Department of Geology • University of

VOLUME 10 NUMBER 2

Summary of formations and faunas of the Permian Back Creek Group in the Southeast Bowen Basin, Queensland D.J.C. BRIGGS & J.B. WATERHOUSE

Stratigraphy and palaeobotany of East and West Haldon, Main Range, Southeast Queensland M J. DUDGEON

Date of publication: June 1982 SUMMARY OF FORMATIONS AND FAUNAS OF THE PERMIAN BACK CREEK GROUP IN THE SOUTHEAST BOWEN BASIN, QUEENSLAND by D.J.C. Briggs & J.B. Waterhouse

(with 1 Text-figure)

ABSTRACT. In the southeastern Bowen Basin the Back Creek Group is almost entirely marine and comprises, in ascending order, the Büffel, Pindari, Brae, Oxtrack, Barfield and Flat Top Formations. We informally divide the Büffel Formation according to lithology into three members, each having a different fauna, but all of early Permian age. We correlate the upper member with the lower Homevale fauna of the northern Bowen Basin. The upper Homevale fauna is absent in the type Büffel, but is seen in strata mapped as Büffel to the north. The Pindari Formation is poorly fossiliferous in the type section. A marine fauna unmatched elsewhere in eastern characterizes the Brae Formation. The Oxtrack Formation has a distinctive small fauna known from New Zealand and , but not yet recognized elsewhere in the Bowen Basin. The thick, fine-grained Barfield Formation matches through its lithology and fauna the lower or restricted Ingelara Formation of the southwestern Bowen Basin. The Flat Top Formation contains a basal fauna like that of the Barfield, two successive younger faunas which match those of the Peawaddy and lower Blenheim Formations of the southwestern and northern Bowen Basin, and small overlying faunas of uncertain age.

INTRODUCTION The Permian sequence in the southeastern Bowen Basin has been divided into three major units : in ascending order, the Camboon Andesite, the shallow-marine Back Creek Group, and the fresh and brackish water Blackwater Group. In the southeastern Bowen Basin these units are exposed in a belt running roughly northwards from just south of Cracow Station, where they emerge from beneath Mesozoic sandstone of the , to north of Baralaba, where they are obscured by Cainozoic cover (Fig. 1 ). Six named formations are recognized in the Back Creek Group in this region. Wass (1965), Olgers et al. (1966), Dear et al. (1971), Molían et al. (1972), Whitaker et al. (1974) and Gray & Heywood (1978) accepted a four­ fold subdivision of the group into the Büffel, Oxtrack, Barfield and Flat Top Formations respectively. (See McClung 1981, table 4, p.18). Flood et al. (1981) recognized two additional formations, the Pindari and the Brae, between the Büffel and the Oxtrack Formations. This paper will summarize the stratigraphy, faunas, and correlations of the Camboon and Back Creek rocks. Part 1. STRATIGRAPHY CAMBOON VOLCANICS Derrington et al. (1959) defined the Camboon Andesite as ‘grey and purplish-grey to locally greenish-grey andesite tuffs and agglomerates’

