Correlation of Events Affecting the Moine Rocks Bordering the Sound of Sleat, Inverness-Shire, Scotland
Total Page：16
File Type：pdf, Size：1020Kb
CORRELATION OF EVENTS AFFECTING THE MOINE ROCKS BORDERING THE SOUND OF SLEAT, INVERNESS-SHIRE, SCOTLAND A thesis presented for the degree of Doctor of Philosophy by J.A. James 1976 Department of Geology, Bedford College, U niversity of London. ProQuest Number: 10098319 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10098319 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.Q. Box 1346 Ann Arbor, Ml 48106-1346 ABSTRACT The study area lies within the marginal part of the Caledonian orogen of the Northwest Highlands of Scotland. The aim of the thesis was to attempt to correlate events from the marginal Moine thrust zone eastward into the Mobile Belt. The correlations included stratigraphy, structure and metamorphism. Stratigraphie correlations were restricted to Moine lithologies hitherto undifferentiated; they included rocks on the Sleat Peninsula of Skye, and in Eastern Knoydart. Structural and metamorphic events are closely related, and developed as a result of two distinct orogenic episodes. The earliest of these orogenic episodes occurred during the Pre- Cambrian and resulted in deformation on a regional scale producing tight, often flat lying structures. The metamorphic grade increased from west to east. M icrofabric studies enabled a close correlation between the second phase of deformation and the advance of the meta morphic front. The youngest orogenic event is the Caledonian event which produced open profile, upright structures, associated with a second metamorphic event, which also advanced from east to west. It has proved possible to correlate structural and metamorphic events over an area of some 1,100 sq.kms. within the Moine nappe. Further studies established that structural and metamorphic events recorded in the Moine nappe may be extended to include the underlying Tarskavaig nappe. Wider correlations were also attempted; firstly in immediately adjacent areas and subsequently on a more regional scale. The dis cussion of regional correlations includes data presented in the litera ture for areas both within the Moine thrust zone and within the Mobile Belt. Although the suggested correlations may be only tentative, there would appear to be some basis for regional correlation. ACKNOWLEDGEMENTS The project was initiated and supervised by Dr. D. Powell to whom thanks are due for help in the field and later discussions. I am grate ful to him for constant enthusiasm and for providing the opportunity to work in the Highlands. His advice and criticism s during the final stages of this project were particularly appreciated. The study was financed by a Natural Environment Research Council grant which is gratefully acknowledged. Of the many colleagues in the Geology Departments of Bedford College (London U niversity), and the University of Adelaide, South A ustralia, especial thanks are due to N. Chamley, B. Jackson and Dr. P. Banham (Bedford College), and J. Cottle, R. Glen and W. Laing (University of Adelaide) for advice and assistance. Appreciation is extended to Dr. T. Hopwood and Professor R.W. Rutland for helpful criticism of the final manuscript. During the field work, numerous people provided hospitality and kindness. In particular, I am deeply grateful to Shaunehan MacDonald, Isabel Moore, K irstie Mclnnes, Angus Peter McLean, Don and Alison Pomfret, Mr. E. Bailey, the staff at Camusrory Adventure School, and the factor of Knoydart, Mr. Lewis. I would also like to thank Shoras and Roddie for their almost constant attention to my unreliable car. I am indebted to Mrs. L. Clark and Mrs. J. Brumby for typing the t h e s i s . Finally, I extend my sincere thanks to my parents, family, and especially to Patrick, for their constant optimism and encouragement, and their unfailing belief that it was all possible. TABLE OF CONTENTS Page No. CHAPTER 1 . INTRODUCTION 1.1 Regional setting 1.2 Outline of problems and of thesis aims 1.3 Methods of investigation 1.4 Thesis plan CHAPTER 2 . PREVIOUS RESEARCH AND GEOCHRONOLOGY CHAPTER 3 . STRATIGRAPHY 30 3.1 Introduction 30 3.2 Description of lithologies 30 3.2.1 The Lewisian 30 3.2.2 The Moines of Morar and central Knoydart 33 3.3 The Moines of Skye 38 3.3.1 Introduction 38 3.3.2 The Tormore Psammite 38 3.3.3 The Armadale Sequence 40 3.3.4 Discussion of relations between the different 41 groups of Moine, the Lewisian and their positions within the Moine nappe. 