| Computer Code: |
YA |
Preferred Map Code: |
YA |
| Status Code: |
Pending Upgrade |
| Age range: |
Ashgill Series (OA)
— Ashgill Series (OA) |
| Lithological Description: |
Very silty mudstones with abundant siltstone laminae and scattered thin beds of sandstone. Units of thick-bedded sandstone locally present. Slump folding and destratification commonly present. |
| Definition of Lower Boundary: |
Sharp incoming of mudstones with siltstone laminae and no burrows, above burrow mottled mudstones of the Nantmel Formation. Locally rests sharply on top of Doldowlod Conglomerate Member of Nantmel Formation. |
| Definition of Upper Boundary: |
Either gradational and taken at incoming of sandstone dominant sequence of Scrach Formation, or sharp, where overlain by mudstones lacking silt laminae of the Cwmere Formation or Tycwtta Mudstones. |
| Thickness: |
Up to 1200 metres. |
| Geographical Limits: |
Central Wales. |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Road section on A470 at base of hill, known as Yr Allt, north of Newbridge on Wye. |
| Reference(s): |
| 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. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E179
|
