BENTONITE LAYERS IN SVALBARD: CONSTRAINING SOURCES OF VOLCANISM, GEOCHRONOLOGY, AND RELATIVE PLATE MOTIONS DURING THE PALEOCENE AND EOCENE
Throughout the sedimentary sequence are prominent bentonite clay horizons of volcanic origin. There are a number of potential sources of these layers, including continental rifting events in the high Arctic and the formation of the North Atlantic Igneous Province (NAIP). Here we focus on the chemical fingerprinting and high precision U-Pb dating of Paleocene bentonites. Geochemical analyses indicates that ash layers just above the basal unconformity bear a close chemical affinity with the Kap Washington Group in north Greenland, while later Paleocene ashes appear to have come from rift volcanism in the Nares Straight. Bentonites of unknown provenance have been used to date the PETM in this stratigraphic sequence. The basal bentonites are successfully dated here, providing a precise time of foreland basin formation and therefore also the change in plate motions that instigated the West Spitsbergen Orogeny. Dating of later layers provides accurate deposition rates in the basin, which appear to increase as the Central Basin matured. These findings corroborate previous findings of the timing of rift volcanism in the Arctic, they provide a precise time of first active spreading in the Labrador Sea, and improve the regional geochronology for the mid- to late-Paleocene.