TONGBAN, HYACINTHE;THIERRY JACQUIN, Université de Paris-XI, Orsay, France, BRUNO COURME, Ecole des Mines de Paris, Laboratoire de Géologie, Paris, France and ROBERT DUNAY, Mobil North Sea Ltd., London,U.K.

Abstract: Three Dimensional Seismic Stratigraphic Architecture Of The Neogene Depositional Systems Of The North Viking Graben: Restoration Of The Missing Sections

The Mesozoic-Cenozoic succession of the Norwegian offshore is deeply truncated. Only the toes of Neogene large-scale clinoforms are preserved. However, using seismic stratigraphy criteria and log calibration, it is possible to assign a precise age and an environmental interpretation to these remnant features. Four major second-order Transgressive/Regressive facies cycles have been recognized within the Mio-Pliocene succession.

The lowermost Miocene T/R cycle is represented in the northern North Viking Graben area solely by sandy remnant valley-fill and/or mounded deposits assigned to the Utsira Formation.

The upper Miocene T/R cycle unconformably progrades over the Lower Miocene cycle, showing large deltaic complexes along the Norwegian shoreline.

The lower Pliocene T/R cycle is highly prograding, with several high-frequency sequences. The transgressive phase is recorded as widely distributed condensed shales, covering the various Utsira lowstand fans. The regressive phase is composed of progradational deltas and massive lowstand fans.

The upper Pliocene T/R cycle is bounded at the base by the most prominent unconformity of the Neogene, which has caused the deep erosion observed offshore Norway. The upper Pliocene transgressive deposits are systematically preserved above the unconformity in the shallow-water environments.

The Pleistocene T/R cycle is bounded at the base by a widespread erosional surface, which is probably linked to the glaciations at 2.1 My.

The three dimensional model of the Neogene North Sea environments constrains the pattern of the erosion at the three major unconformities (Miocene, Late Pliocene, Early Pleistocene). The corresponding amount of uplift and linked missing sections have been calculated for each surface.

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England