The BGS Lexicon of Named Rock Units — Result Details

Wroot Formation

Computer Code: WROT Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Aalenian Age (JA) — Bajocian Age (JB)
Lithological Description: The formation comprises mudstones with interbedded siltstones and sandstones. Mudstones and siltstones are pale grey to grey-green or purple, waxy, poorly to non-calcareous and carbonaceous. The interbedded sandstones are very fine- to fine-grained, pale grey to white, poorly cemented and carbonaceous.
Definition of Lower Boundary: The lower boundary is characterised by a downward change from sandstone and siltstone lithologies to harder, grey, marine, Lower Jurassic siltstones, sandstones or mudstones (Cerdic Formation). It coincides with a down-section increase in gamma values and in velocity. The boundary between the West Sole Group and the Lias Group in the North Sea is a major erosive break.
Definition of Upper Boundary: The upper boundary is normally defined by a downward change from sandstones or siltstones with interbedded mudstones and limestones (Strangways Formation) to variegated siltstones and mudstones. There is a corresponding down-section increase in gamma values and decrease in velocity.
Thickness: Up to 95 m.
Geographical Limits: Southern North Sea Basin (quadrants 41-43, 46-48, 52).
Parent Unit: West Sole Group (WSTS)
Previous Name(s): West Sole Group (WSTS)
Alternative Name(s): Dogger Formation
Northampton Sand Formation
Pentland Formation
Saltwick Formation
Werkendam Shale Formation
Grantham Formation
Stratotypes:
Type Section  North Sea Well 47/3b-4 between 1117 and 213.5 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 42/24-1 between 369 and 437 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 47/10-1 between 1671.5 and 1747 m (Lott and Knox, 1994). 
Reference Section  North Sea Well 48/3-3 between 1137 and 1248 m (Lott and Knox, 1994). 
Reference(s):
Lott, G K and Knox, R W O'B. 1994. 7. Post-Triassic of the Southern 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