TIDAL DEPOSITS AND COAL-BEARING FORMATIONS

This paper deals with the barrier coastal environments of the continental sea are the main paleogeographic conditions ia the Upper Palaeozoic coal-bearing formations in the south of China and in the Middle, Upper Carboniferous coal-bearing formations in the north of China. The tidal deposits are one of the important deposits of those parts in coal-bearing formations and the storm deposits can be usually found. Some main coal seams are formed in the peat flats where the tidal currents are the main hydrodynamic conditions. The concept of "peat flat" is set forth by the author. It is a important type of the coal-forming environments in the Upper Palaeozoic coal-bearing formations in the south of China and in the Middle, Upper Carboniferous coal-bearing formations in the north of China. The difinition of the peat flat is as follows: mangrove forests or other tidal plants having a similar bioecology in ancient time can be grown in the intertidal flats and some supertidal flats of the tropical and subtropical zones and the peat deposits can be formed from which over a large area. Such environments of coal formed directly in the tidal flats are called peat flats. The concept of peat flats is not same as that of peat swamps. Peat flats belong to marine facies and peat deposits are formed in the tidal current action where the water level changes frequently and the tidal currents have double directions. The water medium belongs to brackish water or sea water and coalfoming plants are the tidal plants with which some marine organisms can be lived. The features of coal seams formed on peat flats are as follows: The coal seams distributed wide and stablely and contrasted easily. The thickness of coal seams changes more and their divergence is notable. The sulphur content is higher. These features are of great use as important signs for the work in the geologic survey and exploration of the coal field.