In this paper, a reinterpretation of the older 14C ages of the Pleistocene substrate of the Holocene barrier-lagoon system of three coastal localities in southern Brazil is presented (Hermenegildo, Cassino, and Curumim). Sedimentological, geochronological, palynological, and diatom analyses of a sedimentary deposit formed in an estuarine/shallow marine environment are examined. This sedimentary deposit is presently found between 22 and 25 m depth below sea level in the Pinheira coastal plain. Results from all studied sites indicate that the deposit was formed under a former sea level of Marine Isotopic Stage 3 (MIS 3) that may have oscillated in the study region between 5 and 23 m depth below present sea level, from 36.2 to 47.7 ka. These results are reinforced by studies of nearby sites, including southeast Brazil. The Pleistocene substrate of the Holocene lagoonal-barrier system, at depths lower than 5 m below sea level, seems to correspond to sedimentary deposits of the Pleistocene barrier formed during MIS 5, while at depths greater than 5 m below sea level, they might correspond to sedimentary deposits that were formed during the relative high sea levels of MIS 3.
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