Paleoproterozoic Positive δ13C Excursion in Henan, China
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Abstract A positive δ 13C excursion in Palaeoproterozoic carbonate sequences in Henan, China is reported in this paper. Carbon isotope analyses of samples from Wuzhiling and Huayu Formation of Songshan Group, a well-preserved Palaeoproterozoic-carbonate sequences in northern Henan, China present δ 13C values range from −1.0‰ to 4.2‰PDB, with a mean at 2.5‰PDB. Results of microscope observation, oxygen isotope, and Mn/Sr ratio indicate that Wuzhiling Formation suffered stronger alternation than Huayu, which suggested a higher initial δ 13C excursion of Wuzhiling Formation than present known value. The positive δ 13Ccarb excursions of Wuzhiling Formation support the Lamagundi Event as early oxygenation of the terrestrial environment, was also recorded in Palaeoproterozoic carbonate sequences in Henan, China. Keywords: positive δ13C excursionHenan/ChinaPaleoproterozoicatmospheric oxygenation Acknowledgments This work was supported by the National Basic Research Program of China (973 Program, No. 2007 CB815601). We are grateful to Prof. Guan Baode and Dr. Zhao Taiping for providing help to sample. We wish to thank Prof. Chen Yanjing and Dr. Liu Jun for their critical reading of an earlier version of this manuscript and providing the constructive opinions for the article.Keywords:
Excursion
Guan
ABSTRACT The stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope values of bone collagen are frequently used in paleodietary studies to assess the marine contribution to an individual's diet. Surprisingly, the relationship between stable isotope these values characteristics and the percentage of marine foods in diet has never been effectively demonstrated. To clarify this relationship, the stable isotope values and radiocarbon dates of nine humans and one sheep from Herculaneum, all who perished simultaneously during the AD 79 eruption of Vesuvius, were determined. Significant differences were found in the radiocarbon dates which are attributable to the incorporation of “old” carbon from the marine reservoir. The magnitude of the observed differences was linearly correlated with both δ 13 C and δ 15 N values allowing the response of each isotope to increasing marine carbon in collagen to be independently verified. Regression analyses showed that for every 1‰ enrichment in δ 13 C and δ 15 N, 56 years and 34 years were added to the radiocarbon age, respectively. Predictions of the maximum marine reservoir age differed considerably depending on which stable isotope was considered. This discrepancy is attributed to some degree of macronutrient scrambling whereby nitrogen from marine protein is preferentially incorporated in collagen over marine carbon. It is suggested that the macronutrient scrambling explains the observed relationship between δ 13 C and δ 15 N from Roman coastal sites and should be considered when interpreting any diet which is not dominated by protein. Nevertheless, without knowing the degree of macronutrient scrambling in different dietary scenarios, the accuracy of dietary reconstructions is severely compromised. Am J Phys Anthropol 152:345–352, 2013. © 2013 Wiley Periodicals, Inc.
δ15N
Isotopes of nitrogen
Isotope Analysis
Carbon fibers
Scrambling
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