The Assynt District in the Northwest Highlands is a veritable treasure trove of geological features, the most famous – amongst geologists – being the Moine Thrust. Perhaps less well known is that Assynt also hosts the most extensive cave systems in Scotland, developed in the Cambro-Ordovician Durness limestone. These two features are, of course, linked: Caledonian thrusting and folding resulted in thickening and fracturing of the limestone strata, allowing/enhancing the development of large cave systems.
{"title":"Book reviewCaves of Assynt (3rd edition), edited by TJ Lawson & PNF Dowswell. Grampian Speleological Group, Edinburgh, 2022. £20.00, 211 pp., ISBN 978-1-739735-0-3","authors":"M. Krabbendam","doi":"10.1144/sjg2023-002","DOIUrl":"https://doi.org/10.1144/sjg2023-002","url":null,"abstract":"The Assynt District in the Northwest Highlands is a veritable treasure trove of geological features, the most famous – amongst geologists – being the Moine Thrust. Perhaps less well known is that Assynt also hosts the most extensive cave systems in Scotland, developed in the Cambro-Ordovician Durness limestone. These two features are, of course, linked: Caledonian thrusting and folding resulted in thickening and fracturing of the limestone strata, allowing/enhancing the development of large cave systems.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46277419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Michael A. Taylor, Andy McMillan, S. Stewart, L. I. Anderson
A slab of cephalopod limestone bears a dedicatory Latin inscription on the mausoleum built around 1684 by Sir John Clerk of Penicuik (1649–1722) for his wife Elizabeth Henderson (1658–83) at St Mungo's Church, Penicuik, near Edinburgh, Scotland. The stone is identified on sedimentological and palaeontological evidence and historical context as Ordovician ‘orthoceratite limestone’ from Sweden, probably the island of Öland, rather than Carboniferous cephalopod limestone from the much nearer Closeburn area of Dumfriesshire. ‘Orthoceratite limestone’ was little used in Great Britain, and mainly as paving, so its use in a funerary monument is unusual. It is, however, paralleled by contemporary examples at Winchester Cathedral. The Penicuik slab was probably imported either directly from Sweden, or through Rotterdam or another Netherlands entrepôt. It is the only surviving historical example of this stone known in Edinburgh and the Lothians, probably because of changing fashions, building demolition and renewal of worn paving. The inscription shows errors of composition, carving and installation, ascribed to inexperience or haste. The employment of ‘orthoceratite limestone’ is interpreted as seeking to emulate Roman use of marbles and similar ornamental stones. It contributes to the Penicuik mausoleum's significance as a pioneering example of classical or Antique architecture.
{"title":"The geological and historical milieu of an ornamental cephalopod limestone (‘orthoceratite limestone’, Ordovician, Sweden) used in the Clerk Mausoleum (1684), St Mungo's Kirkyard, Penicuik, Scotland","authors":"Michael A. Taylor, Andy McMillan, S. Stewart, L. I. Anderson","doi":"10.1144/sjg2022-007","DOIUrl":"https://doi.org/10.1144/sjg2022-007","url":null,"abstract":"A slab of cephalopod limestone bears a dedicatory Latin inscription on the mausoleum built around 1684 by Sir John Clerk of Penicuik (1649–1722) for his wife Elizabeth Henderson (1658–83) at St Mungo's Church, Penicuik, near Edinburgh, Scotland. The stone is identified on sedimentological and palaeontological evidence and historical context as Ordovician ‘orthoceratite limestone’ from Sweden, probably the island of Öland, rather than Carboniferous cephalopod limestone from the much nearer Closeburn area of Dumfriesshire. ‘Orthoceratite limestone’ was little used in Great Britain, and mainly as paving, so its use in a funerary monument is unusual. It is, however, paralleled by contemporary examples at Winchester Cathedral. The Penicuik slab was probably imported either directly from Sweden, or through Rotterdam or another Netherlands entrepôt. It is the only surviving historical example of this stone known in Edinburgh and the Lothians, probably because of changing fashions, building demolition and renewal of worn paving. The inscription shows errors of composition, carving and installation, ascribed to inexperience or haste. The employment of ‘orthoceratite limestone’ is interpreted as seeking to emulate Roman use of marbles and similar ornamental stones. It contributes to the Penicuik mausoleum's significance as a pioneering example of classical or Antique architecture.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49008697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ray Perman is a writer and journalist, a former Chair of the James Hutton Institute in Edinburgh, and a Fellow of the Royal Society of Edinburgh, of which James Hutton was a founding member. There have been five previous biographies of Hutton, but this thoroughly researched volume offers a detailed account of the life and work of the Great Man. It includes insights into his personality and explanations for some of the mysteries surrounding him. We are shown the society in which he lived, in the period described as The Enlightenment, and in which Hutton was both a product and a co-driver.
