| Computer Code: |
WHHU |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Namurian Stage (CN)
— Namurian Stage (CN) |
| Lithological Description: |
The term Whitehurst Group is introduced for strata, mostly Namurian in age, that are broadly equivalent to the Bowland Shale and Millstone Grit groups as defined formally for onshore England (e.g. Aitkenhead et al., 1992). The terms Bowland Shale Formation and Millstone Grit Formation are formally defined here as the offshore lithofacies equivalents of these groups. The Bowland Shale Formation is composed of basinal mudstones, whereas the Millstone Grit Formation encompasses a range of turbidite, delta-slope, deltaic, and fluvial braidplain facies. The Whitehurst Group is widespread in the central part of the UK Southern North Sea. Its southern limit is defined by onlap against the London-Brabant Massif. It is absent over the crest and southern flank of the Mid North Sea High, largely due to erosion following Variscan uplift. The base of the Whitehurst Group is regionally diachronous, ranging between late Asbian (Late Dinantian) and mid-Namurian in age. Underlying strata, where penetrated, are mainly Dinantian to early Namurian fluviodeltaic and minor marine sediments (Fame Group) or Dinantian platform carbonates (Zeeland Formation). Locally in the south, the Whitehurst Group rests on Lower Paleozoic basinal marine sediments. In the north of the area, and locally elsewhere, the Whitehurst Group is unconformably overlain by the Rotliegend Group. In central and southern areas, the Whitehurst Group is generally overlain conformably by the Conybeare Group. Onshore, the top of the Millstone Grit Group is marked by the Gastrioceras subcrenatum marine band, which coincides with the Namurian/Westphalian boundary (refer to Stubblefield and Trotter, 1957; Aitkenhead et al., 1992). Offshore, however, specific marine bands can be recognized only in cored sections, and the base of the group is therefore taken at the base of the lowermost coal seam, being up to 100 m above the Namurian/Westphalian boundary in those wells with good biostratigraphic control. |
| Definition of Lower Boundary: |
The base of the Whitehurst Group is regionally diachronous, ranging between late Asbian (Late Dinantian) and mid-Namurian in age. Underlying strata, where penetrated, are mainly Dinantian to early Namurian fluviodeltaic and minor marine sediments (Fame Group) or Dinantian platform carbonates (Zeeland Formation). Locally in the south, the Whitehurst Group rests on Lower Paleozoic basinal marine sediments. |
| Definition of Upper Boundary: |
In the north of the area, and locally elsewhere, the Whitehurst Group is unconformably overlain by Permian desert sediments of the Rotliegend Group. In central and southern areas, the Whitehurst Group is generally overlain conformably by coal measures of the Conybeare Group. |
| Thickness: |
1600 m +. |
| Geographical Limits: |
none recorded or not applicable
|
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| Cameron, T D J. 1993. 5. Carboniferous and Devonian 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. |
| Aitkenhead, N, Bridge, D M, Riley, N J, and Kimbell, S F. 1992. Geology of the country around Garstang. Memoir of the British Geological Survey, Sheet 67 (England and Wales) |
| Stubblefield, C J and Trotter, F M, 1957. Divisions of the Coal Measures on Geological Survey Maps of England and Wales. Bulletin of the Geological Survey of Great Britain, No.13, p.1-5. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
