LATE PERMIAN PALEOGEOGRAPHICAL EVOLUTION AND ITS CONTROL ON COAL ACCUMULATION IN SOUTHWEST CHINA

摘要

The research areas include Guizhou, southern Sichuan, and eastern Yunnan, where abundant coals are preserved in Late Permian strata. These areas constituted major parts of the Upper Yangtze Plate during the Late Paleozoic. Late Permian key faunas and floras and their combinations in the areas and some important outcrop sections are studied and the multiple division of Late Permian strata are recommended. For chronostratigraphy, we divide late Permian into Longtanian and Changxingian. The first discoveries of the typical Changxingian ammonoids such as Sinocelites sichuanensis and Pseudotirolites qianjiangensis in C_(12) coal seam of the Huoshaopu coal mine, Panxian County, western Guizhou, and the Changxingian Brachiopod fauna in B_4 marker limestone of the Yanbeihou Section, Zhijin .County, western Guizhou make it possible to correlate Late Permian in vast areas. For lithostratigraphy, we divide Upper Permian into the Longtan Formation (Wuchiaping Formation and Middle and Lower Members of Xuanwei Formation) and Changxing Formation (Wangjiazai Formation, Dalong Formation, and Upper Member of Xuanwei Formation). The Longtan Formation is subdivided into the Lower and Upper Members. We also reconstruct the Late Permian fossil assemblage zones and apply tonstein markers in the correlation of major stratigraphical boundaries and coal seams. The Xuanwei Formation of eastern Yunnan is mainly composed of non-marine clastic rocks. The Longtan and Changxing Formations in western Guizhou and southern Sichuan consist of transitional marine and non-marine intebedded clastic rocks and limestones and the Wuchiaping and Changxing Formations in eastern and southeastern Guizhou, the eastern part of southern Sichuan, and the south part of eastern Yunnan consist of carbonate and siliceous rocks.