Ray Perman是一名作家和记者，曾任爱丁堡詹姆斯·赫顿研究所主席，也是爱丁堡皇家学会会员，詹姆斯·赫顿是该学会的创始成员。赫顿之前有五本传记，但这本经过深入研究的书详细描述了这位伟人的生活和工作。其中包括对他的个性的见解，以及对围绕他的一些谜团的解释。我们看到了他所生活的社会，在被描述为启蒙运动的时期，赫顿既是一个产物，也是一个共同驱动者。
{"title":"Book reviewJames Hutton: The Genius of Time, by Ray Perman, Berlinn Ltd. Edinburgh, 2022, £25, hardcopy and ebook, 290 pp., ISBN 978-1-78027-785-1","authors":"C. Braithwaite","doi":"10.1144/sjg2022-013","DOIUrl":"https://doi.org/10.1144/sjg2022-013","url":null,"abstract":"Ray Perman is a writer and journalist, a former Chair of the James Hutton Institute in Edinburgh, and a Fellow of the Royal Society of Edinburgh, of which James Hutton was a founding member. There have been five previous biographies of Hutton, but this thoroughly researched volume offers a detailed account of the life and work of the Great Man. It includes insights into his personality and explanations for some of the mysteries surrounding him. We are shown the society in which he lived, in the period described as The Enlightenment, and in which Hutton was both a product and a co-driver.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44294175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Tipping, T. Kinnaird, Kirsty Dingwall, Irvine Ross
Excavation and survey of archaeological sites have in recent years generated new data on the chronology of river terraces on the River Dee between Banchory and Peterculter in Aberdeenshire. Terrace fragments have been mapped and correlated on altitudinal grounds, for the first time. Five terrace surfaces are identified and named, refining the terminology of the British Geological Survey (Merritt et al . 2003). Three are distinct surfaces within the Lochton Sand and Gravel Formation. The relation between them, regional deglaciation and the formation of the Late Devensian Loch of Park, north of Crathes, suggests some time separated their development. Below these, a fourth terrace, the Camphill Terrace, is dated to before the Windermere Interstadial by finds of Late Upper Palaeolithic flints. The Camphill Terrace is argued to have been the active valley floor within the Younger Dryas also. Timing of incision from the Camphill Terrace is not understood: interpretations are different at three archaeological sites. The youngest terrace fill and surface, the Maryculter Terrace, began to form c . 5000 years ago.
