南海北部陆坡峡谷区海底滑坡体的识别与年代界定研究

Submarine landslide is one of the marine geological disasters which have great harmfulness, extraction of landslides information in submarine stratum and analysis of their scale, frequency and time is the foundation to study the mechanism of landslide, and also the premise to assess the stability of buried landslide. The past research on the identification of submarine landslide is mainly based on the geophysical method, and lack of high quality core for verification and dating study on submarine landslide events. Therefore, this project takes the holes DLW3101 and DLW3102 as study object, which respectively sampled at the top and bottom of the canyon in the northern continental slope, South China Sea. Firstly, we establish the sedimentary sequence and chronostra- tigraphy framework for DLW3101 hole to make a reference for identifying submarine landslide in DLW3102 hole; Comprehensive use of granularity, clay minerals, carbonates, geochemical testing data combine with the sedimentary structures to analyze sedimentary facies and sedimentary interface of DLW3102 hole; By analysis of the acoustic stratigraphic data, we compare DLW3102 hole with DLW3101 hole to identify submarine landslide body, and determinate the age, size, frequency of the submarine landslide in DLW3102 hole. This research not only can provide a basis for the mechanism study of deepwater submarine landslide, but also provide a reference for disaster prevention and mitigation in subsea engineering activities.

海底滑坡是具有巨大危害性的海洋地质灾害之一，提取海底地层中的滑坡信息，分析其发生的规模、频率和年代是进行滑坡成因机制研究的基础，也是评估海底埋藏滑坡体稳定性的前提。以往对海底滑坡的识别研究主要是基于地球物理手段开展的，还缺乏高质量的岩芯进行滑坡事件的验证及发生年代研究。为此，本申请以南海北部陆坡峡谷区顶部（无滑坡区）取得的DLW3101孔和峡谷区底部（滑坡区）取得的DLW3102孔为研究对象。建立DLW3101孔的沉积序列和地层年龄框架，为滑坡体的识别做参考依据；综合运用粒度、地化、粘土矿物、碳酸盐等测试数据结合沉积构造特征对DLW3102孔进行沉积相分析和沉积界面划分；在声学地层资料分析的基础上，通过与DLW3101孔的对比，确定DLW3102孔的滑坡沉积层，并界定滑坡事件发生的年代、规模和频次。研究成果可为深水区海底滑坡的触发机制研究提供基础，并为各类海底工程活动提供防灾减灾参考。

海底滑坡是具有巨大危害性的海洋地质灾害之一。目前国内外在海底滑坡识别方面的研究，主要是基于地球物理手段开展的，还缺乏高质量岩芯对海底滑坡体进行精细的识别研究。本基金以南海北部陆坡峡谷区顶部（无滑坡区）取得的DLW3101孔和峡谷区底部（滑坡区）取得的DLW3102孔为研究对象。利用碳酸盐含量、磁化率数据及底栖有孔虫δ18O曲线与LR04标准曲线、IODP站位的氧同位素曲线进行综合对比，建立了DLW3101孔MIS8以来的地层年龄框架；综合运用沉积物粒度、化学元素、碳酸盐含量等指标的变化特征，建立DLW3101、DLW3102孔的沉积序列。结合沉积构造特征，如样品中的局部侵染、斜向层理和斜向颜色突变层等，识别出DLW3102孔的14个滑坡层位，并根据沉积构造特征，分析了滑坡运动形式和规模。14个滑坡， MIS2期发生1次，MIS5期发生3次，MIS7期发生5次，MIS9期发生1次，MIS11期发生4次，识别出的滑坡主要发生在深海氧同位素波动的暖期。研究成果可为深水区海底滑坡的触发机制研究提供基础，并为各类海底工程活动提供防灾减灾参考。