| Computer Code: |
WTA |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Famennian Age (DA)
— Tournaisian Age (CT) |
| Lithological Description: |
The formation consists of a lower conglomeratic facies (the Conglomerate Member) and an upper heterolithic unit (the Red-Grey, or Heterolithic) Member.
The Conglomerate Member consists of red sandstones, conglomerates and mudstones, and is markedly different in texture and composition from the underlying beds. The sandstones and conglomerates are rich in lithic debris and there is an abundance of calcrete in the mudstones, the facies being arranged in fining-upwards couplets. Thin sheets of intraformational conglomerate and overlying rippled sandstone occur within the mudstones.
The upper part of the formation (Red-Grey Member) is predominantly red, but is characterised by the incoming of sporadic grey-green sandstones and pebbly sandstones with well preserved plant fragments. The sandstones occur at the bases of fining-upwards sequences capped by calcretised red mudstones. Grey mudstones with spores, coalified plant debris and lingulids appear higher in the member, along with a few sheets of phosphatised pebble conglomerate. The topmost beds of the formation are red and grey sandstones with mudstone interbeds capped by a mature, calcareous sandstone with well-rounded quartz pebbles and sparse marine brachiopods and bryozoa. |
| Definition of Lower Boundary: |
The base of the formation is disconformable in northern exposures, resting on an erosion surface of the Gupton Formation, and transitional over an interval of 2 to 5 m in the south. |
| Definition of Upper Boundary: |
The upper boundary of the formation with the Avon Group is as described for the top of the Skrinkle Sandstones Subgroup. |
| Thickness: |
About 60 m at the type locality of West Angle Bay, comprising 43 m beds of the Conglomerate Member and 17 m of the Red-Grey Member. |
| Geographical Limits: |
Pembroke Peninsula. |
| Parent Unit: |
Skrinkle Sandstones Subgroup (SES)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North side of West Angle Bay [SM 852 034] (Barclay et al., 2015). |
| Reference Section |
South side of West Angle Bay [SM 852 034] (Barclay et al., 2015). |
| 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. |
| Bassett, M G, and Jenkins, T B H. 1977. Tournaisian conodont and spore data from the uppermost Skrinkle Sandstones of Pembrokeshire, South Wales. Geologica et Palaeontologica, Vol. 11, 121–134. |
| Dolby, G. 1971. Spore assemblages from the Devonian-Carboniferous transition measures in south-west Britain and southern Eire. Colloque sur la stratigraphie du Carbonifère, Les congrès et colloques de l'universite de Liège, Vol. 55, 267-274. |
| Higgs, K T, Clayton, G, and Keegan, J B. 1988. Stratigraphical and systematic palynology of the Tournaisian rocks of Ireland. Special Paper of the Geological Survey of Ireland, No. 7. |
| Marshall, J D. 1977. Sedimentology of the Skrinkle Sandstones Group (Devonian–Carboniferous), south-west Dyfed. Unpublished Ph.D thesis, University of Bristol. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
