| Computer Code: |
SUB |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Courceyan Substage (CF)
— Chadian Substage (CI) |
| Lithological Description: |
Pale grey well-sorted crinoidal limestone, oolitic in upper part. Deposited in a shallow marine setting. |
| Definition of Lower Boundary: |
Taken at the junction between the dolomitised packstones of the underlying Black Rock Limestone Subgroup and the undolomitised crinoidal limestones of the Bed. The boundary needs further investigation. |
| Definition of Upper Boundary: |
Taken at the junction of crinoidal limestone of the Bed and the oolites of the overlying Gully Oolite Formation. Boundary needs further investigation. |
| Thickness: |
6m at Southmead, near Bristol, to 21m in the Tytherington area. |
| Geographical Limits: |
Bristol area [ST 60 74], Tytherington area [ST 67 88] and Monmouth and Chepstow area [ST 53 93]. |
| Parent Unit: |
Gully Oolite Formation (GUO)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
South face of Grovesend Quarry, Tytherington, north of Bristol. Entire sequence seen, comprising 21m of very fossiliferous crinoidal limestones. The lower contact with dolomites of Black Rock Limestone Subgroup is seen, as is the upper contact with the Gully Oolite Formation. It is currently uncertain which of these units should be considered the Parent of the Sub-Oolite Bed. |
| Reference(s): |
| Vaughan, A, 1905. The palaeontological sequence in the Carboniferous Limestone of the Bristol area. Quarterly Journal of the Geological Society of London, Vol.61, 181-307. |
| Kellaway, G A and Welch, F B A. 1955. The Upper Old Red Sandstone and Lower Carboniferous rocks of the Bristol and the Mendips compared with those of Chepstow and the Forest of Dean. Bulletin of the Geological Survey of Great Britain, No.9, p.1-21. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
