Integration of the Old and New Lake Suigetsu (Japan) Terrestrial Radiocarbon Calibration Data Sets

The varved sediment profile of Lake Suigetsu, central Japan, offers an ideal opportunity from which to derive a terrestrial record of atmospheric radiocarbon across the entire range of the 14C dating method. Previous work by Kitagawa and van der Plicht (1998a,b, 2000) provided such a data set; however, problems with the varve-based age scale of their SG93 sediment core precluded the use of this data set for 14C calibration purposes. Lake Suigetsu was re-cored in summer 2006, with the retrieval of overlapping sediment cores from 4 parallel boreholes enabling complete recovery of the sediment profile for the present “Suigetsu Varves 2006” project (Nakagawa et al. 2012). Over 550 14C determinations have been obtained from terrestrial plant macrofossils picked from the latter SG06 composite sediment core, which, coupled with the core's independent varve chronology, provides the only non-reservoir-corrected 14C calibration data set across the 14C dating range.Here, physical matching of archive U-channel sediment from SG93 to the continuous SG06 sediment profile is presented. We show the excellent agreement between the respective projects' 14C data sets, allowing the integration of 243 14C determinations from the original SG93 project into a composite Lake Suigetsu 14C calibration data set comprising 808 individual 14C determinations, spanning the last 52,800 cal yr.