宁夏中卫长流水剖面沉积物中稀土元素及其环境意义

通过对我国西北腾格里沙漠前缘凹地－宁夏长流水剖面第四纪沉积物中稀土元素、分布模式、特征参数和稀土元素之间以及其他元素相关系数研究，探讨了该区河湖相沉积物的物质来源及气候环境演化过程。初步认为该凹地第四纪晚期近７万年以来沉积物经历了三次较大的干冷／温湿气候环境演化并存有４～５次亚一级的气候冷暖阶段性变化。其中在约２．７ｍ处，湖相沉积层中大多稀土元素有突变现象，可能代表了全新世大暖期（９３００～５３００ａＢＰ）在该区的反应。同时，认为风成砂是进入该区沉积体系的主要物源并保留母岩特征，但也不排除凹地周围侏罗纪基岩受风化剥蚀后随水带入沉积体系。该剖面的沉积物大致以风成砂、河流沉积、湖泊沉积旋回叠覆与气候干冷、冷湿、温湿趋于同步变化的模式。总体以干旱荒漠环境为主导，化学风化相对微弱，生态环境十分脆弱。

REE of Sediments of the Changliushui Section at Zhongwei County of Ningxia Province and the Environmental Significance

Reported in this paper are the REE distribution patterns,character parameter and correlation coefficient between REE &primary elements in Quarternary sediments of Changliushui section developed at a depressed qully at Zhongwci County of Ningxia Rcgion, ncar the southcrn margin of the Ala Shant Desert in North－West China.The material source of the fluvo－lacustrine deposits and the evolutionary of the climate and the environment in the desert front area also discussed here in the section,there are three main climatic and environmental changes from dry and cool to warm and moist during deposition,and four or five secondary climatic fluctuations.At the depth of 2.7 m,the content of REE change very clearly.It seems a eflection of temperate period of Holocene in the area (9300～54300 a.B.P.).REE characters show that the source of the aeolian sans of the deposit area mainly came from surrounding parent rock material. Additionally,it also possible that the weathered material of Jurassic rock was brougt into the sedimentary series by washing.The chane of sedimentary facirs from aeolion to fluvial thcn to lacustinc origins synchronusly coincied with the changc of climate from dry－cold cold-moist to warm moist.The arid desert environment is dominant,in which the chemical and wethering processes are weak.