The BGS Lexicon of Named Rock Units — Result Details

Fjerritslev Formation

Computer Code: FJEV Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Hettangian Age (JH) — Sinemurian Age (JS)
Lithological Description: This formation has been encountered only in Well 22/5b-5, in the UK Sector of the Central North Sea, where grey mudstones pass upwards into sandstones. In the type section, in Denmark, the formation comprises grey and dark grey, calcareous mudstones with frequent beds of argillaceous limestone and sporadic fine-grained sandstones. Offshore in the type well (N7/9-1 of the Norwegian Sector), Deegan and Scull (1977) described dark grey to grey brown mudstones grading up into siltstones.
Definition of Lower Boundary: In North Sea Well 22/5b-5 the lower boundary is marked by a downward transition from grey mudstones to white sandstones interbedded with red-brown calcareous mudstones (Triassic).
Definition of Upper Boundary: In North Sea Well 22/5b-5 the top of the formation is a sharp downward change from mudstones (Cromer Knoll Group) to sandstones.
Thickness: 16 m in North Sea Well 22/5b-5.
Geographical Limits: Known only in North Sea Well 22/5b-5 in the UK Sector of the North Sea, but it is more extensive in the Norwegian Sector and into Denmark.
Parent Unit: Not Applicable (-)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  North Sea Well 22/5b-5 between depths 311.5 and 3127.5 m. Description for the North Sea: Deegan and Scull (1977); Description for the UK Sector: Lott and Knox (1994). 
Reference(s):
Deegan, C E and Scull, B J. 1977. A standard lithostratigraphic nomenclature for the Central and Northern North Sea. Report of the Institute of Geological Sciences, 77/25; NPD Bulletin No.1. 
Lott, G K and Knox, R W O'B. 1994. 7. Post-Triassic of the Southern North Sea. In: Knox, R W O'B and Cordey, W G (eds.) Lithostratigraphic nomenclature of the UK North Sea. [British Geological Survey, Nottingham]. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable