Crustal Architecture of the Northern Barents-Kara Sea Continental Margin

Alexander Minakov¹, Jan Inge Faleide², Vladimir Glebovskiy³, Rolf Mjelde¹, and Yuri Podladchikov^4
1Earth Science Department, University of Bergen, Bergen, Norway.
²Department of Geosciences, University of Oslo, Oslo, Norway.
³Department of Integrated Geological and Geophysical Research, VNIIOkeangeologia, St.Petersburg, Russia.
⁴Physics of Geological Processes, University of Oslo, Oslo, Norway.

Development of the northern Barents-Kara Sea continental margin was initiated by Cenozoic spreading on the Gakkel Ridge. The break-up led to detachment of a fragment of continental crust - the Lomonosov Ridge - which represents a prominent topographical feature in the Arctic Ocean.
The present study addresses an examination of general characteristics of the deep structure and the evolution of the northern Barents-Kara Sea continental margin from integrated analysis of potential fields and sparse seismic profiles.

The algorithm of the gravity inversion took into account the density differentiation of the upper mantle caused by complexities of the temperature distribution with depth. A plate cooling model which relates changes in temperature to the rate of extension and the age since rifting was implemented. An exponential density-depth relationship in the sedimentary cover was used for gravity analysis along the transects. A final constraint was to satisfy both the gravity field and the state of isostatic equilibrium. Following these criteria an iterative inversion was performed.
A series of crustal-scale geotransects illustrating the architecture of the continental margin was constructed using the gravity inversion technique, seismic reflection profiles and depths to magnetic sources estimates.

The overall crustal architecture revealed by the transects exhibits a narrow and steep continent-ocean transition which is characteristic of sheared more than rifted margins. This may reflect a short-lived phase of shear during breakup prior to the opening of the Eurasia Basin. The break up was initiated at the Paleocene-Eocene transition and was likely linked to the opening of Labrador Sea-Baffin Bay system.

A numerical modeling using finite element method was applied to explain the observed structure of the continental margin and to test the proposed kinematics of lithosphere breakup. It is supposed that the shear heat released at the initial stage of breakup could efficiently localize deformations resulting in the steep and narrow continent ocean transition.
The pattern of the sedimentary thickness distribution in the Nansen Basin was influenced by Plio-Pleistocene glacial fans deposited in front of the Franz-Victoria and St. Anna troughs. These sediments were derived from uplifted and eroded areas in the Barents-Kara Sea region.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia