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):
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. 
Robertson, T, 1927. South Wales Coalfield, part 2. Abergavenny, 2nd Edition.Memoirs of the Geological Survey of Great Britain, p.42. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E232