Enhanced airborne dispersal of silicic tephras during the onset of Northern Hemisphere glaciations, from 6 to 0 Ma records of explosive volcanism and climate change in the subpolar North Atlantic

摘要

A 6-m.y.-long composite marine record of explosive silicic vollcanism from five Ocean Drilling Program sites in the subpolar North Atlantic was compared with several marine records of global and local paleoclimate proxies (benthic delta(18)O and ice-rafted debris records). Coarsening and high frequency of occurrence of Icelandic tephras were recorded in 3.6-3 Ma sediments, suggesting that these tephras were dispersed farther from the source by enhanced westerly winds over the subpolar North Atlantic. The Ar-40/Ar-39 ages were determined by laser probe on K-feldspar and biotite phenocrysts of tephras that were erupted from the Jan Mayen volcanic system. Compared to the tuned paleomagnetic age model, the Ar-40/Ar-39 dating (0.618 +/- 0.007 Ma to 4.90 +/- 0.05 Ma) yields a new age model that postdates by 155 k.y. the inception of ice rafting on the Iceland Plateau during the cold marine isotope stage M2 (i.e., 3.3-3.14 Ma). [References: 25]