Offshore Red River fault and slope sediments in northern South China Sea: Implications for paleoceanography and uplift of the Tibet Plateau.

摘要

This dissertation documents structure of the offshore Red River fault, characteristics of mass transport deposits, and features of migrating submarine canyons in the South China Sea. The research data include 2-D/3-D seismic reflection and borehole data covering the Yinggehai, Qiongdongnan, and Pearl River Mouth Basins along the northern margin of the South China Sea. This new work reduces a gap in knowledge of the slip history of the poorly documented offshore Red River fault, enriches our understanding of the seismic characteristics of mass transport deposits and submarine canyons, and addresses implications for mechanisms of the India-Asia collision and paleoceanographic reconstruction of the South China Sea.; This work investigates strike-slip tectonics of the offshore Red River fault in the Yinggehai basin and speculates on its implications for uplift of the Tibet plateau. Three successive deformation stages associated with the offshore Red River fault are sinistral movement before the middle Miocene, slip reversal between the middle Miocene and Pliocene, and dextral movement after Pliocene. Our research findings support a two-stage model for the evolution of the India-Asia collisional orogen. Before the middle Miocene, sinistral movement of the Red River fault likely linked to spreading of the South China Sea, thereby supporting plausibility of continental extrusion. After the middle Miocene, distributed shortening better explains a low rate of dextral accommodation of the Red River fault in response to the continuing India-Asia collision. Dextral movement of the Red River fault after Pliocene, rapid accumulation of thick sedimentary deposits, and overpressure development provide a background favoring slope failure and multiple mass transport events in the Yinggehai and Qiongdongnan basins. Three-dimensional seismic characterization of the morphology, architecture, and evolution of these mass transport deposits enhances our understanding of slope failure processes, and serves as an analog for mass transport deposits in regions lacking 3-D data.; Morphology and architecture of migrating submarine canyons in the Pearl River Mouth Basin suggest interaction between bottom currents and gravity flows within submarine canyons. The evolution of these migrating submarine canyons indicates that northeastward bottom currents have existed at least from the middle Miocene to present in the study area. The intensification of bottom currents may reflect shoaling of major ocean seaways and increased vigor in oceanic circulation in the South China Sea as a result of global cooling after the middle Miocene.