| Computer Code: |
MFLD |
Preferred Map Code: |
notEntered |
| Status Code: |
Full |
| Age range: |
Sinemurian Age (JS)
— Sinemurian Age (JS) |
| Lithological Description: |
The dominant lithology is a creamy micrite in beds up to 0.3 m thick; large ammonites common, interbedded with thick (up to 10 m) calcareous mudstones |
| Definition of Lower Boundary: |
The lower boundary is taken at the base of the first significant limestone above the Saltford Shale. |
| Definition of Upper Boundary: |
The upper boundary is not exposed, but is presumed to be at the upward change from a dominantly limestone/medium grey mudstone sequence to the dark grey mudstones of the Charmouth Mudstone Formation. |
| Thickness: |
Approximately 20 m. |
| Geographical Limits: |
The member has been mapped south-east and north-west from the village of Street. It dies out southwards around the village of Butleigh where individual units of the Blue Lias Formation merge into a single unit. |
| Parent Unit: |
Blue Lias Formation (BLI)
|
| Previous Name(s): |
Division D [Obsolete Name and Code: Use MFLD]
(-4996)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| none recorded or not applicable |
| Reference(s): |
| Donovan, D T, and Kellaway, G A. 1984. Geology of the Bristol district: Lower Jurassic rocks. Memoir of the British Geological Survey, Bristol Special Sheet (England and Wales). |
| Donovan, D T. 1956. The zonal stratigraphy of the Blue Lias around Keynsham, Somerset. Proceedings of the Geologists' Association, Vol. 66, 182-212. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E296
|
