A late Quaternary palynological record from the southeastern margin of Brazil: Implications for the evolution of palaeoceanography, palaeoclimates and vegetation over the last 109 kyr

Abstract

Integration of late Quaternary continental and marine proxies allows improved reconstruction of palaeoenvironment and palaeoclimates models for the south-eastern coast of Brazil. In this paper, we analyse pollen, fern spores, and dinoflagellate cysts in a marine sediment core (GL74) over the last ∼109 kyr. Results showed that, between 109 and 89.5 kyr, low sea levels promoted the expansion of herbaceous taxa across open areas while climatic conditions were relatively warm and humid, as indicated by the high frequency of Atlantic rainforest Ombrophilous forest pollen types and abundant of fern spores. Between ∼79–49 kyr, higher concentrations of palynomorphs were recorded, which were likely related to the low relative sea level during the last glacial period. During this interval, there was a decrease in tree pollen grains and an increase in shrub and herbaceous pollen grains, indicating cold and relatively dry weather conditions. In the Holocene period, the low deposition of palynomorphs may have been influenced by the gradual submergence of the central part of the Brazilian coast. This process was associated with warm and humid climatic conditions, as suggested by the expansion of rainforests and the presence of hygrophyte/aquatic taxa and fern spores, as well as the retraction of grassland pollen types. Dinocyst assemblages suggest that nutrient-rich waters and/or the presence of upwelling cells were dominant between ∼109–88 kyr, but gradually reduced between 88 and 65 kyr (and/or ∼ 88–20 kyr) under the influence of subtropical fronts. The study culminated in the dominance of unproductive warm water in the upper column between 65 and 0.5 kyr.