The Northern Highland and Grampian terranes
The Northern Highland and Grampian terranes together comprise an extensive tract of structurally complex and generally high-grade metamorphic rocks within the Caledonian orogenic belt of Scotland (Fig. 4.1). This part of the orogen is dominated by two thick sequences of mainly Neoproterozoic metasedimentary rocks. The older sequence comprises the Moine Supergroup of the Northern Highland terrane, and possibly also the Dava Succession of the Grampian terrane. Both were deposited between c. 1000 Ma and c. 870 Ma, and subsequently affected by a controversial Knoydartian tectonothermal event at c. 800 Ma. The younger Dalradian Supergroup of the Grampian terrane accumulated between c. 800 Ma and the Early Cambrian during the break-up of the late Precambrian supercontinent Rodinia and the formation of the Iapetus Ocean. Inliers of Archaean to Palaeoproterozoic orthogneisses (Fig. 4.1) probably represent fragments of the Laurentian continental basement on which the Moine and Dalradian successions accumulated.
Caledonian orogenesis in the North Atlantic region resulted from the closure of the Iapetus Ocean and the convergence of three crustal blocks: Laurentia, Baltica and Avalonia (Soper & Hutton 1984; Pickering et al. 1988; Soper et al. 1992b). Early orogenic activity along the Iapetan margin of Laurentia resulted from an arc-continent collision that occurred during initial ocean closure in the Early to Mid-Ordovician. This phase of the Caledonian orogenic cycle is known as the Grampian event and it affected both the Northern Highland and Grampian terranes. Ocean closure and final amalgamation of crustal blocks occurred in the Late Silurian
Figures & Tables
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.