CalPal - University of Cologne Radiocarbon Calibration Program Package

14 Reasons to Calibrate Glacial 14C-Ages using the SFCP Age-Model

  1. Because annual ice layers are counted further back in time in GISP2 (55.6 ka; Meese et al. 1994; Sowers et al.1993)
    2. than in GRIP (Johnsen et al. 1992; 1997).
  2. Because 14C-data from coral samples also dated by U/Th TIMS (Bard et al. 1993, 1998; 2000) agree perfectly (far within error limits) with 14C-ages on GISP2-synchronised foraminifera from the North Atlantic cores ODP-609 and V23-81, back to 30 ka calBP (Jöris and Weninger, 1998).
  3. Because the long-term trend of the Greenland GISP2 age model is supported by the long-term trend of the Antarctic Vostok ice core age model (Petit et al. 1999), which is
  4. itself synchronised with the orbitally tuned marine SPECMAP chronology (Martinson et al.,1987).
  5. Because the Late Glacial Maximum (LGM sensu stricto) in GISP2 coincides precisely with the northern hemispheric summer insolation minimum.
    Because the older part of the GISP2 chronology is well-dated by a number of global volcanic markers, most notably:
  6. the ash of the Toba Mega-Eruption (~70 ka calBP),
  7. the North Atlantic Ash Zone II (~52 ka calBP)
  8. and the Campanian Ignimbrite (~40 ka calBP).
  9. These volcanic markers are additionally radiometrically dated by 39Ar/40Ar, K/Ar, and 14C as well as chronostratigraphically fixed in the oxygen isotope signatures of marine cores.
  10. Because the GISP2 time-scale agrees well with the U/Th TIMS dated d18O record from Hulu Cave stalagmites, China (Wang et al. 2001).
  11. Because the d18O record of the 14C-dated North Atlantic core PS2644 (Voelker et al. 1998; 2000) gives a large series of 14C-ages which agree well over the entire span of the last 30 ka with the 14C-data record from the Japanese Suigetsu varves (Kitagawa and van der Plicht 1998; 2000).
  12. Further support for the GISP2 vs GRIP age-model is given by 14C-ages at ~20.0 ka 14C-BP which calibrate to an age of ~24.0 ka calBP which coincides nicely with the age of the LGM (sensu stricto) as independently measured by 14C-ages for the last glacial Northern European maximum ice advance (Brandenburg stage).
  13. We observe that in the Holzmaar varve chronology there exist 8,500 varves between LGM and onset of GI 1e. which also supports the GISP2 age model.
  14. The SFCP-Timescale (Shackleton, Fairbanks, Tzu-chien Chiu, and Parrenin, 2004) is based on a series of paired 14C and 230Th measurements on pristine corals (Fairbanks, Mortlock, Chiu, Guilderson, Cao, Kaplan, and Bloom, submitted 2003). It modifies the published age models for ice cores collected from Greenland and Antarctica in such a manner that they are mutually consistent to within a few hundred years.

Index