Mantle contribution to Late Paleozoic glaciations of SW Gondwana

Abstract

During the Mississippian to Pennsylvanian, mountain-building processes, changes from marine to continental sedimentary paleoenvironments, and the formation of mountain glaciers dominated the landscape from the margin to cratonic zones of SW Gondwana. These surface processes occurred conspicuously during a tectonic stage with incipient and oblique to parallel subduction, strike-slip deformation, and high-temperature magmatism between the foreland and cratonic areas. However, these first glaciations of the Late Paleozoic Ice Age, or LPIA, would have been strongly controlled, among other processes, by uplift, as suggested by recent low-temperature thermochronology and stratigraphic studies. Given that the Mississippian of SW Gondwana was not affected by major crustal thickening and deformation associated with orogenic growth, and that uplift and relief creation were also reported in pericratonic and cratonic areas, at first glance, these elevations might be related to mantle dynamics. In this work, we support this theory based on paleo-elevation and paleo-isostatic analysis supported by calculations of the crustal thermal state considering observational and isostatic paleoelevation models. We compare our isostatic elevations, residual topographies, and changes of observational and isostatic topographies, with dynamic topography models calculated for the Late Paleozoic, for the time lapse analyzed. We propose that mantle forces during slab window formation or by the occurrence of a mantle plume might have conducted the required uplift, by combining mantle thinning and upwarping forces in the asthenosphere. As with Late Miocene to present-day scenarios in southern Patagonia, we propose that without additional mantle forcing, the extended LPIA glaciations may not have occurred in SW Gondwana, particularly at mid latitudes, similar to the Miocene to Pleistocene glaciations of Patagonia.