Charleville Queensland
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l:250,000 GEOLOGICAL SERIES-EXPLANATORY NOTES CHARLEVILLE QUEENSLAND I I \ NT. I . I \ I QLD i I \- - -·-·-·- L·-·1 • VI."· i I SA r- - --·- ..r~.,< I I i N.S.W. r~ 0 j ·,J""·---. I VIC. ' SHEET SG/55-10 INTERNATIONAL INDEX COMMONWEALTH OF AUSTRALIA STATE OF QUEENSLAND 1:250,000 GEOLOGICAL SERIES-EXPLANATORY NOTES Charleville, Qld SHEET SG/55-10 INTERNATIONAL INDEX COMPILED BY D. SENIOR Published by the Bureau of Mineral Resources, Geology and Geophysics and issued under the authority of the Hon. R. W. C. Swartz, M.B.E., E.D., M.P, Minister for National Development 1971. COMMONWEALTH OF AUSTRALIA DEPARTMENT OF NATIONAL DEVELOPMENT MINISTER: THE HON. R. W. C. SWARTZ, M.B.E., E.D., M.P. SECRETARY: L. F. BOTT, D.S.C. BUREAU OF MINERAL RESOURCES, GEOLOGY AND GEOPHYSICS DIRECTOR: N. H. FISHER GEOLOGICAL BRANCH: ASSISTANT DIRECTOR: J. N. CASEY STA TE OF QUEENSLAND DEPARTMENT OF MINES MINISTER: THE HON. R. A. CAMM UNDER SECRETARY: E. K. HEALEY GEOLOGICAL SURVEY OF QUEENSLAND CHIEF GOVERNMENT GEOLOGIST: J. T. Wooos Printed in Australia by the Tasmanian Government Printer, Hobart Explanatory Notes on the Charleville Geological Sheet Compiled by Daniele Senior The Charleville Sheet area was mapped in 1968 as part of a regional geological reconnaissance of the Great Artesian Basin undertaken by the Bureau of Mineral Resources and the Geological Survey of Queensland. Air-photographs at a scale of approximately 1 : 50,000 taken by the RAAF in 1954 provide a complete coverage of the area. Cadastral maps at a scale of 1 inch to 4 miles are available from the Queensland Department of Public Lands, Brisbane, and the photomosaics at 1 inch to 1 mile scale and 1 :250,000 planimetric maps from the Division of National Mapping, Canberra. Access to the area is good. Bitumen roads connect Charleville Town with Brisbane (Warrego Highway) and Augathella (Mitchell Highway). Graded and formed roads join Charleville with Quilpie to the west (Diaman tina Developmental Road), Adavale to the northwest, and Cunnamulla via Wyandra to the south (Mitchell Highway). Most of these roads are negoti able in all weather, although 4-wheel-drive vehicles are desirable on the unsealed roads after heavy rain. Charleville (population about 6000) is the only centre of settlement and serves the whole area. It has an all-weather runway and receives scheduled air-services from Sydney and Brisbane. Previous investigations Before the 1968 survey ( Senior et al., 1969) there had been few regional geological investigations in the Charleville Sheet area. However, regional studies of the geology of Queensland (Whitehouse, 1940, 1941, 1954), of the subsurface water supplies in the Great Artesian Basin ( Ogilvie, 195 4), and of duricrust ( W oolnough, 192 7) are relevant. Tanner ( 1966, 1968) discussed the Palaeozoic rocks beneath the Great Artesian Basin and specifically the Adavale Basin with reference to the area mapped. Heikkila ( 1966) described the Palaeozoic of the Adavale Basin, including the Cooladdi and Westgate Troughs in the Charleville Sheet area. Gravity, seismic, and aeromagnetic surveys cover most of the area, and are particularly concentrated in the northwest; Bouguer anomalies are shown on the map. Table 1 summarizes the results of these surveys. Six oil exploration wells were drilled in the area (Table 5) and are discussed in the Economic Geology section. 3 TABLE I-GEOPHYSICAL SURVEYS YEAR ABB RE VIATED TITLE REFERENCE Seismic sun•eys 1959-1960 Quilpie-Thargomindah Charleville Hier & Spivey, 1962 seismic survey 1961 Seismic survey Adavale area Hier & Spivey, 1961 1962 Reconnaissance survey Charleville Fjelstul, 1962 North area 1963 Detail survey Quilberry Creek Fjelstul & Beck, 1963 Prospect 1965 Augathella seismic survey AMOSEAS, 1965 1966 Adavale Basin detail survey Fjelstul & Rhodes, 1966 Gravity surreys 1960 Gravity traverse Quilpie to Roma Langron, 1962 1964 Semi-detailed gravity survey, Ada Darby, 1966 vale Basin 1964 Southern Queensland reconnais Lonsdale, 1965 sance gravity survey Aeromagnetic survey 1961 Aeromagnetic survey of Quilpie Rollins, Steenland & Charleville-Thargomindah area Hier, 1961 PHYSIOGRAPHY The geomorphology of the area was discussed in detail by Mabbutt (Appendix 5 in Senior et al., 1969). The main drainage features are the south-flowing Warrego River which rises north of the area, and the Ward and Langlo tributaries (Fig. 1). The main channels have the braided habit characteristic of western Queensland. As the mean annual rainfall is small ( Charleville: 19 inches) and the potential evaporation exceeds 7 5 inches, all streams are ephemeral. The tributary systems begin to flow with between ½ and 1¼ inches of.local rain of at least moderate intensity, but the major chan nels are dependent on widespread rain (Mabbutt, Appendix 5 in Senior et al., 1969). The Warrego River, which has a hilly catchment area, has a potential yield of 700,000 acre feet. The main channels flow at intervals of one to two years; floods in the Warrego reach the Darling every other year. Extensive flooding of the alluvial plains occurs about twice per decade, fol lowing more than 4 inches of rain. A Tertiary land surface is preserved as small remnants of silcrete in the Charleville Sheet area ( Fig. 1, unit 1 ) . Partial erosion of the land surface produced a dissected tract ( unit 2) consisting of mesas and low rounded hills, stripped of silcrete, and some red-soil plains which are derived from the breakdown of chemically altered Cretaceous and Tertiary rocks. The red soils commonly occur on flat surfaces or the flanks of anticlines. 