The BGS Lexicon of Named Rock Units — Result Details

Nansen Formation

Computer Code: NANN Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Hettangian Age (JH) — Pliensbachian Age (JE)
Lithological Description: East Shetland Basin: Fine- to coarse-grained, fairly well sorted, partly calcite-cemented, pebbly/granulitic, white to pale brown sandstones. Pebbles concentrations often form basal lags of upward-fining beds. Cross-bedding, wave-rippled lamination and burrows occur in places. Occasional thin mudstone beds with marine fossils also occur in some parts of the sequence, and can be recognised in geophysical logs by their distinct gamma-ray peaks (a large peak is often seen in the middle part of the formation). Beryl Embayment and South Viking Graben: The formation is composed almost entirely of fine-to coarse-grained, quartzose, mud-free sandstones. They are often kaolinitic. The sandstones are stacked in c. 8 m-thick, occasionally upward coarsening, units. Sedimentary structures and bioturbation are rare. Near the top of the formation a unit of muddy sandstone, with carbonaceous wisps and laminae, causing relatively high gamma values, often occurs. Thin beds of pebbly, silty mudstone cause distinct gamma-ray peaks near the base and the middle of the formation.
Definition of Lower Boundary: In the Beryl Embayment and East Shetland Basin the base is defined by a downward change from sandstone to interbedded sandstone, mudstone and minor coal (Statjjord Formation). This coincides with a downward increase in gamma values. In the East Shetland Basin the formation rests directly on the red, argillaceous, Triassic deposits (Cormorant Formation).
Definition of Upper Boundary: The upper boundary is defined by the downward change from mudstones (Amundsen and Darwin formations) to sandstones and a distinct down-section decrease in gamma values. Velocity increases down-section where the top of the Nansen Formation is calcite cemented.
Thickness: Up to 60 m in the East Shetland Basin and up to 75 m in the Viking Graben.
Geographical Limits: East Shetland Basin, Viking Graben and Beryl Embayment, North Sea quadrants 9, 210, and 211.
Parent Unit: Banks Group (BAKS)
Previous Name(s): Calcareous Sandstone Bed (-5192)
Lower Beryl Sandstone 2 (-5193)
Middle Formation (-5194)
Nansen Member (-5195)
Statfjord Formation (STAT)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea Well 211/24-1 between 3112 and 3158.5 m below KB. Deegan and Scull (1977), revised by Richards et al. (1993). 
Reference Section  North Sea Well 211/27-1A between 3193 and 3209 m (Richards et al., 1993). 
Reference Section  North Sea Well 3/15-2 between 3607 and 3645.5 m (Richards et al., 1993). 
Reference Section  North Sea Well 9/13-15 between 3600 and 3651 m (Richards et al., 1993). 
Reference Section  North Sea Well 9/19-5A between 3842 and 3910.5 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. 
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] 
Richards, P C. 1991. The evolution of Lower Jurassic coastal plain and fan delta sediments in the Beryl Embayment, North Sea. Journal of the Geological Society, London, 148, 1037-1047. 
Richards, P C. 1989. Lower and Middle Jurassic sedimentology of the Beryl Embayment, and implications for the evolution of the northern North Sea. Unpublished Ph.D. thesis, University of Strathclyde. 
Richards, P C. 1990. The early to mid-Jurassic evolution of the northern North Sea. In: Hardman, R F P and Brooks, J (eds.) Tectonic events responsible for Britain's oil and gas reserves. Special Publication of the Geological Society, London, No.55, 191-205. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable