GEOC 3 |
| We use a transect of 32-lake surface sediments across large gradients of precipitation, relative humidity, and vegetation in the southwestern USA to study factors affecting sedimentary äDwax. äD values of C28 n-acids show significant correlation with äDP values (R2 = 0.76) with an apparent isotopic enrichment of ~ 99 ± 8 ‰. Leaf waxes from plants grown under controlled conditions (RH = 80, 60, 40 %) show a small increase in D/H ratios as RH decreases. However, the isotopic effect of RH on äDwax along the entire transect is apparently countered by the opposing influence of vegetation. The correlation between äDP and äDwax values is higher (R2 = 0.84) in the drier portions of the transect than in the wetter regions (R2 = 0.64). This study validates the use of D/H ratios of sedimentary leaf waxes as a proxy for precipitation äD variations, with particularly high fidelity in dry regions. |
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Modern Calibrations and Terrestrial Applications of Stable Isotope Paleo Proxies
9:00 AM-12:10 PM, Sunday, August 19, 2007 Boston Park Plaza -- St. James Rm, Oral
Division of Geochemistry |