Timing the Oligocene-Miocene uplift of Afro-Arabia: Insights from clay mineralogy and geochemistry

For tens of millions of years, up until the late Eocene, Afro-Arabia was subjected to intense chemical weathering under warm and wet climatic conditions. Geodynamic quiescence promoted the development of a widespread carapace of etchplains that capped the stable continent. Starting in the late Eocene, the impingement of the Afar mantle plume on the base of the Afro-Arabian lithosphere resulted in domal uplift across large areas surrounding the Red Sea. The carapace of deeply weathered rocks flexed, eroded, and eventually became incised, facilitating the erosion of underlying pristine rocks. Since at least the early Oligocene, the Afro-Arabian dome has been draining into the Levant Basin of the Eastern Mediterranean, providing the basin with an outstanding sedimentary record of the large-scale uplift. In this study, we evaluate stages in the rise of Afro-Arabia by probing the mineralogical and geochemical properties of Oligocene-Miocene clay recovered from the Levant Basin boreholes. The lower part of the siliciclastic section in the Levant Basin, dating back to 33 Ma, is composed of kaolinite-rich sediments sourced from the weathering and erosion of Neoproterozoic crystalline rocks of the Arabian-Nubian Shield. We interpret them as erosion products of the etchplains that once capped Afro-Arabia and were dismantled during the early stages of mantle-induced domal uplift. Higher up in the siliciclastic section, illite-smectite gradually becomes more prominent at the expense of kaolinite, reflecting further uplift and downcutting into the pristine bedrock. Since the early Miocene, fluvial incision was enhanced by the superimposed effects of regional doming and flexural uplift along the Red Sea Rift margins. By 20-15 Ma, the proportion of illite-smectite surpassed that of kaolinite in the Levant Basin sediments, signifying the substantial elevation of Afro-Arabia and the establishment of high topography. The sedimentary fill of the Levant Basin allows tracking the peeling of the rising continent and offers unique, independent constraints on the uplift process.