Bimodal character of the Late Paleozoic glaciations in Argentina and bipolarity of climatic changes

The Upper Paleozoic sedimentary rock sequences of Argentina show an outstanding record of climatic fluctuations during this interval and the complexity and rapidity of the climatic changes. There were two distinct events of cooling or glacial periods: the older in the “middle” Carboniferous (late Viséan–Bashkirian) and the younger in the Early Permian (Asselian–Tastubian), and these were separated by a long-lasting interval of warming during the Late Pennsylvanian. It is postulated that climatic fluctuations in the northern paleotemperate realm may have had the same causes as in Argentina, and that these periods of cooling and warming probably occurred at the same time in both hemispheres. In western Argentina and central Patagonia the occurrence of the Early Permian glacial phase and the absence of the younger phases like those present in eastern Argentina and South Africa, suggest that during the final deglaciation in Gondwana thawing gradually progressed to the east, then located closer to the paleopolar region.