The BGS Lexicon of Named Rock Units — Result Details

Dolwen Formation

Computer Code: DOG Preferred Map Code: DoG
Status Code: Full
Age range: Comley Series (EC) — Comley Series (EC)
Lithological Description: Fine- to medium-grained sandstone with siltstone, pebbly sandstone and conglomerate.
Definition of Lower Boundary: Unexposed. Seen in the Bryn-teg Borehole, the base appears to lie unconformably on rocks of the Bryn-teg Volcanic Formation.
Definition of Upper Boundary: Overlain by the Llanbedr Formation. The boundary is conformable and transitional.
Thickness: 575m
Geographical Limits: Core of the Dolwen Pericline (upper part); lower part proved in the Bryn-teg Borehole, SH63SE/1 [SH 6992 3214] .
Parent Unit: Harlech Grits Group (HGG)
Previous Name(s): Dolwen Grits (-1512)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  West and south of Bryn-teg Farm. 
Partial Type Section  Afon Crawcwellt. For the purple sandstones at the top of the Formation. 
Reference(s):
Allen, P M and Jackson, A A. 1978. Bryn-teg Borehole, North Wales. Bulletin of the Geological Survey of Great Britain, No. 61. 
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. 
Matley, C A and Wilson, T S. 1946. The Harlech Dome, North of the Barmouth Estuary. Quarterly Journal of the Geological Society of London, Vol.102, 1-40. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E135