c units approved by Subcommittees are also f i l e d (see also p. 26). 2.

Reservation of Names for Proposed Units

(i) The appropriate volumes of the Lexique Stratigraphique International, published in Paris by the Sub-commission for the Stratigraphic Lexicon, should f i r s t be searched, if they are available. Volumes (fascicules) 5a to 5h cover Australia: 5a-5g by States and T e r r i t o r i e s , w i t h publication dates ranging f r o m 1958 to 1966; and 5h (1975) covers the whole of A u s t r a l i a for publications to the end of 1968. If the name appears in the L e x i c o n i t is available only for the unit to which the published name refers. (ii) The Divisional Subcommittee on Stratigraphic Nomenclature in the State in which the proposed unit occurs, may be consulted. Local records of names published since the Lexique, or of names reserved as advised in bimonthly Variations Lists of the C e n t r a l R e g i s t r y , may enable a quick check on the availability of a proposed name. The Queensland, New South Wales, and South A u s t r a l i a n Subcommittees maintain such records, compiled f r o m the Variations Lists, and they are available for reference through the respective Conveners. (iii) Proposed names, if not found in the Lexicon or advised by the Divisional S u b c o m m i t t e e as being unavailable, should be referred to the Assistant Director (Special Projects and Geoscience Services), Bureau of Mineral Resources, GPO Box 378, Canberra C i t y A C T 2601, f o r the a t t e n t i o n of the Stratigraphic Indexer. S u f f i c i e n t i n f o r m a t i o n should be given about the l o c a t i o n of the unit, the precise f o r m of usage proposed (i.e. f u l l s t r a t i g r a p h i c name, not just the geographic component), and author(s), to enable the name, if i t is available, to be adequately recorded. The S t r a t i g r a p h i c Indexer checks the name against the C e n t r a l Register of published s t r a t i g r a p h i c names and the register of reserved names. The author is then i n f o r m e d whether the name is available or not.

Australian Procedures

26.

If the name is p r e - e m p t e d the author is i n v i t e d to submit a l t e r n a t i v e s . Where there is room for doubt, or a judgement is required, the S t r a t i g r a p h i c Indexer r e f e r s the inquiry to the Convener of the S t r a t i g r a p h i c N o m e n c l a t u r e C o m m i t t e e . If a new geographic name is to be introduced the relevant State Surveyor-General's D e p a r t m e n t should be consulted. If the name is available, i t is reserved for the author, who is advised in w r i t i n g accordingly. Blank d e f i n i t i o n cards and instructions f o r obtaining approval f o r the c o m p l e t e d d e f i n i t i o n s f r o m the relevant Divisional S u b c o m m i t t e e are enclosed w i t h the l e t t e r . Names are reserved f o r f i v e years, unless they are published before then.

Approval of Definitions of Units before Publication

The d e f i n i t i o n card should be f i l l e d out f o l l o w i n g the p a t t e r n of the specimen d e f i n i t i o n card (Figures 4a and 4b, pp. 28 and 29) and should then be sent to the Subcommittee for the State or T e r r i t o r y * in which the unit occurs. The Subcommittee satisfies itself t h a t the proposed d e f i n i t i o n is in accord w i t h the I n t e r n a t i o n a l Stratigraphic Guide. Any alterations required are carried out by agreement w i t h the author. Once the d e f i n i t i o n is approved the signed card is lodged w i t h the C e n t r a l R e g i s t r y , where i t is available f o r r e f e r e n c e . A copy may be retained by the S u b c o m m i t t e e . Prospective authors are reminded t h a t reservation of a name and getting approval f o r the d e f i n i t i o n of a unit give no standing to t h a t u n i t . P r i o r i t y and standing are established only by publishing in a recognised s c i e n t i f i c or t e c h n i c a l p u b l i c a t i o n (see ISG, 3.D and N o t e 5, p. 8). D e f i n i t i o n s should be published, if possible, in the f o r m approved by the Divisional Subcommittee, and preferably in the same publication in which the name of the unit is f i r s t used. Although some s c i e n t i f i c journals are r e l u c t a n t to publish definitions because of the high cost of p r i n t i n g or f o r other reasons, there are several journals which, as a s c i e n t i f i c service, welcome definitions w i t h or w i t h o u t an accompanying paper; they include the f o l l o w i n g : (i)

Queensland Government Mining Journal

(ii)

Records of the Geological Survey of New South Wales

(iii)

Quarterly Australia

(iv)

(Australasian) Oil and Gas Review

Geological

Notes

the

Geological

Survey

South

The foregoing procedures are summarised graphically in Figure 5 (p. 30).

