Late holocene paleoenvironmental reconstruction from beachrocks and hybrid carbonates in southeastern Brazil

Abstract

Contrary to the assertion of “the relative climate stability of the Holocene over the last 11,700 years”, many studies reveal climatic and relative sea level (RSL) fluctuations during the Late Holocene. This work presents dated records of carbon isotopes in faciological profiles of hybrid carbonates (hybrid carbonates and bindstones) associated with beachrocks (quartzarenites and bioclastic quartzarenites) in the Parati beach, Espírito Santo state, southeast coast of Brazil, during the last 2600 years. The concentrations of Si, Ca, Mg, and Sr (μg.g−1) and the molar ratios of Sr/Ca, Mg/Ca and Sr/Mg, associated with the values of δ13C and δ18O, enabled the differentiation of the abiotic and biotic origin of the cementation processes of the identified lithofacies. The results obtained show fluctuations in sea surface temperature (SST) between 2600 and 700 years cal. BP. The different conditions of lithofacies formation indicate changes in ocean circulation (such as temperature, salinity, intensification of South Atlantic Central Water - ACAS) and in climate (precipitation and evaporation) on a local and regional scale during the Late Holocene. The evidence observed in the beach of Parati can be added to the hypothesis of coupling between the variability of the Brazil Current associated with AMOC (Atlantic Meridional Overturning Circulation) and the positioning and intensification of the SACZ (South Atlantic Convergence Zone), during the Late Holocene on the southeastern shelf of South America.