Breakup Magmatism and Paleogene Paleoenvironment: Initial Results from IODP Expedition 396 on the Mid-Norwegian Continental Margin

Continental breakup in the NE Atlantic was associated with mafic magmatism recorded by basalt flows, volcanogenic sediments, magmatic underplates, and intrusive sheet complexes in the nearby sedimentary basins and continental crust. The voluminous magmatism is concomitant with the global hot-house climate in the Paleogene, and the injection of magma into organic-rich sedimentary basins is a proposed mechanism for triggering short-term global warming during the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma). IODP Expedition 396 drilled 21 holes along three transects on the mid-Norwegian continental margin to sample 1) Paleogene sediments along the Vøring Transform Margin and in hydrothermal vent complexes, and 2) basalt deposits from the Vøring Marginal High into the oceanic Lofoten Basin. A total of 2 km of core were recovered, including more than 350 m of basalt, 15 m of granite, and 900 m of late Paleocene to early Eocene sediments. Wireline logging data were recorded in eight holes. All the sites were located on industry-standard 2D and 3D seismic data. In addition, high-resolution seismic data were acquired in 2020 and 2022 over all the 21 Expedition 396 boreholes and 5 legacy ODP/DSDP sites using R/V Helmer Hansen. The seismic surveys included three P-Cable 3D cubes covering the 14 boreholes on the Modgunn (5), Mimir (5), and Skoll (4) transects. A comprehensive core-log-seismic integration program is ongoing for each site, based on an integration of high-resolution biostratigraphy, core and log based petrophysical data, and seismic modelling. The expedition recovered the first sub-basalt cores on the mid-Norwegian continental margin, recovering 15 m of granite. It furthermore collected the first samples from an Outer High at Site U1574, recovering both pillow basalts and hyaloclastites. These cores documented a shallow marine depositional environment of the emergent Eldhø volcano located near the foot of the Vøring Plateau. Finally, we drilled five holes through the upper part of a hydrothermal vent complex with a very expanded Paleocene-Eocene Thermal Maximum (PETM) interval dominated by biogenic ooze and volcanic ash deposits, documenting the temporal correlation of intrusive breakup magmatism in the Vøring Basin and a major hypothermal event. Collectively, the Expedition 396 sample archive offers unprecedented insight into tectonomagmatic processes in the NE Atlantic, including links to both rapid and long-term climate variation in the Paleogene.