3: The Dalradian rocks of the west coast of the Tayvallich peninsula

Abstract

Introduction The west coast of the Tayvallich Peninsula provides a continuously exposed section through the Crinan Grit, Tayvallich Limestone and Tayvallich Lava formations, and therefore straddles the boundary between the Middle and Upper Dalradian (Rast 1963), and possibly the base of the Cambrian (Downie et al 1971). The section is reached by following the road southwards from Tayvallich Village and taking the right fork signposted KIELS. Follow this road for five miles to Kiels House (Fig. 1) where there is a gate across the road \[NR 696806] and park on the grass verge. The road and turning places are inadequate for coaches. The geological traverse to be followed from this locality is approximately six miles and the return walk (along the road) four miles. By parking a vehicle at Tighavullin [NR 729853\] (Fig. 1) on the way to Kiels House from Tayvallich the return walk can be avoided. General Geology The peninsula was mapped by Peach for the Geological Survey (Peach et al. 1911). By discovering pillow lavas in Tayvallich, Peach established the existence of extrusive basic rocks in the Dalradian of the South-West Highlands, and also by observing pipe amygdales and using flow morphology, established the stratigraphic sequence of the area, i.e. that the Crinan Grit is the oldest formation exposed on the peninsula. The rocks of the area are folded into a syncline (Tayvallich Syncline) whose hinge plunges 20°–50° SSW. Associated with the axial plane of this structure there is a strong slaty cleavage. Subsequent episodes of . . .