The BGS Lexicon of Named Rock Units — Result Details

ST MAUGHANS FORMATION
Computer Code: SMG  Status Code: FORMAL ENTRY 
Preferred Map Code: SMg 
Age or Age Range: [ DL ] EARLY DEVONIAN  to [  ]  
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: Parent Unit Code:
LOWER OLD RED SANDSTONE  LORS
Previous Name(s): Previous Code(s):
ST MAUGHAN'S GROUP  SMG 
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):
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). 
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. 
Brandon, A. 1989. Geology of the country between Hereford and Leominster. Memoir for 1:50 000 Geological Sheet 198. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
Map Code Sheet Name
E  234
E  216
E  263
E  249
E  232
E  233
E  198
E  197
E  212
E  213
E  199
E  230
E  214
E  181
E  250

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