Paleoenvironmental Reconstruction off Southern Brazil during a Glacial Period (66.5–47 kyr BP): Continental and Oceanic Environments

Abstract

Souza Pereira de Avila, A.; Leonhardt, A., and Diniz, D., 2020. Paleoenvironmental reconstruction off southern Brazil during a glacial period (66.5–47 kyr BP): Continental and oceanic environments. Journal of Coastal Research, 36(6), 1204–1214. Coconut Creek (Florida), ISSN 0749-0208.Based on the palynological record of core REG 972, this work aimed to reconstruct the paleoclimatic and paleoenvironmental history from 66.5 to 47 kyr BP at the south Brazilian continental margin, as well as to identify the influence of continental discharge in the southern portion of the Rio Grande Cone. Nineteen samples were processed following the standard methodology for palynological studies. Organic matter (OM) content was measured in the sediments. The age model was established according to 18O isotopes analyses in benthic foraminiferal tests. The studied interval corresponds to a glacial interval, divided in palynozones (PZs): PZIa (66.5–64.5 kyr), PZIb (64.5–53.5 kyr), and PZII (53.5–47 kyr). PZIa was characterized by drier conditions, with grassland and salt marsh taxa dominance (Cyperaceae and Amaranthaceae). During PZIb and PZII, the increase of Bryophyta, Pteridophyta, Araucaria angustifolia, Arecaceae, and Alchornea triplinervia points to wetter and warmer conditions that may be related to the beginning of marine isotope stage 3 and later to the sea-level rise. In the oceanic environment, the presence of freshwater algae and marine indicators lead to the conclusion that marine conditions prevailed during Rio Grande Cone sedimentary formation, even under low sea-level conditions when terrigenous influence was stronger. The data on OM content, dinoflagellate taxa, and mean sea level changes point to a period of low productivity during PZI. In PZII, a period of higher productivity took place because of Subantarctic Shelf Water influence, bringing cold and nutrient-rich waters to the area.