The BGS Lexicon of Named Rock Units — Result Details

Mynydd-Tarw Group

Computer Code: MYT Preferred Map Code: notEntered
Status Code: Full, pending ratification
Age range: Harnagian Substage (OG) — Harnagian Substage (OG)
Lithological Description: Blue-grey, cleaved mudstones and shales with silt or grit laminae, sporadic ashes or ashy grit as well as dirty blue grits or sandstones.
Definition of Lower Boundary: Drawn at base of shale and mudstone with ash and grit of the Mynydd-Tarw Group where it rests conformably on the Gardden-Fawr Ash of the Gwern-Feifod Group.
Definition of Upper Boundary: Drawn at conformable upward passage from flaggy mudstones and shales of the Mynydd-Tarw Group to the Cwm-Clwyd Ash of the Allt-Tair-Ffynnon Beds.
Thickness: Not defined.
Geographical Limits: Clwyd, Wales.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Mynydd-Tarw, West of LLanarmon, Dyffryn-Ceiriog, Clwyd, Wales. 
Reference(s):
Cantrill,T C, and others. 1914. Denbighshire and Shropshire district. Summary of Progress of the Geological Survey of Great Britain, for 1914, p.7. 
Williams, A and others, 1972. A correlation of Ordivician rocks in the British Isles. Geological Society of London Special Report No.3. 
Wedd, C B, Smith, B, King, W B R and Wray, D A. 1929. Geology of the country around Oswestry. Memoir of the Geological Survey of Great Britain, Sheet 137. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable