Lewisian

Park Graham

Description

The first 2,500 million years of the geological history of Britain are stored in the gneisses of the Lewisian Complex of North West Scotland. This book explores the long journey of discovery in which this history has been gradually deciphered since the end of the 19th Century when these rocks were first investigated in detail. The usual tools of stratigraphic investigation were of no value in dealing with such a complex assemblage of highly deformed and metamorphosed rocks; there was no fossil evidence and few signs of recognisable sedimentary strata.This book charts the increasing sophistication of the geochronological and geochemical techniques used to decipher the complex. The first important breakthrough was the recognition that a set of intrusive metamorphosed dykes could be used, perhaps, to separate episodes of deformation and metamorphism that occurred before the dykes were intruded, from those that occurred subsequently.Geochronological dating methods evolved from the first relatively crude potassium-argon and uranium-lead dates in the 1950s to the present amazingly accurate lead isotope dates. Geochemical techniques have also advanced to the point when mafic igneous assemblages can be identified as having oceanic volcanic arc signatures or were the products of intra-continental magmatism. Thus, from a stratigraphy composed of three events, Scourian, dyke intrusion and Laxfordian, has grown a complex history covering many separate events of igneous, metamorphic and tectonic activity spanning 2,500 million years of Precambrian time.Much of the extensive literature on the Lewisian is highly specialised and not easily accessible to the general reader; this book is an attempt to distil the most important results of this research into a more user-friendly form. It will appeal to many geologists including students, geological visitors to the North West of Scotland and academics seeking a readable account of remarkable and significant advances in earth science.

Sujets

• Sciences et techniques
• Northern Scotland

Informations

• Publié par: Dunedin Academic Press
• Date de parution: 01 mai 2022
• Nombre de lectures: 0
• EAN13: 9781780466408
• Langue: English
• Poids de l'ouvrage: 7 Mo

