| Computer Code: |
PLB |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Frasnian Age (DR)
— Famennian Age (DA) |
| Lithological Description: |
[Obsolete: use PNYF] The Plateau Beds Formation unconformably overlies the Brownstones Formation. A slight angular discordance between the formations is present on Bannau Sir Gaer and Fan Brycheiniog (Allen, 1964; Lovell, 1975). Descriptions were given by Hall et al. (1973) and Taylor and Thomas (1975). The formation comprises red-brown and purple quartzitic sandstones, locally pebbly and conglomeratic, and interbeds of red-brown mudstone. The sandstones are generally harder than the Brownstones, and form resistant cappings to the Brecon Beacons. |
| Definition of Lower Boundary: |
Sharp junction where the formation unconformably overlies the softer drab red sandstones of the Brownstones Formation, a slight angular discordance between the formations being visible locally, as on Bannau Sir Gaer and Fan Brycheiniog. A quartz granule bed marks the base of the formation. |
| Definition of Upper Boundary: |
At sharp junction where the red sandstones of the formation are overlain by the grey and grey-green sandstones of the Grey Grits Formation. |
| Thickness: |
Up to 36 m. |
| Geographical Limits: |
North crop of the South Wales Coalfield from Pont Clydach [SO 740 194] and Blaen Onneu [SO 167 169]. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Cliffs at head of the Duffryn Crawnon valley, Powys, South Wales [SO 0908 1547 to SO 0930 1518]. Lovell, 1978a, b. |
| Reference(s): |
| Lovell, R. 1975. Abercriban, Powys. Pp. 72-73 in Friend, P. F. and Williams, B. P. J. (editors). International Symposium on the Devonian System (P.A.D.S. 1978) September 1978. A field guide to selected outcrop areas of the Devonian of Scotland, the Welsh Borderland and South Wales. The Palaeontological Association. |
| Strahan, A, Gibson, W, and Cantrill, T C. 1904. The geology of the South Wales Coalfield, Part V. The country around Merthyr Tydfil. First Edition. Memoir of the Geological Survey of Great Britain. Sheet 231 (England and Wales). |
| Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. |
| Lovell, R W W. 1978a. The sedimentology and stratigraphy of the Upper Old Red Sandstone and Lower Limestone Shales of the South Wales Coalfield. Unpublished PhD thesis, University of Bristol. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E232
E230
E213
E214
|
