Tectonic studies: annual meeting 1982

Abstract

Report of a meeting of the Tectonic Studies Group held at University College, Cardiff, 15–17 December 1982. The meeting was organized by Dr G. D. Williams. On the first day of the conference two field trips were held: the first to the Gower Peninsula led by R. Graham (Swansea) and the second to Pembroke led by G. Williams (Cardiff). In both cases, Variscan structures—thrusts, folds and shear zones—were studied. Also on 15 December, a workshop on techniques and uses of the orthographic net was presented by Declan DePaor (Galway). The main contributions of the AGM were given on 16 and 17 December. During the first session, theoretical aspects of deformation were considered. J. S. Whalley (Portsmouth) and W. H. Owens (Birmingham) considered errors arising in calculating strain ellipsoids from two dimensional data using the program PASE5. D. DePaor (Galway) showed how the use of rank 3 tensors permits the description of complex structures in a simple way and he illustrated this using a zone of heterogeneous simple shear. Stress risers on a mesocopic scale are commonly observed, and A. Morris and J. Ague (Detroit) argued that features such as sedimentary pebbles, porphyroblasts, quartz veins and bed thickness variations may create a strain-sink effect that initiates and localizes deformation. C. J. Talbot (Dundee) discussed the effect of inverse and counter folding in incompetent layers and illustrated his talk with common examples from the Moines of the Fort William area and basic sheets in the Limpopo Belt. Transpression was