黄土地层中的CaCO3与环境

本文根据大量观察分析,对黄土地层中的CaCO₃含量、存在形式、淀积深度进行了研究,并进行了分类。结果表明,不仅CaCO₃含量能够反映气候变化,而且其存在形式和淀积深度同样能反映气候变化;其淀积深度很少受时间影响,比含量更能可靠地用于气候研究。

CaCO3 and Sedimentary Environment of Loess Strata

CaC0₃ content. existing form and iUuvial depth in loess strata are studied in this paper. In order tomake clear the relation between CaC0₃ content and climate, the author firstly classify CaC0₃ into fivetypes and their relation with climate are discussed as follows. (1) High fragmental CaC0₃ content indi-cater weak leaching and arid climate, low content indicates intense leaching and humid climaie. (2) IlluvialCaC0₃ is secondary CaC03that formed by leaching and illuviating, and the content of secondary CaC0₃ ishigher than 5%. The illuvial GaC0₃ is riot realiable for reconstructing the climate, but generally, low con-tent represents humid climate and high content arid climate. However, dense accumulation of CaC0₃ mayindicates humid climate. (3) ,Contemporaneous remnant CaC0₃ is the residu al of leaching that occuredduring the development of soil, the content of CaC0₃ is less than 5% and the less the content is，the moreliumid the climate. (4) Deuterogenic residual CaC0₃ (with the content less than 5%)is the remant ofleaching that look place during the development of the overlying soil, the abandance of CaC0₃ is low andcan not reflect the climate of the soil strata growth. (S) Evaporated CaC0₃ was the precipitates that desertposited at the top layer of soil during the intensive evaporate process, and its content represented the desertclimate with a mean annual rainfall less than 100mm. Loess and palaeosoil containing thin film and. stain but not concretions was developed under the climate。with mean annual rainfall less than 450mm, (continued on page 54)