Abstract
Early Eocene sediments in northwest Denmark contain over 180 well-preserved volcanic ash layers, likely sourced from the North Atlantic Igneous Province (NAIP) between 56.0 and 54.6 Ma. Most of these ashes are basaltic, widespread, and represent a phase of unusually large and explosive eruptions that is coincident with the opening of the northeast Atlantic Ocean. Explosive basaltic eruptions of this magnitude are unheard of in historical times and in the current geological record. Here, we combine analyses of glass sulfur concentrations and variations in morphology and vesicularity of pristine volcanic glass grains to explore the possible eruptive processes promoting such widespread basaltic ash dispersal. We suggest that these ashes formed in shallow subaqueous environments (<200 m water depth) where they fragmented and rapidly quenched during explosive hydromagmatic activity. We speculate that magma-water interaction during the opening of the northeast Atlantic was the main cause of this unusual explosive basaltic activity.
Highlights
The North Atlantic Igneous Province (NAIP) is a vast complex composed of massive continental flood basalts, widespread sill intrusions, and large volcanic centres surrounding the margins of the present-day northeast Atlantic Ocean and Labrador Sea [Figure 1; Á Horni et al 2017; Saunders et al 1997; Storey, Duncan, and Tegner 2007]
In this study we analysed the matrix glass in basaltic ash layers deposited in early Eocene sedimentary strata in Denmark
These ashes were sourced from the North Atlantic Igneous Province during the opening of the northeast Atlantic Ocean
Summary
The North Atlantic Igneous Province (NAIP) is a vast complex composed of massive continental flood basalts, widespread sill intrusions, and large volcanic centres surrounding the margins of the present-day northeast Atlantic Ocean and Labrador Sea [Figure 1; Á Horni et al 2017; Saunders et al 1997; Storey, Duncan, and Tegner 2007]. The formation of the NAIP is of significant scientific interest because it coincides with both the breakup of the northeast Atlantic Ocean and the extreme climate perturbations of the late Paleocene and early Eocene, including the Paleocene-Eocene Thermal Maximum (PETM; [Saunders 2016; Schmitz et al 2004; Storey, Duncan, and Swisher 2007; Storey, Duncan, well-preserved tephra layers from the NAIP are exposed subaerially in northwest Denmark (Figures 1 and 2) due to recent glaciotectonic activity [Pedersen 2008]. The negative series is composed of a heterogeneous range of ash compositions (from basalt to rhyolite) that are often heavily
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