| 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. |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
