| Computer Code: |
PEG |
Preferred Map Code: |
PEG |
| Status Code: |
Full |
| Age range: |
Sheinwoodian Age (SS)
— Sheinwoodian Age (SS) |
| Lithological Description: |
Mudstones with greywacke sandstones, medium- to coarse-grained in thick beds, many isolated, but commonly in packets, forming 20%-100% of the packet. |
| Definition of Lower Boundary: |
Diachronous within the lower Wenlock; closes with the upper boundary near the lateral margins of the turbidite basin. Underlying formation: Nant-ysgollon Shales. |
| Definition of Upper Boundary: |
Diachronous within the lower Wenlock (see lower boundary). Overlying formation : Nantglyn Flags. |
| Thickness: |
Various, 0- >100m |
| Geographical Limits: |
Erected in 1969 in isolation, for the Newtown area only. Subsequent mapping has joined the outcrop to that of the Denbigh Grits in Clwyd via the Llangadfan Syncline, Potter (1971), Cummins (1967), BGS 1:50k sheet 150 (Bala), Alder (1976), Campbell (1983), BGS 1:50k sheet 120 (Corwen), and GS 1" Old Series Sheet 60 (Montgomery). |
| Parent Unit: |
Not Available (!)
|
| Previous Name(s): |
Denbighshire Grits and Shales [Obsolete Name and Code: Use PEG]
(-4248)
|
| Alternative Name(s): |
Denbigh Grits Formation
|
| Stratotypes: |
| Type Section |
Not designated (better sections probably on adjacent ground to west). Representative locality : Penstrowed Quarry [SO 0676 9088], west of Newtown, Powys. |
| Reference Section |
Penstrowed Quarry. |
| Reference(s): |
| Cummins, W A. 1963. The geology of the northern part of the Llangadfan Syncline, Montgomeryshire. Unpublished PhD thesis, University of Liverpool. |
| Campbell, S D G. 1983. The geology of an area between Bala and Betws-y-Coed, North Wales. Unpublished PhD Thesis, University of Cambridge. |
| Cummins, W A. 1957. The Denbigh Grits: Wenlock greywackes in Wales. Geological Magazine, Vol.94, 437-451. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E165
E179
E151
E164
E150
E180
E120
E137
|
