西沙珊瑚礁区的第四纪事件

本文简要介绍了西沙珊瑚礁区第四纪期间(2.5Ma 以来)的事件沉积作用类型、特征及其时空分布。珊瑚礁区与典型冰川作用区、冰川外围区相似,依然是冷期与暖期相互交替的气候旋回。冷期向暖期变换为渐变关系,而暖期向冷期转换则为突变关系。2.5Ma 以来有30个以上的冷暖气候旋回。ESR 测年最大值达到1.26MaB.P.,末次冰期风成沉积物的下限,ESR 测定为70000aB.P.。

QUATERNARY EVENTS IN XISHA CORAL REEF REGION

This paper states that the lowest boundary of Quaternary System in Xisha Coral Reef re-gion dates back to 2.48 Ma B.P.,8 to 27 m below the first appearance of Globigerinoides trun-catulinoides and is corresponding to the polarity boundary between Matsuyama and Gauss Ch-ron.In lithostratigraphic sequence the boundary exhibits a non-sedimentation boundary and tal-lies with the top of the consolidated wackes one.The main event of sedimentation in Xisha Coral Reef region falls into three categories:Eo-lian Sedimentation,Hurricane and Strong Tidal Sedimentation and Volcanic Eruptive Sedi-mentation.The oxygen isotope data suggest that there existed over 30 warm-cold climatic cycles duringthe Quaternary Period in Xisha Coral Reef region.The transition from warm episodes to coldepisode progressed gradually but the reverse transition leaped rapidly.The paper summarized all the main events in Xisha Coral Reef region since 2.48 Ma B.P.,together with their position in borehole profiles,characteristics in occurrence and the maincarbon and oxygen-isotope features.The Last Glacial Event and the Last Interglacial Event wererecorded almost completely,and their profile were preserved.This is the basis of global changecomparison.The maximum value of ESR dating is 1.26 Ma B.P.,Differences exist between the ESRdatings and those ages inferred from the isotope curve.The ESR ages seem to be much young-er.