Mykura, W. and Newsier, J. 1976. The Geology of Western Shetland (Explanation of One-inch Geological Sheet Western Shetland; comprising Sheet 127 and parts of 125, 126 and 128). Edinburgh HMSO. Provided courtesy of the British Geological Survey. Crown copyright, 1976. 'Systematic Series hand specimens' and 'List of Geological Survey Photographs' both Copyright UKRI.
The geology of Western Shetland (Explanation of one-inch geological sheet Western Shetland; comprising Sheet 127 and parts of 125, 126 and 128)
By W. Mykura, and J. Newsier, with a contribution by P. A. Sabine
Bibliographic reference: Mykura, W. and Newsier, J. 1976. The Geology of Western Shetland (Explanation of One-inch Geological Sheet Western Shetland; comprising Sheet 127 and parts of 125, 126 and 128). Edinburgh HMSO.
Natural Environment Research Council. Institute of Geological Sciences. Memoirs of the Geological Survey of Great Britain Scotland
The Geology of Western Shetland (Explanation of one-inch geological sheet Western Shetland; comprising sheet 127 and parts of 125, 126 and 128)
By W. Mykura, B.Sc., F.R.S.E. and J. Newsier, D.Sc., F.R.S.E. with a contribution by P. A. Sabine, D.Sc., F.R.S.E.
Edinburgh Her Majesty's Stationery Office, 1976. First published 1976.© Crown copyright 1976. ISBN 0 11 880160 0
The Institute of Geological Sciences was formed by the incorporation of the Geological Survey of Great Britain and the Museum of Practical Geology with Overseas Geological Surveys and is a constituent body of the Natural Environment Research Council
Preface
The Western Shetland map comprises Sheet 127 of the one-inch-to-one-mile Geological Survey series together with parts of sheets 125, 126 and 128. This means that it has been possible to include the whole of the Walls Peninsula of Shetland and its adjacent islands. The descriptions in the present Memoir, however, exclude that part of the map which lies to the east of the Walls Boundary Fault and which is more properly treated in connexion with the Central Shetland (128) Sheet.
The original survey of the Western Shetland area was carried out between 1931 and 1934 by the late G. V. Wilson, Dr. S. Buchan, the late D. Haldane, Mr. J. Knox and Dr. T. Robertson. While the area was completely covered by field maps on the scale of six-inches-to-one-mile, no one-inch map of the district was published at that time because of the intervention of urgent economic work elsewhere. Following a decision to rectify this lack after a lapse of many years, it was desirable that the original survey should be updated and the re-examination was entrusted to Mr. W. Mykura in 1961. Although his revision was based on the maps of the original surveyors the application of modern techniques of structural mapping and sedimentology necessitated a complete coverage of the Walls area on what was virtually a resurvey. This has resulted in a very considerable re-interpretation of the strata and structures which has an important bearing not only on Shetland geology but on the interpretation of the Scottish Caledonides as a whole.
The memoir was written by Mykura with the exception of Chapters 3, 13 and a large part of 16. These were written by Dr. J. Phemister based on the original survey by Haldane supplemented by his own field studies, particularly in Muckle Roe. Chapter 2 is a summary by Mykura of the relevant part of a paper by Phemister which is in press at the time of writing. The mapping of the ground east of the Walls Boundary Fault is based on work by J. Phemister, Dr. F. May and Dr. P. A. Sabine.
The identification of the Old Red Sandstone fish remains was carried out by Dr. R. S. Miles and the fossil plants were named by Professor W. G. Chaloner. Mr. P. J. Brand collected many of the fossils and compiled the faunal lists. The geological photographs of the area were taken by the late W. Fisher.
The new chemical rock analyses quoted in this memoir are by Messrs. W. H. Evans, J. M. Nunan and C. Park (Laboratory of the Government Chemist) and the isotopic age determinations by Dr. N. J. Snelling. Mr. Mykura was assisted in his petrographical work by advice from Mr. R. W. Elliot and F. May.
The memoir was edited by Mr. G. S. Johnstone with the assistance of Dr. J. D. Peacock.
