Abstract: The Longtan Formation in Baohetang Mine,Middle Hunan,is dominated by shallow water delta deposits The coal accumulation occurred on the tide-influenced lower delta plain No.1 and No.2 coal seams developed in peat swamps of abandoned delta plain,whereas No.3 coal seam formed on active delta plain Abandoned delta plain was the better coal-accumulating place In the abandoned period of delta,the tidal current had stronger reworking on the coal seams deposited on the lower delta plain,resulting in the redistribution of plant debris or surface layers of soft oxidated peat in the peat swamps,changing the distribution of coal thickness and coal quality,and forming the special "bark sapropel coal".