Cretaceous Paleogeography of Africa

Michael L. Hulver, A. M. Ziegler, David B. Rowley, Dork Sahagian

Five stage-length maps (Valanginian, Aptian, Cenomanian, Coniacian, and Maestrichtian) of Africa integrate topography/bathymetry, lithofacies, tectonics, and climatically sensitive sediments. These reconstructions differ from currently available maps in their level of detail and accuracy, and in that computer routines were developed to plot all aspects of the maps, including lithofacies patterns. Bathymetric contours were determined from community paleoecology and from thermal subsidence models of the newly opening Atlantic and Indian Oceans. Topographic contours have been estimated from uplift models of rift shoulders, as well as from the erosion and sedimentation record of both the internal and marginal basins.

The uplift of rift shoulders from Nigeria to Sudan is suggested by the extensive Nubian and equivalent sandstones across north Africa. This Benue-Ngaoundere-Abu Gabra rift system approximately paralleled the paleoequator, and its shoulders must have experienced the high rainfall normally associated with the intertropical convergence zone (ITCZ). In fact, these mountains would have served as a high level heat source, and would have pinned the ITCZ to their summits. Such a system tends to reduce seasonal excursions of the ITCZ, and may have influenced the high biological productivity represented by the oil source rocks of the Arabian peninsula. These source rocks also lie on the equator and could have resulted from a shelf incursion of the equatorial divergence zone, which is controlled by the ITCZ.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.