Using the N/C ratio to correct bulk radiocarbon ages from lake sediments: Insights from Chilean Patagonia |
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| Institution: | 1. Renard Centre of Marine Geology, Ghent University, Krijgslaan 281 (S8 WE13), Ghent, Belgium;2. Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Campus Isla Teja, Valdivia, Chile;3. Geological Institute, ETH Zürich, Sonneggstrasse 5, Zürich, Switzerland;4. U.S. Geological Survey, Anchorage, 4210 University Drive, Anchorage, United States;5. EPOC, UMR CNRS 5805, Univ. Bordeaux, Allée Geoffroy St Hilaire, Pessac 33615, France;6. Department of Environmental Science, Alaska Pacific University, Anchorage, AK 99508, United States;7. Wrangell-St. Elias National Park and Preserve, Copper Center, AK 99573, United States |
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| Abstract: | The offset between AMS radiocarbon ages obtained on bulk lake sediments and the true age of deposition was evaluated at four sites in Northern Chilean Patagonia. Our results show that the bulk radiocarbon ages are systematically older by 300 to 1100 years. In this region free of carbonate and carbonaceous rocks, we argue that this difference results from variable inputs of terrestrial organic carbon from the Holocene soils that cover the lake watersheds. For the four studied lakes, the age offset is clearly related to the fraction of terrestrial carbon preserved in the lake sediments, which was estimated using the N/C ratio of the bulk organic matter. We propose that N/C measurements can be used to significantly improve chronologies based on radiocarbon dating of bulk lake sediments. |
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