Extrait

THE LEWISIAN
BRITAIN’S OLDEST ROCKS
GRAHAM PARK
To all those geologists in many different countries who, over the years, have been my companions at conferences and field excursions, and who have shared with me the excitement of geological discovery.
CONTENTS
Sourced illustrations
Preface
Acknowledgements
1 Introduction
PART I: THE PIONEERS
2 Early ideas
3 The 1907 Memoir
4 Sutton & Watson 1951: the Scourian and the Laxfordian
5 Mapping of the Outer Hebrides
PART II: GATHERING THE DATA
6 The Loch Maree Group and the Inverian
7 The 1960s re-mapping of the Mainland
8 Problems of correlation and nomenclature
9 Geochronology: initial steps
10 Nature and origin of the ‘Fundamental Complex’
11 Re-mapping of the Hebrides
12 The 1971 Lewisian Conference: a summary of progress
13 The Mainland revisited
PART III: MODELS and HYPOTHESES
14 Introduction of the shear zone model
15 Kinematic models
16 Petrogenesis I: the Scourian Complex
17 Petrogenesis II: the Proterozoic
18 Towards a Lewisian chronology
19 The wider picture: tectonic models
Glossary
References
Index
SOURCED ILLUSTRATIONS
REPRODUCED BY PERMISSION
Figure 1.2 © Shutterstock, 717438754, by Pecold.
Figure 1.3 Park, R.G., Stewart, A.D. and Wright, D.T. (2002) The Hebridean terrane. In: Trewin, N.H. (ed.) The Geology of Scotland. 4 th edition. Geological Society, London (fig. 3.1).
Figures 2.1 , 2.2A , B MacCulloch, J. (1819) A description of the Western Islands of Scotland, including the Isle of Man, comprising an Account of their Geological Structure, with Remarks on their Agriculture, Scenery and Antiquities. 3 volumes, Archibald Constable, Edinburgh; Hurst, Robinson, London.
Figure 3.1 Cassell’s Universal portrait gallery, Werner & Son, Dublin.
Figures 4.1 , 4.2 Sutton, J. and Watson, J. (1951) The pre-Torridonian metamorphic history of the Loch Torridon and Scourie areas in the North-west Highlands and its bearing on the chronological classification of the Lewisian. Quarterly Journal of the Geological Society, London, 106 , 241–307 (plates XIX, XX).
Figure 5.1 , 5.2 Jehu, T.J. and Craig, R.M. (1927) Geology of the Outer Hebrides, vol. IV. Royal Society of Edinburgh, Transactions, 55 (plate V; p. 621).
Figure 5.3 Kursten, M. (1957) The metamorphic and tectonic history of parts of the Outer Hebrides. Edinburgh Geological Society, Transactions , 17, 1–31 (fig. 23).
Figures 5.4A , B Dearnley, R. (1962) An outline of the Lewisian complex of the Outer Hebrides in relation to that of the Scottish mainland. Quarterly Journal of the Geological Society, 118 , 143–176 (fig. 3).
Figures 5.5 , 5.7 , 5.8 Dearnley, R. (1963) The Lewisian complex of South Harris. Quarterly Journal of the Geological Society, 119 , 243–312 (plate 27; figs 5, 11).
Figure 6.5 , 6.8 Park, R.G. (1964) The structural history of the Lewisian rocks of Gairloch, Wester Ross. Quarterly Journal of the Geological Society of London, 120 , 397–434 (figs 4, 13).
Figure 6.9 Peach, B.N., Horne, J., Gunn, W., Clough, C.T. Hinxman, L.W. and Cadell, H.M. (1884) Report on the Recent Work of the Geological Survey in the North-West Highlands of Scotland, based on the Field Notes and Maps. Quarterly Journal of the Geological Society, London, 44 , 378–441 (plate XXX).
Figure 6.10A , B Park, R.G. (1970a) The structural evolution of the Tollie antiform – a geometrically complex fold in the Lewisian north-east of Gairloch, Ross-shire. Quarterly Journal of the Geological Society of London, 125 , 319–349 (fig. 11).
Figure 6.14 Park, R.G. (1966) Nature and origin of Lewisian basic rocks of Gairloch, Ross-shire. Scottish Journal of Geology, 2 , 179–199 (fig. 7).
Figure 7.2 Cresswell, D. (1972) The structural development of the Lewisian rocks on the north shore of Loch Torridon, Ross-shire. Scottish Journal of Geology , 8 , 293–308 (fig. 2).
Figures 8.1 , 8.2 Park, R.G. (1969) Structural correlation in metamorphic belts. Tectonophysics, 7 , 323–338 (figs 1, 2).
Table 8.2 Park, R.G. (1970b) Observations on Lewisian chronology. Scottish Journal of Geology, 6 , 379–399 (tables 2, 3).
Figure 10.1 Myers, J.S. (1970) Gneiss types and their significance in the repeatedly deformed and metamorphosed Lewisian Complex of Western Harris, Outer Hebrides. Scottish Journal of Geology, 6 , 186–199 (fig. 3).
Figure 10.4A , B Bowes, D.R., Wright, A.E. and Park, R.G. (1964) Layered intrusive rocks in the Lewisian of the North-West Highlands of Scotland. Quarterly Journal of the Geological Society, London, 120 , 153–192 (figs 4, 7).
Figure 10.5 Guice, G.L., McDonald, I, Hughes, H.S.R., MacDonald, J.M., Blenkinsop, T.G., Goodenough, K.M., Faithfull, J.W. and Gooday, R.J. (2018) Re-evaluating ambiguous age relationships in Archaean cratons: implications for the origin of ultramafic-mafic complexes in the Lewisian Gneiss Complex. Precambrian Research, 311 , 136–156 (fig. 2a).
Figure 11.1 Watson, J.V. (1968) Post-Scourian metadolerites in relation to Laxfordian deformation in Great Bernera, Outer Hebrides, Scottish Journal of Geology , 4 , 53–67 (fig. 2).