{"title":"Some geomorphological implications of recent archaeological investigations on river terraces of the River Dee, Aberdeenshire","authors":"R. Tipping, T. Kinnaird, Kirsty Dingwall, Irvine Ross","doi":"10.1144/sjg2022-010","DOIUrl":"https://doi.org/10.1144/sjg2022-010","url":null,"abstract":"\u0000 Excavation and survey of archaeological sites have in recent years generated new data on the chronology of river terraces on the River Dee between Banchory and Peterculter in Aberdeenshire. Terrace fragments have been mapped and correlated on altitudinal grounds, for the first time. Five terrace surfaces are identified and named, refining the terminology of the British Geological Survey (Merritt\u0000 et al\u0000 . 2003). Three are distinct surfaces within the Lochton Sand and Gravel Formation. The relation between them, regional deglaciation and the formation of the Late Devensian Loch of Park, north of Crathes, suggests some time separated their development. Below these, a fourth terrace, the Camphill Terrace, is dated to before the Windermere Interstadial by finds of Late Upper Palaeolithic flints. The Camphill Terrace is argued to have been the active valley floor within the Younger Dryas also. Timing of incision from the Camphill Terrace is not understood: interpretations are different at three archaeological sites. The youngest terrace fill and surface, the Maryculter Terrace, began to form\u0000 c\u0000 . 5000 years ago.\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48507370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Remains of the chondrichthyan Psephodus Morris and Roberts, 1862, consist mainly of isolated tooth plates. The genus has a range from Late Devonian (Famennian) to Late Mississippian (Serpukhovian). The most complete specimen is a partially articulated set of teeth and tooth plates of the type species, P. magnus, from the early Serpukhovian of East Kilbride, Lanarkshire, Scotland. A row of minute nodes is present along the basal margins of the Lophodus-like and Helodus-like teeth of the East Kilbride specimen. This distinguishes these teeth from typical Lophodus-like and Helodus-like teeth. As in Helodus simplex, some specimens of Psephodus display varying degrees of fusion of teeth from the same labiolingually oriented file into tooth plates. However, unlike Helodus simplex, some specimens of Psephodus display fusion of mesiodistally separated tooth plates, each representing a fused tooth file, into a larger tooth plate. Psephodus, which crosses the Devonian-Carboniferous boundary, may be ancestral to other Mississippian holocephalians, such as Cochliodus or Chondrenchelys, in which dentitions consist of a few tooth plates with only few, or no, separate teeth. An unpublished watercolour by Agassiz's artist Dinkel depicts five tooth plates, which can be designated as syntypes of P. magnus. A lectotype for Psephodus crenulatus is designated.
{"title":"The Palaeozoic genus Psephodus (Chondrichthyes, Cochliodontiformes) and the transition from teeth to tooth plates in holocephalians","authors":"W. Itano","doi":"10.1144/sjg2021-016","DOIUrl":"https://doi.org/10.1144/sjg2021-016","url":null,"abstract":"Remains of the chondrichthyan Psephodus Morris and Roberts, 1862, consist mainly of isolated tooth plates. The genus has a range from Late Devonian (Famennian) to Late Mississippian (Serpukhovian). The most complete specimen is a partially articulated set of teeth and tooth plates of the type species, P. magnus, from the early Serpukhovian of East Kilbride, Lanarkshire, Scotland. A row of minute nodes is present along the basal margins of the Lophodus-like and Helodus-like teeth of the East Kilbride specimen. This distinguishes these teeth from typical Lophodus-like and Helodus-like teeth. As in Helodus simplex, some specimens of Psephodus display varying degrees of fusion of teeth from the same labiolingually oriented file into tooth plates. However, unlike Helodus simplex, some specimens of Psephodus display fusion of mesiodistally separated tooth plates, each representing a fused tooth file, into a larger tooth plate. Psephodus, which crosses the Devonian-Carboniferous boundary, may be ancestral to other Mississippian holocephalians, such as Cochliodus or Chondrenchelys, in which dentitions consist of a few tooth plates with only few, or no, separate teeth. An unpublished watercolour by Agassiz's artist Dinkel depicts five tooth plates, which can be designated as syntypes of P. magnus. A lectotype for Psephodus crenulatus is designated.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44895471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mesacanthus mitchelli is an important taxon in elucidating relationships amongst stem chondrichthyans, being the best known and most abundant of the oldest known acanthodiform acanthodians. Here we note some newly recognised morphological features and describe the histological structure of the endoskeleton and dermal elements. The jaws are preserved as a single layer of irregularly tessellate bone-like mineralisations. A mandibular bone is not present, contrary to previous descriptions. Fin spines have a wide central cavity that is more than half the width at mid-spine level. Prepelvic spines have a very narrow leading edge ridge and a wide open pulp cavity. Head sensory lines are enclosed by a pair of tesserae with a smooth crown, flat base and concave sides, bordering the sensory line canal. The tiny body scales have a relatively large pulp cavity in the embryonic zone. The large size of the eyes relative to the head and body size in Mesacanthus mitchelli, the structure and small size of the scales relative to those of other acanthodians of a similar size, and the wide central pulp cavity in the spines, all indicate that the species is likely to have undergone paedomorphism.
