高校地质学报2018，Vol.24Issue(1)：56-64,9.DOI:10.16108/j.issn1006-7493.2017070
美国比格内尔山黄土的地球化学特征及其古气候意义
Geochemical Characteristics of the Loess in Nebraska,U.S., and Their Paleoclimatic Implications
摘要
Abstract
Loess is one of the most extensive surficial geologic deposits in Nebraska,U.S..The deposition rate of the Peoria Loess was extremely fast during the last glacial period, especially in Bignell Hill, the Mass Accumulation Rate is highest in the word. It is still controversial to interpret the cause of the mass dust in the central Great Plain.In this paper,the compositions of Nd-Sr isotopes,major, trace elements and rare earth elements of the loess deposit were investigated on the Bignell Hill section in Nebraska.The results suggest that chemical compositions of the Nebraska loess are relatively homogeneous. Compared with the upper continental crust and the Luochuan loess in China,the contents of Fe and Mg are relatively low,and the contents of K and Na are relatively high in the Nebraska loess.Nd-Sr isotopic compositions indicate there is another source with higher 87Sr/86Sr and lower εNd,except the primary provenance of White River Group. The second source is likely to be glacial deposits which were derived from the area of Laurentide Ice Sheet, its contribution even as high as 30%~45%.The chemical index of alteration of Nebraska loess is about 65.7,lower than Luochuan loess in China,showing a weak chemical weathering intensity.The variation of CIA,Na/K and carbonate content in Bignell Hill section reveal a dry and cold climatic condition and weak weathering during Peiria Loess deposit(25~18 ka).This climatic condition was beneficial to the production and deposition of dust thus generated extremely high mass accumulation rate during that time.关键词
内布拉斯加/黄土/化学风化/Nd-Sr同位素Key words
Nebraska/Loess/Chemical wenthering/Nd-Sr isotope分类
天文与地球科学引用本文复制引用
杨洋,张瀚之,刘连文..美国比格内尔山黄土的地球化学特征及其古气候意义[J].高校地质学报,2018,24(1):56-64,9.基金项目
国家自然科学基金(41230526 （）
41690111) （）
