The BGS Lexicon of Named Rock Units — Result Details

Penrhyn Du Member

Computer Code: PD Preferred Map Code: PD
Status Code: Pending Upgrade
Age range: Arenig Series (OR) — Arenig Series (OR)
Lithological Description: Fine-grained bioturbated muddy sandstones.
Definition of Lower Boundary: Conformably overlies thickly bedded pale weathering sandstones of the Trwyn yr Wylfa Member.
Definition of Upper Boundary: Conformable and gradationally overlain by well-bedded sandstones of the Machroes Member.
Thickness: 35-40m
Geographical Limits: Pwllheli area, northwest Wales.
Parent Unit: St Tudwal's Formation (STUD)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Partial Type Section  Machroes (top of formation). Young, T P, Gibbons, W and McCarroll, D. 2002. 
Type Section  Penrhyn Du, between Porth Bach and the old lifeboat station. Young, T P, Gibbons, W and McCarroll, D. 2002. 
Reference Section  St Tudwals Island West. Young, T P, Gibbons, W and McCarroll, D. 2002. 
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). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E134