The BGS Lexicon of Named Rock Units — Result Details

Swch Gorge Tuff Formation

Computer Code: SGT Preferred Map Code: SGT
Status Code: Pending Upgrade
Age range: Soudleyan Substage (OY) — Soudleyan Substage (OY)
Lithological Description: Grey porcellanous felsic ash-flow tuffs and interbedded volcaniclastic sandstones, with local thin mudstones.
Definition of Lower Boundary: Conformably overlies mudstones and siltstones of the Pen-plaenau Siltstone Formation.
Definition of Upper Boundary: Conformably overlain by mudstones of the Allt-tair-ffynnon Formation or Teirw Siltstone Formation.
Thickness: 30 to 90m
Geographical Limits: Not defined.
Parent Unit: Not Available (!)
Previous Name(s): Swch Gorge Tuff (-1816)
Alternative Name(s): none recorded or not applicable
Stratotypes:
none recorded or not applicable
Reference(s):
Brenchley, P J, 1978. The Caradocian rocks of the North and West Berwyn Hills. Geological Journal, Vol.13, 137-164. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E120 E136 E137