Pap. Dep. Geol. Univ. Qd, 10(2): 69-82, June 1982 70

Text-fig. 1 Distribution of Permian formations of the Back Creek Group in the southeast Bowen Basin, emended from Dear et al. (1971) and Whitaker etal. (1974). We have grouped the Brae and Pindari Formations, and north of Theodore, the Oxtrack Formation, for reasons of scale. 71 unconformably underlying the Back Creek Group. They gave the type area as ‘near Camboon Homestead’ in error for Camboon Woolshed, 24 km north­ west of Cracow (Dear et al. 1971). Derrington et al. set no specific lower limit to their formation, and some authors (Molían et al. 1972; Dickins & Malone 1973) have included in it the entire sequence of igneous and sedi­ mentary rocks between the Auburn Complex and the Back Creek Group. Dear et al. (1971) restricted the term to cover the upper part of this sequence, showing that the lower part (called the Torsdale Beds and regarded as mostly Carboniferous) consists of predominantly acidic lavas and pyroclastics, and various sediments. Although andesite is predominant, a diversity of igneous rock types is present, and we suggest that the neutral term volcanics may prove to be more appropriate and more widely applicable for the Camboon rocks. There does not appear to be any clear difference between the Camboon and the Lizzie Creek Volcanics, which occupy an almost comparable strati­ graphic position in the northern part of the Bowen Basin, and McClung (1978, fig. 1, p. 19) has referred the Camboon Andesite of the southeast Bowen Basin to the Lizzie Creek Volcanics. However the name Camboon (Derrington et al. 1959) has priority over Lizzie Creek (Malone et al, 1966). Formational units within the volcanics have been distinguished in the north by Isbell et al. (1960), and there are several distinct units in the south, which are of formational status though not yet formally named. Therefore the Camboon Volcanics might be treated as a group. On Cracow Station, two different igneous rock types, neither matching the lithologies described from the Camboon type area by Derrington et al. (1959) directly underlie the Back Creek Group (Briggs 1979). Subvitreous, massive and laminated ?ignimbrite underlies the sediments on Büffel Hill, whilst on either side along strike at least 70 m of interbedded compact and highly vesicular basalt takes its place. The contacts of these with each other and with Camboon Andesite are not exposed. Molían et al. (1972) and Hey wood (1974) showed that andesites are accompanied by basalts and ignimbrites to the north. These are separate and mappable and may be named as distinct units within the Camboon Volcanics. Marine fossils are unknown from the volcanic sequence in the south­ eastern Bowen Basin. But Dear et al. (1971) mapped as Camboon a sequence of interbedded marine sediments, lavas and tuffs of the Prospect Creek Folded Zone in the Eungella-Cracow Mobile Zone, and reported marine faunas resembling those of the Büffel Formation through most of this sequence, and directly above it.

BACK CREEK GROUP

The Back Creek Group was named by Derrington et al. (1959) for the Permian, mostly marine, formations between the Camboon Volcanics and the younger Permian non-marine sequences of the southeast Bowen Basin, as has been reviewed by McClung (1981). Dickins & Malone (1973) extended 72

the name well beyond its original definition in applying it to rocks of similar and dissimilar appearance throughout the Bowen Basin but we prefer to restrict the group to the southeast Bowen Basin. Major faunal breaks, including one in the type area (Wass 1965, and later workers), and terrestrial deposits interrupt the marine sequence in various parts of the basin. In the southeastern Bowen Basin, the constituent formations of the group are based on type sections separated by considerable distances, instead of a continuous sequence, and this has lead to multiple names, increased risk of miscorrelation, and omission of units. Büffel Formation The Büffel Formation was defined by Wass (1965) from Büffel Hill, which provides the type section across its northwestern flank. The type section runs through a syncline and takes in some Camboon volcanics (Flood et al 1981) though Wass did not realise this. The Büffel Formation has been found almost as far north as Baralaba (Dear et al. 1971) and has been described as principally limestone and siltstone. One of us has recently re-examined the formation in its type area and has divided it into three parts (Briggs 1979), for the present treated as informal members within the Büffel Formation.

Lower (Sandstone) Member. This member consists of fossiliferous marine volcanoclastic sediments, predominantly of very fine sand grade, coloured dark green where fresh and brown where weathered. Its outcrop is confined to the neighbourhood of Cracow Station, where it occupies what appears to be an erosional depression 2.3 km wide along strike in the underlying volcanics. The member can be divided into three units according to the dominant biogenic constituents: a lower unit (up to 36 m thick) containing abundant bioclasts derived entirely from brachiopods and molluscs, a middle unit (up to 16-20 m thick) containing, in addition, abundant bryozoan material, and an upper unit (over 6 m thick) in which bioclasts are rare. Because of irregularities in the base and top of the member, the total thickness does not exceed 45 m in any one place. Brachiopods, including Lissochonetes, a new aulostegid genus, Terrakea, Trigonotreta, Tomiopsis, Notospirifer, bivalves (Eurydesma, Deltopecten and others), gastropods (Keeneia, Peruvispira and IMourlonia) and bryozoans are abundant. Tomiopsis denmeadi (Campbell), Lissochonetes cracowensis (Etheridge), a species of the new aulostegid, and Stenopora ovata Lonsdale are confined in the Büffel Formation to this member.

