Net relative vertical movements of continental surfaces can be identified and compared on an intercontinental scale by calculating percentages of flooding on continents at specific time intervals in the geologic past and then plotting the percentages on the corresponding hypsometric curves. Once a sea level curve is determined, the effects of sea level change can be subtracted from the elevation of the points on the curves, thereby giving the actual directions of net movements relative to sea level. Substantial net uplifts relative to other continents are indicated for Europe and Australia between the Albian and Turonian, for North America in the Cenozoic and for Africa between the Eocene and present. Narrower estimates of the time of uplift are not yet possible because the hypsometric curves are highly generalized and the paleogeographic data contain an unknown amount of error. Estimates of sea level changes suggest a late Cretaceous sea level elevation of about 200 m above present sea level. If correct, all areas that were covered by the late Cretaceous sea and that now lie above 200 m have been uplifted since the Cretaceous. The largest areas of uplift are in the Western Interior of North America and in northern and northeastern Africa, suggesting that uplift of these areas could account for the large net uplift during the Cenozoic in these two continents. The uplift in northern and northeastern Africa appears to be related, in part, to plateau uplifts and rifting. The origin of uplift in the Western Interior is less clear but may be an isostatic adjustment following late Cretaceous to early Tertiary driving subsidence and sediment loading in the Western Interior foreland basin. © 1979.
