A New Accumulation Model of Coal Seams in France Extensional Basins

Journal of China University of Geosciences, Vol. 11. No. 3, p. 297-301, September 2000ISN I002-0705Printed in chinaA New accumulation model of coal Seams inFrance Extensional basinsWang HuGenfaFaculty of earth Resources, China University of Geosciences, Wuhan 430074, ChinaABSTRACTCA This paper, based on the sedimentary features of the coal seams in the typical extensionalaulted)coal basins between two inland mountainous areas of the Central Massif (France) dealswith the accumulation mechanism and the corresponding sedimentary-tectonic conditions of thesethick coalbeds, and proposes a new coal accumulation model for the Inland lacustrine-basIn thickcoalbeds. The presence of a great number of gravity-flow sediments such as detrital flow, dilutedslurry flow or turbidity-current sediments in the coal seams, and that of the contemporaneousgravity slump and deformation structure in the coal seam itself both indicate that the lacustrine environment in the accumulation of the thick coalbeds was characterized by the relatively deep floodand violent sedimentation. This model can not only interpret reasonably the accumulation mechanism of the thick coalbeds developed in the fault basins in the Central Massif, France, but alshow its features distinctively from these of the accumulation model of the traditional thickcoalbeds.KEY WORDS thick coalbeds, accumulation model, sedimentary architecture, Central MassiffranceThe coal geologists have studied the sedimentary condi- were formed in Late Carboniferous-Permian. The two basinsions and accumulation patterns of coals in intra- mountainous involved in the present paper are small continental fault basinsfault basins(Hu et al., 1998; Wang, 1997: Wu et al., 1997: Fig. 1), among which the Cevennes and Montceau-LesLi, 1988 Bordonne et al., 1986; Vetter, 1986; Teichmullernd Teichmuller, 1982)and also the accumulation model forthick coalbeds Wang et al.Wang, 1997, Wu et al., 1996: Esterle and Ferm, 1994). Es-pecially, the authors of this paper observed and studied inail the strata outcropping in two continental intra-mountaious faulted (extensional)basins in France, and obtained somenew knowledge about the origin of coalbeds in fault basins(Wang, 1997), providing a sound basis for further comparison of the coalbedsSEDIMENTARY CHARACTERISTICS OF THICKCOALBEDS IN CEVENNES BASINThe fault basins developed in the Central Massif, franceThis study is supported by National Natural Science Foundation ofChina (No. 49902012), and by the Project of the High School Skele-ton Teachers and Younger Teachers Foundation of the Ministry of Education of chinaFigure 1. Location of the two coal basins in the CentralManuscript received May 8. 2000.中国煤化工1nebn2Manuscript accepted May 16, 2000.YHCNMHGWang HMines bauns cover an atoi nf legs than I ID km20mFigure 2. Accumulation characteristics and sedimentary setting of the Sans-Nom thick coal seam in the Cevennes coalbasin, France. a. distribution of strata and coalbed on two sides af the Malperthus gravity decollement fault: b. gravityslump strueture in coalbed e, relationship hetween contemporaneous deformational thick coalbed and strata.The cosl-besring series is nearly :500 m thick(Stephanian. C,, and consists mainly of conglomerate, sandstonesiltstone, mudstone and coalbeds. The cnal measures werelormed in an active extensional tectonic setting, and the gravi-ty slump structures ure extremely abundant in the sedimentailling sequences (WangThe maximum thickness of the major coiled, Sins-Nomcoalbed : 63-67 (ine Prediction in the Late Menzie Fault Basins of Northhinese)astern China. Bening: Gcological Publishing House. 32-44. Wu C, Ii s. Huang F, 1997, Analysix on the Sedimentary Conditions153-217(in Chineseof Ultra- Thick Coalbeds in Fushun Hasin. Coal Gcology and ExTeichmuller M, Teichmuller R, 1982. The (reological Basic af Coalploration, 25(2): 1-6(in ChineseFormation. In: Stach E. Mackuwsky M-Th, Teichmuller M. et Zhang R, Wu C, LI S, et al, 1999. Accumulation Dynamie Mechaal, eds. Textbook of Coal Petrography. Berlin: Gebr uder born-ism of the Main Coal Seam of the Eocene Guchengzi FormatonVetter P, 1986. Les Formations Limniques du Carbonifere SuperieurFrance, Soc Geol France,NS, 149:7 14中国煤化工CNMHG