Middle (Limestone) Member. Limestone, generally regarded as the typical lithology of the Büffel Formation, is mostly confined, in the type section, to an interval about 30 m thick near the middle of the formation. In the syncline west of Cracow Homestead, this member consists of interbedded finely laminated silty calcilutite (poorly washed biosparite and packed biomicrite) and thick-bedded calcarenite and calcilutite (poorly washed to unsorted bio­ sparite), the proportion of thick bedded limestone increasing northwards. 73

Chert is common in this area as primary void fillings and secondary replace­ ments, and small igneous pebbles are scattered over two horizons. Dear et al. (1971) and Whitaker et al. (1974) described several isolated occurrences of Büffel limestone between Cracow Station and Banana, some or all of which may belong to this member. In the type area the member is richly fossiliferous throughout, containing brachiopods (Streptorhynchus, Echinalosia, Taeniothaerus, the new aulostegid genus, Terrakea, Auriculispina, Cleiothyridina, Trigonotreta, Tomiopsis, Notospirifer), bivalves (Eurydesma, Deltopecten, Etheripecten), gastropods (Keeneia, Peruvispira), Conocardium, bryozoans, coral (Euryphyllum), Pelmatozoa and a sponge. The productoid brachiopod originally described as Horridonia mitis Hill and which we now believe is Marginifera or an ally, is confined to a thin interval near the middle of the member, where it is very abundant. It is known only from Cracow Station. A major disconformity apparently separates the lower and middle members of the formation, for mapping indicates removal of the upper, and most of the middle unit of the lower (sandstone) member in places, and corresponding onlapping of the middle (limestone) member onto the lower member (Briggs 1979). The lithologies of the two members are totally different and do not interfinger or intergrade.

Upper (Siltstone) Member. The uppermost member of the Büffel Formation in the type area consists of some 55 m of pale fossiliferous argillaceous to arenaceous limestone bands alternating with recessive calcareous siltstone, in cycles 3 to 10 m thick. Unlike the middle member, coarse calcarenite and calcirudite are absent. The limestones contain considerable terrigenous material, bioturbation is widespread, and crinoidal skeletal material is relatively sparse. Chert, made up largely of silicified sponge spicules, is present north of Büffel Hill. The member has not been identified definitely north of the type area. The distinctive fauna includes Echinalosia sp., Anidanthus springsurensis Booker, Camerisma sp., Tomiopsis ovata (Campbell), and other species, but no Eurydesma or aulostegids. The member seems to lie conformably on the middle member.

Pindari Formation Flood et al. (1981) named the Pindari Formation after the location of the type section, the Pindari Hills, west of the Cracow-Taroom road. Wass (1962) employed the name and concept of the Pindari Formation informally, but later Wass (1965) abandoned the term, to apparently include the beds in the Büffel Formation. Later workers (Molían et al. 1972; Whitaker et al. 1974) treated at least some of the strata now included in the Pindari Formation as part of the Oxtrack Formation. The lower part of the formation includes well sorted very fine to coarse quartzose lithic arkosic arenite, containing plant remains in some places and brachiopod spines in others. The upper part of the formation (the only part exposed in the type section) consists of interbedded feldspathic (tuffaceous) 74 very fine sandstone and siltstone containing few fossils, mainly large sponge spicules, some brachiopod spines, and indeterminate fenestrate bryozoans. Briggs (1979) stated that the arenite appears to fill an erosional depression in the Büffel Formation at one locality, which would indicate that the basal Pindari contact is least locally disconformable. Flood et al. (1981) stated that the maximum thickness of about 100 m is seen in and near the type section, and that to the north and south the formation thins rapidly to a few metres. They suggested that the formation may also be present in GSQ drillhole Banana NS1 (see Gray & Heywood 1978). At Rose’s Pride mine, some 13 km north of Büffel Hill, about 18 m of quartzose arkosic arenite containing abundant marine fossils underlie the Oxtrack Formation and directly overlie volcanics. The relationship of this arenite, mapped as Büffel Formation by Wass (1965) and later workers, to the sequence on Cracow Station is unknown. Lithologically it partly resembles, and may correlate with, the lower part of the Pindari Formation on Cracow Station, although marine fossils are almost entirely lacking there. Alternatively, it is possible that the correlative of the Rose’s Pride arenite is missing on Cracow Station because of a disconformity between the Büffel and Pindari Formations. The Rose’s Pride sequence includes abundant Streptorhynchus, Wyndhamia cf. brittoni (Maxwell), Taeniothaerus, new aulostegid, Anidan thus, Eurydesma and other brachiopod and mollusc genera.

