Glacial to Holocene terrigenous organic matter input to sediments from Orca Basin, Gulf of Mexico — A combined optical and biomarker approach

• Published in: Earth and Planetary Science Letters
• Main Authors: Meckler, A. N., Schubert, C. J., Hochuli, P. A., Plessen, B., Birgel, D., Flower, B. P., Hinrichs, K.-U., Haug, G. H.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier 2008
• Subjects: deglaciation; organic matter source; kerogen; bulk parameters; meltwater; Meier; Yvon; Orca
• Online Access: https://doi.org/10.1016/j.epsl.2008.04.046

In this study we assessed changes in the contribution of terrigenous organic matter (OM) to the Gulf of Mexico over the course of the last deglaciation (the last 25 kyr). To this end, we combined optical kerogen analyses with bulk sedimentary, biomarker, and compound-specific carbon isotope analyses. Samples were obtained from core MD02-2550 from Orca Basin (2249 m water depth at 26°56.77N, 91°20.74W) with temporal resolution ranging from multi-decadal to millennial-scale, depending on the proxy. All proxies confirmed larger terrigenous input during glacial times compared to the Holocene. In addition, the kerogen analyses suggest that much of the glacial OM is reworked (at least 50% of spores and pollen grains and 40% of dinoflagellate cysts). The Holocene sediments, in contrast, contain mainly marine OM, which is exceptionally well preserved. During the deglaciation, terrigenous input was generally high due to large meltwater fluxes, whereby discrepancies between different proxies call for additional influences, such as the change in distance to the river mouth, local productivity changes, and hydrodynamic particle sorting. It is possible that kerogen particles and the terrigenous biomarkers studied here represent distinct pools of land-derived OM with inputs varying independently. Copyright © 2008 Elsevier. Received 18 November 2007; revised 15 April 2008; accepted 25 April 2008. Available online 13 May 2008. We would like to thank Laurent Labeyrie, Viviane Bout-Roumazeilles, Yvon Balut, and the crew of R/V Marion Dufresne for a successful cruise in the Gulf of Mexico. Hsin-Chi Lan is thanked for preparing the samples dated at ETH. Hans Thierstein provided expertise on nannofossil assemblages. P. Meier, U. Kegel, G. Schettler, and O. Scheidegger are gratefully acknowledged for their help with sample preparation and measurements. Julius Lipp assisted with lipid extractions and Heather Hill provided helpful comments on an earlier version of this manuscript. We furthermore thank Phil Meyers and an anonymous ...