The Continental Record of Marine Isotope Stage 3 (MIS 3; ~60–25 ka) in Central Argentina: Evidence from Fluvial and Aeolian Sequences

Abstract

Marine Isotope Stage 3 (MIS 3) is characterized by high climatic variability<br />resulting from numerous centennial to millennial scale events. The environmental<br />and climatic reconstruction of this interval is restricted by the sparsity of<br />high-resolution (centennial-scale) terrestrial records in most of South America. This<br />contribution is an attempt to reconstruct the general environmental and climatic<br />conditions of southern South America during MIS 3 by means of continental<br />records located in central Argentina; this is an extensive and heterogeneous region<br />made up of diverse geomorphological settings under different climatic conditions.<br />Therefore, the main features of several aeolian and fluvial records situated in different<br />geomorphological settings across the region are overviewed. The results<br />indicate the predominance of regional aggradation during MIS 3 with differences in<br />the accumulation rates and dominance of either aeolian or fluvial deposits<br />depending on the geomorphological setting. The aggradation process was interrupted<br />by stability intervals evidenced by paleosols in the San Rafael plain, the San<br />Luis paleo-dunefield, the eastern Sierras Pampeanas piedmont and the eastern<br />Pampean plain. The paleosols might represent lapses of decreasing aeolian input<br />and perhaps more humid conditions. In addition, paleobiological indicators from<br />alluvial sequences suggest higher temperatures and water availability between 35<br />and 31 ka in the Andean piedmont, while dry subhumid or strongly seasonal<br />conditions with alternating subhumid-humid phases were inferred in the eastern<br />Pampean plain during MIS 3. These intervals tend to cluster during the second part<br />of MIS 3, and might reflect the environmental responses to some of the climatic oscillations that occurred during MIS 3. Detailed analysis and a more adjusted<br />chronology are needed to correlate the aeolian and fluvial episodes along with the<br />stability intervals at regional and continental scales.