The BGS Lexicon of Named Rock Units — Result Details

Hafotty Formation

Computer Code: HF Preferred Map Code: Hf
Status Code: Full
Age range: Comley Series (EC) — St David's Series (ED)
Lithological Description: Grey, thinly-bedded turbiditic sandstones and mudstones interbedded with manganiferous mudstones.
Definition of Lower Boundary: Sharp conformable contact on coarse-grained, thick bedded turbiditic sandstones of the Rhinog Formation.
Definition of Upper Boundary: Conformably overlain by coarse-grained turbiditic sandstones of the Barmouth Formation.
Thickness: 170 to 300m
Geographical Limits: Harlech Dome, North Wales.
Parent Unit: Harlech Grits Group (HGG)
Previous Name(s): Hafotty Group (-312)
Alternative Name(s): Manganese Group
Trwyn Y Fulfran Formation
Stratotypes:
Partial Type Section  Haffoty mines. On hillside above Llanaber. Basal contact and up to 30m of overlying beds are exposed. 
Reference(s):
Woodland, A W. 1939. The petrography and petrology of the Lower Cambrian manganese ore of West Merionethshire. Quarterly Journal of the Geological Society of London, Vol.95, 1-35. 
Andrew, A R. 1910. The geology of the Dolgelly gold belt, North Wales. Geological Magazine, Vol.7, 159-171, 201-211, 261-271. 
Woodland, A W. 1938. Petrological studies in the Harlech Grit Series of Merionethshire. Geological Magazine, Vol.75, 366-382 and 440-454. 
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. 
Cowie, J W, Rushton, A W A and Stubblefield, C J, 1972. A correlation of Cambrian rocks in the British Isles. Special Report of the Geological Society of London, No.2, p.26. 
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. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E119 E135 E149