Dating Lake Sediments Using Compound‐Specific 14 C Analysis of C 16 Fatty Acid: A Case Study From the Mount Fuji Volcanic Region, Japan

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 C 16 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 14 C age between the C 16 fatty acid and a plant leaf at the widespread (Amagi‐Kawagodaira) tephra layer revealed a lake reservoir age of 1,003 ± 73 14 C years at ca. 3,150 cal BP, which is consistent with the modern lake reservoir age and the 14 C age of the C 16 fatty acid in the core top sediments, within error. The reservoir‐corrected 14 C age of the C 16 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 C 16 fatty acid has the potential to date lake sediments after reservoir age correction, even in sediments with limited occurrence of plant macrofossils.