Styx Basin

Location Map

 Styx Basin in relation to Australia

Map showing the location of Styx Basin in relation to Australia
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Basin Details and Geological Overview

The Styx Basin is a small Early Cretaceous intracratonic sag basin straddling the central Queensland coast near the town of St Lawrence. The basin covers an area of approximately 300km2 onshore and 500km2 offshore, under water depths of up to 100 metres. The maximum known thickness of sediments is 387 metres from a coal exploration bore, but magnetic data suggest a thickening offshore.

The Styx Basin probably developed by subsidence of the Strathmuir Synclinorium, an older feature containing Permian Bowen Basin strata. Styx Basin sediments lap onto Permian strata in the west, but are faulted against them in the east. The basin plunges gently to the north under the waters of Broad Sound but the general dip of the Styx Coal Measures sequence is to the east. In the southern part of the basin, it is bounded to the east by a post-depositional high-angle reverse fault. Adjacent to this fault, the Cretaceous sediments are folded and faulted. The known strata of the basin are referred to as the Styx Coal Measures and consist of quartzose, calcareous, lithic and pebbly sandstones, pebbly conglomerate, siltstone, carbonaceous shale and coal. The environment of deposition was freshwater, deltaic to paludal with occasional marine incursions.

The coals at the base of the Styx Coal Measures lie within the oil window and could potentially generate petroleum, however, there is no known evidence that generation of oil or gas has occurred from this succession. The offshore Styx Basin lies entirely within the Great Barrier Reef Marine Park, in which petroleum exploration activity is prohibited. Coal was mined in the first half of the 20th century with a total production of 1.76 million tonnes, but reserves are currently not of economic importance.

Basin Summary Table

STYX BASIN
State(s) Queensland
Area (km2) Offshore 500
Onshore 300
Maximum thickness (m) 400
Age Range Early Cretaceous
Basin Overlies Permian sediments of the Strathmuir Synclinorium.
Underlies Neogene alluvium and shelf sediments.
Subdivisions -
Other -
Indicators Knowledge Regional geophysical and some outcrop data onshore; regional geophysical only offshore.
Basin type Small graben.
System(s) Capricorn.
Water Depth (m) 0 - < 100.
Exploration Status Frontier
Wells 0
Seismic line-km Not determined, but very sparse.
Discoveries Nil
Shows Nil
HC evidence -
Geology Source(s) No mature source.
Reservoirs Early Cretaceous sandstones.
Seals Early Cretaceous shales.
Trap types No valid traps have been identified.
Palaeogeographic summary Early Cretaceous (Albian) non-marine (?fluvio-deltaic) coal measures, with one minor marine incursion.
Timing Oil generation No evidence of generation.
Gas generation No evidence of generation.
Trap formation No evidence of valid traps.
Other key times Basin fill has been highly disturbed by later events.
Other important information The offshore Styx Basin lies entirely within the Great Barrier Reef Marine Park, in which petroleum exploration activity is prohibited.
Geoscience Australia products available -

Key References

Author(s) Year Title
Benbow, D.D. 1980 The petroleum prospects of the Great Barrier Reef region. The Australian Petroleum Production and Exploration Association (APEA) Journal, 20 (1), 159-175
Benstead, W.L. 1976 In R.B. Leslie, H.J. Evans and C.L. Knight, (Editors), Economic geology of Australia and Papua New Guinea. Volume 3. Petroleum. Australasian Institute of Mining and Metallurgy, Monograph Series, 7, 446-447
Department of Resource Industries, Queensland 1989 Petroleum Resources of Queensland: Review to June 30, 1989. Petroleum Resources Assessment and Development Subprogram, Department of Resource Industries, Queensland, 177-178

Topic contact: petroleum@ga.gov.au Last updated: November 27, 2012