摘要
本文着重对兰州九州台黄土剖面上部的马兰黄土及全新世黄土3个样品及其下部的古土壤层(9层)共21个样品进行了系统的化学元素分析。结果表明,九州台黄土剖面中仅有微弱的元素分异现象;REE分布模式揭示,兰州九州台不同时代的黄土具有相同的物源区并与洛川黄土物源相似。在过去百万年时间尺度内,兰州九州台黄土形成于干旱、半干旱生物气候环境下的弱碱性介质条件和氧化环境中。
Systematic element analysis of 21 samples from the Jiuzhoutai loess section have been conducted recently. On the basis of variations in element contents, REE distribution patterns, characteristic values of the elements related to REE and also regional correlations, the material sources, formation processes and environments of loess are discussed in the present paper.Studies show that there took place weak element differentiation in the Jiuzhoutai loess section. The REE distribution patterns demonstrate that the loesses of different ages in the Jiuzhoutai loess section possess a common provenance,similar to that of the Luochuan loess. δU(aver-aging 0.65) and δCe(0.97) values and Eu/Sm ratios(0.19) revealed that the loess was deposited in an oxidation environment with weakly basic mediums under arid or subarid climate conditions. Furthermore, it was estimated that during the formation of S4 under such climate conditions, the annual average temperature was in the range 8-9.5℃, 2-3.5℃ higher than that at the present time, and the annual average precipitation varies from 350 to 450 mm, 100 mm higher than that today.
出处
《地球化学》
CAS
CSCD
北大核心
1991年第1期79-86,共8页
Geochimica
