The BGS Lexicon of Named Rock Units — Result Details

Nant-Ysgollon Mudstone Formation

Computer Code: NYG Preferred Map Code: NyG
Status Code: Full, pending ratification
Age range: Wenlock Epoch (SW) — Wenlock Epoch (SW)
Lithological Description: Mudstones.
Definition of Lower Boundary: Overlies the palr grey-green mudstones of the Dolgau Mudstone Formation.
Definition of Upper Boundary: Overlain by thinly bedded mudstones and siltstones of the Nantglyn Mudstones Formation.
Thickness: 30 to 125m
Geographical Limits: Northern and central Wales.
Parent Unit: Not Applicable (-)
Previous Name(s): Wenlock Shales (-933)
Nant-Ysgollen Mudstone Formation (-4819)
Nant-Ysgollen Shales (-2348)
Pegwn Mudstones (-1098)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Tarannon area near Llanbrynmair, side stream off the Afon Cwm celch, southwest of Ffridd yr Ystrad (hill). Wood, 1906. 
Reference(s):
Wood, E M R. 1906. On the Tarannon Series at Tarannon. Quarterly Journal of the Geological Society, London, Vol.62, 644-701. 
Davies, J R, Fletcher, C J N, Waters, R A, Wilson, D, Woodhall, D G and Zalasiewicz, J A, 1997. Geology of the country around Llanilar and Rhayader. Memoir for 1:50 000 Geological Sheets 178 and 179. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E179 E136 E164 E150 E120 E137