 The area is underlain by Black Rock slate , Burrington Oolite and Clifton Down Limestone of the Carboniferous Limestone Series , which contain ooliths and fossil debris on top of Old Red Sandstone , and by Dolomitic Conglomerate of the Keuper . Evidence for Variscan orogeny is seen in the sheared rock and cleaved shales . In many places weathering of these strata has resulted in the formation of immature calcareous soils . 
