Deep Structure of the Continent-Ocean Transition Zone from 3D Gravity Modelling at the Norwegian Continental Margin (Vøring and Møre Basins)

Yuriy Maystrenko and Magdalena Scheck-Wenderoth
GeoForschungsZentrum Potsdam, Germany

           The Norwegian continental margin is a passive volcanic margin which was affected by several rifting events during the Permian, Triassic and Jurassic. One significant stage of extension occurred during the Late Jurassic-Early Cretaceous, leading to formation of the deep Vøring and Møre Basins, where more that 8 km of Cretaceous sediments deposited. Finally in the Late Paleocene - earliest Eocene (~55 Ma b.p.), continental break-up resulted in the formation of oceanic crust and subsequent post-break-up subsidence.
         The major objective of this work was to create a 3D density-model in order to solve some uncertainties concerning the deep crustal structure of the study area. A 3D structural model of the Norwegian continental margin has been used for 3D gravity modelling. This initial 3D structural model was derived from refraction and reflection seismic data and well data. 3D gravity modelling was performed with the Interactive Gravity and Magnetic Application System (IGMAS), which allows to calculate the gravity effect of a 3D model by triangulation between predefined structural levels.
          According to the results of the 3D gravity modelling, the western parts of the Vøring and Møre Basins are characterized by high-density bodies within the lower crust with the same densities like oceanic layer 3B. The latter supports the presence of underplated lower crust beneath the Norwegian continental margin which has been already inferred from the OBS data. In addition to these high-density bodies, zones of increased density in the lower continental crust have been derived from gravity modelling. A relatively lightweight mantle underlies the oceanic crust of the study area, whereas mantle density is larger below the continental part of the margin. Furthermore, a local wedge of the lightweight “oceanic”mantle has been modelled along the Jan Mayen Lineament within the continental part of the lithosphere. This suggests an increased temperature at the mantle level beneath the Jan Mayen Lineament which is the continental continuation of the oceanic Jan Mayen Fracture Zone. Our results indicate, that the continental crust and, even the continental mantle may have been locally modified during the continental break-up in Late Paleocene - earliest Eocene times.

AAPG Search and Discover Article #90066©2007 AAPG Hedberg Conference, The Hague, The Netherlands