末次冰盛期-全新世东海陆坡滑塌沉积的地质年代与沉积学证据

Geological ages and sedimentology proofs of landslide layers from Last Glacial Maximum to Holocene in continental slope of the East China Sea

基于东海陆坡区OT12-01孔长度为5.35 m沉积物AMS 14C测年、高分辨率粒度分析和XRF岩芯元素扫描数据,识别出了末次冰盛期(LGM)至全新世期间发生的多次滑塌事件。研究发现,OT12-01孔全新世晚期沉积层缺失,LGM至全新世期间呈现AMS 14C年龄模式频繁倒转、沉积物粒度、元素比值垂向上多处突变或"错动"等特征,保存了LGM至全新世非连续的沉积记录。OT12-01孔沉积物主要来源于低海平面时期的长江/黄河物质,OT12-01孔是由中国大陆陆源物质在东海陆架经水动力分选,细颗粒被搬运至东海陆坡后,发生多次滑塌形成。LGM时期物源供给是OT12-01孔形成滑塌沉积的重要因素,末次冰消期海平面快速上升可能是高频滑塌沉积的触发原因,而低海平面时期甲烷水合物溢出、频繁的地震和火山喷发可能是海底滑坡作用发生的诱因。

Core OT12-01 is located in middle continental slope(28°19'N,126°59'E)of the East China Sea,where water depth is 406 m.The length of Core OT12-01 is 5.35 m.Kuroshio Current is main current system flowing through the area.Twenty-six foraminifera samples of Core OT12-01 were selected for dating.Foraminifera are mainly composed of Uvigerina peregrina(U.peregrina),Globigerinoides ruber(G.ruber)and Orbulina universa(O.universa),mixed with planktonic foraminifera on surface water.All calendar ages in this paper are chronological data.Calendar correction age of Core OT12-01 bottom is 23519 a before present.We have selected 535 samples for particle size analysis.XRF element scanning analysis has been taken for Core OT12-01.Base on data of sediment AMS14C ages,high resolution granularity analysis,and element scanning,Core OT12-01 reveals multiple collapse events from Last Glacial Maximum(LGM)to Holocene in continental slope of the East China Sea.Sedimentary layers of Core OT12-01 show missing in Holocene and exhibit frequent reversal of age patterns,features of vertical mutation or dislocation on granularity and element ratios.They contain discontinuous sedimentary records from LGM to Holocene.Sediments of Core OT12-01 mainly originated from paleo-Changjiang River/Huanghe River when the sea level was low.The sediments were transported to continental slope of the East China Sea through hydrodynamic separation,and then Landslides were formed after collapse.Rapid rise of sea level in the last deglaciation may be the trigger of high frequency landslides deposition.Methane hydrate spills,frequent earthquakes and volcanic eruptions at low sea level may be the cause of submarine landslide.