Palaeogeography And Coal-accumulation Of The Yan'an Formation In Binchang Mining Area

In this paper,theories about Petrology, sedimentology,lithofacies palaeogeography and coal geology are combined and synthesized to study the sedimentary characteristics of Yan'an Formation in Binchang mining area. The sedimentary facies of the research region is recognized and the sedimentary system is categorized. River-Lake depositional system are engendered in this area. Single factor analysis associated with multi-factor analysis is applied to draw the paleogeographic map in Middle Jurassic Yan'an Formation. The paleogeographic figure shows that lakeside facies are the most common facies during the first period of Yan'an Formation. The major facies of the second period is delta facies which grown up and the lake facies is degenerated during this period. The middle formation is uplift in the third period of Yan'an Formation during which the meandering river facies are developed together in rest area. The coal accumulating environment in the research region is peat bog that developed from lakesaide. The coal is formulated in shallow lake deposit system. The 4# coal layer who has a larger thickness and spreads widely in the research area is regarded as the research objectives. Analysis result show that the coal beds thickness is highly positively correlated with thickness of the 4# coal bed.The coal-accumulation model is the lakeside depression. The coal-rich zone in the research region is roughly from Jujia to Xipo among the center of the mineral area. The coal rich center that coincidence with the subsiding center is depressed in the center of the mineral area.