下扬子深水相大隆组黑色岩系对晚二叠世末大洋缺氧事件的响应及其油气地质意义

South China is an important area for the study of oceanic anoxic events (OAEs) during the late Permian (Changhsingian). However, the Permian-Triassic Boundary (PTB) archives in the Lower Yangtze Region, in particular in the deep-water settings, have not been well constrained. This application will focus on the sedimentary response to OAEs in three newly discovered deep-water sections of Dalong Formation in Xuancheng and Jingxian cities, Anhui province. In addition, the significance of petroleum geology will also be investigated owing to the high total organic carbon (TOC) content of the black rock associations in Dalong Formaiton. The current application is of great importance both in scientific researches and practical applications. At first, the occurrences and sedimentary models will be investigated based on basic geological observations. Then, we will study the responses of sedimentary and geochemical characteristics to environmental changes in details, including oceanic anoxia, upwelling, sea-level, hydrothermal activity, continental weathering, volcanism and among others. Analyses of integrated multi-environmental factors can help us to get the basic features of environmental changes. Moreover, we will find out the spatio-temporal distributions of anoxic waters in different water depths/regions, in the context of the regional stratigraphic frameworks, and explore the evolution mechanisms of OAEs. At last, the relationship between OAEs and the accumulation of organic matters will be discussed based on the studies of petroleum geological features of Dalong Formation. After that, we will discuss the development model of source rock and evaluate the petroleum potential of Dalong Formation in the Lower Yangtze Region, South China.

我国华南地区是研究晚二叠世末全球大洋缺氧事件的重要基地，但仍缺少下扬子区深水相剖面的约束。本项申请，拟以新近在安徽宣城和泾县发现的3个大隆组深水相剖面为研究对象，开展对大洋缺氧事件的响应研究。此外，考虑这套黑色岩系富有机质，同时开展油气地质意义研究，因而可望具有重要的基础科学与实践应用意义。首先，通过系统的基础地质研究，查明大隆组的基本发育特征和沉积模式。在此基础上，仔细识别包括海洋缺氧、上升流、海平面变化、热水活动、陆源风化和火山活动等环境变化的沉积学和地球化学响应，综合对比多种环境因素，厘清环境变化的基本规律和特征。然后，基于对缺氧事件的精细分析，在区域地层格架中查明不同水深/地区的缺氧水体在时空上的分布，探讨缺氧事件的形成机制。最后，在有关大隆组油气地质特征研究的基础上，揭示缺氧事件和有机质聚集的关系，建立优质烃源岩的发育模式，明确下扬子地区大隆组的油气地质意义。

二叠纪末的全球大洋缺氧事件被认为是同时期生物大灭绝和华南优质烃源岩发育的主要原因之一，但目前针对其性质和形成机制仍不甚清晰。本项申请，以安徽宣城和泾县发现的3个大隆组深水相剖面为研究对象，开展对大洋缺氧事件的响应研究，具有重要的基础科学与实践应用意义。首先，使用传统沉积学方法对野外剖面和室内薄片进行了详细的观察，并结合前人研究成果，建立了大隆组基本发育特征和沉积模式。在此基础上，利用生物组合、沉积特征、黄铁矿硫同位素、氧化还原敏感元素（Mo, V, U）、Mo/TOC、Co×Mn、Cd/Mo、Eu*等地质与地球化学数据识别了包括海洋缺氧、上升流、热水活动和火山活动等环境变化。综合对比多种环境因素，认为华南地区长兴期早期和晚期经历了两次严重的底层水缺氧，而在生物灭绝线附近出现了一次短暂缺氧，同时还发现缺氧强度和古生产力直接存在一定联系，指示全球大规模的缺氧事件可能是导致生物灭绝的主要原因之一。此外，大隆组高有机质富集可能与华南地区北缘盆地独特的古地理-古海洋-古气候条件有关，上升流和频繁的火山作用对促进当时古生产力提供了丰富的营养物质。