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D/H variation in terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance

Li, Chao and Sessions, Alex L. and Valentine, David L. and Thiagarajan, Nivedita (2011) D/H variation in terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance. Organic Geochemistry, 42 (1). pp. 15-24. ISSN 0146-6380.

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We analyzed D/H ratios of common terrestrial leaf wax lipids in a 1400 year sediment core from the Santa Barbara Basin (SBB) to test whether they accurately record terrestrial climate in Southern California. The D/H ratios of long chain n-alkanes vary substantially with depth, but are poorly correlated with other terrestrial climate proxies. Interference from fossil hydrocarbons may be at least partly responsible. Long chain n-alkanoic acids exhibit nearly constant downcore D/H ratio values. This constancy in the face of known climatic shifts presumably reflects a substantial residence time for leaf wax compounds in terrestrial soil and/or on the basin flanks. Alternatively, the isotopic composition of meteoric waters in Southern California may not covary with climate, particularly aridity. However, the δD values of n_(-C22) and n_(-C24) fatty acids, commonly attributed to terrestrial aquatic sources, are partially correlated with Southern California winter Palmer Drought Severity Index, a tree ring-based climatic proxy (R^2 0.25; p < 0.01) on multi-centennial scales with an inferred ca. 215 year time lag. The improved correlation of these biomarkers can be explained by the fact that they are not stored in terrestrial soil nor are subject to interference from fossil hydrocarbons. Our study indicates that the SBB is unlikely to preserve high resolution leaf wax D/H records that can serve as quantitative paleoclimate proxies, though some qualitative information may be retained. More generally, the sources of lipids in marginal marine basins need to be carefully evaluated prior to attempting paleoclimate reconstruction based on the leaf wax D/H proxy.

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Sessions, Alex L.0000-0001-6120-2763
Additional Information:© 2011 Elsevier Ltd. Received 21 May 2010. Received in revised form 22 September 2010. Accepted 24 September 2010. Available online 1 October 2010. Associate Editor—S. Schouten. We are grateful to D. Sachse and an anonymous reviewer for helpful comments and suggestions. We also thank Captain M. Stein and the crew of the R/V New Horizon for assistance in collecting samples. We are grateful to A. Schimmelmann (Indiana U.) for providing varve counts and many valuable discussions of the data, and to A. Tripati (U. Cambridge) for assistance in picking forams. E.R. Cook, G.M. MacDonald and D.J. Kennett kindly provided raw data and significant discussions on the paleoclimatic records of Southern California and western America. The research was funded by NSF Award EAR-0311824 to A.L.S. and D.L.V.
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Official Citation:Chao Li, Alex L. Sessions, David L. Valentine, Nivedita Thiagarajan, D/H variation in terrestrial lipids from Santa Barbara Basin over the past 1400 years: A preliminary assessment of paleoclimatic relevance, Organic Geochemistry, Volume 42, Issue 1, January 2011, Pages 15-24, ISSN 0146-6380, DOI: 10.1016/j.orggeochem.2010.09.011.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:23117
Deposited By: Ruth Sustaita
Deposited On:28 Mar 2011 20:21
Last Modified:03 Oct 2019 02:43

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