Development of the Arabian-Nubian shield and the tectonic boundary conditions of the first Cryogenian snowball Earth

In the Neoproterozoic Era, following a prolonged interval of non-glacial climate, the Earth entered a global glaciation known as the Sturtian Snowball Earth. To gain insight into the initiation of this glaciation and the mechanisms responsible for planetary cooling, we present stratigraphic, geochronologic and isotopic data from volcanics and sediments of a back-arc basin associated with the proto-Arabian-Nubian Shield in northern Ethiopia where deposition occurred for 100 million years in the lead-up to glacial onset. Stratigraphic and geochronological data sets support the interpretation of rapid glacial initiation ca. 717 Ma synchronous in Ethiopia and North America. Based on time-calibrated chemostratigraphy and geologic data, we propose that enhanced subaerial weathering of mafic lithologies, and thus higher planetary weatherability that lowered CO2, began ~50 Myr prior to the initiation of the Sturtian Glaciation. The accretion of Arabian-Nubian Shield volcanic arcs in the tropics during this time likely played an important role in increasing global weatherability, contributing to the initiation of the first Cryogenian Snowball Earth.