中国陆架海MIS5(74~128 ka)以来地层及其沉积环境

The stratigraphy and depositional environments of China’s sea shelves sinceMIS5(74-128)ka

基于中国海陆架28个晚第四纪钻孔实测数据和典型高分辨率地震剖面的综合地层分析,对比区内已有46个钻孔的研究成果,系统地开展晚第四纪地层特征识别和沉积环境重建。研究表明,MIS5以来中国海陆架沉积记录了3次明显的海侵过程,发育了3个相对完整的海相地层。其中,渤海和东海MIS3和MIS1相对较薄,而黄海海相地层较厚。渤海和黄海末次冰期的地层保存较少,东海外陆架末次冰期地层发育完整,较完整地记录10万年以来的沉积记录。南海晚更新世内陆架以滨岸和陆相沉积为主,外陆架为滨岸和浅海沉积;全新世发育浅海沉积。总体上,中国海陆架晚第四纪以来沉积环境演变依次是MIS5(74~128 ka)的浅海-滨海海相沉积,MIS4(60~74 ka)陆相潟湖-河流-滨海河口相沉积,MIS3(24~60 ka)浅海相-滨海潮坪沉积,MIS2(12~24 ka)/LGM时期陆相-河流相沉积,MIS1(现在~12 ka)/全新世海侵潮流砂和浅海泥质沉积。此外,新构造运动和区域沉降作用对地层的发育和保存具有一定的影响。上述认识为深入研究中国晚第四纪沉积与全球气候变化对比提供直接依据。

Based on the comprehensive analysis of 28 boreholes of late Quaternary sedimentation and the high-resolution seismic profiles,the authors studied the stratigraphic characteristics identification and sedimentary environment rebuilding by comparing the results of other 46 boreholes as references in China’s sea shelves.Three distinct transgression processes were discovered in the shelves of China’s sea areas,with 3 marine strata well preserved.The strata of MIS1 and MIS3 are relatively thin in the Bohai Sea and the East China Sea,but thick in the Yellow Sea.There exists little sedimentation of Last Glacial period in the Bohai Sea and the Yellow Sea,but there have been quite integrated sedimentation units without obvious hiatus in the East China Sea since 100 ka B.P..There were coastal and continental deposits in the inner shelf and nearshore and neritic deposition in the outer shelf of the South China Sea during late Pleistocene,with neritic sedimentation in Holocene.As a whole,the sedimentary environment changes of China’s sea shelves since MIS5 in turn primarily were neritic and offshore deposits in MIS5(74-128 ka),continental sedimentation of lagoon-fuvial-coast in MIS4(60-74 ka),neritic and tidal flat deposits in MIS3(24-60 ka),terrestrial or fluvial sedimentation in MIS2(12-24 ka),and tidal sand ridge and neritic deposition in Holocene.Furthermore;the neotectonic movement and regional subsidence also influenced the late Quaternary stratigraphic development and their preservation in China seas.The results will provide direct evidence for the study of China’s Quaternary sedimentation and global climate changes.