HR: 1340h
AN: T23A-1212    [Abstracts]
TI: Integrated crustal models, characterisation of crustal lithology and geodynamic implications - southwestern Barents Sea.
AU: * Barrere, C
EM: cecile.barrere@ngu.no
AF: NGU / NTNU, Leiv Eirikssons vei 39, Trondheim, 7491, Norway
AU: Ebbing, J
EM: jorg.ebbing@ngu.no
AF: NGU / NTNU, Leiv Eirikssons vei 39, Trondheim, 7491, Norway
AU: Gernigon, L
EM: laurent.gernigon@ngu.no
AF: NGU / NTNU, Leiv Eirikssons vei 39, Trondheim, 7491, Norway
AB: Our 3D model covers the offshore extension of the Norwegian Caledonides, which constitutes of a series of basement high and deep basins. Our 3D model integrates density and magnetic modelling with the interpretation of seismic refraction and reflection data and helps to characterize the different basement units. Furthermore, the 3D model allows characterizing the crustal configuration and contributes to our understanding of the geodynamics processes that affected the region and are expressed in the basement lithology variability. The model is based on interpretation of profiles constrained by refraction and reflection seismic. Well data were integrated to adjust the depth of the sedimentary layers. The geological interpretations are based on onshore- offshore links and onshore petrophysical sampling. The distribution of density, magnetic susceptibility and Q- ratio values allows distinguishing the different basement units (Precambrian gneiss, Caledonian Nappes, granitic plutons and mafic intrusions). One model explains the long-term persistence of the Loppa High as a high since Devonian times. The 3D model allows mapping the gneiss dome sitting along the west side of the Loppa High and other localised intrusions. At the east of the Loppa High, the model highlights a thickening of the Caledonian nappes important enough to overprint the Precambrian basement magnetic signature. Our basement unit map raises the question why the magnetic signal of the Caledonian basement is so representative at the east of the Loppa High whereas onshore its signal is weak and does not cover the Precambrian basement signal. The combination of our regional geophysical modelling with a more detailed study of the seismic interpretation allows proposing a geodynamic scenario for the Loppa High installation. We link the Loppa High geometry and composition to the installation of a gneiss dome syn-tectonic with the development of the Bjørnøyrenna Fault Complex. Initiated in Devonian times, the development of the Bjørnøyrenna Fault Complex and installation of the gneiss dome installations led to a rotation of the basement blocks rotations. As a consequence the Caledonian nappes in the east have been preserved, while the Caledonian layers have been eroded due to an uplift of the western part.
DE: 0903 Computational methods: potential fields (1214)
DE: 1020 Composition of the continental crust
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3002 Continental shelf and slope processes (4219)
DE: 8038 Regional crustal structure
SC: Tectonophysics [T]
MN: 2007 Fall Meeting