The BGS Lexicon of Named Rock Units — Result Details

Samlesbury Formation

Computer Code: SAML Preferred Map Code: notEntered
Status Code: Full
Age range: Chokierian Substage (CH) — Alportian Substage (CO)
Lithological Description: A dark grey mudstone, common thin shaly mudstones, subordinate sandstone and siltstone, and locally in the Bradford area, a thick, coarse-grained, cross-bedded sandstone (Brocka Bank Grit).
Definition of Lower Boundary: The sharply conformable base of the formation is taken at the base of the dark grey shaly mudstone of the Isohomoceras subglobosum Marine Band with eponymous fauna, where the formation overlies the interbedded sandstone, siltstone and mudstone succession of the Silsden Formation. Where the marine band is absent from the interval, the base of the formation is taken at the top of the Lower Follifoot Grit in the southern part of the Askrigg Block, or the base of a mudstone succession with Lingula in the Stainmore Trough. In the southern part of the Central Pennine Basin it is taken at the base of the first thick quartz-feldspathic sandstone of Chokierian to Alportian age, present above the Bowland Shale Formation.
Definition of Upper Boundary: The sharp conformable base, of the dark grey shaly mudstone of the Hodsonites magistrorum Marine Band, including eponymous fauna, overlain by the siltstone-dominated lower part of the Hebden Formation, underlain by the mudstone-dominated succession of the Samlesbury Formation. Where the marine band is absent from the interval, the top of the formation equates with the base of the Cayton Gill Shale in the south of the Askrigg Block (Wilson, 1977) and the base of the Mousegill Marine Beds in the Stainmore Trough (Owens and Burgess, 1965).
Thickness: Lancaster 64m; Bradford 75m; less than 30m thick along the southern part of the Askrigg Block, and in the Stainmore Trough the succession is no more than 20m thick.
Geographical Limits: The Craven Basin of north Lancashire and north Yorkshire, between Lancaster [SD 47 61], Pendle Hill [SD 80 41], Skipton Moor [SE 00 50] and Harrogate [SE 30 55] and the southern part of the Askrigg Block and the Stainmore Trough.
Parent Unit: Millstone Grit Group [See Also MIGR] (MG)
Previous Name(s): Kirkbeck Formation [Obsolete Name And Code: See SAML And HEBD] (KBF)
Middleton Grit Group [Obsolete Name And Code: Part Of SILS; See Also MN] (MDGT)
Sabden Shales (SDSH)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Composite section: The River Darwin at Samlesbury Bottoms [SD 618 291] shows dark grey mudstones and common marine shales, including the marine bands that define the base and top of the formation. Moore, 1930; Price et al.1963. 
Partial Type Section  Stonehead Beck, Cowling, North Yorkshire, comprising a continuously exposed 40m succession including the base Chokierian stratotype, which equates to the base of the Samlesbury Formation, and defines the position of the Mid-Carboniferous Boundary. Riley et al.,1995 
Reference(s):
Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. 
Price, D, Wright, W B, Jones, R C B, Tonks, L H and Whitehead, T H. 1963. Geology of the country around Preston. Memoir of the Geological Survey of Great Britain, Sheet 75 (England and Wales). 
Moore, E W J. 1930. A section in the Sabden Shales on the River Darwen, near Blackburn. Journal of the Manchester Geological Association, Vol.1, 103-108. 
Brandon, A, Aitkenhead, N, Crofts, R G, Ellison, R A, Evans, D J and Riley, JN J, 1998. Geology of the country around Lancaster. Memoir of the British Geological Survey, Sheet 59 (England and Wales). 
Riley, N J, Claoue-Long, J C, Higgins, A C, Owens, B, Spears, A, Taylor, L and Varker, W J. 1995. Geochronometry and geochemistry of the European mid-Carboniferous boundary global stratotype proposal, Stonehead Beck, North Yorkshire, UK. Annales de la Societe geologique de Belgique, Vol.116, 275-289. 
Stephens, J V, Mitchell, G H and Edwards, W N. 1953. Geology of the country between Bradford and Skipton. Memoir of the Geological Survey of Great Britain, Sheet 69 (England and Wales). 
Owens, B and Burgess, I C. 1965. The stratigraphy and palynology of the Upper Carboniferous outlier of Stainmore, Westmorland. Bulletin of the Geological Survey of Great Britain, N.23, 17-44. 
Wilson, A A. 1977. The Namurian rocks of the Fewston area. Transactions of the Leeds Geological Association, Vol.9, 1-42. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E059 E069 E075