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):
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. 
Williams, A and others, 1972. A correlation of Ordivician rocks in the British Isles. Geological Society of London Special Report No.3. 
Cantrill,T C, and others. 1914. Denbighshire and Shropshire district. Summary of Progress of the Geological Survey of Great Britain, for 1914, p.7. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable