Hydroclimate and vegetation changes in southeastern Amazonia over the past ∼25,000 years

Abstract

Stable isotope analysis of plant waxes (δ13Cwax and δDwax) along with detailed pollen data provide a new perspective on vegetation and precipitation variability in Serra Sul de Carajás, southeastern (SE) Amazonia, over the past ∼25 cal kyr BP. The δDwax record indicates drier conditions during the Last Glacial Maximum (LGM) and a transition to wetter conditions into the Holocene, while the δ13Cwax data reveal that vegetation did not experienced C3/C4 shifts and remained dominated by C3-plant communities. Under glacial conditions C3-savanna was prominent on the Serra Sul plateau with tropical forest areas limited to the lower slopes. Tropical forests expanded upslope and forest patches developed on the plateau as a response to more humid and warmer conditions during the Holocene. Pollen data indicate a shift towards more open landscape of savanna, woodlands, and open forests during the mid-Holocene. The δDwax record exhibits a distinct moisture variability during the Holocene, not always coherent with the vegetation data (pollen), especially during the mid-Holocene interval. Our study confirms the complexity and the overall lack of coherence among Holocene moisture proxy records throughout the monsoon domain in South America and suggest that Holocene local moisture conditions might not follow the regional monsoonal variability. Our data further stress the need for more multi-proxy reconstructions of hydroclimate patterns in SE Amazonia.