贵州新民剖面晚二叠世碳同位素变化特征及有机碳埋藏的意义

根据碳循环模式，通过无机碳和有机碳碳同位素记录，半定量-定量地计算了贵州新民剖面晚二叠世有机碳埋藏分数forg，同时结合表征古海洋初级生产力的疑源类、藻类与菌孢的丰度值，详细分析了有机碳埋藏分数forg、古海洋生产力与岩石中保存的残余TOC之间的耦合关系。该研究发现新民剖面晚二叠世初级生产力较有机碳埋藏分数forg对残余TOC的贡献更大。但这一结果仍需进一步论证:新民剖面和煤山剖面forg与δ13Ccarb的高度相关性暗示forg主要受控于δ13Ccarb，而在Kump碳循环模型中忽略了晚二叠世火山活动对无机碳同位素组成的重要影响。

Variations of Carbon Isotope and the Significance of Organic Carbon Burial in the Late Permian at Xinmin Section,Guizhou Province

The fraction of organic carbon burial(forg) is calculated on the basis of the carbon cycle model with the records of carbon isotope composition on both carbonate and organic matter in the late Permian at Xinmin section,and the abundance of acritachs,algae and microbes which represents marine primary paleo-productivity is examined.We discuss the relationship among forg,marine paleo-productivity and the content of residual TOC in details.Residual TOC is determined by the combinations of the primary productivity,organic carbon burial fraction(forg) and burial redox conditions.But the data in Xinmin section and Meishan section show that the paleo-productivity plays a dominant role on the value of residual TOC.But this conclusion still needs further proof: we found that forg is mainly controlled by δ13Ccarb by Kump’s model,in which it concluded increased volcanism leads to only small changes in δ13Ccarb,and set the carbon isotope value of volcanic activity and weathering as δw =-5‰.That is to say,a series of secondary environmental effects caused by volcanism were ignored,such as "volcanic winter",ocean acidification,smoke and other toxic substances and so on,all of which had great impact on the marine environment.However,large-sized volcanism in the Late Permian could result in serious perturbation to marine carbon cycle.Therefore,the model still need to be further improved on calculating organic carbon burial fraction quantitatively or semi-quantitatively during this special geological period.