Sedimentary and tectonic evolution of the North Depression in the Cevennes coal basin,France
Exemplified by the North Depression of the Stephanian Cevennes coal basin on the Massif Central in France,this paper discusses the sedimentary dynamics and synsedimentary structures in relations to basin tectonism.Spatially,the synsedimentary faults control the morphology and thickness of clastic rock bodies and coal seams,and the peribasinal faults control the geometry and sedimentary facies and palaeogeographic framework of the basin.The differences in fault actvity and intensity lead to the basin subsidence or the laternal migration of the depocentres and coal rich zones, and to the tectonic evolution of the basin from a half graben through a graben to a new type of half graben. The deposition and filling of the basin during different stages are interpreted to be in response to tectonic activity,and the modes and intensity of basin filling and tectonism are in turn closely bound up with the variations in the Stephanian peribasinal palaeostructural stress fields.