In the Yorkshire dales the Carboniferous rocks assume an aspect very different from that which obtains in the South. Beds of detrital sediment, sandstones, shales and occasional ironstones and thin coals separate the limestones into well-defined beds. These limestone beds have received various names of local significance (Hardraw Scar, Simonstone, Middle, Underset, Main and many others), and owing to the country being little disturbed by faulting and being much cut up by the streams, they stand out as escarpments on either side of the valleys. The first indication of the intercalation of thick detrital deposits within the massive limestone is seen in Ingleborough and Penyghent; but as the rocks are traced north the detrital matter increases in quantity and the limestones diminish, until in Northumberland the whole Carboniferous series assumes the Yoredale phase, and consists of alternations of detrital and calcareous beds, no massive limestone being seen.