3:52 PM - 4:07 PM
[MIS19-13] Oxygen isotope fluctuations of pollen fossils from Lake Suigetsu, Japan
Keywords:Palaeoclimate, Stable isotope, Pollen, Cell sorter, Suigetsu
Lake Suigetsu (35°35'N, 135°53'E, 0 m a.s.l.), Fukui prefecture, is one of the Mikata Five lakes, which measures 3 km east-west by 3 km north-south, with the maximum water depth of ca. 34 m. Lake Suigetsu preserves annually laminated sediments over the last ca.70 kyr with a significant number of event layers that allows precise correlation among parallel cores. Two long cores (SG93, SG06) have previously been recovered from the centre of the lake. An exceptionally precise age model has been established for the cores through a combination of over 800 radiocarbon (14C) dates and high precision varve count (Staff et al., 2011; Marshall et al., 2012; Schlolaut et al., 2012; Bronk Ramsey et al., 2012). In this study, we used well-dated SG06 cores and extracted pollen fossils using cell sorter.
Cell sorter is able to characterise particles using optical parameters (mainly fluorescence), and separate specific particles using electrostatic deflection. Pollen fossils can be isolated by cell sorter without fluorescent dyes using cell sorter because sporopollenin constituting pollen grains is naturally auto-fluorescent (Tennant et al., 2013). After chemical and physical pre-treatments, pollen-enriched suspension was introduced into the cell sorter and extracted half a million pollen fossils from each sample. After drying and weighing, δ18O value of the high-purity pollen pellets were determined using High Temperature Conversion Elemental Analyzer (TC/EA, Thermo Scientific) in the University of Tokyo.
The oscillation of the δ18O value of the extracted pollen pellets roughly mirrored that of the NGRIP, showing typical climatic transitions that characterise the Late glacial period. Our results strongly imply that the stable isotope signal of fossil pollen grains is keeping record of past climate changes.