六盘山群沉积物磁化率记录的早白垩世气候变化  

The climate change during 128.11-119.05 Ma recorded by the susceptibility of the sediments of Liupanshan Group

作　　者：戴霜[1] 黄永波[1] 赵杰[1] 朱强[2] 刘俊伟[1] 孔立[1] 张明震[1] 胡鸿飞[3] 

机构地区：[1]西部环境教育部重点实验室兰州大学资源环境学院,甘肃兰州730000 [2]中国科学院寒区旱区环境与工程研究所,甘肃兰州730000 [3]中国人民武装警察部队黄金第二支队,内蒙古呼和浩特010010

出　　处：《地学前缘》2010年第3期242-249,共8页Earth Science Frontiers

基　　金：国家自然科学基金项目(40972025;40721061;40571017);教育部新世纪人才计划项目(NCET-07);国家重点基础研究发展计划"973"项目(2005CB422001);高等学校学科创新引智计划项目(B06026)

摘　　要：白垩纪气候环境研究对认识现今全球环境格局的形成具有重要意义,现有的白垩纪环境变化记录均来自海洋沉积物,本文通过对我国中部六盘山地区六盘山群地层沉积与岩石磁化率测量分析,获得了128.15～115.82Ma期间陆相沉积物记录的气候变化信息。结果显示磁化率值总体较低,以125Ma为界大致可以分为前低后高两个阶段;结合岩石磁学测量及沉积相、岩石中铁含量与磁化率变化关系分析,认为岩石磁化率主要与源区磁性矿物的种类及含量有关,据此揭示六盘山地区在该时间段气候总体为干热环境,并可分为128.15～125Ma间气候相对湿热和125～115.82Ma间气候相对温湿两个阶段。磁化率记录的这种气候转变与海洋沉积物记录的全球海平面温度变化趋势一致,但相对海平面温度由升高到降低的转折时间提前约1.7Ma。The research on the Cretaceous climate is crucial for understanding the formation of the present global environmental pattern.The previous records of the Cretaceous climate were obtained from the marine sediments.In this study,based on the analyses of the sedimentary and susceptibility data of the sediments of the Liupanshan Group exposed in the Liupanshan area （central China）,we obtained the climate records during 128.15-115.82 Ma from the terrigenous sediments.The susceptibility values are lower totally and can be classified into two segments,i.e.the lower values prior to 125 Ma and the higher values after 125 Ma.The analysis of the sedimentary environment,of the contents of magnetic minerals and the TFe in the rocks,and of their relationship with the susceptibility enhancement suggested that the susceptibility values are predominantly determined by the kinds and the contents of the magnetic minerals from the source region,which indicated that the susceptibility values can be used to interpret the climate change in this time window.The climate during 128.15-115.82 Ma was significantly arid and hot.Moreover,the variation of the susceptibility values revealed that the climate changed at ca.125 Ma from relatively wet and hot during 128.15-125 Ma to relative wet and warm during 125-115.82 Ma.This is consistent with the variation of the global sea surface temperature （SST）,but the time of this transition was 1.7 Ma earlier than the time of remarkable change of the global SST recorded by the marine sediments,which probably suggested that the continent was more sensitive to the climate change than the ocean.

关 键 词：磁化率 气候变化 六盘山群 早白垩世 

分 类 号：P318[天文地球—固体地球物理学]