The Swedish Time Scale: A potential calibration tool for the radiocarbon time scale during the Late Weichselian

The Swedish Time Scale (STS) is a ca. 13,300-yr-long varve chronology that has been established for the Swedish east coast from >1000 overlapping clay-varve diagrams. We describe the present state of the STS and illustrate the application of this worldwide unique varve chronology for AMS radiocarbon measurements. The results are compared to other C-14-dated calendar-year chronologies: dendrochronology, laminated lake sediments and U/Th. Our data set agrees with the oldest part of the dendrochronological calibration curve, and with AMS C-14-dated lake lamination data and U/Th on corals down to ca. 12 ka calendar years sp. Further back in time, the AMS-dated part of the STS partly compares well with lake lamination chronologies and shows that the difference between C-14 and calendar yeats decreases rapidly between 12,600 and 12,800 calendar years sp. Such a development seems to contrast with U/Th measurements on corals. We suggest that the cause for the divergence among three supposed calendar-year chronologies lies in the fact that the data points on the marine C-14-U/Th curve are more widely spaced in time than the tightly grouped set of terrestrial AMS C-14 dates, and thus are not able to reflect short-term changes in atmospheric C-14. Therefore, we argue that the use of the pre-Holocene part of the calibration program is premature and inadvisable.