LOCAL AND REGIONAL INFLUENCES ON LEAF WAX δD VALUES IN LAKE SEDIMENTS IN EASTERN MESOAMERICA

Leaf wax δD values in paleoclimate records are a rapidly developing tool to determine how precipitation and aridity have changed through time. Previous studies have demonstrated a variation in fractionation of δD from precipitation and biomarker hydrogen isotope values due to biosynthesis and other environmental factors including elevation, precipitation patterns, and vegetation types, varying from region to region. This study focuses on identifying these variations in δD from precipitation and long chain fatty acids derived from terrestrial sources to apply the findings to downcore studies.

Lake core top samples were taken from over 100 sites through the Trans-Mexican Volcanic Belt to the Yucatán Peninsula and south through Guatemala, Honduras and El Salvador. Abundances of long chain fatty acids are compared across an environmental, elevational, and latitudinal gradient, and vary among lake types, such as natural reservoirs via dammed lakes. δD values along an elevational gradient in the Yucatan Peninsula into the highlands of Guatemala will be compared to those of meteoric water and lake water samples to determine the apparent fractionation between the water source and leaf wax δD. Based on the meteoric water line for the Mesoamerican region, we expect to find less negative leaf wax δD values in the lowlands of the Yucatán Peninsula and more negative leaf wax δD values in the highlands of the Trans-Mexican Volcanic Belt, due to the combined impacts on rainout from the orographic effect and variations in aridity. The results of this study will be interpreted in the context of variations in vegetation, elevation, aridity, and precipitation patterns to assess the predominant environmental influences on leaf wax δD values in Mesoamerica.