Published online by Cambridge University Press: 01 May 2009
The acute F1 folds in the Isle of Man possess Caledonoid axial planes and plunge predominantly to the north-eastern or south-western quarters at a low angle. Synchronous F1 cross-folding is locally developed and plunges steeply to the north-west or south-east. The axial planes of these acute structures have the same steep Caledonoid orientation as their orthodox associates and they share the same first axial-plane cleavage (S1). The generation of the cross-folding is related to original culminations and depressions in the Caledonoid hinges of the large-scale F1 folds. Comparison is made with early cross-folding in other parts of the Caledonides.