Abstract: Changguang coalfield is located in northwestern Zhejiang.The coal-bearing formations of the Late Permian are widely distributed in the lower Yangtze region and have long been known as the Longtan formation with depositional features and great amount of bark in coal seams.This paper deals mainly with the origin of bark liptobiolite and its depositional environment.As a result of the Permian tectonic movement,many large and small basins came into existence in South China where were deposited sandstone,siltstone,shale,thin一bedded limestone and coal seams.Most of the valuable coalfields were formed during this time.The coal-bearing formation in Changguang basin contains chiefly four coal groupsA.B,C and D,in which C coal seam is rather thick,its thickness may reach 1.3-2 m and especially its western part can be mined. C coal seam is usually interspersed with some lenses of skeletal limestone or shell limestone.Both these limestones consist of abundant marine fossils such as brachiopods, pelecypods,crinoids,etc.It is evident that these beds of skeletal limestone bearing marine fossils represent temporary inundatien of coastal swamp by the sea.Based on the sedimentary analysis,a set of sediments including C coal seam show the depositional features of the marine swamps lowlands.C coal seam is mainly dull bituminous coal whose structure is rather simple.It contains a large percentage of suberinite (average 67%)sometimes up to 80-95%,which indicates that there is a close relationship between the depositional environment and the Permian coal-forming plant communities.It is more important to note that the bark coals originate from the selective decomposition of plant materials,that other materials such as lignin,cellulose,protein and their diagenesis products are wholely decomposed and drifted by flowing water and that resistant materials become concentrated under a reducing condition.Hence the bark coal may also be called bark liptobiolite.The bark liptobiolite in this region can be grouped into two types:the first one which develops from plants after decomposition, forms coal in situ, and the second one is hypautochthonovs coal, which develops from plant remains transported not far fiom their original sites.These two types of coal occur more often in this coal basin than in other regions.Under the microscope, in reflected light is dark grey and usually shows orange-yellowish subcrinite fluorescence.Location:Niutoushan No.1 Vitrinite R^o_max0.77%,Suberinite R^o_max0.27%,Niu-toushan No. 6. Vitrinite R^o_max1.06%,Suberinite R^o_max0.67%,typical bark coal (suberinite above 80 %):V^r₁55.86%,H^r₁ 7.11%,S^g_Q 3.85%,A^g₁ 12.19%.Besides, pyrite and clay minerals are usually scattered in seams and these bituminous coals influenced by the sea are characterized by the presence of high sulphur (3.8-6.6%)The results suggest that these coal seams are formed in coastal marine swampy lowlands and the depositional environment is suitable for concentration of plant fragments.Obviously,the formation of bark coals may be affected generally by the following factors:depositional environment,the type of deposition and the coal-forming plant communities.