The portion of Greenland lying south of the seventieth parallel, so far as known, is composed of pre-Cambrian granites, gneisses, and schists -- of which the gneisses are most widely distributed -- with later intrusives, both acidic and basic, and a few isolated areas of sedimentaries of doubtful geologic age.
Along both the mid-eastern and midwestern coasts are widespread areas of Tertiary basalt, which have locally preserved from erosion the fossiliferous Tertiary and Cretaceous sedimentaries of the west coast, and the Tertiary sedimentaries of the east coast. This belt of basalts separates the pre-Cambrian area of the south from the northern extent of similar gneisses, granites, and schists.
This northern area of pre-Cambrian rocks, like the southern, is the northeastward extension of the old Canadian shield, and though locally affected by tectonic disturbances at various periods, is generally quite similar throughout its extent. It slopes toward the north and west. Along its northern and northwestern boundaries it is overlapped by Paleozoic sedimentaries from the Cambrian to the Carboniferous, some of the formations being richly fossiliferous.