| Computer Code: |
BCSH |
Preferred Map Code: |
BCSH |
| Status Code: |
Pending Upgrade |
| Age range: |
Onnian Substage (ON)
— Onnian Substage (ON) |
| Lithological Description: |
Black and dark-grey graptolitic shales. Pyritous. |
| Definition of Lower Boundary: |
Base disconformable on Pen-y-Garnedd calcareous tuffs and tuffites in West Berwyns or The Bryn Siltstone Formation in the North Berwyns. |
| Definition of Upper Boundary: |
Unconformably overlain by the siltstones of the Dolhir Formation. |
| Thickness: |
Thickness of type section - c.30 metres. Thickness of lateral variation - 0-30 metres. |
| Geographical Limits: |
Not defined. |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
Blaen Y Cwm Beds [Obsolete Name and Code: Use BCSH]
(-4447)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Bala, Sheet 136. |
| Reference(s): |
| Brenchley, P J. 1978. The Caradocian rocks of the North and West Berwyn Hills. Geological Journal, Vol. 13, 137-164. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E120
|
