摘要
安徽巢湖平顶山地区上二叠统大隆组主要为硅质泥岩和泥岩互层沉积。通过对该剖面微体古生物化石丰度的统计分析发现,其演化可划分出4个阶段:Ⅰ(繁盛阶段)→Ⅱ(衰亡阶段)→Ⅲ(恢复阶段)→Ⅳ(大衰亡阶段)。利用微量元素Cu、Ni和Zn估算了巢湖平顶山剖面古生产力,其平均值为1.48gC/m2d,与北美二叠系黑色页岩的古生产力平均值(1.40gC/m2d)和现代海洋大陆架的初级生产力(如委内瑞拉大陆架为1.50gC/m2d)较为一致。大隆组中有机碳质量分数为0.26%～5.49%,有机质富集程度和古生产力大小与岩性关系密切:泥岩和粉砂质泥岩里有机质最为富集且古生产力较高;而在硅质泥岩中,两者含量相对较低。分析了有机质富集过程(从生物物质到沉积有机质,再到埋藏有机质)中各环节的主要影响因素,表明海洋古生产力是有机质富集的主导因素和前提条件,直接影响沉积物中的有机质含量,而海洋表层初级生产力的大小受上升流、营养盐和海水深度等环境因素综合影响;在埋藏有机质阶段,其主控因素为沉积环境中的氧含量和沉积速率等。综合研究表明,本剖面中有机质富集为生产力模式,即:岩石中有机质的富集受古生产力的影响最大,其次为沉积环境中的氧含量。其中,古生产力由生产者贡献,但是受消费者的丰度影响较大。
The Upper Permian Dalong Formation in Pingdingshan section, Chaohu area, is an inter- bedding deposition composed mainly of siliceous mudstone and mudstone. Through the statistical analysis of the micro-fossils abundance in Pingdingshan section, we found that its evolution can be divided into four stages： the flourish stage, the decline stage, the recovery stage and the large decline stage. The average paleoproductivity calculated by Cu, Ni, and Zn in this section is 1.48 gC/m^2d, which is consistent with the previously reported data （1.40 gC/m^2d） for the black shale of the Phosphoria Formation, a Permian phosphate deposit in northwestern United States, and also similar to that of the modern deposit in the Cariaco Basin, Venezuela （1.50 gC/m^2d）. The content of total organic carbon （TOC） in the Upper Permian Dalong Formation ranges from 0.26% to 5.49%. TOC and the paleoproductivity is closely related with the host lithology. The results show that high TOC and high paleoproductivity occur in the mudstone and the silty mudstone, while relatively low in the siliceous shale. This paper analyzes the main factor affecting the organic matter enrichment process, which is from organisms to deposited organic matter to burial organ- ic matter. It indicates that the paleoprodnctivity which controls the organic matter in sediments is the predominant factor and the prerequisite for the enrichment of organic matter in rocks. The primary productivity of the marine surface is influenced by several environmental factors, such as upwelling, nutrient salts, depth and so on. And the main factors which affect the organic matter enrichment are the sedimentation rate and the oxygen content at the stage of deposited organic matter. The comprehensive research indicates that the main factors which affect organic matter enrichment in this section are the paleoproductivity, and then the oxygen content of sedimentary environment. The paleoproductivity is determined by the abundance of primary producers, while, affected mainly by the abundance of customers.
出处
《古地理学报》
CAS
CSCD
北大核心
2010年第2期202-211,共10页
Journal of Palaeogeography：Chinese Edition
基金
国家自然科学基金项目(编号:40839903)
中国石油化工股份有限公司海相油气勘探前瞻性项目"海相优质烃源岩形成的地球生物学过程"(编号:G0800-06-ZS-319)
教育部高等学校博士学科点专项科研基金项目(编号:20060491502)资助
关键词
有机质
微体化石
地球生物学模式
古生产力
巢湖
上二叠统大隆组
organic matter, microfossil, geobiology pattern, paleoproductivity, Chaohu, Upper Permian Dalong Formation
