7: The Dalradian rocks of the Loch Leven area

Abstract

Introduction The object of this guide is the examination of the stratigraphy and structure of the Lower Dalradian “Ballachulish” Succession shown in Table 1 (see Bailey 1960). The rocks of the area are particularly rich in sedimentary structures which are an essential element in the erection of a stratigraphic succession in structurally complex areas (Bailey 1960, pp. 20–1). In this respect the excursions no more than complement the excellent descriptions given by Bailey (1960) in the Memoir for Sheet 53 of the Geological Survey of Scotland. The localities have also been chosen, however, to give an introduction to the structural techniques that have to be employed in such rocks in order that the three-dimensional geometry of the folds and their time-sequence may be understood. General Geology The distribution of the major lithostratigraphic formations is shown in Figure 1, locally modified after Sheet 53 of the Geological Survey of Scotland. Bailey’s (1934 Scotland. Bailey’s (1960) view of the structure is exemplified by section AA of Sheet 53. In essence, Bailey envisaged three recumbent folds, the Appin Syncline, the Kinlochleven Anticline and the Ballachulish Syncline (highest) facing towards the north-west. The lower limbs of the two synclines have been considerably affected by tectonic sliding (the Fort William and Ballachulish Slides respectively) and the pile of recumbent folds have been deformed by a series of secondary antiforms and synforms (Bailey 1960, pp. 110–15). Figure 2 shows the present authors’ modified version of the structure based on the methods discussed below. The north-east trending recumbent folds . . .