{"title":"New information on the Early Devonian acanthodian Mesacanthus mitchelli from the Midland Valley of Scotland","authors":"C. Burrow, J. D. Den Blaauwen, M. Newman","doi":"10.1144/sjg2021-004","DOIUrl":"https://doi.org/10.1144/sjg2021-004","url":null,"abstract":"Mesacanthus mitchelli is an important taxon in elucidating relationships amongst stem chondrichthyans, being the best known and most abundant of the oldest known acanthodiform acanthodians. Here we note some newly recognised morphological features and describe the histological structure of the endoskeleton and dermal elements. The jaws are preserved as a single layer of irregularly tessellate bone-like mineralisations. A mandibular bone is not present, contrary to previous descriptions. Fin spines have a wide central cavity that is more than half the width at mid-spine level. Prepelvic spines have a very narrow leading edge ridge and a wide open pulp cavity. Head sensory lines are enclosed by a pair of tesserae with a smooth crown, flat base and concave sides, bordering the sensory line canal. The tiny body scales have a relatively large pulp cavity in the embryonic zone. The large size of the eyes relative to the head and body size in Mesacanthus mitchelli, the structure and small size of the scales relative to those of other acanthodians of a similar size, and the wide central pulp cavity in the spines, all indicate that the species is likely to have undergone paedomorphism.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46432358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. J. Drake, E. Gomez‐Rivas, R. Ickert, D. Macdonald
The Deeside Limestone Formation (DLF), outcropping in western Aberdeenshire, comprises the eastern margin of a distinctive Upper Dalradian mixed siliciclastic–carbonate system of Ediacaran age which may be correlated southwestwards for more than 400 km to County Donegal in Ireland. A reconstructed stratigraphic column suggests three broad vertical sequences (S1–S3), each comprising a general upward proportionate increase in calcium carbonate with respect to quartz, locally capped by metalimestones (L1–L3). A simple explanation for this upward change lies in the differing physical response of the two heterolithic components under the same hydrodynamic process, with the heavier quartz grains preferentially enriching the bedload and the finer carbonate mud fraction, the suspended load. The three metalimestone intervals are observed only in central/eastern parts of the field area, suggesting a lateral facies variation. The predominance of calcareous–siliciclastic bed-scale compositional mixing within the DLF suggests sedimentation on the Dalradian shelf comprised contemporaneous mixing of the siliciclastic and carbonate fractions prior to subsequent re-mixing during transportation downslope into the deep water, punctuated by pulses of point-sourced siliciclastic input.
{"title":"Temporal and spatial variations in calcium carbonate deposition in a mixed siliciclastic–carbonate deep marine system: the Ediacaran Deeside Limestone Formation, Aboyne, Scotland","authors":"S. J. Drake, E. Gomez‐Rivas, R. Ickert, D. Macdonald","doi":"10.1144/sjg2021-017","DOIUrl":"https://doi.org/10.1144/sjg2021-017","url":null,"abstract":"The Deeside Limestone Formation (DLF), outcropping in western Aberdeenshire, comprises the eastern margin of a distinctive Upper Dalradian mixed siliciclastic–carbonate system of Ediacaran age which may be correlated southwestwards for more than 400 km to County Donegal in Ireland. A reconstructed stratigraphic column suggests three broad vertical sequences (S1–S3), each comprising a general upward proportionate increase in calcium carbonate with respect to quartz, locally capped by metalimestones (L1–L3). A simple explanation for this upward change lies in the differing physical response of the two heterolithic components under the same hydrodynamic process, with the heavier quartz grains preferentially enriching the bedload and the finer carbonate mud fraction, the suspended load. The three metalimestone intervals are observed only in central/eastern parts of the field area, suggesting a lateral facies variation. The predominance of calcareous–siliciclastic bed-scale compositional mixing within the DLF suggests sedimentation on the Dalradian shelf comprised contemporaneous mixing of the siliciclastic and carbonate fractions prior to subsequent re-mixing during transportation downslope into the deep water, punctuated by pulses of point-sourced siliciclastic input.