Global tectonic setting and climate of the Late Neoproterozoic: A climate-geochemical coupled study

Whereas the snowball Earth hypothesis seems to account for most of the major features of the Neoproterozoic glacial records, the causes that drove the Earth into a snowball state remain largely open to debate. Most of the mechanisms leading to the initiation of a snowball Earth are based on the existence of the unusual preponderance of land masses in the tropics. However, the time of the youngest Neoproterozoic glaciation is characterised by a rather widely distributed geography from low-to-high latitudes. In the absence of reliable knowledge of Neoproterozoic topography, two series of coupled ocean-atmosphere climate model simulations were carried out with a Late Neoproterozoic paleogeography (580 Ma) and solar luminosity reduced by 6% relative to today, the first one with flat continents and the second one with mountain ranges that mimic the Pan-African Orogen occurring at this time. Those climatic simulations coupled to the long-term carbon cycle have allowed to better constrain the atmospheric pCO₂ and the associated climate by the time of the youngest late Proterozoic glaciation. The Pan-African Orogen runs result in a snow accumulation pattern compatible with a regional-scale glaciation more less extensive while the no relief runs do not succeed in initiating any glaciation. These results could give additional support to the inferences from many authors that some of the glacial deposits originally attributed to a snowball-like glaciation could in fact be the consequence of a more localised glaciation due to the important orogen occurring at the end of the Neoproterozoic.