Abstract
The «Causse Comtal» (Aveyron, France) : geology, , hydrogeology and inventory of main caves The «Causse Comtal» (S = 265 km2) forms a sedimentary bridge between the «Causses du Quercy» in the west and the «Grands Causses» in the east. With a middle humid climate (P -1000 mm/y, T = 9,4° C, Evap . = 450-500 mm/y), this plateau karst presents two aquifer levels in the Lower and Middle Jurassic separated by a marlous layer. These formations cover a paleozoic basement (sandstone, argillite from Carboniferous and Permian, crystalline rocks). The hydrogeological basins are controlled by E-W reverse faults due to the N-S pyrenean compression. The main spring is near Salles-la-Source in the west part (middle discharge : 840 l/s ; flood : 10 m3/s) ; it drains a 50-55 km2 area. The morphological and speleological evolution is subordinated to an erosion surface from Upper Cretaceous-Tertiary. Often stopped up (blocking), the numerous fossil caves probably date from the end of Cenozoic era. The large subterranean passages (activ or semi-activ galleries ; ex : Tindoul de la Vayssière) are plio-quaternary.
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