A New Record of Boudinage-structure from Scotland

Abstract

The peculiar tectonic structure called “boudinage” by Lohest (5, pp. 471–2), has recently been found in Unst, Shetland Islands, by Professor H. H. Read (8, pp. 134–8), who has also noted its occurrence in tie Durn Hill quartzites of Banffshire (9, p. 471).What would now be termed boudinage-structure was seen by Ramsay in North Wales, and was described in 1866 in these words (6, and. fig. 18): “In the great quarry west of the Ffestiniog and Trawsfynydd fault the cleavage dips from 45° to 50° north-west, the inclination of the beds being about 35° in the same direction, and a greenstone dyke runs through them between the cleavage-planes…, bulging and thinning off in a rapid succession of oval-shaped masses of 3 or 4 feet in length. Associated with it are quartz veins ccurring principally at the points between the separate bulgings of the greenstone.”