| Computer Code: |
CDRL |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Holkerian Substage (CQ)
— Holkerian Substage (CQ) |
| Lithological Description: |
Dark grey crinoidal and splintery limestones, with chert in the upper part. |
| Definition of Lower Boundary: |
Taken at the appearance of dark limestones of the Cheddar Limestone Member above the ooidal and ooidal/crinoidal limestones of the Burrington Oolite Subgroup. Boundary equates with local base of the Clifton Down Limestone Formation. |
| Definition of Upper Boundary: |
Taken at the incoming of pale grey ooidal limestones of the Cheddar Oolite Member above the dark limestones of the Cheddar Limestone Member. |
| Thickness: |
30-37m in the Cheddar area. |
| Geographical Limits: |
Chedder [ST 48 54] area, central Mendip. Passes laterally into rocks of the Clifton Down Limestone Formation in all directions. |
| Parent Unit: |
Clifton Down Limestone Formation (CDL)
|
| Previous Name(s): |
Cheddar Limestone Formation
(-758)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Section |
North side of the Cheddar Gorge, Mendip, Somerset. The entire unit is exposed [35m thick] and comprises dark grey crinoidal limestones. The lower contact with the underlying Clifton Down Limestone and the upper contact with the overlying Cheddar Oolite Member are exposed. (see Green and Welch, 1965.) |
| Reference(s): |
| Green, G W and Welch F B A, 1965. The geology of the country around Wells and Chedder. Memoir of the Geological Survey of England and Wales, Sheet 280. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E280
|
