Tertiary history of C4 biomass in the Great Plains, USA
- 1Department of Earth Sciences, University of California, Santa Cruz, California 95064, USA, and Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA
- 2Department of Earth Sciences, University of California, Santa Cruz, California 95064, USA
Abstract
We use the carbon isotope composition of paleosols to reconstruct the history of C4 biomass on the Great Plains from ca. 23 to 1 Ma. The proportion of C4 biomass was uniform and moderate (12%–34%) throughout the Miocene, increased between 6.4 and 4.0 Ma, and reached modern levels by 2.5 Ma. Ecological changes in Great Plains ungulates preceded the increase in C4 biomass. The contrasts in the paleosol and ungulate records may indicate initial development of C3 grasslands after the middle Miocene or a greater role for ecological interactions within communities in structuring ungulate faunas. Contrasts in paleosol records from different continents point to regional rather than global controls on the evolution of C4 grasslands.
Footnotes
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↵* dlfoxumn.edu
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↵GSA Data Repository item 2003116, Tables DR1 and DR2, isotopic and locality data for all samples, is available online at www.geosociety.org/pubs/ft2003.htm, or on request from editing;cageosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301-9140, USA.
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- Accepted May 25, 2003.
- Received February 17, 2003.
- Revision received May 15, 2003.
- Geological Society of America
