The BGS Lexicon of Named Rock Units — Result Details

Hen-Dy-Capel Ironstone Member

Computer Code: HDCI Preferred Map Code: HdC
Status Code: Pending Upgrade
Age range: Caradoc Series (O4) — Caradoc Series (O4)
Lithological Description: Oolitic ironstone.
Definition of Lower Boundary: Overlies dark grey mudstone, with minor sandstone and siltstone, of the Llanengan Formation. Boundary is probably a disconformity or non-sequence.
Definition of Upper Boundary: Overlain by mudstones and siltstones, with sandstones, of the Trygarn Formation, or undivided Nant Ffrancon Subgroup siltstones and fine-grained sandstones.
Thickness: 4-6m
Geographical Limits: Pwllheli area, northwest Wales.
Parent Unit: Nant Ffrancon Subgroup (NFR)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Reference Section  Small quarry at Llanengan. Young, T P, Gibbons, W and McCarroll, D. 2002. 
Type Section  Hen-dy-Capel Quarry. 
Reference(s):
Young, T P, Gibbons, W and McCarroll, D. 2002. Geology of the country around Pwllheli. Memoir of the British Geological Survey, Sheet 134 (England and Wales). 
Young, T P, 1991. A revision of the age of the Hen-dy-capel Ooidal Ironstone (Ordovician), Llanengan, North Wales. Geological Journal, Vol.26, 317-327. 
Trythell, R J B, Eccles, C, Molyneux, S G and Taylor, W E G, 1987. Age and controls on ironstone deposition (Ordovician) North Wales. Geological Journal, Vol.22, 31-43. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E134