MESOZOIC PALEOCLIMATE OF AFRICA

During the Mesozoic, Africa underwent tremendous paleogeographic changes, evolving from a completely integrated component of Pangea to a distinct landmass with outlines similar to what we recognize today. In concert with these dramatic paleogeographic changes, African climate also experienced profound shifts. Following the Permo-Triassic extinction approximately 250 Ma, African terrestrial environments experienced an increase in both temperature and rainfall. During the Triassic and Early Jurassic, African environments were heavily influenced by the Pangean megamonsoon, but in the Late Jurassic, regional climate patterns begin to reflect zonal atmospheric circulation. Semi-arid to arid conditions with seasonal rainfall patterns prevailed over much of the continent during the Late Jurassic and Early Cretaceous, with exceedingly dry environments in the continental interior. In the Late Cretaceous, rainfall increased in some parts of Africa, giving rise to warm, wet environments in the low latitudes.

Samples collected from boreholes drilled in the center of the Congo Basin chart the evolution of African climate through the Jurassic and Cretaceous. XRD analysis of material sampled from paleosol B-horizons reveals mineralogical indicators of aridity, and oxygen and hydrogen isotope analysis of pedogenic phyllosilicates provides quantitative estimates of paleotemperature. These data indicate that Late Jurassic and Early Cretaceous environments in central Africa were hot and arid, but became wetter in the Late Cretaceous.