The BGS Lexicon of Named Rock Units — Result Details

Shale Group [May Be Obsolete = Part Of Millstone Grit]

Computer Code: SH Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Arnsbergian Substage (CG) — Yeadonian Substage (CY)
Lithological Description: Dark grey, blue and black shales with bands of grit, sandstone and quartzite. The sandstones are lenticular.
Definition of Lower Boundary: Drawn at base of sandstone of the shale group where it rests conformably on shale of the basal grit.
Definition of Upper Boundary: Drawn at conformable upward passage from dark shales of the Shale Group to brown, green and yellow sandstones and quartzites of the Farewell Rock.
Thickness: About 100 metres thick.
Geographical Limits: North Crop of South Wales Coalfield.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Middle Shales
Stratotypes:
Type Area  North crop of South Wales Coalfield, Wales. From Nolton, near Haverfordwest, Dyfed, to the River Clydach, near Abergavenny. 
Reference(s):
Jones, D G, 1974. The Namurian in South Wales. "In" Owen, T R. The Upper Palaeozoic and past-Palaeozoic rocks of Wales. 
George, T N. 1970. British Regional Geology, South Wales, Third Edition. British Geological Survey. 
Robertson, T, 1927. South Wales Coalfield, part 2. Abergavenny, 2nd Edition.Memoirs of the Geological Survey of Great Britain, p.42. 
Barclay, W J, Jackson, D I, Mitchell, M, Owen, B, Riley, N J, White, D E, Strong, G E and Monkhouse, R A. 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny. Memoir of the British Geological Survey. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E232