A NEW ANALYSIS OF HOLOCENE PALEOENVIRONMENTS IN THE SOUTHERN PANTANAL WETLANDS (BRAZIL) USING LAKE SEDIMENT CORES

The objective of this project was to investigate the Holocene paleoenvironmental evolution of the Nhecolândia region of the Pantanal wetlands, situated in western Brazil. The Pantanal is the world’s largest tropical wetland, and it is important to patterns of global biodiversity and the carbon cycle. Regionally, the Pantanal is also a critical upstream water resource for a number of growing cities in South America, but climate change threatens to alter the hydrology of the wetlands. More research is needed to understand how the Pantanal wetlands respond to climate change, and lake sediments are one of the key archives available to accomplish this goal. Nhecolândia has long fascinated geomorphologists, due to the presence of nearly 10,000 circular to ovate ponds of varying hydrochemistry, which dot the landscape along the southern fringe of the Taquari River megafan. There are very few well-dated paleo-records from the southern Pantanal, so to address this knowledge gap, sediment cores were collected from several of these ponds using a vibrocoring device. This project focused on developing geochemical and sedimentological indicator data from saline pond strata. Cores were sub-sampled approximately every five cm, and total organic carbon, percent carbonate, and terrigenous grain size data were generated using standard techniques (e.g., LECO, total carbon coulometry, and laser diffraction particle size measurements) for each sample. Further, the history of sediment accumulation for these cores has been constrained using radiocarbon dating of lake mud. In each of the cores, an abrupt shift is recorded in organic matter, carbonate, and fine particle content, which we interpret to reflect a significant environmental transition in the mid-late Holocene. Future research will examine this transition in detail, and integrate observations from Nhecolândia with paleo-records from elsewhere in the Pantanal.