3D Seismic Analysis Reveals the Origin of Ambiguous Erosional Features at a Major Sequence Boundary in the Eastern North Sea: near Top Oligocene

Abstract

The near top Oligocene unconformity is a major sequence boundary in the eastern North Sea Basin. It is characterized by erosional scarps below the boundary and a pronounced basinward shift in onlap above. The shift in onlap has previously been interpreted as caused by a major fall in sea level. Detailed 3D seismic analysis of a 20 by 20km area at and basinward of the uppermost Oligocene clinoform breakpoint reveals that the erosional scarps were caused by undercutting of steep clinoforms by contour-parallel currents and resulting mass wasting whilst the lowermost onlap package consists of a contour-parallel drift deposited as the erosive currents waned. The 3D seismic analysis corroborates a recent analysis based on regional 2D seismic data, which found that the erosional scarps and the geometry of the onlap sequence were indicative of a major shift in sediment input directions and not necessarily associated with any change of sea level. The paper thus demonstrates the utility of local 3D seismic analyses as a form of "ground truthing" regional basin analyses based on widely spaced 2D seismic grids.DAVIES, R.

Oligocene climate changes controlling forced regression in the eastern North Sea

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Fluid flow features in hydrocarbon plumbing systems: What do they tell us about the basin evolution?

“…8H and 9E) support the existence and suggested direction of contour currents during the Oligocene. The study by Hansen et al (2004) likewise exemplifies Oligocene contour parallel deposits and erosion in the Norwegian-Danish Basin.…”

Structural, Sedimentologic, and Sea-Level Controls on Sand Distribution in a Steep-Clinoform Asymmetric Wave-Influenced Delta: Miocene Billund Sand, Eastern Danish North Sea and Jylland

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