Carbon and Strontium Isotopes of Late Palaeozoic Marine Carbonates in the Upper Yangtze Platform,Southwest China

查看全文 作　　者：Huang Sijing and Zhou Shaohua State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology, Chengdu, 610059, Sichuan, China Geological Institute, University of Copenhagen, Oster Voldgade 10,DK-1350 Copenhagen K,Denmark 出　　处：《Acta Geologica Sinica(English Edition)》索引1997年第71卷第3期,共11页 基　　金：This study was supported by the National Natural Science Foundation of China Grant No.48970116 摘　　要：238 marine carbonate samples were collected from seven sedimentary sections ofthe entire late Palaeozoic (Permian, Carboniferous and Devonian) in the Upper Yangtze Plat-form, southwest China. Based on the absence of cathodoluminescence and very low Mn (gener-ally<50 ppm) contents of the samples, it is thought that they contain information on the orig-inal sea water geochemistry. The results of isotopic analyses of these samples are presented interms of δ¹³C and ⁸⁷Sr/⁸⁶Sr ratios versus geological time. The strontium data, consistent withother similar data based on samples from North America, Europe, Africa and other areas inAsia, support the notion of a global consistency in strontium isotope composition of marinecarbonates. The strontium data exhibit three intervals of relatively low ⁸⁷Sr/⁸⁶Sr ratios in thelate Middle Devonian to early Late Devonian, Early Carboniferous and Early Permian, corre-sponding to global eustatic high sea level stands. The lowest ⁸⁷Sr/⁸⁶Sr ratio recorded in theLate Permian was probably caused by substantial basalt eruptions in the Upper Yangtze Plat-form at the time. Three corresponding periods of relatively high δ¹³C values at roughly the samethe intervals were caused by a relatively high rate of accumulation of organic carbon duringsea level rises at these times. The deposition of coal was probably responsible for the increaseof sea water δ¹³C at other times. The δ¹³C values drop dramatically near theDevonian/Carboniferous, Carboniferous/Permian and Permian/Triassic boundaries, con-sistent with other similar data, which further support the notion that geological time boundariesare associated with mass extinction and subsequent rejuvenation. 关 键 词：UPPER Yangtze Platform Late PALAEOZOIC marine carbonate CARBON and STRONTIUM ISOTOPES