GENERATION OF THE TAY NAPPE, SCOTLAND, BY LARGE-SCALE SE-DIRECTED SHEARING

Recent mapping in the Glen Shee Area, Central Scotland. has revealed a n array of several large-scale Fl folds within the 'Flat Belt' of the Tay Nappe. Strata within the 'Flat Belt', forming part of the lower li mb of the Tay Nappe, are thus not entirely inverted, and the tradition al view that the Na?pe in this area comprises a single SE-facing, recu mbent anticline is rejected. It is demonstrated that the sense of shea r of D2 was top-to-the-SE, resulting in NW-verging F2 folds by strong D2 strain partitioning. Strain estimates indicate a displacement of 10 -50 km during D2 shearing. In the proposed model, originally upright F 1 folds were modified by a major D2 shearing event that produced a sha llow NW dipping S2 foliation in the 'Flat Belt', The upper limit of D2 deformation forms the boundary between the strongly deformed and inve rted 'lower limb' and the right-way-up 'upper limb' which is undeforme d by D2, and is now mostly removed by erosion. The D2 shear event was responsible for the gross stratigraphic inversion in the Flat Belt. Th e Tay Nappe is considered here as formed by a crustal-scale shear zone ; in this model there is no necessity to invoke a root zone.