Assessing late Quaternary paleohydrology in the Bolivian Amazon through plant waxes

Climate variability during the end of the Pleistocene and the Holocene has been widely investigated in tropical South America, where precipitation is primarily controlled by the South American Summer Monsoon. Despite numerous regional syntheses, the existence and role of an east-west tropical South American precipitation dipole remain debated.

Here we present a new paleo-hydrological record from Laguna Larga, a ria lake located in the Llanos de Moxos (Bolivian lowlands). We analyse plant-wax n-alkanes and their hydrogen and carbon stable isotopes, together with portable XRF elemental data, to reconstruct hydroclimate, vegetation and erosion changes in the southwestern margin of the Amazon rainforest over the last 13 kyr BP.

Our results reveal hydrological fluctuations that influenced catchment vegetation. These variations highlight the dominant role of precipitation in shaping seasonally flooded savannahs such as the Llanos de Moxos, with implications for land cover dynamics, biodiversity, and human occupation.

This record provides new insights into late Quaternary rainfall variability in southwestern Amazonia and contributes to the ongoing discussion on large-scale precipitation patterns into tropical South America.