The Cenozoic development of the Norwegian margin between 60 and 64°N can be described in terms of five, unconformity-bounded, megasequences: Paleocene–lowermost Eocene (65–51 Ma), Lower Eocene–lowermost Oligocene (51–31 Ma), Lower–upper Oligocene (31–24 Ma), Miocene–Pliocene (24–1.9 Ma), and Pleistocene (1.9 Ma–present). Each sequence is constructed of systems tracts, varying in type and number between sequences. In the Møre Basin (62–64°N), lowstand wedges dominate and form an offlapping, regressive pattern. In the Northern North Sea Basin (60–62°N), lowstand, transgressive and highstand systems tracts are present, showing a more variable framework.The variability observed is interpreted to reflect the response of sediment supplied, both in time and space, into different basin physiographies related to the overall tectonic context of the two areas. The Northern North Sea Basin in the Cenozoic received sediments generated from the basin margins in periods of uplift and lowstand. Clastic systems probably prograded into a gradually-shallowing central basin area, formed as a response to decaying, post-rift subsidence, margin uplift and sediment fill. The Møre Basin, in contrast, acted as a margin to incipient and on-going North Atlantic rifting, and the basin physiography was that of a more steeply inclined slope facing the northwest. Larger water depths caused sediment wedges to be restricted to the basin margin rather than acting as fill of the central basin area such as occurs in the North Sea. The offlapping pattern probably records repeated uplift of the Norwegian mainland, shedding sediments into the basin.

Three-dimensional seismic reflection data are used to image littoral deposits within the lower Brent Group, northern North Sea. Seismic attribute maps within the unit indicate the development of parallel, highamplitude stripes up to 15 km in length, 50-100 m wide and spaced 150-200 m apart. In map view these features trend NE-SW to ENE-WSW and are arranged into 'sets' that display subtly different orientations. Well data in regions where these anomalies are well developed indicate pronounced anomaly-perpendicular thickness variations in sand-rich beach-ridge facies within the Etive Formation and coals and mudstones within the overlying Ness Formation. Based on these observations, the high-amplitude anomalies are interpreted as the seismic expression of coal-filled swales, whereas the adjacent zones of low amplitude are interpreted to represent the cores of sand-rich beach ridges. The geometry of beach ridges identified in the Etive Formation compares favourably with sedimentological and geometric data from modern beach ridges. The results of this study have implications for (1) the stratigraphic context and preservation of beach ridges, (2) datum selection when attempting stratigraphic correlations within the Brent Group, and (3) the exploration and production of hydrocarbons from beach ridge-type reservoirs.

No abstract

No abstract