The BGS Lexicon of Named Rock Units — Result Details

Twiston Sandstone Member

Computer Code: TTS Preferred Map Code: notEntered
Status Code: Full
Age range: Holkerian Substage (CQ) — Holkerian Substage (CQ)
Lithological Description: Pale to dark grey, locally bioclastic siliceous, calcareous, thin- to thick-bedded, fine- to medium-grained sandstone.
Definition of Lower Boundary: Lower boundary taken at sharp base of sandstone of the Twiston Sandstone Member where it rests conformably on mudstones and thin calcisiltites of the Hodder Mudstone Formation (undifferentiated) and unconformably on limestones of the Embsay Limestone Member in the Lothersdale Anticline.
Definition of Upper Boundary: Top is a conformable upward passage from sandstone of the Twiston Sandstone Member to mudstones and thin calcisiltites of the Hodder Mudstone Formation (undifferentiated). Upper boundary taken at the base of the lowermost mudstone in a succession dominated by mudstone.
Thickness: To 4m.
Geographical Limits: Southern limb of Clitheroe Anticline [SD 82 44], and the Lothersdale Anticline [SD 93 44] and Skipton Anticline [SE 00 54] within the Craven Basin, northwest England.
Parent Unit: Hodder Mudstone Formation (HOM)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Stream section 0.23km northwest of Clough Head, Twiston, near Clitheroe, Lancashire, England. Full thickness seen. 
Reference Section  Embsay Beck, near Skipton, north Yorkshire, England. Sandstone underlain by shale of the Hodder Mudstone Formation (undifferentiated). 
Reference Section  Disused Quarry at Dowshaw Delf, near Skipton, north Yorkshire, England. Angular unconformity above Embsay Limestone Member seen in section. 
Reference(s):
Earp, J R, Magraw, D, Poole, E G, Land, D H and Whiteman, A J, 1961. Geology of the country around Clitheroe and Nelson. Memoir of the Geological Survey of Great Britain, Sheet.68, England and Wales, pp.346. 
Riley N J. 1990. Stratigraphy of the Worston Shale Group (Dinantian) Craven Basin, north-west England. Proceedings of the Yorkshire Geological Society, Vol. 48, 163-187. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable