The BGS Lexicon of Named Rock Units — Result Details

St Maughans Formation

Computer Code: SMG Preferred Map Code: SMg
Status Code: Full
Age range: Early Devonian Epoch (DL) — Early Devonian Epoch (DL)
Lithological Description: Interbedded purple, brown and green sandstones and red mudstones with intraformational conglomerates containing calcrete clasts.
Definition of Lower Boundary: Placed at top of Bishop's Frome ('Psammosteus') Limestone Member of the Raglan Mudstone Formation.
Definition of Upper Boundary: At base of Brownstones and (locally) Senni Beds, where sandstone-dominated sequences begin.
Thickness: c.400-700m.
Geographical Limits: Welsh Borderland.
Parent Unit: Ditton Subgroup (DTG)
Previous Name(s): St Maughan's Group (-1190)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  M 50 Motorway section, near Ross-on-Wye (Allen and Dineley, 1976). 
Type Area  Vicinity of the village of St Maughan's, Gwent. 
Reference(s):
Brandon, A. 1989. Geology of the country between Hereford and Leominster. Memoir for 1:50 000 Geological Sheet 198. 
Pocock, R W, 1940. South Wales and Bristol district. "In" Summary of Progress for 1938, p.25-26. Geological Survey of Great Britain. (London: Her Majesty"s Stationery Office). 
Welch, F B A and Trotter, F M. 1961. Geology of the country around Monmouth and Chepstow. Explanation of one-inch geological sheets 233 and 250. Memoir of the Geological Survey of Great Britain. 
Allen, J R L and Dineley, D L. 1976. The succession of the Lower Old Red Sandstone (Siluro-Devonian) along the Ross - Tewkesbury Spur Motorway (M50), Hereford and Worcester. Geological Journal, Vol.11, 1-14. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E198 E216 E232 E263 E249 E233 E234 E230 E212 E197 E213 E214 E199 E181 E250