贵州乐康P/T界线无机碳同位素特征及其意义

贵州乐康深水海槽相中的无机碳同位素研究表明,晚二叠世由于局限环境,区域内生物贫乏,相对应的碳同位素值比同期其他剖面中碳同位素值偏低。而在长兴阶晚期,由于受区域内火山作用的影响,在剖面界线之下发育另一个碳同位素负异常,之后碳同位素有所回升,直至界线附近降低为最低值。早三叠世由于绝灭之后的生物复苏缓慢,无机碳同位素表现为低正值。碳同位素特征显示,碳同位素的变化受到了生物和环境等多种因素的综合控制。

THE CARBON ISOTOPIC COMPOSITION AT THE P/T BOUNDARY FOR THE LEKANG SECTION AND ITS ENVIRONMENTAL SIGNATURES

The carbon isotopic composition at the Permian-Triassic boundary in shallow-marine carbonate platforms has been extensively documented. This paper presents the carbon isotopic composition for deep marine carbonate from the Lekang section, Guizhou Province. The values of δ 13 C for the upper Permian rocks in the section are lower than those for other contemporaneous sections in South China, and are proved to be related to the spareness of the organism in limited environment. The anomaly of δ 13 C values was observed beneath the Permian-Triassic boundary (late Changhsingian). Based on the sedimentary characteristics for the section, it was inferred that the significant variation of the carbon isotopic composition originated from the largely voluminous volcanism in the area during late Changhsingian. At the Permian-Triassic boundary the value of δ 13 C decreases sharply to-4.0%. The samples from the lower Triassic exhibit low positive δ 13 C values, suggesting slow recovery of creatures after the extinction.