Drastic climatic shift at～2.8 Ma as recorded in eolian deposits of China and its implications for redefining the Pliocene-Pleistocene boundary
会议名称：《中国科学院地质与地球物理研究所第十届(2010年度)学术年会》
会议日期：2011年
学科分类：070903[理学-古生物学与地层学(含：古人类学)] 0709[理学-地质学] 07[理学]
基 金：supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KZCX2-YW-Q1-03) the National Natural Science Foundation of China(Grant No. 40572106)
摘 要：There has been a long-running debate over the position of the Pliocene-Pleistocene boundary,i.e.1.8 Ma versus 2.6 *** study presents litho- and pedo-stratigraphic characteristics,grain size,magnetic susceptibility,and dust sedimentation rates for ’red clay’-loess sequences over northern China,in order to assess the drastic climatic event(s) recorded in the quasi-continuous eolian deposits,and to readdress the position of the Pliocene-Pleistocene *** complete Chinese loess sequences,33 soil-loess couplets have been identified and labeled with Si-Li ***,the base of Chinese loess has been designated at the bottom of loess unit ***,a typical loess layer within the uppermost ’red clay’ is identified and formally designated here as L34 and the soil unit between L33 and L34 as S33, which lowers the basal age of Chinese loess from 2.6 Ma to～2.8 *** the Neogene ’red clay’ and the overlying Quaternary loess are both of windblown origin,they have quite different pedogenic *** loess consists of alternating reddish soil and yellowish loess layers,while the ’red clay’ is composed of soils with much redder colour and carbonate nodule *** general,thered clayhas been subjected to stronger pedogenic processes than the overlying loess,and can be regarded as an extremely thick soil *** alternation of loess and soils reflects large-scale oscillations between glacial and interglacial conditions,whereas the well-developed ’red clay’ deposition indicates a relatively stable climate ***～2.8 Ma,shortly before the Gauss/Matuyama boundary,the eolian sequences show a sedimentary transition from the well-weathered ’red clay’ to the alternating loess and paleosol deposits,accompanied by coarser particle size,increased dust accumulation rates,and change of magnetic susceptibility *** indicate a large climatic shift from long-lasting warm-humid conditions to large-amplitude cold-dry and warm-humid fluc