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

本研究方案重点分析了澳大利亚西北陆架Browse盆地晚中新世-上新世至今的沉积发育。这一时间间隔的特点是沉积记录发生重大变化，最明显的记录是中新世-上新世边界周围热带生物礁发育的区域衰退，这与洋流控制的漂流沉积的开始和随后的控制相吻合。这种古环境变化的关键控制因素以前还没有被详细研究过。以下(部分有争议的)假说将被检验：(1)盆地沉降是不同的，并在6 Ma左右强烈增加，最终超过支持洋流控制沉积的生物礁生产。沉降量的增加可能与研究区以北2 0 0~5 0 0公里澳大利亚-班达弧碰撞带的构造载荷有关，也可能与S地幔对流下沉控制的动态地形有关。(2)始于6 Ma左右的主要海平面变化使生物礁的生长因反复暴露和溺水而减弱，盆地普遍较高的长期沉陷支持了漂流沉积埋藏中新世生物礁。(3)澳大利亚与班达弧的碰撞限制了印度尼西亚的横流，改变了Browse盆地的洋流格局，导致了生物礁的消亡和漂流沉积的主导。(4)晚中新世-上新世-现代断裂和褶皱是澳大利亚-班达弧碰撞的远场结果，重塑了Browse盆地的形态，集中了以前被生物礁覆盖的地区的强流。

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.