Brae Formation Námed from Brae Holding, the Brae Formation of Flood et al. (1981) previously has been mapped within the Büffel by Wass (1965), and within the Oxtrack by Malone et al. (1969), Molían et al. (1972), Dear et al. (1971) and Whitaker et al. (1974). The most characteristic lithology is a green to buff mudstone, which, in the lower part in the type area west of the Pindari Hills, contains calcareous concretions and sandstone horizons. Bioturbation is common. In the type section the formation is about 160 m thick and rests with apparent conformity on the Pindari Formation. The Brae Formation can be traced from the type area northwards to west of Cracow town, where it is obscured by younger sediment (Flood et al. 1981). Just to the north on the Cracow-Theodore road, and in GSQ Mun- dubbera 5^8 core on Gyranda Station (Gray & Heywood 1978), the Brae Formation is absent and the Oxtrack Formation directly overlies volcanics. The formation reappears further north and was recorded by Flood et al. (1981) east of Theodore, west of and at the Leichhardt Highway crossing of Lonesome Creek, and near Banana in CSQ Banana core NS 1 (as the interval recorded by Gray & Heywood (1974) as ‘Büffel Formation correlative’). Our observations indicate it is absent on Mount Breast, but one of us (J.B.W.) has found the characteristic Brae lithology and fauna as far north as Thuriba Homestead in the Duaringa Sheet area. In the type area, marine fossils are mostly confined to the upper part of the formation. Brachiopods include species of Echinalosia, Cancrinella, Trigonotreta and Notospirifer, and several genera less common in the eastern 75

Australia Permian, such as Lethamia, Stenocisma, Martiniopsis, Spinomartinia and Pustuloplica, based in unpublished studies by J.B.W. Paraconularia is found near the base of the formation.

Oxtrack Formation Derrington et al. (1959) named the Oxtrack Formation from the type area, Oxtrack Creek, where fossiliferous brown-white banded limestone containing abundant crinoid ossicles is exposed. No top or bottom is visible here, as the outcrop is surrounded by extensive plains of alluvium. Derrington et al. and several subsequent authors have also included in the formation siltstones and sandstones from other localities, but Flood et al. (1981) have placed most of these in the Brae Formation. The formation, as restricted by Flood et al. (1981), has been traced as far south as Cracow Station and north beyond Mount Ox, and forms several apparently discrete lenses. We do not know its full extent further north, but we have found typical Oxtrack lithologies on Mount Breast. In the Cracow region the Oxtrack Formation contains a small but abundant fauna dominated by Echinalosia maxwelli (Waterhouse), Terrakea cóncava Waterhouse, Tomiopsis ingelarensis (Campbell) subsp. confusus (Waterhouse), and new species of Trigonotreta, Cancrinella and Streblochondria (J.B.W., in prep.)

