Précisions sur certains genres d'ostracodes non-marins du crétacé inférieur ("cocobeach") du Gabon et description de quelques nouvelles espèces

L'étude des Ostracodes du puissant ensemble de sédiments à dominance lacustre du Crétacé inférieur du Gabon et du Congo, connu sous le nom de Cocobeach, a permis de dégager certains caractères de quelques genres d'Ostracodes, qui ne figurent pas dans leurs descriptions originales. Cinq espèces nouvelles ont été décrites

Précisions sur certains genres d'ostracodes non-marins du crétacé inférieur ("cocobeach") du Gabon et description de quelques nouvelles espèces Details on Some Lower Cretaceous (Cocobeach) Non-Marine Ostracod Genera from Gabon and Description of Some New Species

L'étude des Ostracodes du puissant ensemble de sédiments à dominance lacustre du Crétacé inférieur du Gabon et du Congo, connu sous le nom de Cocobeach, a permis de dégager certains caractères de quelques genres d'Ostracodes, qui ne figurent pas dans leurs descriptions originales. Cinq espèces nouvelles ont été décrites. The study of Ostracods in the thick sequence, which is composed predominantly of Lower Cretaceous lacustrine deposits in Gabon and the Congo and referred to as Cocobeach, has led to the recognition of some characteristics not mentioned in the original descriptions of some Ostracod genera. These characteristics are discussed and five new species are described

Continental margin subsidence: A Comparison between the east and west coasts of Africa

Sedimentation rates (corrected for compaction) from along the passive continental margin of Africa between the Equatorial Fracture Zone and Somalia are used to compare the rates of subsidence of the continental crust since early Mesozoic time. Three distinctive subsidence histories can be identified which correspond with basinal areas that have different structural styles: rifted (west coast), sheared (Equatorial and Agulhas fracture zones) and sunk (zones of vertical tectonics in eastern Africa). A comparison of subsidence rates with other tensional margins (NE USA and the North Sea) and a consideration of the plate tectonic history of the African margins leads to the proposal of a geo and thermodynamic model that takes cognizance of the worldwide mid-Cretaceous rheological discontinuity between taphrogenic and epeirogenic basin formation recognized by Kent, and the more generally accepted, purely plate tectonic driven model of margin subsidence. The new suggestion involves a lower Mesozoic worldwide rise in the geothermal gradient in the lithosphere which produces metamorphism of the base of the continental crust and initiates taphrogenesis along lineaments throughout Gondwanaland. A lowering of the geothermal gradient in the lower Cretaceous produces a switch to epeirogenic subsidence, driven solely by sediment loading and thermal contraction, by Aptian/Albian times. The thermal event facilitated continental separation, and sea floor spreading commenced locally at various times along the active taphrogenic belts. Local thermal and tectonic aberrations associated with this phenomenon over print onto the worldwide pattern of marginal basin subsidence. A further rise in the geothermal gradient may have been responsible for renewed taphrogenesis in eastern Africa in Tertiary times