Late Pleistocene coastal dynamics: Insights from new OSL Chronology of Barrier III aeolianites, Southern Brazil

This study investigates the coastal dune deposits of "Barrier III" along the southern Brazilian coast, and in particular along the coastal area close to Osório and Paranaguá. While traditionally attributed to the Marine Isotope Stage (MIS) 5e highstand, emerging evidence suggests this barrier is a complex system incorporating younger deposits from MIS 5a or even MIS 3. The analyzed sequences consist of aeolianites outcropping up to a few meters above present sea level. To ensure high-resolution spatial accuracy, proxy elevations were measured using a GNSS RTK station and referenced to the local geoid model (MAPGEO2015), maintaining a vertical error margin of a few centimeters.

Through geomorphological, granulometric, and morphoscopic analyses, this research re-evaluates the geochronological framework of these deposits by presenting 19 new Optically Stimulated Luminescence (OSL) ages. The findings address a critical scientific debate: while a broad consensus has long placed sea levels during MIS 5a and 5c several meters below present, recent studies increasingly suggest that sea level at that time may have been closer to, or even above, modern levels in certain regions. This study examines the extent to which eustatic oscillations during these substages, and potentially MIS 3, drove sedimentary dynamics capable of shaping dune systems in positions proximate to the modern shoreline.