南海深海平原浊流沉积及其构造意义

This project is aimed to investigate the abyssal plain turbidites in the South China Sea (SCS) by using the core and well-logging data of Site U1431 in the eastern SCS subbasin and Site U1433 in the southwestern SCS subbasin acquired during IODP (International Ocean Discovery Program) Leg 349, combined with regional seismic profiles. The types, sedimentary characteristics and origin of the turbidites will be obtained by core sedimentological analysis (including core observations and core sample analysis) integrated with traditional and FMS (Formation Microscanner) resistivity image logs analyses. The vertical distribution successions of turbidite layers for both sites will be reconstructed on the basis of careful interpretation of the very high-resolution (5 mm) FMS image logs calibrated by core and traditional well logging data. Lateral variations of the turbidites between the eastern sub-basin (Site U1431) and the southwest subbasin (Site U1433) will be investigated through seismic stratratigraphic interpretation constrained by core and well-logging data in order to understand the similarities and differences of turbidite development between both subbasins. Finally, genetic linkages between the tempo-spatial distribution of the abyssal plain turbidites and the regional tectonic events will be explored using the so-called ‘core-log-seismic integration’ (CLSI) method. Implementation of this project will fill the gap in the field of abyssal plain turbidites in China, and is significant for enhancing our understandings of the SCS abyssal plain sedimentation, and for future deep-sea resource exploitation.

利用IODP349航次在南海东部次盆U1431和西南次盆U1433两个站位取得的岩心、成像测井及常规测井资料，结合区域地震剖面，研究南海深海平原浊流沉积及其构造意义。依据岩心观察，结合样品分析和测井解释，确定浊流沉积的类型、特征及成因；根据高分辨率FMS成像测井资料，结合岩心标定和常规测井约束，重建东部次盆和西南次盆深海平原浊流沉积的垂向分布序列；在合成记录井-震连接基础上，通过区域地震地层分析研究两个站位之间浊流沉积的横向分布与过渡关系；通过岩心-测井-地震综合研究，查明两个次盆浊流沉积发育的异同，探讨南海深海平原浊流沉积的发育与重大区域构造事件之间的成因联系。此项目的实施，将填补我国在现代深海平原浊流沉积研究方面的空白，对于深入理解南海深海沉积过程及未来深海资源勘探具有重要意义。

本项目依托IODP349航次的钻探资料，结合区域地震数据，采用现代深海沉积学、地震地层学及岩心-测井-地震综合研究方法，研究南海深海平原重力流沉积物的成因类型、沉积特征、时空分布及构造意义。研究表明，南海深海平原重力流沉积的主要有浊流、碎屑流和滑塌三种类型，以浊流沉积为主。根据物质组成，浊流沉积可以进一步划分为陆源碎屑和碳酸盐两大端元类型。垂向上，南海深海平原重力流沉积的发育始于中新世，以晚中新世最为发育，其次为第四纪。空间上，南海深海平原不同次盆（包括西北、西南和东部次盆）重力流沉积的发育存在较大差异。东部次盆重力流沉积的发育程度明显高于西南次盆；东部次盆陆源碎屑浊流沉积异常发育，而西南次盆则以碳酸盐浊流沉积居多。东部次盆发育于中中新世晚期-晚中新世早期的大量碎屑流及滑塌沉积，可能与16-18Ma开始的南海洋盆向东沿马尼拉海沟的俯冲有关。晚中新世堆积在西北次盆和东部次盆北部的大量陆源碎屑浊流沉积，可能与青藏高原快速隆升、红河断裂带走滑反转和华南挤出有关。东部次盆东北部从上新世晚期开始的陆源碎屑浊流沉积的快速增多，应代表了台湾快速造山过程在深海的响应。西南次盆更新世中-晚期开始的陆源碎屑浊流沉积的突然增多则可能与南海南部陆架重大河系的重组和湄公河直接注入南海有关。本项目研究成果为理解南海扩张期后的地质演变提供了重要的深海重力流沉积学证据。