The BGS Lexicon of Named Rock Units — Result Details

Garth Grit Member

Computer Code: GAG Preferred Map Code: GaG
Status Code: Pending Upgrade
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Quartzose conglomeratic sandstone.
Definition of Lower Boundary: Unconformity on siltstones of Dol-cyn-Afon Formation or mudstones of Dolgellau Formation (both in Mawddach Group): forms the basal unit of the Allt Lwyd Formation.
Definition of Upper Boundary: At base of siltstones and sandstones of the undivided Allt Lwyd Formation.
Thickness: 0 to 70m
Geographical Limits: South central Snowdonia.
Parent Unit: Allt Lwyd Formation (ALL)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  North of Tanygrisiau Dam. Howells and Smith, 1997. 
Reference(s):
Allen, P M and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 [England and Wales]. [London: HMSO.] 112pp. 
Howells, M F and Smith, M. 1997. Geology of the country around Snowdon. Memoir of the British Geological Survey, Sheet 119 (England and Wales). (London: The Stationery Office). 104pp. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E119 E136 E135