The BGS Lexicon of Named Rock Units — Result Details

Yr Arddu Tuffs Formation

Computer Code: YATU Preferred Map Code: YAT
Status Code: Full
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Welded acidic ash-flow tuffs with pyroclastic breccias.
Definition of Lower Boundary: Lies on sedimentary rocks of the Cwm Eigiau Formation.
Definition of Upper Boundary: Underlies part of the Cwm Eigiau Formation.
Thickness: About 200m
Geographical Limits: Limited to an area around Yr Arddu, 6km east of Moel Hebog.
Parent Unit: Snowdon Volcanic Group (SV)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Reference Section  Yr Arddu. 
Howells, M F, Campbell, S D G, Reedman, A J and Tunnicliff, S P, 1987. A fissure-controlled acidic volcanic centre (Ordovician) at Yr Arddu, North Wales. Geological Journal, Vol.22, 133-149 
1:50K maps on which the lithostratigraphical unit is found, and map code used: