Late Pennsylvanian aridification on the southwestern margin of Gondwana (Paganzo Basin, NW Argentina): A regional expression of a global climate perturbation

Abstract

Paleosols of the Paganzo Group preserve a shift from the cool climate of the glaciated high-latitudes of Gondwana to a long-term aridification punctuated by shorter-term fluctuations in moisture regime in the late Carboniferous. A quantitative reconstruction of paleoclimate inferred from the major element chemistry of paleosol horizons and the stable isotope geochemistry of soil-formed minerals and organic matter indicates that the climate varied substantially during deglaciation along the southwestern margin of Gondwana in the Middle Pennsylvanian including two geologically abrupt shifts to notably drier conditions. This dynamic climate terminates in a dry subhumid moisture regime characterized by steppe/dry scrub floral provinces. Quantitative estimates of net primary production during the post-glacial interval inferred from paleosol major element geochemistry are consistent with a mesic soil temperature regime, in agreement with paleotemperatures inferred from pedogenic goethite δD and δ18O. Contemporaneous aridification is well expressed in paleotropical continental records with Middle to Late Pennsylvanian aridification coincident with an abrupt evolutionary change in many marine and terrestrial species. The synchrony of aridification between the high and low paleo-latitudes and concomitant major restructuring of some ecosystems suggests that a paleoclimate change of global nature occurred during the Moscovian and Kasimovian.