4 Sllcrt1f11 surfaces Dissacf11d tracts Rolling downs Sondploins Alluvial ploms -~~~-~___:_'°,:' <KILOMETRES l!IMILES 055/AI0/2: Complete stripping of the Tertiary land surface and underlying altered sediments in the axial zone of anticlines and along the margins of faults has resulted in undulating soil plains, the rolling downs ( unit 3), broken by a few rocky rises. Structural depressions in the area are occupied by the main watercourses and are alluviated ( unit 5). Reworking of Cainozoic sediments has resulted in extensive monotonous sandplains ( unit 4). STRATIGRAPHY Tables 2-4 summarize the stratigraphy of the Charleville Sheet area. Stratigraphic nomenclature of the Devonian Adavale Group follows Tanner (1968) modified by Galloway (1970a, b). Nomenclature of the Jurassic to Lower Cretaceous follows Exon ( 1966), and that of the Rolling Downs Group Vine et al. (1967). Subsurface data are available from six oil exploration wells, logs of water bores, and BMR Charleville Scout Hole 1. Formation tops of the oil exploration wells are given in Table 5. Basement rocks in the Sheet area are predominantly low-grade meta morphics; some granite intrusions occur in the Nebine Ridge. In Tregole 1 and Alba 1, quartz-biotite gneiss was encountered on the flanks of the Nebine Ridge ( Campbell, 1965; Amo seas, 1966). This gneiss is similar to that found associated with granite in the Eulo Ridge, and by extrapolation is presumed to be of Devonian age (Senior et al., 1969). Folded, slightly metamorphosed sediments were intersected in Maryvale 1, Crichton 1, and Lowood 1 (Freeman & Stafford, 1966) ; these sediments were probably metamorphosed at the end of a late Silurian to early Devonian orogeny ( Senior et al., 1969). Within the Sheet area, Devonian sediments have only been identified from Phillips-Sunray Quilberry 1, which was drilled on the northern flank of the Cooladdi Trough. Geophysical evidence shows that similar sediments occur in the Westgate Trough. Both troughs are southern extensions of the Adavale Basin, and contain up to 16,000 feet of sediments of the Devonian Adavale Group (Phillips, 1964). The Gumbardo Formation is the oldest formation in the Adavale Group; only its eastern arkosic facies is present in the Charleville Sheet area. The Log Creek Formation ('Gilmore Formation' of Tanner, 1968) has been divided into a lower shale member and an upper sandstone member (Tanner, 1968). The formation is dominantly marine, the sandstone member con taining pelecypods, brachiopods, rare gastropods, and a few nautiloid frag- 6 TABEL 2: PALAEOZOIC STRATIGRAPHY. Age Rock Unit Lithology Thickness Environment (Map symbol) (in feet) Lower Permian (PI) Sandstone, siltstone, conglomerate 0-800? Continental UNCONFORMITY Upper Devonian to Buckabie Formation Red sandstone, siltstone, mudstone, Several Continental and shallow Lower Carboniferous (D-Cb) varicoloured in part thousand feet in marine troughs Etonvale Formation Siltstone, mudstone and sandstone, Maximum in Shallow marine (Dme) in part calcareous; dolomite excess of 2000 Cooladdi Dolomite Silty and ar$illaceous dolomite; 0-300 Shallow marine Member minor limestone Log Creek Formation Mudstone and siltstone; minor Maximum in Shallow marine, continental Middle Devonian quartz sa.ndstone, labile and sub excess of 2500 labile sandstone Bury Limestone Limestone, dolomite, minor cal ? Shallow marine Member careous siltstone Gumbardo Formation Arkose and arkosic conglomerate Maximum in Continental excess of 2500 UNCONFORMITY Palaeozoic (Pz) Schist, phyllite, granite, quartz biotite gneiss ments, and the shale member corals, pelecypods, brachiopods, bryozoans, and crinoid fragments. McKellar ( 1966a, b) assigns a Middle Devonian (probably lower Middle Devonian) age to the formation. Palynology of the sandstone member confirms a Middle Devonian age ( de Jersey, 1966). The Bury Limestone Member, which is the eastern facies of the shale member of this formation farther north in the basin, occurs in the deeper parts of the Cooladdi Trough but is not present in Quilberry 1 on the flanking shelf; it may also occur in the Westgate Trough. The Etonvale Formation is mainly a elastic formation, with a thin basal carbonate member, the Cooladdi Dolomite. The Cooladdi Dolomite Member is the source of a prominent reflection throughout the Adavale Basin (Tan ner, 1968), but is not everywhere recognizable in the Charleville Sheet area; consequently its distribution in the troughs is difficult to determine. However, in Quilberry 1, 204 feet of Cooladdi Dolomite Member consisting of fine grained elastic material with dolomitized corals was intersected.