A lacustrine carbonate record of Holocene seasonality and climate
- 1Department of Chemistry and Geology, Minnesota State University, Mankato, Minnesota 56001, USA
- 2Scripps Institution of Oceanography, Geologic Research Division, University of California–San Diego, 9500 Gilman Drive, La Jolla, California 92093-0244, USA
- 3U.S. Geological Survey, Earth Surface Processes, Box 25046, MS 980, Federal Center, Denver, Colorado 80225, USA
- 4Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, P.O. Box 808, L-397, Livermore, California 94550, USA
- *E-mail: chad.wittkop{at}mnsu.edu.
Abstract
Annually laminated (varved) Holocene sediments from Derby Lake, Michigan, display variations in endogenic calcite abundance reflecting a long-term (millennial-scale) decrease in burial punctuated with frequent short-term (decadal-scale) oscillations due to carbonate dissolution. Since 6000 cal yr B.P., sediment carbonate abundance has followed a decreasing trend while organic-carbon abundance has increased. The correlation between organic-carbon abundance and the sum of March-April-October-November insolation has an r2 value of 0.58. We interpret these trends to represent a precession-driven lengthening of the Holocene growing season that has reduced calcite burial by enhancing net annual organic-matter production and associated calcite dissolution. Correlations with regional paleoclimate records suggest that changes in temperature and moisture balance have impacted the distribution of short-term oscillations in carbonate and organic-matter abundance superimposed on the precession-driven trends.
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- Received 25 April 2008.
- Revision received 20 January 2009.
- Accepted 22 March 2009.
- © 2009 Geological Society of America