Barfield Formation Derrington et al. (1959) defined the Barfield Formation from a type area near Barfield Station, 22 km southeast of Banana. Subsequent workers have recognized the formation throughout the southeastern Bowen Basin, and consequently have abandoned the other formation names which Derrington et al. proposed for the same sequence elsewhere in the region. Thus Wass (1956), Molían et al. (1972), Whitaker et al. (1974), and Gray & Heywood (1978) equated the Barfield with the Orange Creek, Acacia, and Passion Hill Formations proposed for the Cracow area. Similarly, Dear et al. (1971) equated the Barfield with the Four Mile Mudstone, Cottenham Sandstone and Station Mudstone, which were proposed for the area east of the Banana Fault, treating them as members within the formation. Dear et al. (1971) rejected two other names proposed by Derrington et al. (1959) for this area because they are based on a part of the Barfield Formation apparently duplicated structurally. Gray & Heywood (1978) exhaustively described the lithology of the formation in the Gyranda area. They indicated that the formation was divisible into ‘subunits’ and consists principally of mudstone and shale, and lesser amounts of sandstone, siltstone, tuff, volcanic breccia, conglomeratic mudstone and limestone. Dear et al. (1971) described similar lithologies in the Monto Sheet area. Glendonites and calcareous concretions occur in both areas (Wass 1965; Dear et al. 1971). Some sandstone beds are graded. Reported total thicknesses range from 490 m in the type area to 840 m in the western limb of the Ferguson Syncline (Dear et al. 1971) and 900 m at Back Creek and near Mount Steel (Whitaker et al. 1974). The formation lies apparently conformably 76 on the Oxtrack Formation where this is present, and disconformably on the Brae Formation elsewhere. Gray & Hey wood (1974) recorded marine fossils from all five ‘subunits’ of the formation, but indicated that fossils were most common in the middle one. In the Monto Sheet area fossils occur mainly in the upper part but are locally abundant in the middle part (Dear et al. 1971). Near Gyranda Station the fauna includes the brachiopods Lissochonetes semicircularis Campbell, Wyndhamia blakei Dear (= W. ingelarensis Dear), Terrakea multispinosa Dear, Cancrinella magniplica Campbell (= C. gyrandensis Wass), Cleiothyridina anabathra Waterhouse, Tomiopsis ingelarensis (Campbell), Spiriferellina sp. and other species, various molluscs including Plagioglypta and Prodentalium, and a large Paraconularia (Parfrey 1978), based in unpublished studies by Parfrey (1978) and one of the authors, J.B.W.

Rat Top Formation Derrington et al. (1959) named this formation after Mount Flat Top and designated a type area in the core of the Ferguson Syncline, where no overlying rocks are preserved. The rocks in the type area are relatively resistant and include fine sandstone, siltstone, mudstone, conglomerate, limestone and andesitic lava and tuff (Dear et al. 1971). Fossil are locally abundant. Dear et al. (1971) extended the scope of the formation to include overlying marine, fossiliferous, poorly exposed mudstone and siltstone, included by Derrington & Morgan (1960) as part of the overlying Banana Formation. In this extended sense, the formation is 550 and 610 m thick in the Monto Sheet area (Dear etal. 1971). Whitaker et al. (1974) equated the Flat Top Formation with the Mount Steel Formation, proposed by Derrington et al. (1959) in the Cracow area. Gray & Hey wood (1978) have since shown that the uppermost 100 m of the Mount Steel Formation are probably nonmarine, and belong with the overlying Gyranda Formation. The remaining 400 m or so are said to consist dominantly of ridge-forming marine siltstone, less fossiliferous than the Flat Top Formation in its type area. Unpublished studies by one of us (J.B.W.) on Flat Top sequences north of Theodore reveal three successive faunas in the lower half of the formation. A basal fauna from the type section, and rare elsewhere, is characterized by Tomiopsis dissimilis (Waterhouse) and shares Wyndhamia blakei and Terrakea multispinosa with the Barfield Formation. Filiconcha hillae Dear and Tomiopsis mantuanensis (Campbell) appear here for the first time. In most of the slightly younger localities in the Flat Top Formation, Wyndhamia blakei is replaced by Echinalosia ovalis (Maxwell), and T. mantuanensis becomes more common. Other species of brachiopods and molluscs from these localities include Lissochonetes solida Dear, Filiconcha hillae Dear, Terrakea multispinosa Dear, Atomodesma variabile Wanner and Etheripecten dawsonensis (Runnegar & Ferguson). This fauna may be seen in the well known quarry site beside the highway to Banana about 15 km northeast of Theodore. At what appears to be a slightly higher level, T. multispinosa is replaced by T. brachythaera 77

(Morris). Dear et al. (1971) reported sparse fossils from the poorly outcropping upper half of the formation, including Attenuatella and Tomiopsis mantuanensis (Campbell).

