crosdale coal facies aus

8/19/2019 Crosdale Coal Facies Aus

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Coal facies studies in Australia

Peter J. Crosdale*

Coalseam Gas Research Institute, School of Earth Sciences, James Cook University, Townsville, Qld 4814, Australia

Received 1 January 2003; accepted 12 October 2003

Abstract

Despite the economic importance of coal to the Australian economy, detailed studies of controls on variation in coal type are

remarkably few. However, important contributions have been made in the understanding of coal facies development. Tertiary

lignite deposits of the Gippsland Basin provide key insights into the development of lithotype cyclicity and its relationship to

relative sea-level changes, with individual paling-up cycles being correlated to parasequences. Studies of Permian hard coals

have identified relationships between coal type and surrounding sediments. Unfortunately, these relationships have been widely

over-interpreted in a manner that has diminished their real value.

D 2004 Elsevier B.V. All rights reserved.

Keywords: Depositional environment; Lignite; Black coal; Lithotype; Maceral

1. Coal in Australia

Extraction, utilization and export of coal is well

recognized as a major contributor to the Australian

economy. According to the Australian Bureau of

Statistics, in 2001–2002 coal and associated products

accounted for AUD$13.4 billion, or almost 9%, of all

goods and services exported. Coal production in

1999–2000 was 254 million t of black coal and 66million t of brown coal, making Australia the 4th

largest black coal producing country (behind PR

China, USA and India) and the world’s largest ex-

porter of both steaming and coking coals.

Australian coals are widely distributed both spa-

tially and temporally, with mineable coals found in

most coal-forming periods represented except those

of the Carboniferous (Ward et al., 1995). Economi-

cally, the most important coals are those of the

Permian Sydney– Gunnedah– Bowen Basin of New

South Wales and Queensland and the Late Eocene to

Middle Miocene deposits of the Gippsland Basin in

Victoria. Petroleum products have also been identi-fied as being sourced from many of these coals, e.g.

the gas resources of the Permian Cooper Basin and

the oil and gas resources in Bass Straight (Gippsland

Basin).

The Permian coals are generally hard coals be-

tween high volatile bituminous and anthracite rank,

producing a wide variety of commercial products

including thermal, hard and soft coking, PCI, etc.

The Tertiary coals of Victoria are lignite in rank and

are used predominantly for power generation although

0166-5162/$ - see front matter D 2004 Elsevier B.V. All rights reserved.doi:10.1016/j.coal.2003.10.004

* Tel.: +61-7-3394-3011; fax: +61-7-3394-3088.

E-mail address: [email protected]

(P.J. Crosdale).

www.elsevier.com/locate/ijcoalgeo

International Journal of Coal Geology 58 (2004) 125–130


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Table 1

Author Method Depositional environment/

other comments

Age; Area ASTM rank Ro%

Paleozoic coal basinsDiessel, 1975 Carboniferous,

Hunter Valley

Diessel, 1965, 1970,

1982, 1985, 1986a,b,

1996; Diessel et al.,

1967; Glasspool, 2000

coal petrology, TPI/GI,

sedimentology, vitrinite

reflectance, fluorescence,

mesofossils

first paper on TPI/GI

technique 1982, source

paper for this technique,

relates coal petrography

to sedimentology 1986a;

vertical trends suggesting

overlying marine influence

with some sequence

stratigraphic significance;

explanation to the origin

of inertinites by charring

Permian, Sydney

Basin

bituminous 0.6 – 1.2

Tadros, 1988a,b, 1993 maceral Permian, GunnedahBasin

bituminous

Shibaoka and Smyth, 1975;

Smyth and Cook, 1976

microlithotype, lithotype explanation of dulling up

sequences

Permian, Sydney and

Gunnedah Basins

bituminous

Diessel, 1982 TPI/GI first paper on TPI/GI

technique

Permian, Sydney and

Gunnedah Basins

bituminous

Hunt, 1982, 1989; Hunt

and Hobday, 1984; Smyth,

1989

microlithotype, maceral,

sulphur

relates microlithotypes to a

variety of sedimentary

environments

Permian, Sydney and

Gunnedah Basins

bituminous

Marchioni, 1980 maceral, microlithotype terrestrial/telmatic/limnic—

using Hacquebard and

Donaldson 1969. facies

diagram

Permian, Liddell Seam,

upper Hunter Valley,

New South Wales

hvb

Smyth, 1984 microlithotype relates microlithotypes to a

variety of sedimentary

environments

Permian, Cooper Basin bituminous

Beeston, 1991; Beeston

and Draper, 1991

maceral, palynology,

botany

combines a variety of

techniques to produce a

facies model for coal

deposition

Permian, Queensland bituminous

Cook, 1981 coal petrology, coal

geology

from Permian to

Cenozoic, Australia

Diessel and Smyth, 1995 maceral, microlithotype ternary microlithotype

diagrams with

superimposed clastic

environments

mostly Permian

of Australia

bituminous

and lignite

Hunt and Brakel, 1989 microlithotype relates microlithotypes to

a variety of sedimentaryenvironments

Permian, Australia bituminous

Mesozoic coal basins

Smyth et al., 1992 dispersed organic

matter

lacustrine environments Triassic, Gunnedah

Basin New

South Wales

Gould, 1980 plant megafossils dominantly conifer derived

coals in a moist temperate

climate

Middle Jurassic,

Surat Basin

sub-bituminous

P.J. Crosdale / International Journal of Coal Geology 58 (2004) 125–130126


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extensive research has been done on their liquefaction possibilities.

