The BGS Lexicon of Named Rock Units — Result Details

Gyfenni Wood Shale Formation

Computer Code: GFS Preferred Map Code: GFS
Status Code: Full
Age range: Gorstian Age (SG) — Gorstian Age (SG)
Lithological Description: Mudstones, bedding-fissile, silty, grey-brown (when weathered); largely graptolitic hemipelagite.
Definition of Lower Boundary: Passage into undifferentiated Nantglyn Flags.
Definition of Upper Boundary: (SO 2135 9014) Overlain by Bailey Hill Formation which in places includes the Dingle Mudstone Member at its base.
Thickness: <100m
Geographical Limits: Western parts 1:50,000 map sheet 165 (Montgomery).
Parent Unit: Not Available (!)
Previous Name(s): Lower Ludlow Graptolitic Shales (-4060)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Western parts of 1:50 000 map sheet 165 (Montgomery). 
Reference Section  Gyfenni Wood Forestry track. Base of member not exposed, but top part is very well exposed to the base of the Bailey Hill Formation. 
Type Section  Stream section. 
Reference(s):
none recorded or not applicable
1:50K maps on which the lithostratigraphical unit is found, and map code used:
E165