Part 2. CORRELATIONS Numerous studies have systematically described brachiopods and molluscs from the Bowen Basin, but only a few, Campbell (1965) on Terebratulidina and Runnegar (1967) on Pholadomyoida, are comprehensive in treating whole groups from all or most levels of the sequence. Many species remain to be described. From unpublished studies on faunas from the Brae, Oxtrack, and Barfield Formations, half of the 39 species are new. Of some fifty species of brachiopods and molluscs from the Flat Top Formation, half are new to the region. McClung (1981, p. 28) has also emphasized the need for further systematic study. Clearly the Permian brachiopods and molluscs in the southeastern Bowen basin require further study, and this study should in turn help resolve the conflicts between the correlation schemes proposed by Dear (1972), Dickins & Malone (1973), and McClung (1978).

Büffel and Pindari Formations Dear (1972, p. 4) correlated the Büffel Formation fauna with the Homevale fauna of the northern Bowen Basin, believed to be from the lower part of the Tiverton Formation (Dickins in Malone et al. 1966). Dickins & Malone (1973) and McClung (1978) concurred with this correlation. Dickins (1964) included the Homevale and Büffel faunas in his Fauna II, and McClung (1978) correlated both with the ovata Zone of Runnegar & McClung (1975). The ‘Homevale fauna’ requires elaboration. We have examined the sequence carefully, and would confirm the observation by Isbell (1955) that the main part of the fossiliferous sequence near Homevale may be divided into A, a basal Homevale fauna with Eurydesma and Tomiopsis, B, a lower Homevale fauna containing abundant small productids (Anidanthus, Auriculispina, Terrakea, Echinalosia), Attenuatella (near the top), Tomiopsis and other genera, and C, an upper Homevale fauna characterized by abundant Taenio- thaerus, a new aulostegid genus, Wyndhamia, Trigonotreta, Tomiopsis and other genera. A band containing abundant Lissochonetes separates the two parts. Our observations indicate that in the type section of the Büffel Formation, the fauna of the upper (siltstone) member matches the lower Homevale fauna B. Attenuatella convexa Armstrong at the top of the lower Homevale fauna B (in or close to the Lissochonetes band) suggests correlation with part of the Farley Formation in the (see Armstrong & Telford 1969). The upper Homevale fauna C has been recognized in the sandstone at Rose’s Pride mine described above, and elsewhere in Queensland in the Yarrol Formation and in the Eurydesma-Taeniothaerus faunas of the Cattle Creek Formation (Briggs 1979). We recognise correlatives of both the lower (B) and the upper (C) Homevale faunas widely throughout southern Asia, and suggest from 78 Table Table Tentative 1. correlations ofthe Creek Group Back in the southeastern Bowen Basin. 79 these correlations that the faunas are Tastubian and Sterlitamakian respectively (Briggs 1979; J.B.W. in prep.). We are not yet able to accurately date the lower and middle members of the Büffel Formation, which contain many species not reliably recorded elsewhere (e.g. Tomiopsis denmeadi, IMarginifera mitis, Lissochonetes cracow- ensis, and several undescribed aulostegid species). Their position below the equivalents of the lower Homevale fauna suggests that the faunas of these members may be partly of the same age as other Eurydesma-Keeneia faunas found in the Lochinvar, Allandale and Wasp Head Formations of the Sydney Basin, and the Tamarian Stage (Clark & Farmer 1976) of Tasmania. Precise comparison with these other Early Permain sequences is difficult because they lack several genera found in Büffel faunas. Waterhouse (1976) correlated the Sydney Basin and Tasmanian faunas with the Asselian Stage. Our studies show that the faunas of the Büffel Formation lasted for a much longer interval than appreciated by previous workers (i.e. McClung 1981, fig. 7, p. 26), for not only the interval of socalled fauna II, but for earlier times as well.

