Abstract:
Plant leaf wax hydrogen isotope (delta D (sub wax) ) reconstructions are increasingly being used to reconstruct hydrological change. This approach is based upon the assumption that variations in hydroclimatic variables, and in particular, the isotopic composition of precipitation (delta D (sub P) ), dominate delta D (sub wax) . However modern calibration studies suggest that offsets between plant types may bias the delta D (sub wax) hydrological proxy at times of vegetation change. In this study, I pair leaf wax analyses with published pollen data to quantify this effect and construct the first vegetation-corrected hydrogen isotopic evidence for precipitation (delta D (sub corrP) ). In marine sediments from Deep Sea Drilling Program Site 231 in the Gulf of Aden spanning 11.4-3.8 Ma (late Miocene and earliest Pliocene), I find 77 ppm swings in delta D (sub wax) that correspond to pollen evidence for substantial vegetation change. Similarities between delta D (sub P) and delta D (sub corrP) imply that the hydrological tracer is qualitatively robust to vegetation change. However, computed vegetation corrections can be as large as 31 ppm indicating substantial quantitative uncertainty in the raw hydrological proxy. The resulting delta D (sub corrP) values quantify hydrological change and allow us to identify times considerably wetter than modern at 11.09, 7.26, 5.71 and 3.89 Ma. More generally, this novel interpretative framework builds the foundations of improved quantitative paleohydrological reconstructions with the delta D (sub wax) proxy, in contexts where vegetation change may bias the plant-based proxy. The vegetation corrected paleoprecipitation reconstruction delta D (sub corrP) , represents the best available estimate as proof-of-concept, for an approach that I hope will be refined and more broadly applied. Abstract Copyright (2013) Elsevier, B.V.