Figure 11.2 Watson, J.V. (1969) The Precambrian gneiss complex of Ness, Lewis, in relation to the effects of Laxfordian regeneration. Scottish Journal of Geology , 5 , 269–285 (fig. 3).
Figure 11.5 , 11.6 Coward, M.P. (1972) The structure and origin of areas of anomalously low-intensity finite deformation in the basement gneiss complex of the Outer Hebrides. Tectonophysics, 16 , 117–140 (figs 6, 16).
Figures 12.7 , 8 Park, R.G. and Cresswell, D. (1973) The dykes of the Laxfordian belts. In: Park, R.G. and Tarney, J. (eds) The Early Precambrian of Scotland and related rocks of Greenland. University of Keele, 119–130 (figs 6, 9e).
Figure 12.9 Dearnley, R. (1973) Scourie dykes of the Outer Hebrides. In: Park, R.G. and Tarney, J. (eds) The Early Precambrian of Scotland and related rocks of Greenland. University of Keele, 131–135 (fig. 2).
Figure 12.11 Wright, A.E., Tarney, J., Palmer, K.F., Moorlock, B.S.P. and Skinner, A.C. (1973) The geology of the Angmassalik area, East Greenland and possible relationships with the Lewisian of Scotland. In: Park, R.G. and Tarney, J. (eds) The Early Precambrian of Scotland and related rocks of Greenland. University of Keele, 157–177 (fig. 4).
Figure 13.3A , B Goodenough, K.M., Park, R.G., Krabbendam, M., Myers, J.S., Wheeler, J., Loughlin, S.C., Crowley, Q.J., Friend, C.R.L., Beach, A., Kinny, P.D. and Graham, R.H. (2010) The Laxford Shear Zone: an end-Archaean terrane boundary? In: Law, R.D., Butler, R.W.H., Holdsworth, R.E., Krabbendam, M. and Strachan, R.A. (eds) Continental Tectonics and Mountain Building: the Legacy of Peach and Horne. Geological Society, London, Special Publications, 335 , 103–120 (figs 3, 4).
Figure 13.4 Davies, B. (1974) A layered basic complex in the Lewisian, south of Loch Laxford, Sutherland. Journal of the Geological Society, London, 130 , 279–284 (fig. 1).
Figure 13.5 Davies, F.B. (1976) Early Scourian structures in the Scourie–Laxford region and their bearing on the evolution of the Laxford front. Journal of the Geological Society, London, 132 , 543–554 (fig. 6).
Figure 13.7 Davies, F.B. (1977) The Archaean evolution of the Lewisian complex of Gruinard Bay. Scottish Journal of Geology, 13 , 189–196 (fig. 2).
Figure 13.8 Corfu, F., Crane, A., Moser, D. and Rogers, G. (1998) U-Pb systematics at Gruinard Bay, northwest Scotland: implications for the early orogenic evolution of the Lewisian complex. Contributions to Mineralogy and Petrology, 133 , 329–345 (fig. 2).
Figure 14.6A Park, R.G., Stewart, A.D. and Wright, D.T. (2002) The Hebridean terrane. In: Trewin, N.H. (ed.) The Geology of Scotland. 4 th edition. Geological Society, London (fig. 3.12).
Figures 14.7 , 14.8 , 14.9 Odling, N.E. (1984) Strain analysis and strain path modelling in the Loch Tollie gneisses, Gairloch, NW Scotland. Journal of Structural Geology , 6 , 543–562 (figs 2, 12, 14).
Figures 15.7 , 15.9 Park, R.G., Crane, A. and Niamatullah, M. (1987) Early Proterozoic structure and kinematic evolution of the southern Mainland Lewisian. In: Park, R.G. and Tarney, J. (eds) Evolution of the Lewisian and comparable Precambrian high-grade terrains. Geological Society of London, Special Publications, 27 , 139–151 (figs 5b, 8).
Figure 15.10 Niamatullah, M. and Park, R.G. (1990) Laxfordian structure, strain distribution and kinematic interpretation of the Kenmore inlier, Loch Torridon: anatomy of a major Lewisian shear zone. Transactions of the Royal Society, Edinburgh: Earth Sciences, 81 , 195–207 (fig. 12).
Figures 15.12 , 15.13 Wheeler, J., Windley, B.F. and Davies, F.B. (1987) Internal evolution of the major Precambrian shear belt at Torridon, NW Scotland. In: Park, R.G. and Tarney, J. (eds) 1987. Evolution of the Lewisian and comparable Precambrian high-grade terrains. Geological Society, Special Publications 27 , 153–163 (figs 10, 13).
Figure 15.15 Niamatullah, M. and Park, R.G. (1990) Laxfordian structure, strain distribution and kinematic interpretation of the Kenmore inlier, Loch Torridon: anatomy of a major Lewisian shear zone. Transactions of the Royal Society, Edinburgh: Earth Sciences, 81 , 195–207 (fig. 14).
Figure 16.3 Tarney, J., Weaver, B. and Drury, S.A. (1979) Geochemistry of Archaean trondhjemitic and tonalitic gneisses from Scotland and East Greenland. In: Barker, F. (ed.) Trondhjemites, dacites and related rocks. Elsevier, Amsterdam (fig. 10).
Figure 16.5 Tarney, J. and Weaver, B.L. (1987) Geochemistry of the Scourian complex: petrogenesis and tectonic models. In: Park, R.G. and Tarney, J. (eds) Evolution of the Lewisian and comparable Precambrian high-grade terrains. Geological Society of London, Special Publications, 27 , 45–56 (fig. 3).
Figure 16.9 , 10 Sills, J.D. and Rollinson, H.R. (1987) Metamorphic evolution of the mainland Lewisian complex. In: Park, R.G. and Tarney, J. (eds) Evolution of the Lewisian and comparable