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 (-)
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Previous Name(s): |
none recorded or not applicable
|
Alternative Name(s): |
Syenite or Diorite Intrusions
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Stratotypes: |
Type Section |
Griff No. 4 Quarry. |
Reference(s): |
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. |
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). |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E169
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