鲁西寒武系中部二级层序界面的识别及变化特征

Recognition and Variation Characteristics of Second Order Sequence Boundary in Middle Part of Cambrian in Luxi Area

摘要:

系统整理了以往多个 1∶5万、1∶2 0万区调图幅内地层剖面的生物地层资料 ,结合野外追索 ,利用生物地层 (化石带 )的近似等时性 ,对鲁西地区寒武系中部的二级层序界面进行重点研究。认为该界面赋存在馒头组下页岩段或洪河段与馒头组上页岩段或张夏组下灰岩段之间 ,在鲁西地区普遍存在 ,延伸稳定 ,自西北向东南由假整合→似整合过渡 ,并在西部地区出现明显的沉积间断。界面类型属Ⅱ型不整合。

Abstract:

On the basis of biostratigraphic information of strata profile with the scale of 1∶50000 and 1∶200000, combining with field trace, and using proximate isochronism of biostratigraphic zone, second order sequence boundary in middle part of Cambrian in Luxi area is studied emphatically. It is regarded that this boundary occurs in lower part of shale in Mantou formation, upper part of shale in Honghe formation and Mantou formation and lower part of limestone in Zhangxia formation. It occurs in Luxi area widely with stable strend. It transits from deceptive conformity to paraconformity frome NW to SE, and has an evident sedimentary break in west part. Sequence boundary belongs to Ⅱ type discontinuity.