Early curvilinear fold structures and strain in the Moine of the Glen Garry region, Inverness-shire

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Abstract
Four regional deformation episodes (D1-D4) are recognized in the Moine rocks (Loch Eil and Glenfinnan divisions) of the Glen Garry area, Inverness-shire, NW Scotland. These episodes fall into two groups: early, sub-recumbent D1-D2 structures and later, upright D3-D4 structures. D2 structures occur on all scales and appear, in a regional sense, to be more important than the D1 structures. The D1-D2 structures are only preserved in their original disposition where subsequent upright D3 reworking was minimal, i.e. in the region to the E of the Loch Quoich Line and in low strain augen developed in D3 hinge zones to the W of this structure. The F2 folds are intensely curvilinear and at many localities F2 hinges lie approximately parallel to the N-S trending extension lineation. Examination of these structures in three dimensions and application of the Sanderson (1973) model provides information on the nature and orientation of the regional D2 strain ellipsoid in this part of the Moine. The D2 XY plane is sub-horizontal with the X direction trending approximately N-S. This is markedly different in orientation from the D3 ellipsoid in this region, which, being of post-Glen Dessary Syenite (456 Ma) age, is demonstrably Caledonian. The D2 linear fabrics suggest that the direction of tectonic transport was S to N or N to S, markedly different from the generally accepted WNW-directed movement attributed to Caledonian orogenesis. These findings are consistent with the proposal that the Loch Quoich Line represents an eastern limit of intense Caledonian (D3) reworking, and that the D1-D2 structures are of Precambrian age.