The Cook Formation, an offshore sand ridge in the Oseberg area, northern North Sea

  • Finn Livbjerg
  • Rune Mjøs


In the Oseberg area, the early Jurassic Cook Formation has been subdivided into three units. The lower unit (Cook A) was deposited as a prograding subtidal sand body and the upper unit (Cook C) was deposited as an offshore sand ridge. A thin mudstone unit (Cook B) separates these two sandstone units. The Cook Formation is enclosed by mudstones in which resistivity log peaks have a high degree of correlatability. The stratification visualized by the log correlation provides useful information, revealing the sedimentary history of the Cook Formation; in particular, it is used as a chronostratigraphic framework to describe synsedimentary fault activity at the margin of the Viking Graben. The Cook A Unit thickness from 0 m in the west to 45 m in the east, implying a clastic source area at the eastern margin of the northern North Sea and deposition in response to marine regression. The Cook C Unit shows maximum thicknesses (up to 37 m) centred upon the palaeostructural highs at the margin of the Viking Graben and defines N-S-oriented sand bodies. The sand bodies are interpreted as offshore sand ridges deposited during the marine transgression associated with fault block crest erosion. Subsequent sea-level rise resulted in rapid deepening of marine conditions and the establishment of the lowe-nergy mudstone depositional environments of the Drake Formation. Passive mudstone infilling of the lows levelled the relief created by the sand ridges.


Tidal Current Trace Fossil Sand Body Sand Ridge Stoss Side 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Badley, M. E., Egeberg, T. and Nipen, O. 1984. Development of rift basins illustrated by the structural evolution of the Oseberg feature, Block 30/6, offshore Norway. J. Geol. Soc. Lond., 141(4), 639–649.CrossRefGoogle Scholar
  2. Boyles, J. C. and Scott, A. J. 1982. A model for migrating shelf-bar sandstones in Upper Mancos Shale (Campanian), Northwestern Colorado. AAPG Bull., 66, 491–508.Google Scholar
  3. Erichsen, T., Helle, M., Henden, J. and Rognbakke, A. 1987. Gullfaks. In: Spencer, A. M. et al. (eds), Geology of the Norwegian Oil and Gas Fields, Norwegian Petrol. Soc, Graham & Trotman, London, 273–286.Google Scholar
  4. Fleet, A. J., Clayton, C. J., Jenkyns, H. C. and Parkinson, D. N. 1987. Liassic source-rock deposition in Western Europe. In: Brooks, J. and Glennie, K. W. (eds), Petroleum Geology of North West Europe, Graham & Trotman, London, 59–70.Google Scholar
  5. Gage, M. S. and Doré, A. G. 1986. A regional geological perspective of the Norwegian offshore exploration provinces. In: Spencer, A. M. et al. (eds), Habitat of Hydrocarbons on the Norwegian Continental Shelf, Norwegian Petrol. Soc., Graham & Trotman, London, 21–38.Google Scholar
  6. Gautier, D. L. 1982. Siderite concretions: indicators of early diagenesis in the Gammon shale (Cretaceous). J. Sediment. Petrol., 52, 859–871.Google Scholar
  7. Gaynor, G. C. and Swift, D. J. P. 1988. Shannon Sandstone depositional model: sand ridge dynamics on the Campanian Western Interior shelf. J. Sediment. Petrol., 58, 868–880.Google Scholar
  8. Gjelberg, J., Dreyer, T., Høie, A. Tjelland, T. and Lilleng, T. 1987. Late Triassic to Mid Jurassic sandbody development on the Barents and Mid Norwegian shelf. In: Brooks, J. and Glennie, K. W. (eds), Petroleum Geology of North West Europe, Graham & Trotman, London, 1105–1130.Google Scholar
  9. Hallam, A. and Bradshaw, M. J. 1979. Bituminous shales and oolitic ironstones as indicators of transgressions and regressions. J. Geol. Soc. Lond., 136, 157–164.CrossRefGoogle Scholar
  10. Johnson, H. D. and Baldwin, C. T. 1986. Shallow siliclastic seas. In: Reading, H. G. (ed.), Sedimentary Environments and Facies, second edition, Blackwell Scientific, Oxford, 229–282.Google Scholar
  11. Nio, S.-D. 1976. Marine transgressions as a factor in the formation of sandwave complexes. Geol. Mijnbouw, 55, 18–40.Google Scholar
  12. Nipen, O. 1987. Oseberg. In: Spencer, A. M. et al. (eds), Geology of the Norwegian Oil and Gas Fields, Norwegian Petrol. Soc., Graham & Trotman, London, 379–388.Google Scholar
  13. Roberts, J. D., Mathieson, A. S. and Hampson, J. M. 1987. Statfjord. In: Spencer, A. M. et al. (eds), Geology of Norwegian Oil and Gas Fields, Norwegian Petrol. Soc, Graham & Trotman, London, 319–341.Google Scholar
  14. Slatt, R. M. 1984. Continental shelf topography: key to understanding distribution of shelf sand-ridge deposits from Cretaceous Western Interior Seaway. AAPG Bull., 68, 1107–1120.Google Scholar
  15. Stride, A. H. (ed.) 1982. Offshore Tidal Sands, Processes and Deposits, Chapman and Hall, London, 22 pp.Google Scholar
  16. Swift, D. J. P. 1985. Response of the shelf floor to flow. In: Tillman, R. W., Swift, D. J. P. and Walker, R. G. (eds), Shelf Sands and Sandstone Reservoirs, SEPM Short Course Notes no. 13, 135–242.Google Scholar
  17. Sykes, R. M. 1974. II. Offshore-estuarine regressive sequences in the Neill Klinter Formation (Pliensbachian Toarcian). Bull. Geol. Soc. Denmark, 23, 214–224.Google Scholar
  18. Vail, P. R., Hardenbol, J. and Todd, R. G. 1984. Jurassic unconformities, chronostratigraphy, and sealevel changes from seismic stratigraphy and biostratigraphy. In: Schlee, J. S. (ed.), Inter-regional Unconformities, AAPG Mem. no. 36, 129–144.Google Scholar
  19. Van, Houten, F. B. and Bhattacharyya, D. P. 1982. Phanerozoic oolitic ironstones—geological record and facies model. Ann. Rev. Earth Planet. Sci., 10, 441–457.CrossRefGoogle Scholar
  20. Visser, M. J. 1980. Neap-spring cycles reflected in Holocene subtidal large-scale bedform deposits; a preliminary note. Geology, 8, 543–546.CrossRefGoogle Scholar
  21. Vollset, J. and Doré, A. G. (eds) 1984. A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. Norweg. Petrolm. Direct. Bull., 3, Stavanger, 53 pp.Google Scholar

Copyright information

© Norwegian Petroleum Society 1989

Authors and Affiliations

  • Finn Livbjerg
    • 1
  • Rune Mjøs
    • 2
  1. 1.Norsk Hydro/Store Norske Spitsbergen KulkompaniSvalbardNorway
  2. 2.Rogaland Research InstituteStavangerNorway

Personalised recommendations