The BGS Lexicon of Named Rock Units — Result Details

Fiachanis Gritty Sandstone Member

Computer Code: TCDF Preferred Map Code: notEntered
Status Code: Full
Age range: Neoproterozoic Era (AZ) — Neoproterozoic Era (AZ)
Lithological Description: Predominantly coarse-grained sandstone, with subordinate granular sandstone and basal breccia; breccias and granular sandstones occur at the base of the member, on or near the underlying Lewisian Gneiss; the coarse sandstones gradually become medium-grained towards the top of the member.
Definition of Lower Boundary: NM 3720 9366. Unconformable contact with Lewisian Gneiss.
Definition of Upper Boundary: NM 3730 9366. Highly variable gradational and/or interdigitating transition into overlying Laimhrig Shale Member, which may occur over several tens of metres of stratigraphical thickness, eg NM 3695 9905.
Thickness: 35m-70m in type locality (highly variable elsewhere).
Geographical Limits: Isle of Rhum, Fiachanis.
Parent Unit: Diabaig Formation (TCD)
Previous Name(s): Basal Grit (Millstone Grit) (-3075)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Isle of Rhum, Fiachanis. 
Reference(s):
Black, G P and Welsh, W, 1961. The Torridonian succession of the Isle of Rhum. Geological Magazine, Vol.98, 265-276. 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S060