| Computer Code: |
ACTG |
Preferred Map Code: |
notEntered |
| Status Code: |
Index Level |
| Age range: |
Comley Series (EC)
— Comley Series (EC) |
| Lithological Description: |
[Obsolete: use FA] Coarse quartzo-feldspathic grits and medium-grained lithic sandstones and siltstones. |
| Definition of Lower Boundary: |
Drawn at base of grits of the Tryfan Grits Group where it rests conformably on acid tuffs, ignimbrites and ashes of the Clogwyn Volcanic Group. |
| Definition of Upper Boundary: |
Drawn at unconformable upward passage from sandstones and siltstones of the Tryfan Grit Group to conglomerate of the Cilgwyn Conglomerate. |
| Thickness: |
Approximately 300 metres. |
| Geographical Limits: |
Gwynedd, Wales. |
| Parent Unit: |
none recorded or not applicable
|
| Previous Name(s): |
Tryfan Group [Obsolete Name and Code: Use ACTG, ACTV]
(-4420)
|
| Alternative Name(s): |
none recorded or not applicable
|
| Stratotypes: |
| Type Area |
Nantlle, Gwynedd, Wales. |
| Reference(s): |
| Smith, B and George, T N. 1961. North Wales. British Regional Geology. (London: H.M.S.O.). 97pp. |
| Morris, T O and Fearnsides, W G, 1926. The stratigraphy and structure of the Cambrian Slate Belt of Nantlle, (Caernarvonshire). Quarterly Journal of the Geological Society of London, Vol.82, p.250-303. |
| Wood, D S, 1969. The base and correlation of the Cambrian rocks of north Wales, "in" Wood, A. The Pre-Cambrian and Lower Palaeozoic rocks of Wales. University of Wales Press, Cardiff, p.47-66. |
| Cattermole, P, and Jones, A. 1970. The geology of the area around Mynydd Mawr, Nantlle, Caernarvonshire. Geological Journal, Vol. 7, 111-128. |
| Cowie, J W, Rushton, A W A, and Stubblefield, C J. 1972. A correlation of Cambrian rocks in the British Isles. Special Report of the Geological Society of London, No. 2, p. 26. |
| Morris, T O, "In" Greenly, E, 1945. The Arvonian rocks of Arvon. Quarterly Journal of the Geological Society of London, Vol.100, p.269-284. |
| 1:50K maps on which the lithostratigraphical unit is found, and map code used: |
| none recorded or not applicable |
