HR: 0800h
AN: T11B-0381    [Abstracts]
TI: Integrated geophysical modelling of orogenic structures in the North Sea (NW Europe)
AU: * Lyngsie, S B
EM: sbl@geol.ku.dk
AF: Geological Institute, University of Copenhagen, Oester Voldgade 10, Copenhagen, 1350 Denmark
AU: Thybo, H
EM: ht@geol.ku.dk
AF: Geological Institute, University of Copenhagen, Oester Voldgade 10, Copenhagen, 1350 Denmark
AU: Rasmussen, T M
T11B-0381 AF: Geological Survey of Denmark and Greenland, Oester Voldgade 10, Copenhagen, 1350 Denmark
AU: Lassen, A
T11B-0381 AF: Geological Institute, University of Copenhagen, Oester Voldgade 10, Copenhagen, 1350 Denmark
AB: By integrating potential field data with available reflection and refraction seismic data, we investigate the spatial distribution of large-scale crustal domains and their boundaries in the North Sea area (NW Europe). The North Sea tectonic setting comprises three main terranes: Baltica, Laurentia and Avalonia. The tectonic history of these three continents has been described in many, but the details regarding the continental collision style and location of the continental sutures, as well as the influence of pre-existing Caledonian crustal structures on the later Mesozoic rifting are still controversial.By applying different filters and transformations to potential field data (e.g. calculation of fractional derivatives and integrals, pseudogravity transformation, calculation of the horizontal gradient as well as upward continuation and spectral analysis) constrained by well-data seismic data, we find that much of the crystalline crust in areas previously believed to be of Laurentia affinity may instead be of Baltica affinity, at least in the deep crust. Our modelling indicates that pre-existing crustal thrust planes and shear zones of Caledonian origin and possibly older, have had a significant control on the subsequent Mesozoic rifting. We tentatively suggest, that the north-south trending Mesozoic Viking Graben and Central Graben developed by extensional reactivation of Caledonian collision sutures, and that the location of these important hydrocarbon producing rifts is defined by the rim of Baltica upper and middle crust. However, for the lower crust the picture is somewhat different: The integration of potential field data with deep reflection/wide-angle refraction seismic data reveals fundamental differences between the lithosphere of Avalonia and Baltica. We believe that a significant lineament across the entire North Sea from Scotland to North Germany, revealed in the potential field transformations, corresponds to the lower crustal edge of Baltica which apparently extend across most of the North Sea. This lineament could as such represent the lower crustal and upper mantle suture between lithosphere of Avalonia origin versus lithosphere of Baltica origin in the lower crust and upper mantle. It may be the missing link for the reconstruction of the triple plate collision.
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8104 Continental margins: convergent
DE: 8110 Continental tectonics: general (0905)
SC: Tectonophysics [T]
MN: Fall Meeting 2005