Icehouse-Greenhouse Transition in the Mid-Latitude Gondwana Deposits of the Paraná Basin

The Carboniferous-Permian interval records the icehouse-greenhouse cycle that characterizes the end of the Paleozoic Era in the Paraná Basin (southern Brazil). Geographically situated in the southwestern Gondwana at that time, the Paraná Basin moved towards the north from high to mid-latitudes during this time interval. The marine phase of the basin was represented mostly by shelfal deposits with a very low slope gradient that was impacted by several episodes of expansion and retreat of ice caps throughout the Carboniferous when the most of the basin was situated around 70th to 40th parallels. An invertebrate fossil fauna with moderate species richness and mixing marine and non-marine species chiefly characterize this period. The marine ichnofauna, however, is poorly represented and outstanding shallow freshwater/terrestrial ichnoassemblages demarks deglaciation periods, which become more frequent during the Gzhelian. At the beginning of the Asselian, the freshwater/terrestrial trace fossil assemblages abruptly disappear and give place to non-bioturbated substrates full of plant fragments and preserving a rich Glossopteris Flora, due to the increment on humidity caused by the huge meltwater discharge and the rising temperatures. Body fossils of marine invertebrates and brackish-water trace fossils assemblage occur locally always associated with marine transgressive deposits, giving place to a more stable marine trace fossil assemblage during the Sakmarian/Artinskian. These interglacial conditions remained during almost all the Lower and Middle Permian into the basin, changing to conditions that are arider during the Upper Permian. This period records a variation in rock color, from predominantly gray to red upwards; the marine settings were silted up and gave place to fluvial-lacustrine settings and the extensive development of eolian dunes. This event is marked by an abrupt change in trace fossil and body fossil assemblages and enhanced the record of primitive reptiles as body and trace fossils (tracks, trackways, and coprolites). The abrupt climate change that affected the Paraná Basin was probably triggered by tectonic events that occurred in western Argentina during the Late Paleozoic (e.g., Gondwanides orogeny) and promoted a drastic shift in the ecospace occupation at the end of the Permian.