Computer Code: |
CLU |
Preferred Map Code: |
CLu |
Status Code: |
Full |
Age range: |
St David's Series (ED)
— St David's Series (ED) |
Lithological Description: |
Black pyritous and carbonaceous mudstones and silty mudstones with rare silt laminae and sparse fine-grained sandstone beds. |
Definition of Lower Boundary: |
Conformably overlies sandstone of the Gamlan Formation (Harlech Grits Group). Boundary is transitional over 5m. |
Definition of Upper Boundary: |
Sharply but unconformably overlain by silty mudstone and sandstone turbidites of the Maentwrog Formation. |
Thickness: |
90 to 105m |
Geographical Limits: |
Northern, eastern and southern flanks of the Harlech Dome, North Wales. |
Parent Unit: |
Mawddach Group (MWG)
|
Previous Name(s): |
Clogau Shales
(-792)
|
Alternative Name(s): |
none recorded or not applicable
|
Stratotypes: |
Partial Type Section |
Basal part exposed in Afon Llafar, North Wales. |
Reference(s): |
Allen, P M, and Jackson, A A. 1985. Geology of the country around Harlech. Memoir of the British Geological Survey, Sheet 135 with part of Sheet 149 [England and Wales]. [London: HMSO.] 112pp. |
Waters, C N, Smith, K, Hopson, P M, Wilson, D, Bridge, D M, Carney, J N, Cooper, A H, Crofts, R G, Ellison, R A, Mathers, S J, Moorlock, B S P, Scrivener, R C, McMillan, A A, Ambrose, K, Barclay, W J, and Barron, A J M. 2007. Stratigraphical Chart of the United Kingdom: Southern Britain. British Geological Survey, 1 poster. |
Matley, C A and Wilson, T S. 1946. The Harlech Dome, North of the Barmouth Estuary. Quarterly Journal of the Geological Society of London, Vol.102, 1-40. |
Allen, P M, Jackson, A A, and Rushton, A W A. 1981. The stratigraphy of the Mawddach Group in the Cambrian succession of North Wales. Proceedings of the Yorkshire Geological Society, Vol. 43, 295-329. |
1:50K maps on which the lithostratigraphical unit is found, and map code used: |
E119
E135
E149
|