The age and chronostratigraphical significance of North Atlantic Ash zone II

• DOI: 10.1002/jqs.821
• Publication Date: 2004-03-09T08:01:49Z
• Authors: William E. N. Austin; Lindsay J. Wilson; John B. Hunt
• Keywords: Stadial; Ice core; Tephrochronology

Abstract Rhyolitic tephra with the geochemical characteristics of North Atlantic Ash Zone (NAAZ) II are described from giant piston core MD95‐2006 northeast Ocean. Shard size distribution indicates that represent a wind‐sorted, primary air‐fall deposit, but mode close to 200 μm they too coarse be deposits at site, which lies ca. 1000 km possible source. Randomly sampled shards reveal single population belonging Icelandic transitional alkali magma series, suggesting unlikely ice rafted debris derived icebergs. The probably deposits, transported site by sea within gyre. NAAZ peak coincides rapid climate transition (cooling) end interstadial 15, can assigned an age 53 260±2660 yr BP direct correlation Greenland ice‐core (GISP2) record. A comparison Neogloboquadrina pachyderma (sinistral) relative abundance and GISP2 δ 18 O records, isochron, suggests this climatic event was synchronous across Atlantic. By maxima between two time‐scale is transferred MD95‐2006. Comparison corrected calibrated radiocarbon ages monospecific foraminifers same stratigraphical horizon suggest major differences. These result large variations in atmospheric 14 C concentration highlight significant uncertainties associated calibration during marine isotope stage 3. Copyright © 2004 John Wiley & Sons, Ltd.