Oceanic Environment During the Early Devonian in Longmen Shan Area: Geochemical Evidence from Brachiopod Shells

详细信息   

• 责任者：Cheng Hongguang （Institute of Geochemistry ; Chinese Academy of Sciences ; Guiyang 550002 ; China） ; Li Xinqing
• 刊名：Acta Sedimentologica Sinica
• 出版年：2008
• 卷期：26(6)
• 关键词：早泥盆世 ; Lower Devonian ; 沉积环境 ; depositional environment ; 生物化学 ; biochemistry ; 四川 ; Sichuan
• 页码：p.897-903
• 图表：6 illus., 33 refs.
• 分类号：1200
• issnNo：ISSN1000-0550
• isbnNo：CN62-1038/P

摘要

The Longmenshan section is a classical Devonian section in the world, and hence becomes the focus of Paleozoic paleocliamte studies. But in the early Devonian, it is short of geochemical isotopic attestation for the paleoenvironment. It will affect the comparison of geochemical signals between the Longmenshan and the other areas in the world, and also hinder the studying of the paleoclimate in Paleozoic. In this study, geochemical signals that came from well preserved brachiopod shells were used to discuss the paleoenvironment. The preservation show: brachiopod shells are well; noncathodoluminscence and Mn<250 μg/g, Sr>400 μg/g. It is witness that diagenetic alteration was small and even not. The δ18O values -4.5‰ -9.9‰ was evidently lower than that of other region’s δ18O values (-1.7‰ -6.9‰) in the world. And the trace elements Fe and Mn have inverse isochronous trend to the δ18O values. It is possible that the seawater circulation in the Longmenshan was unsmooth, and its δ18O value was desalinized by the input of continental fresh water. Current study will provide a convincing theoretical basis for contrast of isotope and trace elements on the worldwide scale.