LONG-TERM, MULTI-SCALE PLATE AND GEOTECTONIC INFLUENCES ON PRIMATE PALEOENVIRONMENTS IN WEST AFRICA

The record of primate evolution in Africa extends from perhaps 56 Ma (latest Paleocene), to the archeological record of humans. However, that time represents only the most recent phase of Africa’s paleoclimatic and paleoenvironmental evolution. Africa became an isolated theater of evolution by 120 Ma, following the opening of the South Atlantic. Since 100 Ma, it has drifted ~15° north through the relatively fixed descending limbs of the northern and southern Hadley cells. Using multiple methods, the motion of Africa can be traced through those relatively stable climatic zones, and in the context of a growing South Atlantic and other global-scale phenomenon, significantly altered local and regional paleoenvironments through time. The fossil record of Angola allows evaluation of biotic consequences of those changes. The Turonian through Maastrichtian record is dominated by marine reptiles, which lived in relatively near-shore marine settings, during an interval marked by significant global cooling of sea surface temperatures. These localities were sequentially deposited in arid latitudes, which today host the Benguela Large Marine Ecosystem, but were subsequently transported northward. During the Cenozoic, in Cabinda, the section between Landana, at the base, and Malembo, at the top, spans the Paleocene to the Oligocene-Miocene boundary, during which time Africa drifted north 10°. Malembo has a mammalian fauna including a large primate, hyraxes, a ptolemaiidan, an arsinoithere, and a proboscidean. Today, 10° along the western African coast is the difference between a Welwitschia grove at the northern limit of the Skeleton Coast Desert at Bentiaba and the lowland tropical forest of Cabinda. The global drying trend from Paleogene to Neogene is recognized through fossil mammals from Namibia, but the global trend does not account for hyperaridity as caused by Benguela upwelling, whereas northward drift does. After the northward drift of Africa slowed in the late Oligocene, regional and global events continued to affect African paleoecology, including Miocene aridification induced by uplift along the East African Rift and the global trend from C3 to C4 grasses at about 8 Ma.