下扬子五峰组上升流相烃源岩沉积特征

Sedimentary Characters of the Wufeng Formation Upwelling Facies Source Rock in lower Yangtze area

摘要:

五峰组层状含放射虫硅质类地层是下扬子地区所发育的区域性优质烃源岩之一，为前陆挠折滞流盆地边缘斜坡上升流沉积产物。受上升流强度和阵发周期频率的控制，形成了多个厚度呈周期性变化、硅质生物组成略有不同的硅质岩和硅质页岩互层韵律沉积。五峰组沉积时期，水体缺氧程度高，有机质组成以无定形为优势，原始生烃潜力高，低等藻类和其它浮游生物是其主要生源。受上升流影响，硅质岩和硅质页岩沉积时期有机质的保护机制存在差异，有机质富集程度主要与粘土矿物对有机质较强的吸附和保护能力以及氧化硅矿物转化过程中有机质的损失相关。

Abstract:

The Layered radiolarian cherty deposition of the latest Ordovician Wufeng Formation is one of the regional excellent hydrocarbon source rocks in the Lower Yangtze region and caused by the upwelling in the slope environment of the foreland flexural-break stagnation-flow basin margin. Under the control of the intensity and surging recurrence frequency of the upwelling,the Wufeng Formation is dominated by many siliceous rock/ siliceous shale couplets with different siliceous organisms and periodic variation in thickness.As the deposition under the anoxic environment, the Wufeng Formation mainly has high hydrocarbon potentional amorphous organic matters originated from algae and other pelagic organisms. In the impact from the upwelling, the different protection mechanisms of organic matter happen during the sedimentation of siliceous rock and siliceous shale, while organic carbon mainly relates to the adsorption protection of clay mineral and the loss of organic matter during the siliconoxide mineral transformation.