Using the N/C ratio to correct bulk radiocarbon ages from lake sediments: Insights from Chilean Patagonia

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• 作者：S¨¦bastien Bertr ; Alberto Araneda ; Patricia Vargas ; Patricia Jana ; Nathalie Fagel ; Roberto Urrutia
• 关键词：Old carbon ; Age model ; Soil organic matter ; Chronology
• 刊名：Quaternary Geochronology
• 出版年：2012
• 出版时间：October, 2012
• 年：2012
• 卷：12
• 期：Complete
• 页码：23-29
• 全文大小：1108 K

文摘

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.