--> Tectonic Control from Deep-Marine Syn-Rift Deposits: A 3D Seismic Study in the Western VøRing Basin, Offshore Norway, Athmer, Wiebke; Luthi, Stefan M.; Uribe, German A. G.; Donselaar, Marinus E., #90100 (2009)

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Tectonic Control from Deep-Marine Syn-Rift Deposits: A 3D Seismic Study in the Western VøRing Basin, Offshore Norway

Athmer, Wiebke1
 Luthi, Stefan M.1
 Uribe, German A. G.1
 Donselaar, Marinus E.1

1Department of Geotechnology, Delft University of Technology, Delft, Netherlands.

Deep-marine reservoir sands in turbidite deposits are the main exploration target in frontier areas at passive continental margins such as offshore Norway, offshore Brazil, and offshore West Africa. Their depositional architecture, shape and location are strongly governed by the topography of the slope and basin floor, but the structural effects on the pathway of turbidity currents during rifting are so far only poorly understood. Large-scale relay ramps are found to influence the transport of sediments in fluvial and deltaic systems, and they might also have a significant impact on sediment transportation in subaqueous settings, and thus on the distribution of reservoir sands.

This study was performed using 3D seismic data from the Fenris Graben and Gjallar Ridge area in the north-western part of the
Vøring Basin with the aim to understand the interplay between fault activity and infill of accommodation space in an active rift setting. Different deep-marine sedimentary deposits that developed in the Paleocene syn-rift phase were mapped in detail and described in terms of their geometrical shape, location and thickness distribution before grouping them into sequences to create a conceptual depositional model. Specific attention was paid to deposits close to relay ramps that are part of the en echelon aligned fault system separating the basin from the structural high. Their distribution with regard to the ramp geometry is compared to experimental results of turbidite deposition in a fault-constrained setting in order to determine the possible influence of relay ramps on turbidity currents.

The distribution of the Paleocene syn-rift deposits in the Fenris Graben is found to be highly dependent on the palaeo-topography: In the early syn-rift phase the sedimentary bodies are highly influenced by faulting with alignments parallel to normal faults and basin strike. Greater sediment thicknesses are found to occur on the hanging walls of rotated fault blocks adjacent to the faults. With continued rifting and termination of faulting deposition takes place with blanket coverage, draping the previous basin infill and smoothing out the basin floor topography. Locally, however, thicker deposits occur close to and at the foot of relay ramps, suggesting an influence of these transfer zones on sedimentary flows and inferring the structural high to act as an additional sediment source for the basin infill.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil