Paleogene time scale miscalibration: Evidence from the dating of the North Atlantic igneous province

Igneous activity in the North Atlantic igneous province began with the arrival of the proto-Iceland plume beneath the lithosphere in early Cenozoic time. Sediments between and equivalent to the oldest lavas contain an influx of a diagnostic pollen flora, an influx of the dinocyst Apectodinium, a benthic foraminiferal extinction, nannofossil zone NP9, and a carbon isotope excursion associated with the late Paleocene thermal maximum (LPTM). Lavas immediately overlying the LPTM strata (54.98 Ma on the current time scale), yield U-Pb and Ar-Ar isotopic dates between 57.5 and 60.54 Ma, highlighting a dating discrepancy of up to 5 m.y. Recognition of this disparity, as well as our biostratigraphical correlation, places the LPTM within the early phase of widespread northeast Atlantic margin basaltic volcanism. A later volcanic phase, equivalent to the seaward-dipping reflector series, terminates at 54 Ma. The onset of 60 Ma basaltic volcanism can be linked to ocean water mass perturbations, and the release of ocean-floor methane hydrates thought responsible for the LPTM.