• Problems in the Extension of the Radiocarbon Calibration Curve (10-13 Kyr BP)

      Hajdas, Irena; Ivy-Ochs, S. D.; Bonani, Georges (Department of Geosciences, The University of Arizona, 1995-01-01)
      Radiocarbon dating of varved lake sediments shows that, during the Late Glacial (10-12 kyr BP), the offset between the 14C and the absolute time scales was ca. 1 kyr. Varve counting and accelerator mass spectrometry (AMS) dating were used to build absolute and 14C time scales of sediments from two lakes-—Soppensee, Switzerland and Holzmaar, Germany. The resulting chronologies extend back to ca. 12.9 kyr cal BP (12.1 kyr BP) in the case of Soppensee and to ca. 13.8 kyr cal BP (12.6 kyr BP) in the Holzmaar record. They compare well with each other but differ significantly from the 14C-U/Th chronology of corals (Bard et al.1993; Edwards et al.1993).
    • Radiocarbon Age of the Laacher See Tephra: 11,230 +/- 40 BP

      Hajdas, Irena; Ivy-Ochs, S. D.; Bonani, Georges; Lotter, André F.; Zolitschka, Bernd; Schlüchter, Christian (Department of Geosciences, The University of Arizona, 1995-01-01)
      The Laacher See Tephra (LST) layer provides a unique and invaluable time marker in European sediments with increasing importance because it occurs just before the onset of the Younger Dryas (YD) cold event. As the YD begins ca. 200 calendar years after the LST was deposited, accurate determination of the radiocarbon age of this ash layer will lead to a more accurate age assignment for the beginning of the YD. On the basis of 12 terrestrial plant macrofossil 14C ages derived from sediments from Soppensee, Holzmaar and Schlakenmehrener Maar, we found an age of at least 11,230 +/40 BP for the LST event. This is ca. 200 yr older than the often reported age of 11,000 +/50 BP (van den Bogaard and Schmincke 1985).