From reefs to drift: Miocene/Pliocene sedimentary change in the Browse Basin, NW Australia

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This research proposal focuses on the analysis of the sedimentary development of the Browse Basin, Australian Northwest Shelf, between the late Miocene-Pliocene and today. This time interval is characterised by significant changes in the sedimentary record, most clearly documented by a regional decay of tropical reef development around the Miocene-Pliocene boundary, which coincided with the onset and subsequent domination of current-controlled drift sedimentation. The key controls for this palaeo-environmental change have not been studied previously in detail. Following (partly controversial) hypotheses will be tested: (1) Basin subsidence was differential and strongly increased around 6 Ma, ultimately outpacing reef production supporting current-controlled sedimentation. The increase in subsidence can be related to tectonic loading at the Australia-Banda Arc collision zone ~200-500 km north of the study area, and/or to dynamic topography controlled by convective drawdown in the earth´s mantle. (2) Major eustatic variations commencing around 6 Ma weakened reef growth by recurrent exposure and drowning, and the generally high long-term subsidence of the basin supported drift deposition burying Miocene reefs. (3) The collision of Australia with the Banda Arc restricted the Indonesian Throughflow changing the ocean current regime in the Browse Basin, which led to the demise of reefs and the dominance of drift sedimentation. (4) Late Miocene-Pliocene to recent faulting and folding as a far-field consequence of the Australia-Banda Arc collision reshaped the morphology of the Browse Basin, focusing strong currents in areas previously covered by reefs.