Kingsley Dunham, Director, Institute of Geological Sciences, Exhibition Road, London SW7 2DE
Contents
Preface by the Director
List of illustrations
List of six-inch map
Title page and other preliminaries
Preface by the Director
List of illustrations
Location and Area, Physical Features, History of Research, Summary of Geology, References
Chapter 2 The Lunnister metamorphic rocks
Introduction, Banded Gneiss Group, Calcareous Group, Green Beds Assemblage, Clothister Hill Magnetite and Skarn, Western Unclassed Rocks, Structural Interpretation, References
Chapter 3 The Metamorphic rocks in the Muckle Roe-Northmaven Complex
Introduction, Lithology, Djubi Dale Enclave, Skipadock area, Egilsay, Busta Peninsula, Muckle Roe, Busta Isthmus, Petrography, Siliceous and Semipelitic Rocks, Pelitic Schists, Basic Rocks, Outlying Xenolithic Bodies of Basic Gneiss, Summary
Chapter 4 The Metamorphic rocks of the Walls Peninsula
Introduction, Lithology, Vementry Group, Neeans Group, West Burra Firth Group, Snarra Ness Group, Granite and Pegmatite Veins and Intrusions, Structure, : Geometry of Main Structural Elements, Main Phase of Folding, Phase of Intense Shearing, Kink Bands and Conjugate Kink Folds, Regional Tilting, Late NNW-trending Folds, NE to NNW-trending Faults and Associated Conjugate Folds, Metamorphic History, Possible deformation and mineral growth prior to main tectonizing metamorphism, Main Phase of Folding and Associated Metamorphic Episodes, Retrograde Metamorphism, Late Thermal Metamorphism, References
Field Relationships, North Skerry, Ormal, The Clubb, Petrography, Granite-Gneiss, Foliated Granite, Schistose Rocks, References
Chapter 6 Metamorphic and intrusive rocks of Foula
Introduction, Metamorphic Rocks, Field Relationships, Petrography, Granitic Minor Intrusions, Petrography, Faults and Crush Belts, Reference
Chapter 7 Old Red Sandstone: Sandness Formation
Introduction, Junction between Sediments and Metamorphic Rocks, Sediments below the Clousta Volcanic Rocks, Basal Sediments, Sandstones and Conglomerates below Clousta Volcanic Rocks, Petrography, Conditions of Deposition, Clousta Volcanic Rocks and Associated Sediments, Area East of Brindister Voe, Area West of Brindister Voe, Flora, Petrography, Environment of Deposition, References
Chapter 8 Old Red Sandstone: Walls Formation
Introduction, Lithology, Coast between Wats Ness and Wester Sound, Vaila Sound and Vaila, Gruting Voe, Seli Voe, Scutta Voe and Voe of Browland, Area between Lunga Water and Walls Boundary Fault, Rea Wick-Roe Ness Peninsula, Sedimentary Enclaves within Sandsting Complex, Fauna and Flora, Petrography, Environment of Deposition, References
Chapter 9 Walls Sandstone: Structure
Structures attributed to the First Phase of Folding (F1), Structural Units of the Synclinorium, Northern Limb, Hinge Zone, Southern Limb, Structures attributed to Second Phase of Folding (F2), Comparison with other Areas of Late-Caledonian Folding, References
Chapter 10 Old Red Sandstone: Melby Formation
Introduction, Stratigraphy, Strata below Lower Melby Fish Bed, Lower Melby Fish Bed, Strata between Lower and Upper Melby Fish Beds, Upper Melby Fish Bed, Strata above Upper Melby Fish Bed Melby Rhyolites, Fauna, Petrography, Conditions of Deposition, Holm of Melby, References
Chapter 11 Middle Old Red Sandstone volcanic rocks and sediments of Papa Stour
Introduction, Basal& Lower Tuffs And Sandstones, Rhyolites And Inter-Rhyolitic Tuff, Structure, Geology Of Forewick Holm, References
Chapter 12 Old Red Sandstone of Foula
Introduction, Field Relationships, Conditions Of Imposition, Petrography, Structure, References
Chapter 13 The Northmaven-Muckle Roe Plutonic Complex
Introduction, Early Hypabyssal Intrusions, The Plutonic Complex, Field Relations, Ultrabasic Rocks, Diorite and Gabbro, Granites and Granophyre, Petrography, Ultrabasic Rocks, Gabbro and Diorite, The Larger Granite Masses, The Smaller Acid Bodies and Veins, Late Hydrothermal Activity, Field Relationships, Petrography, Evolution of the Igneous Complex, References
Field Relationships, Petrography, Outer Granite, Inner Porphyritic Granite, Reference
Chapter 15 The Sandsting Granite-Diorite Complex
Introduction, Diorites and Associated Rocks, Granodiorite, Porphyritic Microadamellite and Associated Rocks, Granite, Granite Veining in shattered Sediment within Sandsting Complex, Late fine-grained Acid and Basic Intrusions, The Metamorphic Aureole, Scapolitized Crush Zones within the Sandsting Complex, Structure and Mode of Emplacement of the Complex, References
Introduction, Basic and Intermediate Minor Intrusions: Field Relationships, Northmaven and Muckle Roe, Walls Peninsula and adjacent areas, Petrography, Basic Minor Intrusions, Dykes of Intermediate Composition, Acid Minor Intrusions, Field Relationships, Northmaven and Muckle Roe, North shore of Walls Peninsula and Adjacent Islands, Petrography, References
Chapter 17 Major transcurrent faults
Walls Boundary Fault, Outcrops of Fault, Tectonic History, Direction and Amount of Movement, Melby Fault, Conclusion, References
Chapter 18 Recent and Pleistocene
Mainland, Muckle Roe and Papa Stour, Introduction, Glacial Deposits, Interglacial Deposit, Evidence for Direction of Ice Flow, Corrie Glaciation, Glacial Retreat Phenomena, Periglacial and Post-Glacial Deposits, Peat, Post-Glacial Changes in Sea Level, Foula, References
Clothister Hill Magnetite, Road Metal, Building Materials, Limestone, Peat, Ornamental and Semi-Precious Stones, References
Appendix. List of Geological Survey photographs
Hand specimen photographs from the BGS Systematic Series
British Geological Survey maps — Links to 1:63,360 and 1:10,560 maps
Appendix. List Of Geological Survey Photographs
Index