The Structure of the Balquhidder-Crianlarich region of the Scottish Dalradian and its relation to the Barrovian garnet isograd surface

Synopsis The Balquhidder–Crianlarich region of the Scottish Dalradian has undergone a complex history of deformation and metamorphism. The earliest recognizable phase of folding produced a major NW closing recumbent synform which may be correlated with regional F 2 (nappe forming) folds in the west-central Highlands. This was refolded by upright ENE plunging folds. Minor structures associated with both folding episodes are developed and interference fold patterns occur. The area is bisected by a late sinistral oblique-slip fault system which juxtaposes terrains of significantly different tectonic levels. The metamorphic zonation is inverted. The garnet isograd surface cuts the axial plane of the recumbent synform; thus, peak metamorphism post-dates nappe emplacement. No tectonic means of overturning the metamorphic zonation can be invoked; it follows that metamorphism occurred in a negative thermal gradient.