川东红星地区上二叠统吴家坪组沉积相演化与核形石发育条件  

Sedimentary Facies Evolution and Oncoidal Development Conditions of Wujiaping Formation of Upper Permian in Hongxing Area, East Sichuan

作　　者：易雨昊 朱红涛[2] 陆亚秋[1] 李凯[1] 孟志勇 陈发垚 Yi Yuhao;Zhu Hongtao;Lu Yaqiu;Li Kai;Meng Zhiyong;Chen Fayao(Exploration and Development Research Institute,SINOPEC Jianghan Oilfield Company,Wuhan 430223,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国石油化工股份有限公司江汉油田分公司勘探开发研究院,湖北武汉430223 [2]中国地质大学资源学院,湖北武汉430074 [3]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2024年第12期4546-4563,共18页Earth Science

基　　金：中国石油化工股份有限公司科研项目“红星二叠系页岩气有效开发关键技术研究”(No.P22045);2022—2023年度湖北省博士后创新实践岗位资助。

摘　　要：微生物岩或微生物相关沉积的广泛发育是生物大灭绝之后常见的沉积学响应.近期研究认为中二叠世末灭绝事件是地质历史上第六大生物灭绝事件,但目前关于该灭绝后微生物沉积记录研究较为缺乏.本次研究对川东红星地区HY3井上二叠统吴家坪组底部的一套核形石灰岩展开了详细调查,并分析了其相关地层的沉积相演化.在HY3井茅口组顶部至长兴组底部,共识别出5个沉积相(组合)和11种沉积微相.纵向上,吴家坪组沉积相演化显示出3个整体水深逐步加大的3级海平面变化旋回,其中核形石仅见于吴家坪期第1沉积旋回海侵阶段的中-后期.根据核心和纹层特征,可将HY3井吴家坪组核形石分为4种类型.随着沉积水深加大,核形石的类型、直径、密度等参数在纵向上呈现出3个差异明显的发育阶段,这些参数变化均指示合适的水动力条件是核形石发育的关键因素之一.此外,这些核形石的发育可能还受到生物灭绝和陆源输入的影响.核形石发育层位对应于中二叠世末生物灭绝的灾后期,后生生物多样性锐减为以微生物诱导为沉积机制的核形石发育提供了充足的生态空间.在核形石灰岩之上相邻层位、水深条件相当的地层中,可能由于更靠近煤层,陆源输入增强,导致核形石不再发育.Widespread development of microbiolites or microbial-associated deposits is a common sedimentological response to the aftermath of mass extinctions.Recent studies have suggested that the end-Middle Permian extinction was the sixth largest extinction event in geological history,but the record of microbial deposition after the extinction is still lacking.In this study,the oncoidal limestone at the bottom of Wujiaping Formation of Permian in Well HY3,Hongxing area,East Sichuan,was investigated in detail,and the sedimentary facies evolution of its related strata was also analyzed.From the top of Maokou Formation to the bottom of Changxing Formation in Well HY3,5 sedimentary facies(assemblages)and 11 sedimentary microfacies are identified.The vertical evolution of sedimentary facies in Wujiaping Formation indicates three third-order sea level change cycles where the overall water depth gradually increases.The oncolite is only found in the mid-late transgression stage of the first sedimentary cycle of Wujiaping stage.Based on the characteristics of core and lamination,the oncoids of Wujiaping Formation can be divided into four types.With the increase of sedimentary water depth,the type parameters,diameter and density of oncoids present three distinct development stages from the bottom upward.The changes of these parameters indicate that suitable hydrodynamic conditions are one of the key factors for the development of oncoids.In addition,the development of oncoids may have been influenced by biological extinction and terrigenous inputs.The oncoidal horizon corresponds to the late Middle Permian extinction period,and the sharp decline of epigenetic biodiversity provides sufficient ecological space for the development of oncolite induced by microbes.In the adjacent strata above the oncoidal limestone or in similar water depth conditions,the terrigenous input may be enhanced due to the closer proximity to coal,resulting in the disappearance of oncolite.

关 键 词：晚二叠世 吴家坪组 沉积微相 核形石 生物灭绝 海平面变化 沉积学 页岩气 地球生物学 

分 类 号：P52[天文地球—古生物学与地层学]