贵州新民二叠系—三叠系界线剖面有机碳同位素变化特征及生物地球化学意义  

Variation of Organic Carbon Isotope and Bio-geochemical Significances across the Permian—Triassic Boundary at Xinmin Section,Guizhou,South China

作　　者：胡庆[1] 曹珺[1] 黄俊华[1] 喻建新[2] 张宁[2] 冯庆来[1] 

机构地区：[1]中国地质大学地质过程与矿产资源国家重点实验室,武汉430074 [2]中国地质大学(武汉)生物地质与环境地质教育部重点实验室,武汉430074

出　　处：《地质论评》2011年第3期305-315,共11页Geological Review

基　　金：国家自然科学基金资助项目(编号40839903和40921062)的成果

摘　　要：本文研究了贵州新民二叠系—三叠系界线剖面有机碳同位素(δ13Corg)组成和疑源类、菌藻类丰度的变化特征。δ13Corg在二叠纪末期存在缓慢降低和陡然降低两个阶段:缓慢降低发生于Clarkina yini带中下部,陡然降低出现在Clarkina meishanensis带内部。δ13Corg的缓慢下降与疑源类、菌藻类的丰度值保持在较低的水平相一致;δ13Corg的陡然降低是火山活动海洋生态系的破坏以及可能存在甲烷释放等作用的结果。δ13Corg的缓慢降低和陡然降低表明了海洋环境由渐变到突变的过程。δ13Corg陡然降低之前出现较高值,该层位与绿硫细菌的繁盛层位相对应,说明绿硫细菌可能是造成这一较高值的主要原因。与浅水相剖面相比,新民剖面δ13Corg在早三叠世早期仍然呈下降趋势,说明生态环境持续恶化,海洋生产率低下,生物复苏延缓。Bulk organic carbon isotope compositions and the abundance of acritachs, algae and microbes were examined from the Permian—Triassic boundary at Xinmin section, Guizhou. δ13Corg data highlight environment changes in the latest Permian and show the following features： a gradual decreasing phase begins in Clarkina yini zone, corresponding to the low abundance value of acritachs, algae and microbes; a sharp decreasing phase occurs during Clarkina meishanensis zone, which could be caused by the combination of volcanic activity, marine biological breakdown and a sudden release of methane hydrate. The two phases reflect that the marine environment changed from the gradual transformation to mutation process. δ13Corg exhibit a positive peak before the sharp decrease above the event horizon, and the flourishing of green sulfur bacteria may result in this positive peak. δ13Corg in Xinmin section is still a downward trend in the earliest Triassic compared with some shallow-water sections, indicating deteriorating ecological environment, low marine productivity and delayed biological recovery.

关 键 词：有机碳同位素 二叠系—三叠系界线 疑源类及菌藻类 生物绝灭 新民剖面 

分 类 号：P597[天文地球—地球化学]