The BGS Lexicon of Named Rock Units — Result Details

Wick Sandstone Formation

Computer Code: WISA Preferred Map Code: notEntered
Status Code: Full
Age range: Berriasian Age (KR) — Albian Age (KA)
Lithological Description: Sandstones with interbedded siltstones and mudstones. Sandstones are very fine- to coarse- grained, pebbly, generally poorly consolidated, locally argillaceous and poorly sorted. They are pale grey to grey brown, dominantly quartz sandstones. Glauconite grains, carbonaceous debris and lignite are widespread. Calcareous concretions are common and give high velocity spikes on wireline logs. The Mudstones and siltstones are similar to those of the Valhall formation. They are generally calcareous, medium to dark grey, occasionally pale grey, grey-brown, red-brown and grey-green. They are micromicaceous, pyritic, glauconitic and blocky. Sporadic, thin, white to tan, argillaceous, microcrystalline limestones occur. The Wick Sandstone Formation displays both blocky and serrated signatures on wireline logs, reflecting the massive sandstones units and thinly interbedded sandstones and mudstones units, respectively. In the Inner Moray Firth the formation can be divided into three members (Captain, Coracle and Punt Sandstone members).
Definition of Lower Boundary: Normally taken at a downward change from sandstones with interbedded siltsones and mudstones (Wick Sandstone Formation) to argillaceous strata (Valhall Formation). On wireline logs the boundary is marked by a downward increase in average gamma-ray values and a decrease in average velocity. Where the formation can be divided into members, there are up to three formation bases where Wick Sandstone Formation rests on argillaceous deposits of the Valhall Formation. The base of the Wick Sandstone Formation does not necessarily coincide with the base of the lowest thin sandstone in the Cromer Knoll Group, but is placed at the base of the sandstone-rich sequence (Johnson and Lott, 1993). Locally the Wick Sandstone rests on interbedded sandstones and mudstones of the Kimmeridge Clay Formation (e.g.13/30-1). The lower boundary is then difficult to place on lithological criteria, although mudstones of the Wick Sandstone formation are generally more calcareous and less carbonaceous than those of the Kimmeridge Clay Formation.
Definition of Upper Boundary: The top of the formation is usually taken at a downward change from argillaceous lithologies (Carrack Formation) to sandstones with interbedded siltstones and mudstones. It does not necessarily coincide with the top of the highest thin sandstone in the Cromer Knoll Group, but is placed at the top of the sandstone-rich section. On wireline logs, it is taken at a sharp downward decrease in gamma-ray values and an increase in velocity. Where the Wick Sandstone Formation is divisible into members a vertical succession of up to three formation tops is possible where strata of the Carrack or Valhall formations overlie the sandstone of the three members. Where the formation is undivided or where the Captain Sandstone Member (the highset member) is present, the top is normally taken at a downward change from dark grey, non-calcareous to slightly calcareous, low-velocity mudstone (Carrack Formation) to sandstones and interbedded mudstones (e.g. Well 12/30-1 and 13/11-1). Locally, however, the Captain's Member is overlain by the Valhall Formation (e.g. Well 13/13-1 and 13/14-1). Where the Captain Sandstone Member is absent, the Valhall Formation rests on the Wick Sandstone Member (e.g. Well 13/29-2).
Thickness: Up to 1400 m.
Geographical Limits: Inner Moray Firth and extreme northwestern margins of the Halibut Shelf and Halibut Horst (North Sea Quadrants 11-14 and 17).
Parent Unit: Cromer Knoll Group (CRKN)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea well 12/30- 1 at 962-991 m, 1366-1405 m and 1457-1556 m below KB (Johnson and Lott, 1993). 
Reference Section  North Sea well 13/12- 1 at 1045.5-2144 m (Johnson and Lott, 1993). 
Reference(s):
Stevens, V. 1991. The Beatrice Field, Block 11/30a, UK North Sea. In: Abbotts, I L (ed.) United Kingdom oil and gas fields 25 years commemorative volume. Memoir of the Geological Society, London, 14, 245-252. 
Johnson, H and Lott, G K. 1993. 2. Cretaceous 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