The basic stratigraphic order has been established since the work of Peach, Horne and others. However, the stratigraphic terminology was only formalised relatively recently (early 1970s). The division of the rock sequence into Formations and Groups is shown above. These chiefly apply to rocks younger than the Torridonian Group - starting at the Eriboll Sandstone Group. On palaeontological grounds (naturally), chiefly trilobites within the Fucoid Beds Formation, the succession is established as Lower Cambrian in age. The lower part of the Durness Group is also Lower Cambrian in age. However the uppermost part of this group (not seen in Assynt) is of Ordovician age.

You should compare your stratigraphy defined at Loch Assynt with this succession, showing how your units correlate with these, using the descriptions.

Further information on Lewisian and Torridonian rocks are to be found elsewhere.