Toward Establishing Precise Ar-40/Ar-39 Chronologies For Late Pleistocene Palaeoclimate Archives: An Example From The Lake Suigetsu (Japan) Sedimentary Record

The varved Suigetsu (SG06) sediment core is potentially one of the most important and well-constrained mid-latitude palaeoclimate archives, recording continuous deposition during the last similar to 150 kyrs. Numerous visible and non-visible volcanic ash layers form unique age markers within SG06. These ash layers are too fine and crystal-poor to be directly dated using the Ar-40/Ar-39 technique so the tephra were correlated to proximal volcanic deposits using their glass shard compositions. A high-precision Ar-40/Ar-39 sanidine age of 10.0 +/- 0.3 ka (1 sigma, n = 34, MSWD = 0.71, p = 0.89) was obtained for the SG06-1288 (U-Oki) proximal tephra (Ulleungdo U4). Ar-40/Ar-39 yields a precision of +/- 3% near the younger limit of the method, with improved precision possible for older SG06 samples. Such Ar-40/Ar-39 ages for tephra layers can provide invaluable tie-points within the Lake Suigetsu SG06 sequence, giving independent verification of the core's varve chronology, allowing for the calibration of cosmogenic nuclide production, and providing a precise chronology beyond the varve limit. (C) 2011 Elsevier Ltd. All rights reserved.