Central Register of Stratigraphic Names

A l l the i n f o r m a t i o n indexed prior to 1979 is held on cards. indexes are available:

The f o l l o w i n g major

Author Stratigraphic Name 1:250 000 Sheet area Basin Name Subject (using A M F Thesaurus for key words) Reserved Name Card Index of D e f i n i t i o n s approved by D i v i s i o n a l Subcommittees •Footnote

A l l C o m m o n w e a l t h T e r r i t o r i e s , including the A u s t r a l i a n A n t a r c t i c T e r r i t o r y and other offshore T e r r i t o r i e s , f o r m part of the T e r r i t o r i e s D i v i s i o n of the Society; the D i v i s i o n has its headquarters in Canberra.

Central Register

27.

In . addition, an incomplete index of Papua New Guinea names is held. The o f f i c i a l source of information for Papua New Guinea stratigraphic nomenclature is the G e o l o g i c a l Survey of Papua New Guinea, to the head of which (Chief Government Geologist) enquiries should be addressed.

, A r t i c l e s indexed since D e c e m b e r 1978 have been entered into a computerised data b a s e . I he indexing fields are almost the same as above, the exceptions being that the basin name c a t e g o r y has not been expanded to record major r e f e r e n c e s (mainly in titles) to t e c t o n i c provinces and other structural features, and a detailed locality field and 1:100 000 s h e e t a r e a s have been added. A c c e s s to the information on the data base is gained via any field combinations t h e r e o f . Also included are the various bibliographic details i.e. year publication, publication source, e t c .

or of

The stratigraphic names in the computer base are indexed in a similar fashion to those on the index cards: S t a t e ( s ) in which named unit occurs Major location of unit within r e f e r e n c e Description of how the name was used i.e. whether unit is defined, fully described, described, briefly described or only mentioned Month and year the name is indexed (a new field to f a c i l i t a t e preparation of Variation & Deletion lists) Geological age of unit (if the unit is defined or appears on a map) Additional c o m m e n t s The major advantage of the computer data base is that a name can be retrieved by any field, and s y s t e m a t i c listsings can be printed out. All r e f e r e n c e s published a f t e r 1969 are being t r a n s f e r r e d to the data base from the cards as resources permit. Information about changes of data recorded in the Central Register is made widely available - mainly to Geological Surveys and Universities - by two periodical lists. (i) The bimonthly Variations List contains names reserved in the period covered, listed by S t a t e or Territory, with the name of the proposer; reserved names for each S t a t e that have r e c e n t l y been published, for whom the name was reserved, by whom it was published, the r e f e r e n c e and a short comment on the nature of the r e f e r e n c e (e.g. defined, description only, map r e f e r e n c e only); other names, i.e. names published without prior reservation, the r e f e r e n c e and a short comment on the nature of the r e f e r e n c e ; names of published definitions of units, with the r e f e r e n c e . (ii) A Deletions List of names not published within five years of reservation is distributed once a year. Only those names for which retention is requested are retained - f o r a further five years.

28.

NAME OF UNIT

Summers Sandstone

STATE

Old

New nameZ-varm^km-ef ptH^i^hed-rmmeZ-ftede^hew^-Ufitt-(delete inappropriate terms) PROPOSER/S

W. Smith

RESERVED IN REGISTER OF PROPOSED NAMES

Figure 4a. Specimen Definition Card

PROPOSED PUBLICATION

Date

1/7/84

Initials K . M .

