The Acadian Orogeny: the mid-Devonian phase of deformation that formed slate belts in England and Wales
Published:January 01, 2006
N. H. Woodcock, N. J. Soper, 2006. "The Acadian Orogeny: the mid-Devonian phase of deformation that formed slate belts in England and Wales", The Geology of England and Wales, P. J. Brenchley, P. F. Rawson
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Deformation of the Early Palaeozoic rocks of England and Wales has traditionally been ascribed to a late phase of the Caledonian Orogeny that occurred in end-Silurian time. More recently, it has been recognized that this deformation took place towards the end of the Early Devonian and forms part of the Acadian orogenic belt, which extends from the NE Appalachians through western Europe to Poland (McKerrow 1988) (Fig. 6.1).
The Caledonian mountains, as originally defined by Suess in the early 20th century, extended between Scotland and Norway and were thought to result from the deformation of an Early Palaeozoic geosyncline. It was soon recognized that the Caledonian orogen continues into the Appalachians and East Greenland, flanked to the west by a faunally distinctive foreland sequence of Cambro-Ordovician platform deposits, which includes the Durness succession of NW Scotland. In a seminal pre-plate tectonic interpretation Wilson (1966) saw the Caledonides as the result of closure of a ‘Proto-Atlantic’ ocean that existed in late Precambrian and Early Palaeozoic time, subsequently named the Iapetus Ocean by Harland & Gayer (1972).
In the first plate tectonic model to interpret Caledonian orogenesis in terms of lithospheric convergence driven by ocean spreading and subduction, Dewey (1969a) envisaged closure between two major continental plates, North America–Greenland and Europe, which produced the N–S-striking North Atlantic Caledonides and NE–SW Appalachians. The British Caledonides, located at the intersection of the two margins,
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The Geology of England and Wales
This second edition of The Geology of England and Wales is considerably expanded from its predecessor, reflecting the increase in our knowledge of the region, and particularly of the offshore areas. Forty specialists have contributed to 18 chapters, which cover a time range from 700 million years ago to 200 million years into the future. A new format places all the chapters in approximately temporal order. Both offshore and economic geology now form an integral part of appropriate chapters.
Most of England and Wales is formed from part of a single terrane, Avalonia, and its pre-Cambrian (Neoproterozoic) history is preserved in patches. However the time intervals from the Cambrian to the present day are well represented in our sequences and the Cambrian, Ordovician, Silurian and Devonian systems were all defined here. William Smith's map of England and Wales was the world's first geological map of a country and the British Geological Survey's copy is reproduced in the introductory chapter. This chapter, by the editors, consists of a broad overview aimed particularly at the non-specialist while guiding the reader towards the appropriate succeeding chapters. The volume concludes with a look at the future, from the short-term effects of climate change and sea-level rise to the position of our region in a possible plate tectonic configuration 200 million years hence.
While the authors have taken a ‘dynamic’ view of the evolution of the area over geological time, they have also ensured that the geological evidence on which the interpretations are based is reviewed thoroughly. Hence the volume provides a valuable resource for both Earth scientists and the broader community.