| Computer Code: |
BRYS |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Chadian Substage (CI)
— Chadian Substage (CI) |
| Lithological Description: |
Massive, grey Waulsortian reefs, comprising dolomitised carbonate mudstone with locally abundant spar-filled fenestrae (stromatactoid structure) and sparse crinoid debris. Reefs are locally overlain by and pass into a flank facies comprising thin-bedded dark limestones and dolomites with cherts and thin mudstones. Stratigraphic position of flank facies uncertain and requires further investigation. |
| Definition of Lower Boundary: |
Taken at gradational boundary between medium- to thick-bedded crinoidal argillaceous packstones with chert nodules and shaly partings of the underlying Black Rock Limestone Subgroup, and the dolomitized reef limestones of the Formation. |
| Definition of Upper Boundary: |
Taken at junction of massive dolomitised reef limestones of the Formation and the overlying dark limestones with thin mudstones and cherts of the Linney Head Formation. Where the top of the Formation is in flank facies, the boundary is imprecise but taken at the increase in chert content at the base of the Linney Head Formation. |
| Thickness: |
80 m at type section in south Pembrokshire. |
| Geographical Limits: |
Castlemartin area [SR 95 98], southwest Pembrokshire. Passes northwards into the Black Rock Limestone Subgroup. |
| Parent Unit: |
Pembroke Limestone Group (PEMB)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
Variably accessible cliffs and foreshore at Berry Slade, Castlemartin, south Pembrokshire. Entire formation seen and comprises reef and flank facies. Lower contact with the Black Rock Subgroup and upper contact with the overlying Linney Head Formation seen. |
| Reference(s): |
| Waters, C N, Barclay, W J, Davies, J R and Waters, R A. In press. Stratigraphical framework for Carboniferous successions of Southern Great Britain (Onshore). British Geological Survey Research Report, RR/05/06. |
| George, T N, Johnson, G A L, Mitchell, M, Prentice, J E, Ramsbottam, W H C, Sevastopulo, G D and Wilson, R B. 1976. A correlation of the Dinantian rocks of the British Isles. Special Report of the Geological Society of London, No 7. |
| Dixon, E E L. 1921. The Geology of the South Wales Coalfield, Part XIII , the country around Pembroke and Tenby, being an account of the region comprised in sheets 244 and 245. Memoir of the Geological Survey of Great Britain (HMSO). |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
