The BGS Lexicon of Named Rock Units — Result Details

Phynis Mudstone Member

Computer Code: PHS Preferred Map Code: notEntered
Status Code: Full
Age range: Chadian Substage (CI) — Chadian Substage (CI)
Lithological Description: Dark grey, laminated mudstones, finely micaceous, silty and calcareous, interbedded with dark grey, laminated, blocky and calcareous siltstones.
Definition of Lower Boundary: At the type locality and also in the Whitewell Anticline, the dark grey mudstones rest conformably upon crinoidal packstones of the Clitheroe Limestone Formation. Elsewhere, the mudstones are underlain conformably by lithoclast breccias and boulder beds, packstones, floatstones and grainstones of the Limekiln Wood Limestone Member.
Definition of Upper Boundary: In the Slaidburn and Whitewell anticlines the dark grey mudstones are overlain conformably by pale blue-grey wackestones and packstones of the Whitemore Limestone Member. Elsewhere, the mudstones are overlain by non-micaceous, laminated mudstones interbedded with laminated calcisiltites of the Hodder Mudstone Formation (undifferentiated).
Thickness: Up to 350 m, with the thickest development in the Plantation Farm Anticline.
Geographical Limits: The western part of the Craven Basin, including Cow Ark (SD 65 46), Plantation Farm (SD 66 43), Slaidburn (SD 71 53) and Whitewell (SD64 47) anticlines. Not shown on published maps.
Parent Unit: Hodder Mudstone Formation (HOM)
Previous Name(s): Phynis Shales (-450)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Phynis Beck, 0.16 km SE of Phynis Farm, Slaidburn: the lowest beds lie about 2 m above the crinoidal packstones of the Clitheroe Limestone Formation, the boundary is not exposed. The thickness of the succession exposed is not recorded. Riley, 1990. 
Reference(s):
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. 
Parkinson, D, 1936. The Carboniferous succession in the Slaidburn district, Yorkshire. Quarterly Journal of the Geological Society of London. Volume 92. p.294-331. 
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) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E060 E067 E068