CRUSTAL STRUCTURE OF THE SHEARED SOUTHWESTERN BARENTS SEA CONTINENTAL-MARGIN

Eighteen expanding spread profiles from the southwestern Barents Sea continental margin were studied with a variety of seismic interpretation techniques and in conjunction with seismic reflection data. The velocity-depth profiles from the slope-intercept, Herglotz-Wiechert and τ-sum methods were compared and contrasted to the velocity-depth curve calculated from the iterative forward modelling of the amplitudes. The velocity-depth profiles derived from the τ-sum and forward modelling of the amplitudes were used to produce synthetics in both the X-T and τ-P domains to choose the technique that most accurately represented the data. The results showed the oceanic crust at the Senja Fracture Zone to be different from standard oceanic crust with a higher than average velocity for layer 2 of 5.7-6.4 km s-1 and slightly smaller crystalline crustal thickness. The continent-ocean transition at crustal depths was shown to be narrow, in the range of 10-20 km. Our results were consistent with two different crustal provinces east of the Senja Fracture Zone, the Tertiary marginal basin and the Cretaceous basin region. The velocity-depth curves enabled us, in a gross sense, to suggest the depths to deep sedimentary interfaces and the top of the crystalline crust that were normally not observed in the reflection profiles. Depths down to 20 km were inferred for the base of the sedimentary section in the southwestern Barents Sea. The crust thinned gently towards the continent-ocean boundary at the Senja Fracture Zone, whereas the crustal thickness changed abruptly below the Hornsund Fault Zone at the margin farther north. We associated the change in crustal structure with Cenozoic in the thick crust beneath the Svalbard Platform in the north. The depths to mantle determined on the shelf were consistent with that observed on a deep multichannel seismic line that crosses the area. © 1990.