The BGS Lexicon of Named Rock Units — Result Details

Treffgarne Volcanic Formation

Computer Code: TREV Preferred Map Code: notEntered
Status Code: Pending Upgrade
Age range: Tremadoc Series (O1) — Tremadoc Series (O1)
Lithological Description: Blue-green keratophyric or andesitic lavas, basaltic andesite, purple, red and green andesitic tuffs and volcanic agglomerate.
Definition of Lower Boundary: Drawn at base of Treffgarne Volcanic Group where it rests unconformably on green/grey micaceous shales, sandy mudstones and grits of the Treffgarne Bridge Beds.
Definition of Upper Boundary: Drawn at conformable upward passage from tuffs and volcanic agglomerate of Treffgarne Volcanic Formation to shales, tuff, ashy sandstone and rhyolitic tuff of the Brunel Beds.
Thickness: c.150m
Geographical Limits: Cleddau Valley, south-west Dyfed.
Parent Unit: Not Applicable (-)
Previous Name(s): Treffgarne Andesite Group (-3092)
Treffgarne Andesitic Series (-3093)
Treffgarne Volcanic Series (-3094)
Treffgarne Volcanic Group (-4375)
Alternative Name(s): none recorded or not applicable
Partial Type Section  South end of main quarry by A40 trunk road north of Treffgarne, southwest Dyfed, Wales. 
Type Area  Cleddau Valley, near Treffgarne, southwest Dyfed, Wales. 
Reference Section  Within quarry near Wolfsdale, southwest Dyfed, Wales. 
Thomas, H H, "In" Strahan, A and others, 1914. South Wales Coalfield, part XI, Haverfordwest. Memoir of the Geological Survey of Great Britain. 
Brown, M J and others, 1987. Volcanogenic mineralisation in the Treffgarne area, south-west Dyfed, Wales. Mineral Reconnaisance Programme, Report No.86. British Geological Survey. 
Cantrill, T C and others, 1916. South Wales Coalfield, part XII, Milford. Memoir of the Geological Survey of Great Britain. 
Thomas, H H, and Cox, A H. 1924. The Volcanic Series of Trefgarn, Roch and Ambleston (Pembrokeshire). Quarterly Journal of the Geological Society, Vol.80, p.520-548. 
1:50K maps on which the lithostratigraphical unit is found, and map code used: