| Computer Code: |
TRBB |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Silurian Period (S)
— Early Devonian Epoch (DL) |
| Lithological Description: |
Red, calcretised siltstones with grey to brown massive limestone or dolomite calcretes, sporadic thin sandstones and extraformational and intraformational conglomerates.
Ephemeral nonsaline playa lakes (Allen, 1965a).
Age not known, but likely to be late Silurian to Early Devonian. |
| Definition of Lower Boundary: |
The lower boundary is transitional, and placed where the conglomerates of the underlying Bodafon Formation are overlain by red siltstones. |
| Definition of Upper Boundary: |
The upper boundary is placed at an erosion surface cut in a thick, massive calcrete at the top of the formation on the south side of Traeth yr Ora, where extraformational conglomerate at the base of the Porth-y-Mor Formation is overlain by the calcrete. Note that this is higher than the position cited by Allen (1965a) (Davies, 2005). To the south, the formation is cut out by an unconformity at the base of the Porth-y-Mor Formation. |
| Thickness: |
About 165 m. |
| Geographical Limits: |
Restricted to a narrow outcrop on the south side of Traeth Dulas and a small outcrop on the north side of Traeth Dulas. |
| Parent Unit: |
Dulas Bay Subgroup (DULB)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Low cliffs [SH 487 888 to 489 887], which include the cove of Traeth Bach, north and east of the knoll on the south side of Traeth Dulas. |
| Reference(s): |
| Barclay, W J, Davies, J R, Hillier, R D, and Waters, R A. 2015. Lithostratigraphy of the Old Red Sandstone successions of the Anglo-Welsh Basin. British Geological Survey Research Report, RR/14/02. 96pp. |
| Allen, J R L. 1965. The sedimentation and palaeogeography of the Old Red Sandstone of Anglesey, North Wales. Proceedings of the Yorkshire Geological Society, Vol. 35, 139-185. |
| Davies, J R. 2005. Porth-y-Mor. 221-228 in Barclay, W J, Browne, M A E, McMillan, A A, Pickett, E A, Stone, P, and Wilby, P R. 2005. The Old Red Sandstone of Great Britain. Geological Conservation Review Series, No. 31. |
| 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: |
| none recorded or not applicable |
