皖南石炭纪岩相古地理特征

THE CHARACTERISTICS OF CARBONIFEROUS SEDIMENTARY FACIES AND PALEOGEOGRAPHY IN SOUTHERN ANHUI

本文着重阐述了安徽南部(郯庐断裂带以南)地区石炭纪海陆过渡环境和海洋环境中六个沉积相(包括若干个沉积亚相)的基本特征。据其特征和沉积相在空间的组合型式,分别建立了安徽南部碳酸盐沉积相模式和以陆源碎屑为主的混合型沉积相模式。根据石炭纪七个等时单位的古地理和古构造分析,确定了早石炭世张八岭隆起、铜陵半岛、江南古陆与巢庐坳陷、宣泾坳陷组成的“三隆两坳”古地理格局。此外,文中还阐述了该区石炭纪不同时期的古地理变迁特点和古气候变化特征。

Carboniferous sediments in southern Anhui were mainly deposited in continental-marine transitional and marine environments. The sediments in the tran sitional environment are mainly represented by near-sea lacustrine facies and littoral paludal facies. The sediments in the marine environment can be divided into tidal flat, lagoonal, inshore platform, infralittoral platform and beach facies, and in addition, sedimentary facies composed of a mixture of clastic rocks and carbonate rocks is also well developed. According to the characteristics and associations of sedimentary facies, sedimentary models for Carboniferous carbonate facies and mixed facies dominated by terrigenous clastic rocks in southern Auhui have been constructed respectively. From an analysis of the paleogeography and paleostructure in the early and late Yangttan stage, early and late Datang stage, early and late Weining stage and Maping stage in the Carboniferous, the authors have further ascertained the early Carboniferous paleogeograpical framework of 'three uplifts and two depressions', i. e. a framework of alternate arrangement of the Chaohu depression, Xuanjing depression, Zhangbaling oldland, Tongling peninsula and Jiangnan oldland. On that basis the Conditions and basis for the existence of the above-mentioned oldlands in the Early Carboniferous have been determined. The features of changes of Carboniferous paleogeography and paleoclimates are also dealt with in the paper.