The BGS Lexicon of Named Rock Units — Result Details
Wroot Formation
Computer Code: | WROT | Preferred Map Code: | notEntered |
---|---|---|---|
Status Code: | Full | ||
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 Saltwick Formation Grantham Formation Pentland Formation Northampton Sand Formation Werkendam Shale Formation |
||
Stratotypes: | |||
Type Section | North Sea well 47/03b- 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 48/03- 3 between 1137 and 1248 m (Lott and Knox, 1994). | ||
Reference(s): | |||
Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. | |||
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 |