渭北黄土台塬全新世地层高分辨率研究

HIGH RESOLUTION STUDIES OF THE HOLOCENE LOESS STRATA OF THE LOESS TABLELAND IN THE WEIHE RIVER BASIN

在野外观测研究的基础上 ,对陕西扶风新店村全新世黄土剖面作了详细的地层划分。通过磁化率、粒度、TOC、全铁和碳酸盐含量测定分析 ,进一步揭示渭北黄土台塬全新世季风气候变化的规律。同时 ,阐明了“全新世大暖期”的气候有明显的波动变化 ,尤其是在 6 0 0 0— 5 0 0 0 a B.P.发生了一个干旱气候事件 ,形成黄土堆积 ,使得全新世古土壤分裂成为两层 ,表现为多周期土壤。从 3 10 0 a B.P.开始至今气候变得干旱 ,风尘堆积旺盛 。

A Holocene loess palaeosol profile at Xingdiancun, Fufeng County in Shaanxi province was studied by field investigations and laboratory analysis. It indicates that the loess palaeosol sequence of the loess tableland in this region is rather complete and continuous. This renders a higher resolution study of the Holocene strata and climatic change. The results show that the warm and humid climate during the Holocene Megathermal (8 500—3 100a B.P.) was actually not constant and continuous. There was an arid phase between 6 000—5 000a B.P. represented by a loess bed (L x) between palaeosols S 1 0 and S 2 0. Climate become dryer since 3 100a B.P. and therefore, eolian loess accumulation became intensified and the topsoil deteriorated.