南海深海沉积过程与机制

Deep-sea sedimentation process in the South China Sea (SCS) has been achieved in recent years with great approaches in both in-situ observation and long-term core sediment record analysis. However, the dynamic modelling of deep-sea sedimentation and the reconstruction of long-term geological dynamic evolution are strongly insufficient. Based on the current research approaches in these two fields, on the one hand, this project will conduct an integration research on observation and modelling of important deep-sea sedimentation processes in the SCS, including turbidity current sedimentation, contour current sedimentation, mesoscale eddy long-distance transport, nepheloid layer cross-slope transport, and deep-sea bottom boundary layer process. Through using the sedimentary dynamic mechanism derived from modelling, on the other hand, this project will reconstruct the dynamic evolution of important sedimentary bodies in the geological history of the deep SCS, including the high-sedimentary-rate sediment drift on the northern slope, the frequently-occurred turbidite sequence in the central basin, and the high-sedimentary-rate hemiplegic sequence in the southwestern basin of the SCS. This proposed study will be a pioneer integration work of the past and present on deep-sea sedimentation dynamic process and mechanism, and will answer some significant scientific questions of the deep-sea sedimentology in terms of process observation and geological record. The project is expected to greatly improve the study on deep-sea sedimentary dynamics and deep-sea sedimentary environment evolution of the SCS, and will contribute significantly to the great-leap-forward development of the deep-sea science in China.

南海深海沉积过程的现场观测和长期沉积记录的岩芯研究在近年来都取得了重要进展，但对深海沉积过程的动力学模拟、以及对地质历史时期沉积动力学演变的恢复却十分缺乏。本项目将基于这两个领域的现阶段研究进展，一方面对南海深海重要沉积过程的观测和模拟开展集成研究，包括浊流沉积过程、等深流沉积过程、中尺度涡远距离搬运作用、雾状层跨陆坡搬动作用、以及深海底边界层过程；另一方面运用模拟获得的沉积动力学机制，再造南海深海地质历史时期重要沉积体的形成过程，包括南海北部陆坡高速沉积物堆积体、南海中央海盆频繁发育的浊积层序、以及南海西南次海盆沉积物快速沉积的控制因素。该项研究将是深海沉积动力过程与机制古今结合研究的先驱性工作，预期将从过程观测和地质记录两个方面回答南海深海沉积学的关键科学问题，有望在深海沉积动力学和深海沉积环境演变上大幅度提高南海深海过程的研究程度，对促成我国深海科学的跨越式发展具有重要意义。

本项目通过继续开展锚系观测的数据采集和沉积物样品的实验补充分析，进行南海深海重要沉积动力过程的观测和模拟集成研究，再造南海深海地质历史时期重要沉积体的形成过程。取得的重要研究成果包括：.1、南海等深流沉积搬运过程的长期观测研究。通过连续7年（2011.8-2018.5）的长期观测，第一次揭示出等深流的速度结构及其季节性变化，南海等深流向西南净搬运量每年约86 Mt，提出等深流是大陆边缘最重要的沉积物搬运过程。.2、南海中尺度涡的三维结构及其对物质输运的影响研究。通过典型强反气旋涡的模拟，发现上层流场呈碗状结构，半径随深度增加而减小，深层为倾斜的柱状气旋式流动，计算显示该中尺度涡能够引起近底约1.56 Mt沉积量搬运。.3、台风触发深海浊流活动的长期观测研究。通过在台湾岸外的高屏海底峡谷长达三年半的锚系连续原位观测，第一次揭示出路径台湾的台风降雨是触发高屏海底峡谷深海浊流发育的直接原因，计算显示浊流每年沿高屏海底峡谷搬运沉积物量达25 Mt。.该项研究是深海沉积动力过程与机制古今结合研究的先驱性工作，提出等深流主导大陆边缘深海沉积的搬运过程、浊流和中尺度涡等中小尺度过程调控陆源沉积物从近岸向深海输运机制。取得的研究成果已在Geology、Chemical Geology、Journal of Geophysical Research: Oceans等国际著名学术刊物发表，对发展我国深海沉积学学科、促成我国深海科学的跨越式发展具有重要意义。