Brae Formation The Brae fauna is a distinctive fauna that cannot be readily matched with any other known fauna in eastern Australia. There are some similarities at a generic level to the fauna of the Oxtrack Formation, so that the two might represent almost contemporaneous faunas of two different facies, or the Brae fauna might be somewhat older. In the northern Bowen Basin the Glendoo Sandstone Member and equivalent may be of about the same age, but this member represents a different marifie environment and its bivalve- dominated fauna (Fauna III B of Dickins, 1964) is difficult to compare with the Brae fauna. The Glendoo Sandstone Member is preceded and succeeded by thick unfossiliferous beds, some of which could be the same age as the Brae Formation.

Oxtrack Formation The Oxtrack Formation, now restricted to beds like those of the type locality, has a very distinctive fauna which we have not recognized elsewhere in the Bowen Basin. The same fauna, characterized by Echinalosia maxwelli (Waterhouse) and Terrakea cóncava Waterhouse, is found in the Fenestella Shale of the northern Sydney Basin and in the upper Letham Formation of New Zealand (Waterhouse 1964, 1976). In the southwestern Bowen Basin, the Oxtrack Formation is likely to match part of the upper Aldebaran Sand­ stone, as Dear (1972) suggested, or as we show in Table 1, an unconformity recognized between the Aldebaran and Freitag Formations by Power (1966).

Barfield Formation Parfrey (1978) correlated the Barfield Formation with the Ingelara (s.l.) and Freitag Formations of the southwestern Bowen Basin, supported by further study by J.B.W. There are many shared species, notably Wyndhamia blakei (= ingelarensis), Terrakea multispinosa, and Cancrinella magniplica, 80 which occur in the lower Ingelara Formation sensu Campbell (1953). Dear (1972) also matched the Barfield with the Ingelara Formation, using Ingelara in the sense of Campbell (1953), but the upper Ingelara of Campbell (1953) has a reduced fauna, and is correlated with the Peawaddy Formation by several authorities. Others have correlated the Barfield Formation with the lower Peawaddy Formation (McClung 1978) (possibly = upper Ingelara) or with the upper Peawaddy (Dickins & Malone 1973). The Barfield fauna is matched by us with the Exmoor fauna (Dear 1972) of the basal Blenheim Formation in the northern Bowen Basin, which has abundant Wyndhamia blakei Dear, as well as Tomiopsis isbelli, characteristic of the is belli Zone of Runnegar & McClung (1975).

Flat Top Formation Like the similar fauna of the underlying Barfield Formation, the basal Flat Top fauna correlates with the Exmoor fauna of the northern Bowen Basin, the lower or restricted Ingelara fauna of the southwest, and the isbelli Zone of Runnegar and McClung (1975). In the two overlying faunas, the characteristic fossil Echinalosia ovalis suggests correlation with the lower E. ovalis Zone of Runnegar & McClung (1975) (McClung 1978). This fauna is also found in the ‘Mantuan Productus bed’ of the upper Peawaddy Formation of the south­ western Bowen Basin (Maxwell 1954) and in the northern Bowen Basin in the Blenheim Formation between the Exmoor and Scottville faunas (from new work by J.S. Jell and J.B. Waterhouse). Terrakea multispinosa is not found in the latter two areas, where only T. brachythaera is known. We have no evidence regarding the correlations of the small faunas reported by Dear (1972) from the upper half of the Flat Top Formation, but from general stratigraphic considerations the rough match with the upper Blenheim Formation suggested by Dear (1972) and Dickins & Malone (1973) is feasible.

ACKNOWLEDGEMENTS We gratefully acknowledge the contributions, in the field and in discussion, especially with our colleagues at the Department of Geology and Mineralogy, University of Queensland, S. Parfrey, P. Heywood, P.G. Flood and J.S. Jell. Figures were drafted with the help of Mrs E. Burdin, Department of Geology, University of Queensland.

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D.J.C. Briggs &, J.B. Waterhouse Department of Geology and Mineralogy University o f Queensland St Lucia, Queensland 4067