城口震旦系岩石学特征及沉积环境分析

THE CHARACTERISTICS OF THE PETROLOGY AND SEDIMENTARY ENVIRONMENTS OF THE SINIAN IN THE CHENGKOU AREA, NORTHERN SICHUAN PROVINCE

介绍了四川城口震旦系剖面的划分方案、岩石类型及岩石学特征,讨论了沉积环境。认为该区早震旦世明月期处于上扬子陆块北缘山前临海盆地的陆相环境;晚震旦世陡山沱期为潮坪—海湾环境,灯影早期为泻湖-广海陆棚-潮坪环境,灯影晚期则从浅水陆棚转变为深水陆棚环境。

This paper discusses Sinian sedimentation in the Chengkou area of Sichuan Province. First-ly, a stratigraphical division is suggested. Then the lithological characteristics are described in details,based on studies with polarizing and electron microscopes, and grainsize and chemical analysis. Final-ly, the sedimentary environments of the Mingyue stage early Sinian are discussed. In this area a pied-mont environment at the basin margin was formed and was located on the northern edge of the UpperYangZi Platform. Sedimentary facies were dominated by continental alluvial fan and mud-debris flowdeposits. During Doushantuo stage of late Sinian the tidal flat-gulf environments dominated this area,and manganese was concentrated in the middle to upper part of a transgresive sequence. The area wasof lagoon-shelf sea-tital flat environments during the early Dengylng stage of the Sinian. The lateDengying stage was of a shallow to deep water shelf environment.