Keywords: 
• transgression events /
• aggregation of eoal under " /
• event"

Abstract: According to traditional coal-forming theory, coal formation was thought to take place in the water (marine) regression period of the transgression and regression cycle, that is, the land facies coal forming model. The author's basic point of view that coal was formed during sea transgression is gradually becoming a theory or model of coal formation, which shows coal formation was transferred gradually to land during the transgression coal forming closely related to transgression. Peat formed in advance was submerged in seawater, as a result, the coal seam formed was of diachronism. This theory and model is originated from the analyzing result of the coal formation in epicontinental sea basin, which is a contribution to coal geology and bring up a new way in the analysis of coal formation. In particular, it puts forward a question on how to evaluate the function of coal seam, in terms of a special sedimentary body in sequence stratigraphy analysis. As the diachronism of coal seams was caused by the transgressive coal formation, whether the top surface or the bottom surface of a coal seam can be taken as an interface of different sequence units remains to be studied in detail. The sea level change of North China epicontinental sea basin in the late paleozoic period is of the feature of high frequency and complexity, that is, the sea level changed with different frequencies and grades and the superposition of them, to cause to form a special unit of sediment body. Long period of sea regression contains many short periods of transgression events; also, there may be relatively short period of regression in the course of transgression. The authors have studied the sedimentary series of transgression events in the coal-bearing strata and the characteristics of transgression sediments coming into contact with coal seams, summed up the points of transgression events and coal formation under the events, studied the mechanism of coal forming with transgression events, and put forward the theory of coal formation with transgression events in epicontinental sea coal aggregational basin. It is believed that the transgression events controlled the aggregation of coal in epicontinental sea basin, the rising of the base level provided favorable condition for the growth of peat swamp, while the large scale of transgression later on stopped the peat accumulation, which put the peat in a deoxidizing environment for a relatively short time for being preserved to form coal, and makes it impossible for very thick coal seams to be formed in such short period of peat swamp. That is to say, coal seams formed in such basin environment are mostly thin coal seams. The essential difference of coal formation with transgression events from that with transgression process is the isochronism. The latter is lacking in isochronism. There is no such continuous sedimentary series between sea facies layers and coal seams in the transgression event coal-forming model as in ordinary transgression process. The bottom floor of the coal seam is root clay, and there is interruption of sedimentation, which can be used as an important interface in dividing high-resolution sequences and the inside units. In the transgression event coal formation model has been proposed in the paper, the authors mainly emphasize the accidental event property. The transgression event played a controlling role in the aggregation of coal in the epicontinental sea basin. Peat accumulation results from the evolution of the environment caused by the rising of base level ahead of transgression. The peat accumulation can be said to take place during the period of sea level oscillation. If the accommodation needed for peat accumulation ion is stable for a long period, thick coal seam could be formed. The fact is that large scales of transgression enlarge the accommodation abruptly, which was not suitable for coal accumulation. Peat was submerged in deep water and coalification took place in a complete deoxidizing condition, also the gelatification was fairly complete. The happening proce