TRANSLATION DE L'AFRIQUE PAR RAPPORT À L´AMÉRIQUE D'APRES L'ETUDE DE LA MIGRATION DES BASSINS SEDIMENTAIRES

Abstract

During the separation between Africa and South America, the African plate underwent epeirogenic undulation, which was reconstruted from paleogeographic studies of the major sedimentary basins, as well as from the history of the ridges. It exhibits a vertical amplitude of 10 3 to 10 4 meters, a wave lenght of 10 5 to 2 X 10 6 meters, and a period of 10 7 to 10 8 years. The litospheri undulation might be a response to vertical moviments (uplifts or subsidences) affecting the astenosphere or the upper mantle. It also might be due to an internal wave front, whose passage would cause vertical displacements. A third alternative would be a horizontal relative moviment of a flexible Iitosphere over a rigid mantle with elevations and depressions. For the African block, the direction of propagation, and the horizontal speed (0,1 to 10 cm/year), calculated from geologic observations on the migration of sedimentary basins, agree with a possible moviment of the African plate, as derived from the data on sea floor spreading for the South Atlantic. It will be very interesting to investigate whether similar studies on the Brazilian sedimentary basins would allow comparable results.