| Autor: |
Yamamoto, Shinya, Nishizawa, Fumikatsu, Yoshimoto, Mitsuhiro, Miyairi, Yosuke, Yokoyama, Yusuke, Suga, Hisami, Ohkouchi, Naohiko |
| Předmět: |
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| Zdroj: |
Geochemistry, Geophysics, Geosystems: G3; May2021, Vol. 22 Issue 5, p1-9, 9p |
| Abstrakt: |
Lake sediments in volcanic regions contain continuous records of past eruptions and their environmental consequences. However, the frequent scarcity of plant material in lake sediments makes it difficult to provide robust age estimates. In this study, we performed compound‐specific radiocarbon analysis (CSRA) of fatty acids in a sediment core from Lake Kawaguchi in the Mount Fuji volcanic region, Japan, to assess their potential for dating sediments. The C16 fatty acid in the core top sediments exhibits an almost identical age (983 ± 56 years BP) to that of dissolved inorganic carbon in the modern lake surface water, which confirms that the carbon of this compound is derived from lake phytoplankton. Comparison of the 14C age between the C16 fatty acid and a plant leaf at the widespread (Amagi‐Kawagodaira) tephra layer revealed a lake reservoir age of 1,003 ± 73 14C years at ca. 3,150 cal BP, which is consistent with the modern lake reservoir age and the 14C age of the C16 fatty acid in the core top sediments, within error. The reservoir‐corrected 14C age of the C16 fatty acid yielded a modeled age of 2,837 ± 78 cal BP for the Mount Fuji Tephra (Omuro scoria‐fall deposit) in the core. This age is in good agreement with the age determined from plant remains in the same core (2,938 ± 29 cal BP), indicating that CSRA of C16 fatty acid has the potential to date lake sediments after reservoir age correction, even in sediments with limited occurrence of plant macrofossils. Plain Language Summary: Radiocarbon (14C) measurements of land plant materials are commonly used to determine the age of lake sediments deposited over the past 50–60,000 years. However, land plant materials are not always abundantly present in lake sediments, which makes it difficult to know precisely when sedimentation occurred. In this study, we measured 14C ages of fatty acids in lake sediments from the Mount Fuji volcanic region and compared them with those of land plant materials to examine whether the 14C ages of fatty acids can be used as an alternative tool to determine the ages of the sediments. Our data showed that the carbon of palmitic acid, a fatty acid with 16 carbon atoms, in the sediments likely originated from phytoplankton and is able to produce depositional age that is comparable to the age determined from land plant materials when subtracting the effect of old carbon contribution in the lake water. This is the first successful case that uses palmitic acid to determine the age of lake sediments, and our method is expected to improve chronologies of lake sediments for sites where land plants are scarce. Key Points: Radiocarbon ages of fatty acids were measured in lake sediment from the Mount Fuji volcanic regionCarbon in the C16 fatty acid is confirmed to be derived from lake phytoplanktonRadiocarbon analysis of C16 fatty acid has the potential to date lake sediments after reservoir age correction [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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