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Seismic Study of Tectonic Control from Deep-Marine Syn-Rift Deposits in the VøRing Basin, Offshore Norway

Athmer, Wiebke 1; Uribe, German A. G.1; Donselaar, Marinus E.1; Luthi, Stefan M.1
1 Department of Geotechnology, Delft University of Technology, Delft, Netherlands.

In the Vøring Basin, offshore Norway, deep-marine turbidite deposits with major hydrocarbon potential developed during the Late Cretaceous - Paleocene rift phase. The location, shape and stacking pattern of these sediments are strongly influenced by the pre-existing topography of the slope and basin floor, but the structural effects on the flow path during rifting are so far only poorly understood. Particularly relay ramps are supposed to act as pathway for turbidity currents and to influence the depositional architecture of submarine deposits. Thus, to be able to create a sound depositional model in a syn-rift setting and to better locate areas with potential reservoir sands the influence of complex basin and slope topography on deposition and flow path needs to be understood and taken into account.

The seismic morphology study was performed on 3D seismic data from the north-western part of the Vøring Basin. Different sedimentary bodies, developed in the syn-rift phase and characterized as deep-marine deposits, were mapped in detail and described in terms of their geometrical shape, location and thickness distribution. Based on their lateral position and spatial relationship to each other single seismic elements are grouped into sequences to create a conceptual depositional model. Specific attention is paid to deposits close to a relay ramp. 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 detailed seismic interpretation of sedimentary sequences leads to an understanding of the interplay between fault activity and infill of accommodation space in an active rift setting. The distribution of syn-rift deposits is highly dependent on the palaeo-topography: The sedimentary sequences are aligned in parallel orientation to normal faults, exhibiting greater sediment thicknesses on the hangingwalls of rotated fault blocks, adjacent to the fault. Locally, within a sedimentary sequence, thicker deposits occur close to and at the foot of relay ramps, suggesting an influence of these transfer zones on sedimentary flows. However, experimental results on the impact of relay ramps on turbidite deposition showed that their effect as flow path on turbidity currents can be regarded as minor in a deep-marine setting, and deposition mainly results from flows shedding directly into the basin.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009