DISCOVERY OF MARINE FOSSILS IN THE SHUANMAZHUANG COAL MEASURES IN INNER MONGOLIA AND THEIR SIGNIFICANCE

The Carboniferous Shuanmazhuang coal measures are distributed in the Borteng and Daqing mountains, Inner Mongolia. They may be divided in ascending order into three units: the Lower Shetai, Upper Shetai and Shuanmazhuang Formations. The coal measures are composed dominantly of terrigenous clastic materials with a total thickness of more than 1000 m. They have long been considered as continental deposits of intermontane basin type. During recent geological investigations, the author has first found bivalve fossils in the Lower and Upper Shetai Formations. These fossils comprise five genera and eight species, such asScizodus sinensis, S.shansiensis, Pterinopectinella kalamailiensis, Wilkingia regularis, Sanguinolites shiqiantanensis and Sedgwickia attenuata. They have provided evidence of the existence of marine sediments in coal measures. On the basis of sedimentological, geochemical, paleo ecological and paleocurrent studies, this paper discusses the types of sedimentary facies of coal measures and their evolutionary trend and the paleogeographic framework of the study area during the Carboniferous.