安徽宣城黄土堆积的磁性地层学与古环境意义  

MAGNETOSTRATIGRAPHY AND PALEOCLIMATIC SIGNIFICANCE OF AN EOLLIAN SEQUENCE FROM THE XUANCHENG AREA,ANHUI PROVINCE

作　　者：乔彦松[1] 郭正堂[1] 郝青振[1] 吴文祥[2] 张仲石[1] 赵华[1] 朱日祥[1] 

机构地区：[1]中国科学院地质与地球物理研究所,北京100029 [2]北京大学,城市环境学院100871

出　　处：《地质力学学报》2002年第4期369-375,共7页Journal of Geomechanics

基　　金：国家自然科学基金项目 (编号 :49894176 )

摘　　要：利用磁性地层学方法对安徽宣城剖面的研究表明 ,B M界限位于剖面中网纹红土的中下部 ,结合光释光测年可以外推出长江中下游地区的典型风成沉积开始形成于 0 85Ma前后。这一年龄对应于一次全球性的气候转型事件 ,在海洋沉积与我国北方的黄土 古土壤序列中均记录了这一气候转型事件。同时 ,0 85Ma对应于中更新世的两大地质事件 ,一是全球冰量的增加 ,二是青藏高原的快速隆升 ,长江中下游地区风成堆积的开始 ,可能是上述两个因素共同作用的结果。A loess-soil sequence near Xuancheng from the Yangtze valley is investigated using magnetostratigraphy and luminescence dating to determine the location of B/M boundary.This boundary is found to be located within the middle-lower part of the so-called plinthitic laterite.,a widely distributed mid-Pleistocene tropical soils in southern China.The magnetostratigraphy data,combining with the OSL age suggests a basal age of the typical eolian depositional loess-soil sequence is about 0 85Ma.This age boundary corresponds to a significant global climate change,also is recorded in the marine sediments and in the loess-paleosol sequence in northern China.It also coincides with two geological events,intensive uplift of the Tibetan Plateau and the extension of the global ice volume.We interpret the onset of eolian loess deposition in the middle-lower reaches of Yangtze River as a result of hydrological and circulation changes associated with above two events occurring at the mid-Pleistocene.

关 键 词：长江中下游 安徽 风成堆积 磁性地层 古环境 海洋沉积 

分 类 号：P642.131[天文地球—工程地质学] P53[天文地球—地质矿产勘探]