珠江深水扇系统沉积和周边重要地质事件

最近的研究发现了位于南海北部珠江口外白云凹陷陆坡深水区的珠江深水扇系统。珠江深水扇系统以珠江为沉积物源、以持续深沉降的白云凹陷为沉积古地理背景、以与全球海退型海平面相反的相对海侵型海平面变化的沉积层序构成了其发育演化的特殊性，并留下了控制沉积的周边重要事件的记录。23.8 Ma等界面沉积速率和岩石地球化学特征均有突变，反映出物源区的变化，可能折射出与青藏高原隆升、南海扩张有关的重要事件，使得古珠江骤然向西部高原拓展，甚至较今天的珠江流域范围还广阔；承载珠江深水扇系统的白云凹陷持续沉降形成了陆坡内盆地，导致21~10.5 Ma BP多个层序深水扇垂向叠置充填的特殊沉积建造；根据60多口井资料建立的相对海平面变化曲线，具有与全球海平面变化相一致的三级旋回和不一致的二级旋回。如果能对珠江深水扇系统实施综合大洋钻探获取更为全面和准确的资料，开展珠江深水扇沉积作用与白云凹陷沉降的深部机制、珠江流域演化、海侵型相对海平面变化的耦合性等研究，将有利于揭示南海扩张、边缘海沉积、海平面变化、中国西部高原隆升事件的相关联系和形成机制。

The Pearl River Deep-water Fan Systems and Significant Geological Events

Recent studies have discovered the Pearl River Deep-water Fan System, located in the deep water slope area of Baiyun Say in the Pearl River Mouth Basin of the South China Sea. With the rich sediments supplied by the Pearl River, under the paleo-geography sedimentary background of Baiyun Sag continuously subsiding, with sedimentary sequences related to relative transgressive sea level change , contrary to regressive eustasy, the Pearl River Deep-water Fan System has specific evolution characteristics, which left the sedimentary record controlled by peripherical significant geological events. The sharp change of deposition rate and lithologic geochemical characteristics about 23.8Ma sequence boundary demonstratesd that sediment source had changed, perhaps related to the uplift of Tibet plateau and spreading of the South China Sea, which led the paleo-Pearl River drainage to expand to western China plateau , maybe much broader than present. Consequently, IODP proposal to drill in the Pearl River Deep-water fan to study the response to the internal mechanism of the Pearl river deep-water fan sedimentation, Baiyun sag subsidence, evolution of the Pearl river drainage , transgressive relative sea level change, as well as the research will reveal the relationship and mechanism among the expansion of the south China sea, the deposition of marginal sea, the relative sea level change, and the uplift of chinese western plateau.