Dinoflagellates and pollen of the Brito-Arctic Igneous Province flora, ODP Hole 104-642E

Palynological studies of the intrabasaltic sediment layers in the lower volcanic series from ODP Leg 104 outer Voring Plateau Hole 642E Cores 102 through 109 indicated abundant pollen and rarer dinoflagellate cysts. The dinoflagellates belong to the Apectodinium hyperacanthum Zone and indicate an age equivalent to nannoplankton Zones NP9-lower NP10 around the Paleocene/Eocene boundary. The pollen and spore assemblage found here in 12 of the samples from the lower volcanic series is of well- preserved and distinctive specimens and contains unusual forms of pollen from the Taxodiaceae and the Hamamelidae. It has not been transported far from vegetation that was dominated by conifer forest with some ferns and deciduous arborescent angiosperms. Nearly identical assemblages are found elsewhere in the Brito-Arctic Igneous Province, in intrabasaltic sediments from eastern Greenland, the Faeroe Islands, the Isle of Mull, and Antrim (Northern Ireland), and above basalt at the Rockall Plateau. The assemblage is also present in sediments around the Paleocene/Eocene boundary in Spitsbergen. This pollen and spore flora is also associated with dinoflagellate cysts of the Apectodinium hyperacanthum Zone in the deposits from eastern Greenland, the Rockall Plateau, and Spitsbergen, suggesting that these are correlative. Assemblages of the same age from the North Sea, Denmark, and the London and Paris Basins are different. Paleobotanical evidence suggests a short survival of the intrabasaltic flora, and that all the deposits considered here are of about the same age. We propose that at around the Paleocene/Eocene boundary a distinct flora, named here as the Brito-Arctic Igneous Province (BIP) flora, occurred on the line of volcanicity stretching from Rockall to the Greenland Sea, and even to Spitsbergen. Geophysical evidence supports our view that the Rockall to East Greenland intrabasaltics are more or less contemporaneous, at about the Paleocene/Eocene boundary. However, the comparable pollen and spore assemblage in the Hebridean province, at Mull and Antrim, is from pyroclastics that may be a little older.

Silicic tephras in ODP Legs 151, 152, and 162

A 6-m.y.-long composite marine record of explosive silicic volcanism from five Ocean Drilling Program sites in the subpolar North Atlantic was compared with several marine records of global and local paleoclimate proxies (benthic d18O 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 40Ar/39Ar 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 40Ar/39Ar 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).