updated to follow: Stratigraphic Guide to the Cromer Knoll, Shetland and Chalk Groups of the North Sea and Norwegian Sea. Felix M. Gradstein & Colin C. Waters (editors), Mike Charnock, Dirk Munsterman, Michelle Hollerbach, Harald Brunstad, Øyvind Hammer & Luis Vergara (contributors). Newsletter on Stratigraphy, vol 49/1 pp71-280, 2016
The definition of the Narve Formation in the Central Graben is after Fritsen & Riis (2000: ‘A revised chalk lithostratigraphic nomenclature’; NPD Report, unpublished) (see Table)
After the Norse god Narve, who was the son of Loke and Sigyn.
Lithofacies associated with the crestal biofacies on Valhall are typically (textural) mudstones and wackestones. Those associated with the “shallow water” pelagic biofacies are varied, though typically bioturbated to laminated chalks or interlaminated chalks and clays indicative of slow sedimentation. Those associated with the “deep water” pelagic biofacies are typically massive chalks. Recognition of allochthonous as against autochthonous chalks is difficult, for which high-resolution study is desirable of the paleobathymetry of foraminifera. Lithofacies in core from the 2/8-A-1 well include bioturbated chalks with Chondrites, Planolites and Zoophycos, and also allochthonous debris flows and slumps with micritic matrices and polymict/non-chalk clasts, indicating affinity with the “shallow water” and “deep water” pelagic biofacies of the Valhall structure respectively. Allochthonous chalks are also observed in core from Mona-1.
The thickness of this formation ranges from zero to a few hundred meters in the study wells. It is thin (typically less than 100 m thick) in wells on structural highs such as Valhall-Hod and Tor in the Norwegian Sector, and thickest in wells in basinal lows such as that in the Roar area in the Danish Sector, and in the northern and western depocenters in the Norwegian Sector.
The formation is present in the Central Graben in the Norwegian and Danish Sectors. It is absent in the 2/2 wells in the Norwegian Sector and in the Lulu-1 well in the Danish Sector. The formation is eroded on crests of structures.
4520-4337 m MD.
2/8-A-1, 2581.5 - 2501.5 m MD.
Picked primarily on seismic and biostratigraphic criteria. The seismic criterion is an onlap surface. The biostratigraphic criterion is penetration of local nannozone UC11.
Picked primarily on biostratigraphic and log criteria. The biostratigraphic criterion is penetration of local microzone FCS13 or local nannozone UC3. The log criterion is a downhole gamma increase indicating penetration of the shales of the Blodøks Formation.
Microzones FCS14-FCS18pp; nannozones UC4-UC11.
Variable “shallow water” and “deep water” pelagic environments are listed in well completion reports.
After Fritsen, A. & Riis, F. 2000. A revised chalk lithostratigraphic nomenclature; NPD Report, unpublished)