Sedimentary Environments and Coal Accumulation of the BaojishanHonghui Basin, Eastern Qilian Mountains

Key words: 
• depositional system /
• coalforming environment /
• coal accumulation /
• Jurassic /
• Basin /
• Qilian Mountains

Abstract: BaojishanHonghui Basin is a typical small scale Jurassic coalforming basin located in the east part of the Qilianshan Mountains. The sequence of the Lower to Middle Jurassic strata is deposited in the sedimentary cycle from the alluvial fan and/or fluvial, to lake delta and lacustrine depositional systems, and fill in the half graben type basin formed by extension of postIndosinian Movement .The complex of the alluvial fanbodies are developed in the vicinity of active fault, from where to another side of nonactive sedimentary boundary, there are gradually replaced by fluvial and wetland swamp system. Peat accumulated directly on the wetland in front of alluvial fans, in where the main coal seams with the features of large thickness and simple fingerlike shape are formed. There are eutrophic or low moor peats in the front swamp of alluvial fans, so that the coal beds with high ash content and sulfur content zonation are formed, as the case may be the space relationship between peat swamps and alluvial fan bodies.