Climatic and vegetational dynamics in southern Brazil between 47.8 and 7.4 cal ka BP: a palynological analysis

Abstract

Vegetation and climate changes in southern Brazil are described based on the palynological analysis from marine core SIS 188, collected on the continental slope, which records the interval between 47.8 and 7.4 cal ka BP. The pollen record indicates that the grasslands dominated the landscape in southern Brazil throughout the studied period. During the last glacial period, the forests were reduced. Between 32.8 and 20.2 cal ka BP, there is an increase in grassland and reduction of arboreal palynomorphs, coinciding with colder and drier climatic conditions of the Last Glacial Maximum (LGM). From 30 to 25.2 cal ka BP, an increase in the sedimentation rate and concentration of most pollen indicators is observed. This change could be related to low sea level, which exposed the continental shelf to eolian erosion and fluvial inputs that transported sediments and palynomorphs to the ocean. A significant decrease in sedimentation rate is recorded between 19.5 and 12.6 cal ka BP, probably related to sea-level rise during deglaciation. During deglaciation and beginning of the Holocene, the increase in arboreal pollen indicates the expansion of forests, reflecting warmer and wetter climate. Heinrich event 1 is marked by a peak in the percentages of the arboreal vegetation at 15.9 cal ka BP. Around 8.5 cal ka BP, there seems to be another interval of higher moisture, indicated by the composition of the palynological association, formed by pteridophytes Blechnum, Huperzia, Polypodiaceae, Pteridaceae and Cyatheaceae. These results show that the palynological record from the SIS188 marine core is sensitive to global climatic changes and can provide a reliable paleovegetational reconstruction for the continental environment. Keywords: Pelotas Basin, paleoclimate, palynomorphs, palynology, Quaternary.