Two seminal papers, one from a worker who had insight into tectonics and sedimentation (Kennedy 1958), the other from a classical stratigrapher who had an eye for detail and great experience in synthesizing data (George 1960), present quite different views of the Midland Valley. This difference of opinion, although now in a different form, still exists over both the nature and role of the Midland Valley in Caledonian geology and the nature and significance of its boundaries.
The Midland Valley spans the gap between the deeper parts of the Caledonian orogen to the north, where the Dalradian block underwent Cambro-Ordovician burial, metamorphism and cooling and the more superficial but more clearly subduction- related region to the south. Research over the past three decades has assumed that in the south we have the preserved sedimentary record that can be directly related to a mechanism (subduc- tion) that may have provided the required scale and intensity of heat and pressure required to metamorphose and deform the rocks to the north.
Establishing the nature of the link between these two regions is critical to an understanding of the Caledonides in the UK, and the Midland Valley of Scotland, being the ground between, is clearly of some significance. However, Lower Palaeozoic rocks of the Midland Valley are poorly exposed being mostly covered by Upper. They are found mainly along its northern and southern margins (Fig. 5.1). This paucity of exposure within the Midland Valley has left much room for speculation about its