The BGS Lexicon of Named Rock Units — Result Details

Glascoed Mudstone Formation

Computer Code: GLMD Preferred Map Code: notEntered
Status Code: Full
Age range: Wenlock Epoch (SW) — Wenlock Epoch (SW)
Lithological Description: Calcareous silty mudstones and siltstones, with limestone nodules, localised thin bentonitic clays, and very fossiliferous containing a diverse shelly fauna, mainly of brachiopods.
Definition of Lower Boundary: Not seen.
Definition of Upper Boundary: At the base of sandstone-dominated beds of the Ton Siltstone Formation.
Thickness: At least 220 m thick.
Geographical Limits: The central part of the (Silurian) Usk Inlier, South Wales.
Parent Unit: Not Applicable (-)
Previous Name(s): Wenlock Shales (-933)
Alternative Name(s): Part Of: Coalbrookdale Formation
Stratotypes:
Type Section  Railway cutting by the Royal Ordnance Factory, near Bryn Farm, Glascoed, 3 km north-west of Usk. Barclay, 1989; Walmsley, 1882, p.5. 
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. 
Walmsley, V G. 1982. In: The Silurian inliers of the south-eastern Welsh Borderland. Lawson, J D, Curtis, M L K, Squirrell, H C, Tucker, E V and Walmsley, V G. Geologists' Association Guide No. 5. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E232