Discussion on Micro-characteristics of Transgressive Event Deposition and Its Coal-forming Mechanism in the Late Paleozoic Epicontinental Sea Basin of North China

Key words: 
• epicontinental sea basin /
• event transgression /
• transgressive event coal /
• transgressive process coal

Abstract: The characteristics of the event transgression and its depositions have been studied by ways of sedimentology, coal geology, paleontology, and geochemistry association with comparative analysis. The results are as follows. The sedimentary assemblage (exposure deposition, coal seam and limestone) have characteristics of regionally correlative, the successive deposition, and facies gap. The key identification mark is the exposure deposition under coal seams. The paleontology has small size and is broken into some fragments. All the characteristics can proof paleontology the depositional environment of high energy water. And there are lower content of monolete spore and Gymnosperm with higher content of trilete spore in the transgressive event deposition. The author found the depositional environment of different beds. The exposure deposition formed in terrestrial environment. Coal beds were formed in the peat moor and preserved under the sea water. Then the differences between transgressive event coal and transgressive process coal can be concluded. Firstly, there are differences in basin characteristics. The transgressive event coals are often found in epicontinental basin while the transgressive progressive coals are found in marginal basins. Secondly, there are differences in coal-forming principle. The former theory emphasis that the peat moor were formed in the abandon stage of the clastic system and then were stopped by the event transgression, the later think that the peat moor were formed in the coast of activity system and were stopped by the slow transgression.