The BGS Lexicon of Named Rock Units — Result Details

Upper Nantglyn Flags Group [Obsolete Name And Code: See NGF]

Computer Code: UNF Preferred Map Code: notEntered
Status Code: Index Level
Age range: Ludlow Epoch (SU) — Ludlow Epoch (SU)
Lithological Description: Comprises ribbon-banded mudstones, blue grey, thin-bedded to shaly. More generally flaggy and in places massive. More weathered than overlying group.
Definition of Lower Boundary: Drawn at the base of the Neodiversograptus Nilssoni zone where ribbon-banded mudstone conformably rests upon part ribbon banded mudstone with more frequent silt of the Bryn Sylldy Formation.
Definition of Upper Boundary: Drawn at the conformable upward passage of sandstones, silty mudstones and disturbed beds of the Upper Nantglyn Flags, with a facies change to striped, silty mudstones and subordinate sandstones.
Thickness: From 75 metres to approx. 600 metres.
Geographical Limits: Nantglyn, Denbighshire.
Parent Unit: Not Entered (?)
Previous Name(s): none recorded or not applicable
Alternative Name(s): Nantglyn Flags Formation
Stratotypes:
Type Area  Through Clocaenog Forest, terminating against the Gwaynynog Fault. Sheet (120) Corwen. 
Type Area  From Tywyn through Eglwysbach to Llanrwst, through Oerfa across the Denbigh Moors as far as Llech Daniel. 
Type Area  From Llansannan through Moel Grugoer to Bylchau. 
Reference(s):
Boswell, P G H, 1926. A contribution to the geology of the eastern part of the Denbighshire Moors. Quarterly Journal of the Geological Society, Vol.82, p.562. 
Warren, P T, Price, D, Nutt, M J C and Smith, E G. 1984. Geology of the country around Rhyl and Denbigh. Memoir for 1:50 000 geological sheets 95 and 107 and parts of sheets 94 and 106. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E107