浙江煤山P/T之交碳同位素对有机碳埋藏的指示意义  

The Organic Fraction of the Total Carbon Burial Flux Deduced from Carbon Isotopes across the Permo-Triassic Boundary at Meishan, Zhejiang Province

作　　者：黄俊华[1] 罗根明[1] 白晓[1] 汤新燕[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

出　　处：《地球科学（中国地质大学学报）》2007年第6期767-773,共7页Earth Science-Journal of China University of Geosciences

基　　金：中国石油化工股份有限公司海相油气勘探前瞻性项目(NoG0800-06-ZS-319)

摘　　要：根据碳酸盐碳同位素和有机(干酪根)碳同位素记录,结合碳循环模式,计算得到了浙江煤山全球二叠系-三叠系界线层型剖面第23-40层的有机碳埋藏分数forg.在第23-24层和第27-29层下部出现forg的两个高峰值,与绿硫细菌反映的两个缺氧环境条件相对应.在第25-26层和第32-34层出现两个forg低谷值,与2-甲基藿烷指示的两次蓝细菌繁盛(第26层和第29层上部到第34层)基本吻合.这些结果反映了forg与埋藏时的氧化还原条件密切相关.forg与总有机碳含量TOC的关系比较复杂,一些TOC较高的层位(如第26层)forg却较低,而一些TOC较低的层位(如第27层)forg却较高,反映了原始生产力对TOC的重要贡献.根据原始生产力和forg得到的原始有机埋藏量,可以校正现今测得的残余TOC.本次研究结果说明,同步有机-无机碳同位素分析,在建立一定碳循环模型的基础上,计算有机碳埋藏分数,可有效指示有机质埋藏状态,进而为建立生物-环境-有机碳埋藏的耦合关系模型提供基础.By combining the carbon cycle model with the records of carbonate and organic （kerogen） carbon isotope composition, this paper presents the calculation of the fraction of organic carbon burial （forg） of beds 23-40 at the GSSP of the Per-mian-Triassic boundary at Meishan, Zhejiang Province. The resulting calculation produces two episodes of forg maxima observed to occur at beds 23-24 and 27-29, which respectively corresponds to the two episodic anoxic events indicated by the flourish of green sulfur bacteria. Two episodic forg minima occurred at beds 25-26 and 32-34, generally coincident with the flourish of cyanobacteria （bed 26 and upper part of beds 29 to 34） as shown by the high value of 2-melthyhopanes. It appears that the forg is related to the redox conditions, with greater forg values observed at the reductive condition. The relationship between forg and the total organic carbon （TOC） content was complex. The forg value was low at some beds with high TOC content （such as bed 26）, whilst high forg values observed at some beds with low TOC content （e. g. bed 27）. This association infers the important contribution of primary productivity to the TOC content. The original organic burial could be thus calculated through the configuration of the function of the primary productivity and forg , which can be used to correct the residual TOC measured in modern time. This investigation indicates that compiling the organic-inorganic carbon isotopes with the carbon cycle model favors to understand the fraction of organic carbon burial, providing information for the reconstruction of the coupling among biota, environments and organic burial.

关 键 词：碳同位素 碳循环 有机碳埋藏 二叠系-三叠系界线 

分 类 号：P736[天文地球—海洋地质]