2. Facies studies

Given the economic importance of coal to the

Australian economy, surprisingly little detailed work

as been done on coal facies, especially on a regional

scale. There are a number of interesting problems

which detailed facies studies would help resolve,

including the large percentage of inertinite in manyof the Permian coals; the development of very thick

(up to 30 m), clean, inertinite-rich coals; the relation-

ship of coal type to sedimentary environment; the

development of lithotype cyclicity; controls on the

distribution of authigenic minerals. While some

aspects of these problems have been dealt with exten-

sively by some authors, many questions remain.

Facies studies of Australian coals reported here

(Table 1) deal predominantly with depositional envi-

ronments and utilize the full range of ‘standard’ and

Author Method Depositional environment/

other comments

Age; Area ASTM rank Ro%

Cenozoic coal basinsMeakin, 1985 palynology Eocene, St Vincent

Basin, South Australia

lignite

Baillie, 1992; Baillie and

Bacon, 1989

Eocene, Bass Basin,

Victoria

George, 1975; Blackburn,

1980, 1985; Lully et al.,

1980; George, 1982; Sluiter,

1984; Kershaw and Sluiter,

1982; Holdgate, 1985,

1996; Holdgate et al.,

1995; Khandekar, 1985;

Mackay et al., 1985;

Kershaw et al., 1987;

Sluiter et al., 1995

lithotypes, plant

megafossils,

lithotypes, palynology,

macerals, proximate

and ultimate analysis,

sequence stratigraphy,

sea level change

explanation of lightening

up of lithotypes using

sequence stratigraphy

and climatic changes

Oligocene/Miocene,

Latrobe Valley,

Victoria

lignite

Partridge, 1982; Smith, 1982 p alynology relates sea level change to

coal formation

Oligocene/Miocene,

Gippsland Basin,

Victoria

lignite

Anderson and Mackay,

1991; Holdgate, 1992;

Blackburn and Sluiter, 1994

lithotype, maceral,

palynology, sea level

change, plant

megafossils

review paper, details of

peat-forming plant

communities, ombrogenous

peats; many references to

unpublished and difficult

to access reports

Oligocene/Miocene,

Victoria

lignite

Partridge, 1997 palynology Miocene, Port Phillip

Basin, Victoria

lignite

Harris, 1980; Holdgate, 1997;

Holdgate and Clarke, 2000

sea level change South Australia;

Australia, New Zealand,

Germany; Australia

lignite

Murray et al., 1997 geochemistry Otway Basin,

Victoria/South Australia

General models

Diessel, 1998; Diessel et al.,

1995, 2000

sequence stratigraphy

Diessel and Gammidge, 1998 vitrinite reflectance

Table 1 (continued )

P.J. Crosdale / International Journal of Coal Geology 58 (2004) 125–130 127


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more novel techniques, e.g. fluorescence and reflec-

tance studies.

Particularly influential in black coal depositional

environment studies have been microlithotype (e.g.Shibaoka and Smyth, 1975; Smyth and Cook, 1976;

Hunt, 1982, 1989; Hunt and Brakel, 1989; Hunt and

Hobday, 1984; Smyth, 1984, 1989; Marchioni, 1980;

Diessel and Smyth, 1995) and maceral (e.g. Diessel,

1982, 1985, 1986a,b, 1996) analyses. These studies

have shown clear relationships exist between petro-

graphic composition of the coal and its enclosing

sedimentary environment. However, these relation-

ships are widely misinterpreted to infer conditions of

the peat-forming mire (see discussions in Crosdale,

1993; Wüst et al., 2001).

It is unfortunate that over-interpretation of petro-

graphic data, especially the maceral facies diagram

(Diessel, 1982), has occurred since these techniques

have a number of potential uses. Foremost is the

grouping and classification of coals based on their

complete and detailed petrography. Following this

classification it is possible to investigate vertical and

lateral changes of individual seams and sequences of

seams within a basin. The maceral and microlithotype

facies diagrams provide us with an easy way to

represent petrographic variability but challenge us to

correctly interpret the meaning.Lignite deposits of the Gippsland Basin have been

of particular interest since very thick coals occur (up

to 200 m) which are characterized by cycles of

paling-up lithotypes. These lithotype cycles have

been investigated by a variety of techniques includ-

ing the study of plant megafossils, palynology,

macerals, proximate and ultimate analysis, other

geochemistry and sequence stratigraphy. These tech-

niques, coupled with regional studies and correla-

tions with off-shore petroleum provinces, have

shown that each lithotype cycle represents a para-sequence (e.g. Anderson and Mackay, 1991; Holdg-

ate et al., 1995). Coupled with detailed restorations

of plant communities, a comprehensive picture of

lithotype development emerges. However, it is still

unclear how these systems work in detail. It is

simply not sufficient to say that rising sea-level

results in a rising water table due to ponding, or

that falling sea level has the opposite effect. Peat-

forming environments also respond strongly to local

climate and local ground water hydrology.

3. Conclusions

Despite some very detailed work in selected depos-

its, coal facies studies are generally poorly representedin Australia. This is especially significant given the

value of coal to the Australian economy and the value

of coal facies studies into understanding the geolog-

ical variability of deposits. However, important stud-

ies on Tertiary lignites and new ways of thinking

about coal development based on standard maceral

analysis have had large impacts.

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