Cenozoic Channel Deposits of the Bowen Basin, Queensland

Yu, Tianjiao1, Dube,Kudzai1, Moss, Professor Patrick1, Abylgazina, Adiya1, Cooling, Jennifer1, Esterle, Professor Joan1

1School of Earth and Environmental Sciences, The University Of Queensland, Australia

During the Late Cretaceous through Cenozoic, uplift and weathering in the northern Bowen Basin region, created a series of deep (up to 150 m) channels that filled with sediments and lava flows. The Australian Cenozoic was a time of great climatic and tectonic change. From the Late Cretaceous as Australia and Antarctica separated and the Australian plate moved northwards, the climate became warmer and drier, and the characteristic modern Australian flora developed. These paleochannels provide an important record of these changes, however their development, age of deposition and the impact of changing weathering conditions are poorly understood. Analysis of core samples confirm that the channel sediments host palynofloras identified as Late Cretaceous to Eocene, and record a change from a fire prone environment to a warm and wet high-density rainforest by the Paleogene. Aridification followed from the Neogene into the Quaternary. Lithological and mineralogical analysis of basaltic lavas from the area indicate they were deposited both as subaerial pahoehoe and sub-aqueous pillow lavas, suggesting that inland lakes covered the landscape at the same time as the volcanisms occurred. These lakes also form carbonaceous mudstones and lignite.

Some channels also floored by tens of metres of breccia that contain angular clasts of underlying Permian strata which fine upwards to conglomerates and sandstones, and also exhibit soft sediment deformation and sedimentary injection features.  These are interpreted as alluvial fans initiated by extensional faulting that may have been seismically active during deposition, and contributed to subsidence resulting in the inland lakes.  Here thick (2 to 4 m) lignites alternating with kaolinite-rich white clays and heavily altered claystones complete the sedimentary sequence that is then capped by basaltic lava flows. The kaolinite-rich clays can have a number of different origins. It may be primary, or weathering products of intrusive quartz rich rhyolite, tuff, or other sediments subjected to hydrothermal alteration beneath the basalts or stripped by humic acids from the lignites. The origins and timing of kaolinite development is being investigated.


Biography

Tianjiao is currently in Honours year in a Bachelor of Environmental Science at UQ, majoring in Earth Resources.

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