| Computer Code: |
MMI |
Preferred Map Code: |
MMI |
| Status Code: |
Full |
| Age range: |
Ashgill Series (OA)
— Ashgill Series (OA) |
| Lithological Description: |
Numerous thin sills of grey-green spessarite, lamprophyre and thicker composite sills of hornblende diorite, commonly melanocratic at the base, intruded into strata ranging from Precambrian to Ordovician (Tremadoc) age. |
| Definition of Lower Boundary: |
Not seen; no information on depth extent of the intrusive complex. |
| Definition of Upper Boundary: |
Taken at the unconformity between the sills and their host rocks and overlying strata of Devonian, Carboniferous and Triassic age. |
| Thickness: |
The individual sills range from c. 1m (lamprophyre), to about 60m (diorite). An aggregate thickness of 100 - 150m is probable |
| Geographical Limits: |
Most westerly occurrences are at the Wrekin, Shropshire. Easterly surface limit is the Nuneaton inlier, between Bedworth (SP 369 875) and Atherstone (SP 300 976). |
| Parent Unit: |
Not Applicable (-)
|
| Previous Name(s): |
none recorded or not applicable
|
| Alternative Name(s): |
Syenite or Diorite Intrusions
|
| Stratotypes: |
| Type Section |
Griff No. 4 Quarry. |
| Reference(s): |
| Bridge, D M, Carney, J N, Lawley, R S, and Rushton, A W A. 1998. Geology of the country around Coventry and Nuneaton. Memoir of the British Geological Survey, Sheet 169 (England and Wales). |
| Eastwood, T, Gibson, W, Cantrill, T C, and Whitehead, T H. 1923. The geology of country around Coventry, including an account of the Carboniferous rocks of the Warwickshire Coalfield. Memoir of the Geological Survey of Great Britain, Sheet 169. (England and Wales). |
| Carney, J N, Glover, B W and Pharaoh, T C. 1992. Pre-conference field excursion: Precambrian and Lower Paleozoic rocks of the English Midlands. British Geological Survey Technical Report, WA/92/72. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
|
E169
|
