The BGS Lexicon of Named Rock Units — Result Details

Gamlan Shale Group [Obsolete Name And Code: Use GN]

Computer Code: GMSH Preferred Map Code: notEntered
Status Code: Index Level
Age range: St David's Series (ED) — St David's Series (ED)
Lithological Description: 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: Not Entered (?)
Previous Name(s): Gamlan Black Shales (-288)
Gamlan Flags And Grits (-3436)
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):
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. 
Watts, W W, 1929. "In" Evans, J W and Stubblefield, C J. Cambrian Handbook of the geology of Great Britain, p.46-48. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable