Volcanic Rifted Margins in the North Atlantic: Causes and Petroleum Implications
Sverre Planke1,2, Henrik Svensen2, and Reidun Myklebust3
1) Volcanic Basin Petroleum Research, Oslo Innovation Park, 0349 Oslo, Norway
(planke@vbpr.no)
2) Physics of Geological Processes (PGP), Univ. of Oslo, Box 1048, 0316 Oslo, Norway
3) TGS-NOPEC, Hagaløkkveien 13, 1383 Asker, Norway
Continental rifting and breakup of the northernmost Atlantic during the Paleogene was
intimately associated with voluminous basaltic volcanism, forming the so-called North
Atlantic Igneous Province (NAIP). West of Greenland, rifting and breakup in the Labrador
Sea occurred prior to the NAIP volcanism. The volcanism started at about 60 m.y. with
eruption of extensive picritic and tholeiitic basalts in west-central Greenland. Impressive
foreset bedded hyaloclastiests and layered lava flows are currently exposed in thousand
meters high cliffs on Nuussuaq. Borehole, seismic, and potential field data show that the
volcanism continued offshore in the Davis Strait and on the southwest Greenland margin.
Seismic and magnetic data in the Labrador Sea further suggest a period of voluminous
magmatic activity at about anomaly 24 time, about 56 million years ago. Even more extensive
volcanic activity is recorded in the Northeast Atlantic. This volcanism is particularly well
understood on the conjugate mid-Norway – northeast Greenland margins. Initial volcanism
occurred at about 60-58 m.y., but ceased during a 3-5 m.y. period prior to breakup. The main
volcanic phase was initiated with intrusive magmatism in the Vøring, Møre and
Danmarkshavn basins, forming extensive sill complexes and associated pipe-like
hydrothermal vent complexes. Continued rifting and volcanism lead to infilling of up to 6 km
thick sequences of seaward dipping basalt flows in rift basins along the continent-ocean
boundary. The lava also flowed across Cretaceous and Paleocene age sedimentary basins,
building out coarse-grained Gilbert-type lava deltas when subaerially erupted lava reached the
coast line. Continuous stretching and subsidence led to subsidence of the eruption centers and
explosive Surtseyan-type volcanism created elongated volcanic mountains in a shallow
marine environment. The intense volcanism was likely caused by an increased mantle
temperature associated with the arrival of a plume head. However, the main breakup
volcanism along the northeast Atlantic rift axis was strongly enhanced by small-scale
convection and decompressional melting. The NAIP volcanism has had a major impact on the
global paleoclimate and local petroleum systems. In particular, heating of organic-rich
sediments by intrusive sills produced sufficient volumes of methane to trigger rapid global
warming in the earliest Eocene.