The BGS Lexicon of Named Rock Units — Result Details

Coire Riabhach Phosphatic Formation

Computer Code: CRPH Preferred Map Code: notEntered
Status Code: Full
Age range: Coniacian Age (KO) — Santonian Age (KS)
Lithological Description: Up to five beds of glauconitic sand with phosphate nodules and fossil casts.
Definition of Lower Boundary: The lower boundary is conformable (or a non-sequence at an erosion surface) with the underlying Lochaline White Sandstone Formation.This is placed at the change from pure-quartz sand up into glauconitic sands.
Definition of Upper Boundary: The upper boundary is unconformable (or a non-sequence at an erosion surface) with chalks of the overlying Gribun Chalk Formation.
Thickness: Usually less than one metre.
Geographical Limits: Limited to the Beinn Iadain area. Because of its relative thinness it is questionable as to whether this bed is a "mappable" unit and as such worthy of formational status. However, it is prominent in sections logged in Morvern and may prove to be the correlative of the basal unit of the Gribun Chalk Formation as mapped on Mull, where glauconite is seen in the sequences associated with erosional surfaces. It might also be a key link with the Northern Ireland succession, where Mortimore et al. (2001) correlate it with the Cloghfin Sponge Formation at the base of the Ulster White Limestone Group.
Parent Unit: Inner Hebrides Group (IHEB)
Previous Name(s): none recorded or not applicable
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Section  Stream section on the west bank of Coire Riabhach, on the northeast flank of Beinn Iadain. The full fivefold glauconitic sand units with phosphatic nodules are visible. 
Reference(s):
Mortimore, R N, Wood, C J and Gallois, R W, 2001. British Upper Cretaceous Stratigraphy. Geological Conservation Review Series. No. 23. (Peterborough: Joint Nature Conservation Committee.) 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
none recorded or not applicable