Evolution of the continental succession of the Quaternary coastal Barrier III in southern Brazil from the last glacial period to the Holocene (MIS 5–MIS 1)

Abstract The sandy Barrier III of the southern Brazilian coast was formed by sea-level high stands correlated to Marine Isotope Stage (MIS) 5, but little is still known about its behavior and evolution between the last glacial period (MIS 4–2, 71–11.7 ka) and the Holocene (MIS 1). A study on luminescence-dated continental sedimentary successions directly overlying MIS 5c (105.9–92.8 ka) marine deposits shows a wet, partially vegetated aeolian system developed between <104 and >82 ka, succeeded by a dry aeolian system accumulated mainly as transgressive sand sheets (TSSs) on interdune flats between ~82 and 10.5 ka. Protosols interbedded with TSSs indicate episodic vegetation expansion between ∼71 and 46 ka. Sediment accumulation was apparently controlled by autogenic (cannibalization, migration of bedforms) and allogenic (sea-level oscillations, climate) processes. Weathering and pedogenesis promoted changes in color and magnetic susceptibility (MS), and the development of redoximorphic features involving Fe and Mn released from weathered minerals. Strong pedogenesis after ∼10.5 ka, probably related to the Holocene climatic optimum (HCO) and orbitally driven increased seasonality and dryness, produced rubification similar to red beds on the barrier top. This study contributes to the understanding of long-term evolution and sedimentary dynamics of coastal barriers and aeolian systems on glacial–interglacial timescales.