Introduction to Geology : Volume 2 Earth History Part II Later Stages of Earth History

The Caledonides and their Forelands ## I Preliminaries The last few hundred million years of Precambrian time saw the initiation of a world-wide network of mobile belts most of which were to remain active until well into the Phanerozoic eon. In Laurasia (Fig. 2.1) this system was built around a fairly small number of cratons; most parts of the system remained mobile at least until the end of Lower Palaeozoic times and some are still in being at the present day. In Gondwanaland, the mobile belts enclosed a rather larger number of smallish cratons; much of this southern network was effectively stabilised well before the end of the Lower Palaeozoic and only a few branches remained active in later Phanerozoic times. The late Precambrian and early Palaeozoic mobile belts of Laurasia will be considered in two groups: first, those which were stabilised by the end of the Palaeozoic era (the Caledonides of Europe and Greenland (this chapter), the Hercynides of Europe and Asia (Chapter 3) and the Appalachians of North America (Chapter 4): and, second, those in which activity continued through Mesozoic and Tertiary times (Chapters 7 and 11). The adjective Caledonian, derived from the Roman name for a part of northern Britain, was originally applied by Suess to the north-east-south-west fold-belt which was developed in Scotland before the deposition of the Old Red Sandstone. This orogenic belt, the Caledonides, extends into England, Wales and Ireland on the one hand and Norway and Sweden on the other (Fig. 2.1). The Caledonian orogenic cycle is therefore the geological cycle which led to the formation of the Caledonides of these regions and, by extension, of the contemporaneous orogenic belts of other areas. The beginning of the Caledonian cycle has not been precisely defmed. Tectonic, metamorphic and depositional events can be recognised at least as far back as 800 m.y. and we regard these early events as phases of a long and The Caledonides and their Forelands URALIDES SIBERIAN =-CRATON-Fi~. 2.1. The mobile belts and cratons ofl.aurasia in mid-Palaeozoic times 17 complex Caledonian cycie. Some authors, however, recognise two cycles in t\_ I:!e evoiution of certain Caledonian belts, the later being taken as the Caledonian cycle. Russian geologists, for example, distinguish a Baikalian cycle preceding a Caledonian cycle, and in Brittany and adjacent regions a Cadomian orogeny terminating at about 500 m.y. has been distinguished. These restrictions seem to us to obscure the essential unity of the long cycle responsible for building the Caledonides. ' ......... Front Matter....Pages i-xii New Themes in Earth History....Pages 1-15 The Caledonides and their Forelands....Pages 16-57 The Hercynides and Uralides with their Forelands....Pages 58-98 The Appalachians and Interior Lowlands of the North American Craton....Pages 99-130 Gondwanaland in Late Proterozoic and Early Palaeozoic Times....Pages 131-158 Gondwanaland in Late Palaeozoic Times....Pages 159-178 The Alpine-Himalayan Belt and the Eurasian Craton....Pages 179-222 Gondwanaland: Disruption of a Supercontinent....Pages 223-251 The New Ocean Basins....Pages 252-281 The Pacific Ocean and its Island Arcs....Pages 282-306 The Cordilleran and Andean Mobile Belts and the North American Crato....Pages 307-340 Back Matter....Pages 341-371