SEVERAL CLUES FOR THE STRATI GRAPHIC DIVISION OF THE PERMO-CARBONIFEROUS OF NORTH CHINA:A REGIONAL APPROACH

There are three marine limestone horizons in the Late Carboniferous Taiyuan Series in the Western Mountain, Taiyuan; i.e.Miaogou-Mao’ergou Limestone,Xiadao Limestone and Dongdayao Limestone from below upwards. Southwards, above Dongdayao Limestone, limestone appears again and the number of its horizons increases gradually southwards.The authors call that interval of strata on the stratotype section the Western Mountain Formation of the Taiyuan Series and the interval of strata above the former the Beidayu Formation, which is the highest horizon of the Taiyuan Series. North of Taiyuan, in the Baode Area of northwestern Shanxi, there occurs limestone characterized by abundant Triticites below the main coal bed equivalent to the bed below Miaogou Limestone, which can be correlated with the Triticites zone in the lower part of the Maping Stage of south China. The authors call it the Baode Formation, representing the lowest horizon of the Taiyuan Series. In the eastern part of the north China platform, i.e.in the area east of the Huanghe River,the Middle Carboniferous sea advanced from east to west, with the main currents coming from the southern side of the Liaodong peninsula.Three fusulinid zones in the Benxi Formation of the Fuzhou Bay had a tandency to overlap westwards.The early Late Carboniferous Triticites sea still pursued this feature. As the northern side of the north China platform adjoined the Mongolian sea trough that was just in the stage of inversion and the terrain was relatively complex, the sea transgression assumed the channelled style.Afterwards, the terrain in the north continued to rise,which resulted in the formation of the long-continued land-scap characterized by being high in the north and low in the south in the Permo-Carbon-iferous sedimentary bosin of north China. The basin began to be subjected to sea transgression from the south from the middle Late Carboniferous on. The seuthern side of the platform adjoined the tranquil continental shelf sea of south China, where the terrain was relatively flat; therefore the sea transgression was"widespread". Controlled by continuous evolution of terrain, sea waters in middle-late Late Carboniferous time, particularly after deposition of Dongdayao Limestone, had a tendancy to retreat contiuously from north ot south.Therefore,brackish sediment were more and nore developed Southwards in the Permian strata.