%0 Journal Article
%T VARIATIONS OF PALEO-WEATHERING INTENSITY OF THE WUCHENG LOESS FORMATION AT XIFENG AND THE IMPLICATIONS ON ENVIRONMENTAL CHANGES<br>西峰剖面午城黄土古风化强度变化与 早更新世季风环境演化*
%A Zhou Xin
%A Guo Zhengtang
%A Peng Shuzhen
%A Hao Qingzhen
%A Xiao Guoqiao
%A Ge Junyi
%A Qin Li
%A <br>周 鑫
%A 郭正堂
%A 彭淑贞
%A 郝青振
%A 肖国桥
%A 葛俊逸
%A 秦 利
%J 第四纪研究
%D 2007
%I 
%X FeD/FeT(free iron/total iron) ratio can be used as a sensitive indicator of the weathering intensity in the Quaternary loess-soil sequences and in the Late Miocene-Pliocene Red Earth Formation.Up to date,high-resolution paleo-weathering record of the Early Pleistocene Wucheng Loess Formation has been only generated in the Lingtai loess-soil section while those for the Xifeng and Changwu sections cover only the past 1.2Ma.This study aims at generating a new paleo-weathering record based on the Wucheng Loess Formation in the Xifeng loess-section.Through analyzing 661 samples from the Wucheng Loess Formation,a paleo-weathering timeseries is obtained that covers the interval from 2.6Ma to 1.2Ma.Then we examine the monsoonal environment changes at extra-obital and orbital scales and attempt to explore the links of paleomonsoon evolution with global climate.In comparison with the portion of the last 1.2Ma,Early Pleistocene weathering is weaker in soils while stronger in loess,indicating rather weak glacial-interglacial contrasts.The Early Pleistocene changes of weathering intensity at orbital frequencies are dominated by the 40-ka obliquity band.This suggests a dominant control of global ice-volume on the monsoon climate in Northern China,probably through modulating the dust accumulation rates and the strength of the winter monsoon.FeD/FeT progressively increases since 1.6Ma in both soil and loess units,suggesting increased summer monsoon intensities.These trends are inconsistent with the marine oxygen isotope record,but match well a series of environmental changes in tropical and sub-tropical regions,suggesting an origin of low-latitude forcing.An early onset of the 100-ka cycles is also observed at 1.6Ma,which is unlikely to be linked to global ice volume.Rather,it is attributable to the modulation of precession by eccentricity and the consequent impacts on the summer monsoon.
%K Early Pleistocene Wucheng Loess Formation
%K FeD/FeT ratio
%K paleo-weathering intensity
%K summer monsoon<br>午城黄土
%K FeD/FeT
%K 古风化强度
%K 夏季风
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=EA07051745CDC8D89D5F01A3A4CFE6A9&aid=6AE3A622B8EC4325&yid=A732AF04DDA03BB3&vid=DB817633AA4F79B9&iid=E158A972A605785F&sid=9107B2E171152411&eid=7C13E30F5EDBE7AB&journal_id=1001-7410&journal_name=第四纪研究&referenced_num=0&reference_num=43