The BGS Lexicon of Named Rock Units — Result Details
Gamlan Shale Group [Obsolete: use GN]
Computer Code: | GMSH | Preferred Map Code: | notEntered |
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Status Code: | Index Level | ||
Age range: | St David's Series (ED) — St David's Series (ED) | ||
Lithological Description: | [Obsolete: use GN] Grey green and in places purple shales, slates and flags interbedded with sporadic grit bands which increase in number and thickness. | ||
Definition of Lower Boundary: | Drawn at the base of the Gamlan Shale Group where shales conformably rest upon grit of the Barmouth Grits. | ||
Definition of Upper Boundary: | Drawn at the conformable upward passage of the Gamlan Shale Group to slate of the Clogau Member. | ||
Thickness: | 430 metres max.approx. | ||
Geographical Limits: | Dolgelly, Gwynedd. | ||
Parent Unit: | none recorded or not applicable | ||
Previous Name(s): | Gamlan Black Shales [Obsolete Name and Code: Use GMSH, GN]
(-288)
Gamlan Flags and Grits [Obsolete Name and Code: Use GMSH] (-3436) |
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Alternative Name(s): | none recorded or not applicable | ||
Stratotypes: | |||
Type Area | Afon Gamlan below the waterfall Rhaidr-Du near Tyn-y-Groes Inn, 8kms north of Dolgelly, Gwynedd. | ||
Reference(s): | |||
Watts, W W, 1929. "In" Evans, J W and Stubblefield, C J. Cambrian Handbook of the geology of Great Britain, p.46-48. | |||
Lapworth, C and Wilson, T S. 1910. "In" Andrew, A R. Geology of the Dolgelly Gold-Belt, North Wales. Geological Magazine, Vol.7, 161 and 163. | |||
1:50K maps on which the lithostratigraphical unit is found, and map code used: | |||
none recorded or not applicable |