THE DIVISION AND CORRELATION OF THE LATE MAOKOU-AGED STRATA IN CENTRAL ANHUI—THE ESTABLISHMENT OF THE YINPING FORMATION AND ITS SIGNIFICANCE

For a long time there exists a diversity of opinions with regard to the division and correlation of the upper part of the lower Permian in central Anhui. The age determination and correlation of the strata yielding no coal, i. e., the lower part of the original Longtan Formation or the so-called Mao- kou Limestone, are not yet resolved because there is no paleontologic evidence. Since 1974, the authors have discovered-two sets of deposits through detailed geologic mapping and fossil collection. The Chaoxian subtype is represented by clastic, siliceous deposits of neritic,littoral and lagoonal facies. The subtype, 4.55-183.50m thick, is composed mainly of shale, carbonaceous shale and silty shale intercalated with siltstone and siliceous rocks with the Shouchangoceras-Gigantopteris-Myalina biota. This subtype is distributed in ateas along the Changjiang （Yangtze）River including Hexian, Hanshan, Chaoxian, Wuwei, Anqing, Huaining, Tongling, Guichi, Xuancheng, Jingxian and Ningguo. The Chaoxian subtype is called the Yinping Formation （new formation name）, whose type section is located at Houdong Village in Yinping, Chaoxian. The Susong subtype consists of neritic platform deposits of carbonate facies and is called the Wuxue Formation which was established by Prof. Chen Xu in 1935. The type locality for the formation is situated in the Dalao Mountains in Guangji, Hubei. The authors propose to use the Zuoshan section, usong, as the type section for this formation. The Wuxue Formation, 38.8-213.4m thick and exposed in Susong, Dongzi, Fanchang and Nanling,is chatacterized by limestone and chert nodular and chert banded limestone, containing the Yabeina-Neomisellina fauna. The Yinping and Wuxue formations rest conformably on the Gufeng tormation, which is composed of siliceous rocks with the Altudoceras-Neopliatifera huangi fauna, and are overlain disconformably by the Longtan Formation （or the Wujiaping Formation）, which is composed of feldspar silicaenite with the Gigantopteris-Lobatannularia flora. The establishment of the Yinping and Wuxue formations is of major significance for the division and correlation of the late Maokou-aged strata in central Anhui, the determination of the means and dividing standard of the Gufeng and Longtan formations, the establishment of the sequence of the Permian in Anhui and the provision of lithofacies and paleogeographic evidence for the Early Permian.