Details

Autor(en) / Beteiligte

• FEAKINS, Sarah J
• KIRBY, Matthew E
• CHEETHAM, Michael I
• IBARRA, Yadira
• ZIMMERMAN, Susan R. H

Titel

Fluctuation in leaf wax D/H ratio from a southern California lake records significant variability in isotopes in precipitation during the late Holocene

Ist Teil von

• Organic geochemistry, 2014, Vol.66, p.48-59

Ort / Verlag

Oxford: Elsevier

Erscheinungsjahr

2014

Link zum Volltext

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• The hydrogen isotopic composition of plant molecular markers in modern vegetation and marine sediments in southern California have been intensively studied. Here we report a late Holocene reconstruction from Zaca Lake in coastal southern California, together with modern hydrological and vegetation studies in the catchment. The small catchment and decadal sampling resolution throughout the 9 m, 3000 yr sedimentary record provided a high resolution terrigenous counterpart of nearby marine records from the Santa Barbara Basin. Today, delta values of precipitation average 51.5 plus or minus 18 (1I, n = 7). Modern plant leaf wax delta values for the C28n-alkanoic acid averaged 1 plus or minus 11 (1I, n = 10) for Quercus agrifolia, with a calculated fractionation relative to precipitation (Imwax/precip) of 946 plus or minus 22 (1I, n = 10); in contrast, there was negligible production of the C28 acid by co-dominant Pinus coulteri. Downcore, the C28 acid delta values ranged between 101 and 177 (mean 150 plus or minus 8, 1I, n = 490). Abundance distributions suggested that the sedimentary C28 acid was dominated by Quercus, implying that paleoprecipitation varied between extremes of 8 and 92 (mean 63 plus or minus 14, compound 1I, n = 490). The 3000 yr leaf wax D/H record from Zaca Lake revealed substantial temporal variability, greater than observed in a speleothem reconstruction of similar resolution. We suggest that the plant-based proxy may magnify the variability by sampling spring precipitation preferentially. Centennial-duration positive isotopic excursions were associated with more sub-tropical moisture sources and drier conditions including during the Medieval Climatic Anomaly, and negative excursions were associated with N Pacific sources and wetter conditions including during the Little Ice Age.