The BGS Lexicon of Named Rock Units — Result Details

Speke Formation

Computer Code: SPEK Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Early Jurassic Epoch (JL) — Early Jurassic Epoch (JL)
Lithological Description: Heterolithic, varicoloured, but usually green or grey, unit of sandstones, siltstones and mudstones.
Definition of Lower Boundary: The lower boundary is defined by the downward change from varicoloured, but usually green or grey, heterolithic sediments to red Triassic sediments (Cormorant Formation). A weak down-section increase in gamma values coincides with the boundary.
Definition of Upper Boundary: The top is marked by a sharp downward change from sandstone dominated, coal-bearing strata (Fladen Group) to argillaceous, coal-free deposits. The boundary coincides with a sharp down-section increase in gamma values.
Thickness: Up to c. 100 m.
Geographical Limits: Unst Basin, North Sea quadrants 1, 2, 209, 210.
Parent Unit: Dunlin Group (DUNL)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  North Sea Well 1/4-1 between 844 and 945 m below KB (Richards et al., 1993). 
Reference Section  North Sea Well 1/4-2 between 731.5 m and 821.5 m (Richards et al., 1993). 
Reference(s):
Johns, C R and Andrews, I J. 1985. The petroleum geology of the Unst Basin, North Sea. Marine and Petroleum Geology, 2, 361-372. 
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] viii + 219 pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable