This thesis will present a key analysis and the results of our researchs on the tectonic behaviour, mainly by folding and shearing, and role, during Variscan deformation, of Waulsortian mudmounds in various sedimentary and tectonic settings of Western Europe, and particularly in Belgium, Brittany and Southern Ireland. In oder to modelise this behaviour and role, seven structural lithofacies from lenticular mudmounds to well-stratified calcareous-shaley series have been defined. By this way, our detailled maping and inventory of structures of deformation - included strain measurements of the elliptically deformed crinoidal osscicles in limestones and shales - in the ductile, brittle or shearing conditions of the Variscan deformations have allowed to define five principles of mechanical relations between these lithofacies. Two models of Waulsortian domain structuration, during the Asturian and Sudetian-II orgonenic phases, have been carried out following these principles. In both models, folding is the essential mode of tectonic structuration, eventually accompanied by shear zones and brittle structures of regional importance or due to local effects of the lithofacies anisotropies. ; (GEOL 3) -- UCL, 1994