藏北羌多—查布地区下二叠统划分与早二叠世动物群特征

DIVISION AND FAUNA CHARACTERISTICS OF LOWER PER-MIAN IN QANGDOI--CHABU AREA, NORTH XIZANG

下二叠统分角木茶卡组和肖茶卡组。角木茶卡组为碳酸盐岩夹玄武岩,局部夹含砾板岩,厚1000—2500m。含(?)类组合 Monodiexodina-Parafusulina,珊瑚组合 LytvolasmaSzechuanophyllum,腕足类组合 Costiferina-Neospirifer-Spiriferella 等。属冷、暖动物群混生类型。肖茶卡组为碳酸盐夹玄武岩,800—2900m。含(?)Neoschwagerina,珊瑚组合 Iranophyllum-Waagenophyllum,腕足类组合 Neospirifer-Spiriferella-Marginifera 等,属暖水型动物群。这些反映了早二叠世时冈瓦纳大陆北缘浅海台地深拗陷带碳酸盐和火山岩的沉积特征。

The early-early Permian deposits are called the Juemucaka Formation, which consists mainly of carbonate rock intercalated with 2-4 layers of basic volcanic rock, and locally with rudaceous slate. It is about 1000-2500 m thick. Juemucaka Formation is rich in animal remains: fusulinids Parafusulina-Monodiexodina, corals Lytvolasma-Szechuanophyllum, and brachiopodas Neospirifer-Spiriferella-Costiferina. It can be correlated with Tunlonggongba Formation in Domar area, China, the upper part of Panjal volcanic rock in Kashmir, the Lower Jamal Formation in eastern Iran, Basleo Bed on Timor Island, and Abreksk Formation on Siberia of USSR.The Late-Early Permian deposits are called Xiaocaka Formation, which consists mainly of carbonate rock intercalated with 1-2 layers of volcanic rock. Its total thickness is 1000-2900 m. It is rich in animal remains: fusulinids Neoschwagering-Verbeekjna-Polydiexodina, corals Iranophyllum-Wentzelella-Waagenophyllum, and brachiopodous Neospirifer-Spirtferella-Marginifera. This formation can be correlated with Lungge Formation in Domar area and Xiaocaka Formation in Chashuang area in China, Zawan Formation in Kashmir, and the Upper Jamal Formation in eastern Iran.The main characteristics of fauna in early-early Permian are that the cold-water fauna and the warm-water fauna are mixed (transitional) or of alternative association type. They are the products in the marginal sea north of Gondwana Land, basically belonging to the cold-water fauna of Gondwana facies. In late-early Permian, the main characteristics of fauna are the warm-water fauna of Tethys-type.At Qixia Stage and Maokou Stage of early Permian, the characteristics of the fauna association changed obviously because of rapid southward retreat of the glaciation on Gondwana Land with the evidently increasing temperature.