This report describes the results of solid geology fieldwork in 1:50 000 sheet 64W
(Newtonmore) resulting from the 2002 summer mapping season. A full revision of the solid
geology at 1:10 000 scale was completed in the north-western part of the sheet (Sheet NN69SE)
while rapid mapping/reconnaissance of the solid geology has been carried out in the remaining
85% of the sheet area The superficial geology of the sheet has been completely revised and will
be described in a separate report.
The north-western part of the sheet contains the transition from the deeper water graded sandy
and silty turbidite deposits of the Corrieyairack Subgroup upwards (and south-eastwards) into
the shallow water sand-dominated deposits of the Strathtummel Subgroup. East of the A9 trunk
road, the Gaick region is confirmed as a single lithostratigraphical package in the Strathtummel
Subgroup recording shallow water depositional conditions, greatly thickened by D2 recumbent
folding. Axial surfaces of these folds dip gently east overall with gently east plunging to subhorizontal fold axes. Axial traces are generally N-S trending. The main regional (biotite)
schistosity is axial planar to these folds and locally, can be seen clearly deforming an earlier
bedding near-parallel biotite fabric. The available evidence for stratigraphical younging is
limited to a few well-washed river sections but shows that regional facing is always to the south
in S2 across the Gaick region. No large-scale F1 folds are recognised with the exception of those
at Crubenmore on the A9. Minor undulations of the main regional fabric mean that the sheet dip
varies between gently north to gently east across open upright north-east-plunging folds, in
marked contrast to the conspicuous pattern of reclined, north-west verging D3 folds deforming
the main regional (S2) schistosity in Glen Truim and farther north-west. There appear to be no
other major fold sets across this part of the Gaick region The Drummochter Dome thus takes the
form of a stack of recumbent D2 folds, modified by steep zones to the north-west (Geal CharnOssian Steep Belt) and south-east (Tummel Steep belt and correlatives). The pattern of early
recumbent folds and later steep belts is similar to that seen in the higher structural levels south of
the Boundary Slide which include the Tay Nappe