扬子陆块下古生界页岩发育特征与沉积模式

为了深入探讨扬子陆块下古生界页岩发育与分布特征、建立沉积模式,系统收集与整理了扬子陆块下寒武统牛蹄塘组与上奥陶统-下志留统五峰-龙马溪组两套富有机质页岩大量数据,选取贵州省三都县渣拉沟及四川省筠连县昭104井两个典型剖面与井岩芯进行了系统观察与采样,对扬子陆块范围内两套富有机质页岩岩性与沉积相发育特征进行了系统分析.研究表明,早古生代以来,扬子陆块受被动大陆边缘扩张与陆缘造山挠曲坳陷两类成盆环境影响[1-2],牛蹄塘组页岩沉积于被动大陆边缘扩张环境,缘于上升洋流与缺氧事件复合沉积模式,富有机质页岩以扬子陆块东南缘深水陆棚-斜坡相区最为发育、厚度最大、有机碳含量最高;五峰-龙马溪组页岩沉积于加里东期周缘前陆造山环境,缘于浅水陆棚-闭塞滞留海湾沉积模式,富有机质页岩以中上扬子陆块东南缘深水陆棚区最为发育、厚度最大、有机碳含量最高.

Characteristics and Depositional Model of the Lower Paleozoic Organic Rich Shale in the Yangtze Continental Block

To further investigate the Paleozoic organic-rich shale development and distribution characteristics in the Yangtze Continental Block, and the depositional model, we systematically collected and compiled large data sets of organic-rich shales for the Lower Cambrian Niutitang equivalent Formation and Upper Ordovician Wufeng-Lower Silurian Longmaxi equivalent Formation. Outcrop in Zhalagou of Sandu county, Guizhou province and Zhao 104 wells Junlian Prefecture, Sichuan Province were selected for the systematic observation, sample tests, sedimentary facies, and so on. Regional reconstruction of paleogeography and correlation between different regions show that the Yangtze block was passive continental margin during the early Paleozoic and peripheral foreland during early Silurian. Niutitang equivalent shales were deposited in a passive continental margin environment, the upwelling nutrient flow and anoxic events in complex depositional model is interpreted for the depositional model of Lower Cambrian shale in Yangtze Block, organic-rich thick shale was mainly developed in the southeastern margin of the Yangtze block deep water shelf to slope facies; Ordovician Wufeng- Lower Silurian Longmaxi equivalent shales were deposited in the Caledonian orogenic front of the periphery foreland environment, organic-rich thick shale was mainly developed in in the anoxic intra-shelf low setting in southeastern margin of the Upper to middle Yangtze block.