The BGS Lexicon of Named Rock Units — Result Details

Hugin Formation

Computer Code: HUGI Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Bajocian Age (JB) — Oxfordian Age (JO)
Lithological Description: The formation comprises sandstones, siltstones and mudstones with minor coal and conglomerates. It is variably fossiliferous with both non-marine and marine shelly faunas. Beryl Embayment: Very fine- to fine-grained sandstone in two main facies: sharp based upward fining, cross-bedded, more or less bioturbated sandstones; uniformly graded rippled, bioturbated and possibly hummocky cross-laminated sandstones. Sandstones are shelly in places and interbedded with siltstones (which are more common in the lower part of the formation). Lenticular bedded siltstones are present, associated with thin coals and bioturbated, sandy siltstones and thin beds of very fine-grained, burrowed sandstones. Two thin lag conglomerates occur, one at the base and one in the middle part of the formation. South Viking Graben: Interbedded sandstones and siltstones, often containing bivalve debris. Sandstones are sharp based, fine upwards from medium to fine grained and often bioturbated. Coals occur at some intervals. In Quadrant 16, the formation comprises very fine- to fine-grained, argillaceous, bioturbated, ripple and parallel laminated, upward coarsening sandstones interbedded with upward fining, cross-bedded sandstones, grey mudstones, coals and pebble lag deposits. In the extreme south of the Viking Graben the formation is dominated by sandstones with sporadic thin coal seams.
Definition of Lower Boundary: Defined by a downward transition from marine sandstones and siltstones/mudstones, with minor coals, to more frequently coal-bearing, generally non-marine and volcanic strata (Pentland Formation). The boundary is difficult to pick out in wireline logs.
Definition of Upper Boundary: The upper boundary is characterised by the downward transition from mudstones and siltstones (Heather Formation) to sandstones with variable amounts of interbedded siltstone and mudstone. The boundary coincides with a down-section decrease in gamma values and an increase in velocity.
Thickness: Up to c. 300 m.
Geographical Limits: Beryl Embayment and South Viking Graben (North Sea quadrants 1, 2, 9, 16, 209, 210) and into the Norwegian sector of the North Sea. The type section is in the Norwegian sector of the North Sea in Well N15/9-2, between the depths 3483 and 3657 m below KB (Vollset and Doré, 1984).
Parent Unit: Fladen Group (FLDN)
Previous Name(s): Angus Sand (-5219)
Beryl Formation (-5220)
Bruce A (-5221)
Bruce B (-5222)
Bruce Upper Sands (-5223)
Massive Sandstone (-5224)
Sand/Shale Unit (-5225)
Upper Beryl Sand (-5226)
Young Upper Beryl Sandstone (-5227)
Alternative Name(s): none recorded or not applicable
Reference Section  North Sea Well 1/4-1 between 700 and 772 m (Richards et al., 1993). 
Reference Section  North Sea Well 9/13-12 between 3362 and 3501 m (Richards et al., 1993). 
Reference Section  North Sea Well 9/19-5A between 3358.5 and 3650.5 m (Richards et al., 1993). 
Reference Section  North Sea Well 16/18-1 between 3667 and 3869.5 m (Richards et al., 1993). 
Vollset, J and DorĂ©, A G. 1984. A revised Jurassic and Triassic lithostratigraphic nomenclature for the Norwegian North Sea. NPD-Bulletin No.3. 
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 (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