丹江谷地晚更新世黄土剖面微量元素地球化学特征研究

Geochemistry characteristics of trace elements in the Loess-paleosol sequence,Danjiang River Valley

文中以丹江河谷二级阶地前缘覆盖的黄土剖面为研究对象,研究Mn、Ni、Cu、Ba、La、Rb、Sr 7种微量元素在剖面中的波动特征,并对比黄土高原典型黄土,探讨其蕴含的古气候意义。结果显示:7种微量元素在剖面中的波动特征是气候变化的直接反映;Mn、Ni、Cu、Ba、Rb在古土壤层(S1、S0)出现高值,在黄土层(Lt、L2、L1)出现低值,La、Sr在黄土层(Lt、L2、L1)含量较高,在古土壤(S1、S0)层含量低,微量元素动态变化特征指示古土壤形成时期气候温暖湿润,成壤作用强,黄土堆积时期冬季风为主导,降水较少,成壤作用较弱;其中在马兰黄土形成时期,气候经历了短暂的温暖期;与黄土高原微量元素总体具有较好的相似性,指示两个区域受后期沉积环境影响基本相同,相比较而言,丹江地区的形成环境较黄土高原暖湿,风化成壤作用强于黄土高原地区。

Based on systematic experiment analysis of trace elements including Mn,Ni,Cu,Ba,La,Rb and Sr for Longquancun profile covered by the front edge of the second terrace in the Danjiang River Valley,these characteristics reveal the weathering intensity of Loess-paleosol sequence and its palaeoclimatic significance since late Pleistocene.At the same time,the typical loess on the loess plateau is compared.Results are shown as follows:the fluctuation characteristics of 7 trace elements in the profile are direct reflection of climate change.Mn,Ni,Cu,Ba and Rb have high values in paleosol layer(S1,S0),low values in the loess layer(Lt,L2,L1);However,La and Sr are high in loess layer(Lt,L2,L1),low in paleosol(S1,S0).The environment changes since late Pleistocene have been clearly recorded by the changes in the trace elements in this area.That is,the climate was warm and the pedogenesis was stronger in the period of the palaeosol formation.In the stage of the loess accumulation,the climate was cold and arid,so the weathering pedogenesis was very weak.Among them,during the period of the formation of Malan loess,the climate experienced a short period of warm.The trace elements in the Danjiang region are similar to those in the Loess Plateau,which indicates that the two regions are basically the same under the influence of the late sedimentary environment.The chemical weathering of LQC profile was stronger than that of the loess and paleosol in Luochuan.