A geomorphological comparison between Eastern Brazil and Africa (Central and Southern)

Abstract

Summary Large parts of central and southern Africa and of eastern Brazil form “stable shield regions” that have escaped orogenic deformation since the late Palaeozoic. Similar erosional processes operating upon similar terrain in both regions have produced series of denudational and depositional land-forms that are closely comparable upon both the continental and local scales. Both sub-continents have been subjected to periodic uplift, and in each the uplifts have conformed to a differential pattern that was repeated for the region at each epeirogenic episode ; in the two sub-continents the general pattern of repeated deformation is similar both in space and time. In both regions, from the Carboniferous until approximately the Jurassic, sedimentation prevailed over denudation, but from the Jurassic onwards denudation exercised the dominant role and the principal features resulting are suites of cyclic land-forms. In each subcontinent the accumulative desert phase of the Triassic was concluded by the outpouring of floods of plateau basalt. The Jurassic denudation produced everywhere a landscape, termed “Gondwana”, of extraordinarily smooth planation, from which all subsequent scenery has been carved. The following denudational cycles and the related deformations and sedimantary phases are common to both regions:— 1. The Gondwana denudational cycle, followed by the late Jurassic deformations and the early and mid-Cretaceous sediments. 2. The post-Gondwana denudational cycle, followed by the mid-Cretaceous disturbances and the late Cretaceous and early Cainozoic sedimentary series. 3. The “African” and “Sul-Americana” denudational cycles, followed by mid-Cainozoic epeirogenesis and late Tertiary marine and continental deposition. 4. The late Cainozoic denudational cycle, followed by epeirogenesis at the close of the Cainozoic and Quaternary sedimentation. 5. Quaternary valley incision and sedimentation. The episodes of uplift and warping synchronized with well-established episodes of orogeny in other parts of the world.