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

本研究拟对澳大利亚西北陆架Browse盆地晚中新世-上新世至今的沉积发育进行分析。这段时间间隔的特点是沉积记录发生了重大变化，最明显的记录是中新世-上新世边界附近热带珊瑚礁发育的区域衰退，这与洋流控制的漂流沉积的开始和随后的统治相吻合。这种古环境变化的关键控制因素以前没有被详细研究过。以下（部分有争议的）假设将得到验证：(1)盆地沉降是不同的，并且在6 Ma左右急剧增加，最终超过了支持电流控制沉积的礁生成。沉降的增加可能与研究区以北200-500 km的澳大利亚-班达弧碰撞带的构造负荷有关，也可能与地幔对流收缩控制的动力地形有关。(2) 6 Ma左右开始的主要海平面上升变化，通过反复暴露和淹没削弱了礁体的生长，而盆地的长期高度沉降支持漂流沉积，掩埋了中新世的礁体。(3)澳大利亚与班达弧的碰撞限制了印尼通流，改变了Browse盆地的洋流状态，导致礁体消亡，以漂流沉积为主。(4)晚中新世-上新世至近代澳大利亚-班达弧碰撞的远场断裂和褶皱重塑了Browse盆地的形态，将强流集中在以前被珊瑚礁覆盖的地区。

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.