Application of three-dimensional seismic data to documenting the scale, geometry and distribution of soft-sediment features in sedimentary basins: an example from the Lomre Terrace, offshore Norway

Abstract

Three-dimensional seismic data are used to document the geometry, scale and distribution of soft-sediment deformation features in the post-rift succession of the Lomre Terrace, offshore Norway. In the Cretaceous to Upper Oligocene succession a polygonal fault network, developed in the in response to compaction and dewatering of the interval, was mapped using dip and azimuth grid-based attributes. In the same stratigraphic interval a series of chaotic seismic reflection packages are developed which are visualized using a volume-based seismic coherency attribute and interpreted as the seismic expression of mobilized mud masses. Immediately overlying the mobilized mud masses are a series of fault-bounded depressions that are interpreted to have formed in response to deflation of the mobilized mud masses caused by loading of the overlying succession. A series of shallow, curvilinear erosion surfaces are present on the seismic horizon bounding the top of the Pliocene succession and represent iceberg-keel plough marks. This study demonstrates that interpretation and visualization of three-dimensional seismic data coupled with attribute analysis provide valuable insights into soft-sediment deformation features in sedimentary basins, in particular the scale, geometry and distribution of such features and their temporal and spatial inter-relationships.

An Early Pleistocene grounded ice sheet in the Central North Sea

“…Randomly oriented, curvilinear, cross-cutting scars (Figs 4 & 6), lightly eroded into the underlying sequence, characterize seismic reflections at up to Comparable features in the North Sea have been interpreted as iceberg-keel ploughmarks by Jackson (2007), and similar features in the Barents Sea are reported by Solheim et al (1988) and on the Måløy plateau by Nygård et al (2004). Graham et al (2007) interpreted iceberg ploughmarks within the Late Pleistocene stratigraphy of the Witch Ground Basin of the North Sea, and modern analogues from former glaciomarine environments may be observed on seismic and multibeam echo-sounder data from the Northern North Sea, the Norwegian shelf, the West Shetland shelf and the North Falklands shelf, among others.…”

“…Most recently Stewart & Lonergan (2011) have inferred up to seven glacial advances in Middle -Late Pleistocene deposits based upon an analysis of cross-cutting relationships in tunnel valley systems. The occurrence of iceberg ploughmarks on seismic data has been discussed by Jackson (2007) and Graham et al (2007), among others.…”

An integrated subsurface analysis of clastic remobilization and injection; a case study from the Oligocene succession of the eastern North Sea

“…As demonstrated by Polteau et al (2008), the general saucer-shaped geometry of the discordant amplitude anomalies is representative of both igneous intrusions and fluidized injected sand. However, the specific conical geometry of some of the injectites in this study is a very characteristic feature for sand injectites (Macleod et al, 1999;Molyneux et al, 2002;Huuse & Mickelson, 2004;Huuse et al, 2007;Jackson, 2007;Shoulders et al, 2007;Cartwright et al, 2008). Likewise, the vertical and lateral extent of the observed injectites is more compatible with sand injectites than igneous intrusions (cf.…”

“…Although Oligocene sand injectites are relatively common in the North Viking Graben (e.g. Huuse & Mickelson, 2004;Jackson, 2007) they are rarely observed in the remainder of the North Sea and this study reports the first documentation of potential Oligocene sand injectites in the eastern North Sea. The injectites demonstrate significant overpressure build-up and remobilization of sand during the Oligocene within the RFH area, suggesting that Oligocene sand injectites may be an overlooked phenomenon in this area, and that other injectites may be found in similar structural and stratigraphic settings.…”

“…injected wings forming directly on top of a depositional sand (e.g. Macleod et al, 1999;Jackson, 2007;Dmitrieva et al, 2012). As mentioned in section 7.1, the discordant amplitude anomalies are interpreted to represent dominantly injected sand, although the presence of thin initial depositional sand (below the seismic threshold) cannot be discarded completely.…”