3.4 The Eastern Knoydart Moine rock groups 46 3.4.1 Introduction 46 3.4.2 The Ladhar Bheinn Pelite 46 3.4.3 The Meall Bhasiter Psammite 47 3.4.4 Modifications of the Eastern Knoydart strati- 47 graphy; correlations of the Ladhar Bheinn P elite and Meall Bhasiter Psammite. 3.5 Summary 50 CHAPTER 4 . EARLY DEFORMATION (D^ AND D^) AND METAMORPHISM (M^) 51 4.1 Introduction 51 4.2 Structures associated with the first phase of 51 deform ation D^^ 4.2.1 D^ structures in the Moine rocks of the thrust 51 z o n e 4.2.2 First phase deformation (D^) structures within 55 the mobile belt 4.3 Structures associated with the second phase of 59 deformation, D^ 4.3.1 D^ structures of the Moine Thrust Zone 59 4.3.2 D^ structures in the mobile belt 68 TABLE OF CONTENTS (cont'd) Page No. CHAPTER 4 . ( c o n t 'd ) 4.4 Correlations of and throughout the area 76 4.5 The "Early" Metamorphism - M^ 79 4.5.1 Introduction 79 4.5.2 Evidence for M^ in the Research area 79 4.5.3 Structural setting of the Knoydart pegmatite 96 4.6 Relationships between and M^ 99 CHAPTER 5 . LATE DEFORMATION (B y, AND D^) AND METAMORPHISM M^ 103 5.1 Introduction 103 5.2 Structures associated with the third phase of 104 de form ation, D^. 5.2.1 Introduction 104 5.2.2 D^ structures of the Moine Thrust Zone 104 5.2.3 D^ structures of the Mobile Belt 118 5.3 Structures associated with the fourth phase of 133 deformation, D^. 5.3.1 Introduction 133 5.3.2 D^ structures of the Moine Thrust Zone 136 5.3.3 D^ structures of the Mobile Belt 139 5.4 Correlations of D^ and D^ throughout the area 140 5.5 Structures associated with Moine Thrust 142 Movements (D^) 5.6 The "Late" Metamorphism - M^ 146 5.6.1 Introduction 146 5.6.2 Evidence for M^ in the Moine Thrust Zone 146 5.6.3 Evidence for M^ in the Mobile Belt 149 5.7 Relationships between D^, D^ and M^ 159 CHAPTER 6 . THE TARSKAVAIG NAPPE 163 6.1 Introduction 163 6.2 Previous work on the Tarskavaig nappe 165 6.3 Stratigraphy of the Tarskavaig nappe 166 6.4 Structure of the Tarskavaig nappe 170 6.4.1 Introduction 170 6.4.2 Pre-Tarskavaig thrust structures 170 6.4.3 Movements on the Tarskavaig thrust plane 172 6.4.4 Post-Tarskavaig thrust structures 173 6.4.5 Structures associated with Moine thrust 177 m ovem ents TABLE OF CONTENTS (cont'd) Page No. CHAPTER 6 . ( c o n t 'd ) 6.5 Metamorphism of the Tarskavaig nappe 177 6 . 6 Correlations between the Tarskavaig nappe and 180 the Moine nappe CHAPTER 7 . DISCUSSION OFPOSSIBLE REGIONAL CORRELATIONS 183 7.1 Introduction 183 7.2 Structural and metamorphic correlations.in 183 immediate adjacent areas 7.3 Regional correlations 187 7.3.1 Introduction 187 7.3.2 Correlations within the Mobile Belt 187 7.3.3 Correlations within the Moine Thrust Zone 194 CHAPTER 8 . SUMMARY OF CONCLUSIONS 196 8.1 Introduction 196 8.2 Stratigraphie correlations 196 8.2.1 Moine lithologies in Skye 196 8.2.2 Moine lithologies in Eastern Knoydart 197 8.3 Structural and metamorphic correlations ^ithin the 197 Research area 8.3.1 Introduction 197 8.3.2 Moine nappe correlations 198 8.3.3 Correlations between the Moine nappe and the 198 Tarskavaig nappe 8.4 Evidence for, and the age of, the two orogenic 199 e v e n ts 8.4.1 The Precambrian Orogeny 199 8.4.2 The Caledonian Orogeny 202 8.5 The evolution of this marginal part of the orogen. 204 REFERENCES 206 APPENDIX 215 TEXT FIGURES Page No. 1. Location and extent of research area, and place names 2 mentioned in text. 2. The rock divisions of the Loch Houm area established by 8 Clough (1910) and his suggested correlations. 3. Stratigraphie and structural successions of the Morar Moine 10 after Richey (1935 and 1937). 4. The stratigraphy and structure of the Morar-Knoydart areas 11 after Richey and Kennedy (1939) ., 5. Kennedy's revised stratigraphy and structure of the Morar- 13 Knoydart areas (1955). 6 . Lambert's stratigraphy of the Morar-Knoydart areas (1958 and 15 1 9 5 9 ). 7. The stratigraphy of the Glenelg and Knoydart areas after 17 Ramsay and Spring (1962). 8 . Correlations of tl^e stratigraphie successions of Richey and 18 Kennedy (1939), Ramsay and Spring (1962), and Powell (1964). 9. The stratigraphie correlation of Western Knoydart and North 19 Eastern Morar suggested by Poole (1966). 10. The stratigraphical successions in the Moinian Assemblage of 21 Western Inverness-shire and Ross-shire, (after Johnstone et al.