Australian Journal of Earth Sciences

Australian Procedures

DEFINITION DERIVATION OF NAME: 'Summers Downs' property; grid reference 12469215, Muttaburra 1:250 000 Sheet area. 2 DISTRIBUTION: The unit is exposed over 50 km in the northeast portion of the Muttaburra 1:250 000 Sheet area (SF 55-9) around the headwaters of the Snake River, TYPE SECTION: 750 m of white quartzose sandstone exposed along the banks of Diamond Creek (a tributary of Snake River), from 12388620 (bottom) to 12398622 (top of section). The top is identified by a light brown fine-medium silty quartz sandstone 2 m thick, the base by conglomeratic sandstone. LITH0L0GY: Sandstone, white, medium-grained, quartzose; massive to thick-bedded; rare cross-bedding; minor interbeds of sandy siltstones (some of which contain invertebrate faunas). THICKNESS: Range 630-960 m . RELATIONSHIPS AND BOUNDARY CRITERIA: Overlies the Carpentaria Marl (Jansen, 1960). Channelling in the marl suggests disconformity. Base of unit defined by prominent 3 m thick coarse-grained conglomeratic sandstone. Conformably overlain by the Jervis Formation (Jansen and Fell, 1964). AGE AND EVIDENCE: Faunas are dominated by bivalves and brachiopods which typify Dickins' Fauna II; viz. Megadesmus gryphoides (de Koninck), Eurydesma hobartense (Johnston), Deltopecten limaeformis (Morris), Ingelarella profunda (Campbell), Anidanthus springsurensis (Booker), and Attenuatella sp. The age is, therefore, Early Permian (Sakmarian/Artinskian): See Runnegar (1969). SYNONYMY: Langley (1921) included these beds in his 'Desert Series'.

Definition Card

u D iEsFr Ii N iM I Ti nI O xN >

(C c o n t i n u e d );

Figure 4b. Specimen Definition Card (continued)

REFERENCES: JANSEN, A.L., 1960. Late Carboniferous stratigraphy of the Windangee area. Proceedings of the Royal Society of Queensland, 63(2), 75-83. JANSEN, A.L., & FELL, B.K., 1964. Upper Palaeozoic sediments in the vicinity of Muttaburra. Ibid., 67(1), 17-28. LANGLEY, F., 1921. A geological reconnaissance of the Murraburra district. Queensland Government Mining Journal, 125, 6-16. RUNNEGAR, B.N., 1969. The Permian faunal succession in eastern Australia. Special Publications of the Geological Society of Australia, 2, 73-98. NOTES: The unit defined above is fictitious. Type section and relationships may, alternatively, be portrayed by graphic lithological column on Continuation card. It is desirable that if possible, limits of unit be defined by reference to top and bottom beds of type section. In practice this is rarely possible, in which case criteria for upper and lower limits of unit should be stated under "Relationships and boundary criteria". Reasons for age assigned should be stated with brief statement of evidence, which may not be palaeontological. Circumstances may require either substantially more or less detail than that given above under each heading. See also c o n t i n u a t i o n cards ( N o .

)

( f o r S u b - C o m m i t t e e use o n l y ) D e f i n i t i o n a p p r o v e d by

Stratigraphic

Nomenclature

Sub-Committee

Signed on

(date)

( f o r Registry use o n l y ) N a m e first p u b l i s h e d b y :

M e m b e r of Sub-Committee

Comments

D e f i n i t i o n p u b l i s h e d by:

29.

Australian Procedures

Field geologist on mapping project

Identify rock units

Select stratigraphic names

Consult Lexique name if available I name not listed in Lexique, or Lexique not available Consult Divisional Subcommittee

published

select

another name

name unavailable

select another name

Consult B.M.R Central Registry

name

select another name

name available

no geographic names l e f t

name may be available unavailable

Consult Surveyor General's Dept. introduce new geographic name

Central Registry reserves name (for 5 years) V

Central Registry advises geologist 8 supplies definition cards

Central Registry notifies reservation in Variations List

Geologist prepares definition Submit definition card to Divisional Subcommittee

definition not approved

definition

Central Registry files definition card

approved

A Geologist publishes definition

Figure 5.

Central Registry records publication

Geologist revises definition

Central Registry notifies publication in Variations List

P r o c e d u r e for reserving, defining, and publishing s t r a t i g r a p h i c n a m e s .