Dynamics of Africa 75 Ma: from plate kinematic reconstructions to intraplate paleo-stresses

Plate reconstruction studies show that the Neotethys Ocean was closing due to convergence of Africa and Eurasia towards the end of the Cretaceous. The period around 75 Ma reflects the onset of continental collision between the two plates, although convergence was still mainly accommodated by subduction, with the Neotethys slab subducting beneath Eurasia. Africa was separated from the rapidly north moving Indian plate by the Owen oceanic transform in the northeast. The rest of the plate was surrounded by mid-ocean ridges. Geologic observations in large basins show that Africa was experiencing continent-wide rifting related to northeast-southwest extension. We aim to quantify the forces and related paleostresses associated with this tectonic setting. To constrain these forces, we use the latest reconstructions of the plate kinematics, while balancing lithospheric body forces, plate boundary forces and the plate's interaction with the underlying mantle. The contribution of dynamic topography to the body forces is accounted for in the model, based on recent publications of reconstructed mantle convective tractions. We model intraplate stresses and compare them with the strain observations. We find that the African plate 75 Ma was mainly driven by slab pull, lithospheric body forces and transform shear tractions. Mechanical equilibrium and the fit to strain observations require the net slab pull, as experienced by the plate, to be unusually low, pointing to the absence of a single continuous Neotethys subduction zone at the time. This corresponds well to reconstructions of micro-continents interfering with the subduction related to the closure of the Neotethys.