The BGS Lexicon of Named Rock Units — Result Details

Amundsen Formation

Computer Code: AMND Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Sinemurian Age (JS) — Pliensbachian Age (JE)
Lithological Description: Dominantly light to dark grey, non-calcareous to calcareous, bioturbated siltstones and mudstones, which are locally carbonaceous and pyritic. The lower beds are, locally, more calcite cemented. Sandstones, particularly in the upper parts of the formation, attain a thickness of 24 m (Well 3/15-3). They are white, grey or brown and locally cemented by calcite or silica. Locally kaolinite, glauconite and mica occur. Upward-coarsening sections are common and reflect the upward decrease in gamma values.
Definition of Lower Boundary: The base is marked by a downward change from mudstones/siltstones to sandstones (Nansen Formation). This is accompanied by a down-section decrease in gamma values and, usually, an increase in velocity.
Definition of Upper Boundary: The upper boundary is defined by a downward change from mudstones (Burton Formation) to siltstones or sandstones. It is accompanied by an often weak, down-section decrease in gamma values and increase in velocity.
Thickness: 6-100 m in the East Shetland Basin, but thins and disappears on highs.
Geographical Limits: East Shetland Basin into the Viking Graben.
Parent Unit: Dunlin Group (DUNL)
Previous Name(s): Amundsen Sub-Unit (-5174)
Dunlin Siltstone Member (-5175)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea Well 211/29-3 between 2993 and 3051 m below KB (Deegan and Scull, 1977). 
Reference Section  North Sea Well 211/18a-24 between 3737.5 m and 3762 m (Richards et al., 1993). 
Reference Section  North Sea Well 3/3-3 between 3300 and 3325 m (Richards et al., 1993). 
Reference Section  North Sea Well 3/15-3 between 3689 and 3794 m (Richards et al., 1993). 
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. 
Bowen, J M. 1975. The Brent Oil-Field. In: Woodland, A W (ed.) Petroleum and the contineental shelf of North-West Europe, 353-361. [Heyden & Son, London] 
Richards, P C, Lott, G K, Johnson, H, Knox, R W O'B. and Riding, J B. 1993. 3. Jurassic of the Central and Northern North Sea. In: Knox, R W O'B and Cordey, W G. 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