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
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This 4th edition of The Geology of Scotland is edited by Dr Nigel Trewin of the Department of Geology and Petroleum Geology at the University of Aberdeen. The volume is greatly expanded from the previous edition with 34 authors contributing to 20 chapters.
A new format has been adopted to provide a different perspective on the geology of Scotland. A brief Introduction is followed by a chapter outlining some of the important historical aspects that in the 19th century placed Scottish geologists at the forefront of a new science.
Scotland is constructed from a number of terranes that finally combined in roughly their present positions prior to about 410 million years ago. Thus the geology of each terrane is described up to the time of amalgamation, providing chapters on the Southern Uplands, Midland Valley, Northern Highland, Grampian and Hebridean terranes. At the end of this section, a brief synthesis summarizes the events that resulted in the amalgamation of the various terranes into the present configuration.
Traditional practice is followed in the description of the Old Red Sandstone, Carboniferous, Permo-Trias, Jurassic, Cretaceous, Tertiary and Quaternary strata. A separate chapter covers Tertiary igneous rocks. An attempt is made to tell the story of the geological evolution of Scotland, rather than catalogue all areas and formations. Priority is given to the onshore geology, encouraging the reader to go into the field and visit some of the world-class geology on show in Scotland. The chapters are broadly-based, attempting to integrate the sedimentary and igneous histories, and summarize changes in palaeogeography and palaeoenvironments.
Economic aspects are covered with chapters on Metalliferous Minerals, Bulk Resources, Coal and Hydrocarbons. A new departure is a chapter on aspects of Environmental Geology and sustainability.
Additionally, this publication contains a colour section of 32 plates, illustrating aspects of Scottish Geology, as well as a coloured geological map of Scotland.