Tephrochronology of the North Atlantic Region: linking marine, terrestrial and ice-core records from OIS 5-2

Major achievements have been made recently regarding the tephrochronology of the North Atlantic area. For the first time a tephra-based correlation between marine cores from the North Atlantic and a terrestrial site on the Faroe Islands of Eemian age (OIS 5e) have been achieved (Wastegard et al., 2005). This is the first time that tephrochronology has been used in order to correlate between marine and terrestrial archives older than OIS 4 in the North Atlantic region. Several new tephras from OIS 5-2 have been identified in North Atlantic sediments and the geochemical composition and distribution of the well-known North Atlantic Ash Zone II (ca 54 ka cal BP) has been refined (Wastegard et al., 2006). The known geographical distribution of other significant tephra strata have been outlined and, as a result, have established important tie-points between diverse palaeoarchives during the last glacial cycle. One important step forward was the identification of the Fugloyarbanki tephra in the NGRIP ice core, where it is dated to 26,740 ± 390 b2k according to the new Greenland Ice Core Chronology (GICC05). This widespread marker horizon has previously been reported in marine cores from the northern North Atlantic Sea and the Labrador Sea (Wastegard et al., 2006). Detection of this tephra for the first time within the NGRIP ice-core provides a pivotal link between marine and ice-core records during the transition between OIS 3/2, enabling an unprecedented insight into the spatial complexity of rapid climatic changes during this time (Davies et al., submitted). Recently another link between marine and ice-core records was established. The FMAZ III ash zone has been described in cores from the Faroe Islands area (c. 33,000 14C years BP), slightly above Heinrich layer 4, and close to the onset of GIS8. An equivalent tephra was recently identified in NGRIP where it is situated right at the peak of GIS8.ReferencesDavies, S.M., Wastegard, S., Rasmussen, T.L., Johnsen, S.J., Steffensen, J.P., Andersen, K.K. and Svensson, A., submitted: Identification of the Fugloyarbanki tephra in the NGRIP ice-core: a key tie-point for marine and ice-core sequences during the last glacial periodWastegard, S., Bjorck, S., Greve, C., and Rasmussen, T.L., 2005: A tephra-based correlation between the Faroe Islands and the Norwegian Sea raises questions about chronological relationships during the last interglacial. Terra Nova 17, 7-12.Wastegard, S., Rasmussen, T.L, Kuijpers, A., Nielsen, T., and van Weering, T.C.E., 2006: Composition and origin of ash zones from Marine Isotope Stages 3 and 2 in the North Atlantic. Quaternary Science Reviews 25, 2409-2419.

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