The BGS Lexicon of Named Rock Units — Result Details

Loch Ard Grit Formation

Computer Code: LADG Preferred Map Code: LAGF
Status Code: Full
Age range: Ediacaran Period (AD) — Comley Series (EC)
Lithological Description: Sandstone, pale buff to green-grey, clean to matrix-rich, coarse, locally gritty, interbedded with purple, grey and black slates.
Definition of Lower Boundary: Outgoing of coarse, chloritic and feldspathic arenites and wackes (at the top of the Ben Ledi Grit Formation) and incoming of pale arenaceous sandstones.
Definition of Upper Boundary: Incoming of abundant black slate with chert (at base of Borfrishlie Slate Formation); contact may be tectonic.
Thickness: 100-200m
Geographical Limits: Ground southwest of Aberfoyle and west of the Loch Tay Fault zone, adjacent to the Highland Boundary Fault, through towards Loch Lomond.
Parent Unit: Southern Highland Group (SOHI)
Previous Name(s): Achray Sandstone (-4744)
Alternative Name(s): none recorded or not applicable
Stratotypes:
Type Area  Loch Ard Forest, Aberfoyle. 
Reference(s):
Tanner, P W G, 1998. Geological mapping of uppermost Dalradian and Palaeozoic rocks, Aberfoyle, Sheet 38E. Minor contract report for Sheet 38E/Southern Highlands Project, unpublished. (Formation known as Loch Ard Transition Group in report). 
1:50K maps on which the lithostratigraphical unit is found, and map code used:
S038