| Computer Code: |
CDHO |
Preferred Map Code: |
notEntered |
| Status Code: |
Index Level |
| Age range: |
Chadian Substage (CI)
— Brigantian Substage (CX) |
| Lithological Description: |
Hard dark grey crinoidal oolitic bioclastic limestone with interbedded dark grey shales and mudstones. |
| Definition of Lower Boundary: |
Boundary is marked by the incoming of more massive oolitic and crinoidal rocks above the relatively unfossiliferous calcite-mudstones of the Clifton Down Group, or where present, the Middle Cromhall Sandstone. |
| Definition of Upper Boundary: |
Change to predominantly arenaceous sandstone facies of the Upper Cromhall Sandstone or the sub-Namurian unconformity. |
| Thickness: |
175 feet (54m). |
| Geographical Limits: |
Bristol and north Somerset area. Lateral facies change to west south Wales and Forest of Dean. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| none recorded or not applicable |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
