科林斯活动裂谷早更新世以来海陆交互阶段的高分辨率沉积记录响应

The young continental margin active rift is a transitional area between continental crust and oceanic crust, as well as interaction between marine and non-marine environments. Sedimentary filling is one of the key issues for sedimentary dynamic study in rift basin. This study is based on the Corinth Active Rift Development study of IODP Expedition 381. By following the latest theoretic progress of earth science system, this research employs data including continuous core, well-logging, seismic, and related analysis, integrating methods of sedimentological (grain size and sensitive components analysis) and geochemical (stable carbon and oxygen isotopes) experiments, and key technologies of describing core in centimeter-scale, establishing integrated lithofacies assemblage sequence profile, and calibrating of major sedimentary boundaries by well-seismic data. This study aims to 1) establish high resolution isochronous stratigraphic framework in the Corinth Active Rift since Early Pleistocene, 2) determine key transgression/regression boundaries during active rift development, 3) analyze transport regime of sediments and sedimentary environments changes, and 4) clarify sedimentary response during the interaction processes between marine and non-marine environments in active rift, which will provide scientific evidences and insights for research on sedimentary filling in the other active rifts under the similar geological settings.

年轻的大陆边缘活动裂谷是洋陆转换及海陆相互作用的过渡区域，其沉积充填一直是裂谷盆地沉积动力学研究的关键问题之一。本申请拟在IODP-381航次关于科林斯活动裂谷研究的基础上，以地球科学系统理论研究新进展为指导，以连续取芯、测井、地震及相关分析化验资料为基础，充分运用沉积学（粒度分析及敏感组分分析）、地球化学（稳定碳、氧同位素分析）等多种研究方法，以厘米级写实性精细化岩芯描述、综合岩相组合序列剖面建立、井-震结合的关键沉积界面标定为手段，建立科林斯活动裂谷早更新世以来的高分辨率等时地层格架，确定活动裂谷形成过程中海侵与海退作用之间的界限，分析沉积物搬运机制与沉积环境变迁规律，明确科林斯活动裂谷海陆交互阶段的沉积记录响应，进而为同类活动裂谷沉积充填研究提供科学依据与借鉴意义。

年轻的大陆边缘活动裂谷是洋陆转换及海陆相互作用的过渡区域，其沉积充填一直是裂谷盆地动力学研究的关键问题之一。本项目依托IODP-381航次科林斯活动裂谷研究，以地球科学系统理论研究新进展为指导，以连续取芯、测井、地震及相关分析化验资料为基础，充分运用沉积学（粒度分析及敏感组分分析）、地球化学（稳定碳、氧同位素分析）等多种研究方法，以厘米级写实性精细化岩芯描述、综合岩相组合序列剖面建立、井-震结合的关键沉积界面标定为手段，结合沉积物元素及碳氧同位素特征、沉积物粒度及搬运过程差异，明确了科林斯裂谷海相与陆相阶段沉积环境特征，在海相阶段，粒径大于4Φ（0.0625μm）的沉积物的累积概率为3.25%~14.32%，平均为8.94%，陆相阶段，沉积物粒径>4Φ（0.0625μm）的累积概率范围为0%~39.70%，粗粒含量较高。建立了科林斯活动裂谷早更新世以来的高分辨率等时地层格架，分析了地中海与科林斯裂谷的周期性连通规律，确定了活动裂谷形成过程中海侵与海退作用之间的界限。科林斯湾的沉积环境从一个伴有间歇性海侵的孤立湖泊（在大约0.5558Ma之前，即558.29mbsf），变成了一个周期性与海洋连接的海湾（在大约0.5558Ma之后）。在573-630mbsf层段，沉积物主要来自科林斯裂谷南缘长的曲流河和半远洋，前者由高密度羽流运输，后者通过悬浮沉降发生沉积。由于水系逆转，在249-323mbsf和540-573mbsf层段，沉积物主要来自河流洪水期间的异重流和半远洋。