Pairing Leaf-Wax Isotopes and Lithogenic Fluxes to Understand the Drivers of Dustiness in the South Pacific

Abstract:

There have recently been several studies (e.g. Martinez-Garcia et al., 2009, Naafs et al., 2012, Keuchler et al., 2013) that use leaf wax biomarker concentrations in addition to inorganic proxies in marine sediments to reconstruct past changes in dust flux to the ocean. Leaf waxes hold potential to inform our understanding of dust entrainment and cycling because their chain-length distributions, concentrations, and stable isotope ratios contain information on environmental parameters in dust source regions. We present a 220 kyr record of paired leaf wax n-alkane δ¹³C and ²³²Th fluxes from Tasman Sea Core Fr1/GC03. Leaf wax δ¹³C values are 7-9‰ more depleted during glacial periods, when there are also 3-4 times higher dust fluxes than during the Holocene. The δ¹³C shifts likely represent a combination of vegetation changes, moisture availability, and changes in the source area of the leaf waxes. By comparing the magnitude and timing of δ¹³C and dust flux changes, we will evaluate the relative influence of vegetation changes, hydrologic shifts, and wind speed increases on the observed changes in dustiness during glacial times.