Breakup volcanism and plate tectonics in the NW Atlantic

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  • M. M. Abdelmalak, Volcanic Basin Petroleum Research, Universitetet i Oslo
  • ,
  • S. Planke, Volcanic Basin Petroleum Research, Universitetet i Oslo
  • ,
  • S. Polteau, Volcanic Basin Petroleum Research
  • ,
  • E. H. Hartz, Universitetet i Oslo, Aker BP
  • ,
  • J. I. Faleide, Universitetet i Oslo
  • ,
  • C. Tegner
  • D. A. Jerram, Universitetet i Oslo, DougalEARTH Ltd., Queensland University of Technology QUT
  • ,
  • J. M. Millett, Volcanic Basin Petroleum Research, Aberdeen University
  • ,
  • R. Myklebust, TGS

Passive margins are the locus of tectonic and magmatic processes leading to the formation of highly variable along-strike and conjugate margins structures. Using extensive new seismic, gravity, and magnetic datasets, complemented by seabed samples and field work, we investigate the tectonomagmatic evolution of the northwest (NW) Atlantic where breakup-related igneous rocks were emplaced during several Paleogene events associated with lithospheric stretching, continental breakup, and the formation of new oceanic basins. Interpretational methods include integrated seismic-gravity-magnetic (SGM) interpretation and seismic volcanostratigraphy. In addition, seabed and field samples were collected and analyzed to constrain the basin stratigraphy, hydrocarbon potential, and the geochronology and geochemistry of the volcanic sequences. Offshore, 2D seismic data reveal several Seaward Dipping Reflector (SDR) wedges and escarpments in the Labrador Sea, Davis Strait, and Baffin Bay. Onshore, eastward prograding foreset-bedded hyaloclastite delta deposits and overlying horizontal lava successions outcrop on Nuussuaq. These hyaloclastites and lava successions are world class analogues to the Lava Delta and Landward Flows volcanic seismic facies units identified offshore. Our mapping results document an aerial extent of the Paleogene breakup-related volcanics of 0.3 x 10(6) km(2), with an estimated volume of 0.5-0.6 x 10(6) km(3). Basalt samples recovered by dredging the Upernavik Escarpment have late Paleocene to/early Eocene ages, whereas the sedimentary samples provide an excellent seismic tie with the stratigraphy and the geology in this frontier area. From the integrated SGM interpretation, we identify a rapidly thinning crust and changes in top and intra-basement seismic reflection characteristics in the oceanic domain correlated with transition between different magnetic domains. The mapping results were subsequently integrated in a plate tectonic model. The plate tectonic reconstruction and basalt geochronology suggest that the majority of the volcanism in the NW Atlantic occurred between similar to 62 and similar to 58 Ma, associated with an increased spreading rate in the Labrador Sea, starting from the onset of the Selandian (similar to 61.6 Ma). A change in the spreading direction during the Eocene (similar to 56 Ma), synchronously with a shift of volcanic activity from the NW to the NE Atlantic, correspond to a northward drift of Greenland and the initiation of the Eurekan Orogeny. Finally, our interpretations reveal a complex rift configuration along the NW Atlantic conjugate margins both prior to and during breakup.

OriginalsprogEngelsk
TidsskriftTectonophysics
Vol/bind760
Sider (fra-til)267-296
Antal sider30
ISSN0040-1951
DOI
StatusUdgivet - 5 jun. 2019

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