A novel approach to varve counting using mu XRF and X-radiography in combination with thin-section microscopy, applied to the Late Glacial chronology from Lake Suigetsu, Japan

Abstract

The Lake Suigetsu 2006 Varved Sediment Core Project (SG06 Project) aims to contribute to the international terrestrial radiocarbon calibration model, extending it to >50,000 cal years BP using the new SG06 sediment record, which shows annual laminations (varves) for most of this period. For varve counting, a novel approach using high resolution X-ray fluorescence (μXRF) and X-radiography was applied, described here in detail for the first time, and applied to the Late Glacial sediments of core SG06. This new technique was carried out alongside conventional varve counting by thin-section microscopy (Schlolaut et al., 2012). This dual approach allows comparison of results from the two independent counting methods on metre to sub-mm scales, enabling the identification and characterisation of differences between the techniques, and quantification of their weaknesses. Combining the results produces a more robust chronology than either counting method could produce alone. The reliability of this dual approach is demonstrated by comparison of the combined chronology with the radiocarbon dataset of SG06, calibrated with the tree-ring derived Late Glacial section of IntCal09.