摘要
位于上扬子板块的贵州、滇东、川南地区发育着丰富的晚二叠世煤炭资源，本文对该区晚二叠世地层、沉积环境和古地理进行系统研究，提出该区岩石地层划分对比方案，在沉积环境方面，提出本区三大相区、五种沉积体系和多种沉积相类型。分龙潭早期、龙潭晚期和长兴期。论述了研究区晚二叠世古地理演化。并对聚煤作用控制因素进行分析，认为煤层发育层位受幕式聚煤作用控制，煤层厚度则与下伏沉积物的沉积环境有关，聚煤有利部位为位于海陆交互相区的黔西地区，有利聚煤的沉积体系为三角洲－潮坪体系。
The study areas include Guizhou,southern Sichuan,and eastern Yunnan,where abundant coal resources are preserved in Late Permian strata.The Late Permian key fauna and flora and their combinations are studied and a scheme of stratigraphic multi subdivision for Late Permian succession are established. Typical Changxingian ammonoids such as Sinocelites sichuanensis and Pseudotirolites qianjiangensis have been found in C12 coal seam of the Huoshaopu coal mine ,Panxian County,western Guizhou,and a Changxingian Brachiopod fauna have been found in B4 marker limestone of the Yanbeihou section,Zhijin County,western Guizhou.This makes it possible to subcorrelate the Late Permian in vast areas of southern China.For lithostratigraphic purposes,the upper Permian is subdivided into the Longtan Formation(Wuchiaping Formation,Middle and lower Members of Xuanwei Formation) and the Changxing Formation(Wangjiazai Formation,Dalong Formation,and upper Member of Xuanwei Formation).The Longtan Formation is subdivided into the lower Member and the upper Member. Synthetic studies suggest that the Late Permian coal bearing sequences in study areas were mainly formed in five depositional systems,including braided river and braid delta system,alluvial plain fluvial system,delta tidal flat system,Lagoon tidal flat system,and carbonate Platform System.The delta tidal flat system is believed to be the most important system for the coal accumulation in western Guizhou.This system can be further divided into the fluvial dominated upper delta plain,fluvial and tide influenced transitional delta plain,and tide dominated lower delta plain and tidal plain environments. The overall paleogeographical units of the Late Permian in the study areas include non marine alluvial plain dominated by fluvial channel, alluvial fan in eastern Yunnan,transitional paralic plain dominated by delta tidal flat system and lagoon tidal flat system in westerm Guizhou and southern Sichuan,marine carbonate platform in eastern and southern Guizhou,eastern part of southern Sichuan,and southern part of eastern Yunnan,and deep water fault basin in the vicinity of Ziyun of southern Guizhou.Lithofacies paleogeographical maps of Early Longtanian stage,late Longtanian stage and Changxingian stage have been drawn based on analysis of various contour maps such as clastic and carbonate rocks ratio,thickness of sandstones,percentage of sandstones,thickness of coal seams,and thickness of strata.The results show overall transgression of the early Longtan stage,overall regression of the late Longtan stage,and re transgression of the Changxingian stage. Late Permian coal accumulation in study area shows strong controls of tectonic activity and sea level changes.Coal accumulation was favored by weak tectonism dominated Late Longtan and Changxing stages,and delta flat depositional system dominated transitional coastal plain.The horizon of a single extensively distributed coal seam was controlled by transgression in the forth order sea level changes which induced episodic(transgressive) coal accumulation. The thickness of coal seams was controlled by the local topographical relieves which are related to microenvironments prior to coal accumulation.
出处
《沉积学报》
CAS
CSCD
北大核心
1998年第2期55-60,共6页
Acta Sedimentologica Sinica
基金
国家自然基金
