4.0 Overview of the Regional Surface and Subsurface Geology of the Duaringa Basin
Duaringa Basin Report on Hydrological Investigations 4.0 Overview of the Regional Surface and Subsurface Geology of the Duaringa Basin 4.1 Introduction The surface geology of the Duaringa Basin project site and surrounding environment is characterised by the surface exposures of the Tertiary age Duaringa Formation sediments and surrounding exposures of the Permian age sediments (Figure 4.1). The Duaringa Formation is composed of interbedded mudstones, shale, oil shale siltstone and lignite beds and rare sandstone, conglomerate and basalt beds (Day et al., 1983). The Permian age sediments are part of the Bowen Basin stratigraphic sequence. The overlying Tertiary age Duaringa Formation does not form part of the formal Bowen Basin stratigraphic sequence. The surface exposures of the Duaringa Formation can be differentiated into recent exposures and older lateritic tablelands. There are also some small outcrops of Tertiary age volcanics exposed through the Tertiary age and Permian age sediments present in and near the Duaringa Basin. The significant rivers, such as the Mackenzie River and Dawson River, which traverse the Duaringa Basin, have deposited large volumes of alluvial sediment in broad braided plains on both the Duaringa Formation and Permian age sediments. The Duaringa Basin along with the Biloela Basin and Hillsborough Basin formed during the opening of the Coral Sea during the Eocene between 52 and 34 million years ago (SRK, 2008). These basins are bounded by NE to SW trending bounding faults along their western margins. Movement along these faults is largely sinistal (left lateral). However, there has been significant downward movement on the eastern side of the fault blocks, which has opened deep asymmetrical grabens (Veevers and Powell, 1994).
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