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47352825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The anisotropy of magnetic susceptibility (AMS) is used to reveal subtle mineral alignment fabrics in apparently isotropic crystalline lithologies, including granites. Such petrofabrics can be produced by emplacement-related magma flow or post-emplacement tectonic strain. However, discriminating between flow-related and tectonic fabrics using field observations alone may be challenging and is usually a broad and arbitrary interpretation. In this contribution, we employ a range of magnetic analyses to characterize the origin of the petrofabric in the c. 425 Ma Ratagain Complex, NW Scotland, a composite Late Caledonian granitic intrusion. Our detailed magnetic analyses reveal that whilst all intrusive units carry an ambient tectonic overprint, critically, this has not developed into an obvious tectonic fabric and contains a horizontal shortening component indicative of transpression. This appears at odds with the well-defined Silurian (Scandian phase) regional transtensional tectonic regime from c. 420–415 Ma onwards. Accordingly, we suggest that either the complex is younger than previously thought or that it existed as a crystal-mush close to the magmatic solidus for a protracted period after its initial emplacement. This study lays the foundations for much-needed further investigations into the detailed emplacement mechanisms, timescales and petrogenesis of individual granitic intrusions, to aid understanding of Late Caledonian tectonics. Supplementary material: Supplementary data to this article are available at https://doi.org/10.6084/m9.figshare.c.5941375 Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/cc/SJG-early-career-research
磁化率的各向异性(AMS)用于揭示明显各向同性的晶体岩性中微妙的矿物排列结构，包括花岗岩。这种岩质组构可以由与侵位有关的岩浆流动或侵位后构造应变产生。然而，仅通过现场观测来区分与流动有关的和构造组构可能具有挑战性，并且通常是一种广泛而武断的解释。在这篇文章中，我们采用了一系列的磁分析来表征苏格兰西北部c. 425 Ma Ratagain杂岩中岩石组构的起源，这是一个复合的晚加里东期花岗岩侵入岩。详细的磁分析表明，虽然所有侵入单元都带有环境构造套印，但重要的是，这并没有发展成一个明显的构造结构，并且包含一个水平缩短成分，表明了逆压作用。这似乎与公元前420-415 Ma以来明确的志留纪(加拿大期)区域张拉构造制度不一致。因此，我们认为，要么该复合体比以前认为的更年轻，要么它在最初就位后很长一段时间内以靠近岩浆固相的晶体糊状存在。该研究为进一步深入研究花岗岩侵入体的详细侵位机制、时间尺度和岩石成因奠定了基础，有助于认识晚加里东期构造。补充材料:本文的补充数据可在https://doi.org/10.6084/m9.figshare.c.5941375上获得主题集合:本文是早期职业研究集合的一部分，可在https://www.lyellcollection.org/cc/SJG-early-career-research上获得
{"title":"Mush ado about the Ratagain Complex, NW Scotland: insights into Caledonian granitic magmatism and emplacement from magnetic fabric analyses","authors":"A. Lawrence, M. Maffione, C. Stevenson","doi":"10.1144/sjg2021-018","DOIUrl":"https://doi.org/10.1144/sjg2021-018","url":null,"abstract":"The anisotropy of magnetic susceptibility (AMS) is used to reveal subtle mineral alignment fabrics in apparently isotropic crystalline lithologies, including granites. Such petrofabrics can be produced by emplacement-related magma flow or post-emplacement tectonic strain. However, discriminating between flow-related and tectonic fabrics using field observations alone may be challenging and is usually a broad and arbitrary interpretation. In this contribution, we employ a range of magnetic analyses to characterize the origin of the petrofabric in the c. 425 Ma Ratagain Complex, NW Scotland, a composite Late Caledonian granitic intrusion. Our detailed magnetic analyses reveal that whilst all intrusive units carry an ambient tectonic overprint, critically, this has not developed into an obvious tectonic fabric and contains a horizontal shortening component indicative of transpression. This appears at odds with the well-defined Silurian (Scandian phase) regional transtensional tectonic regime from c. 420–415 Ma onwards. Accordingly, we suggest that either the complex is younger than previously thought or that it existed as a crystal-mush close to the magmatic solidus for a protracted period after its initial emplacement. This study lays the foundations for much-needed further investigations into the detailed emplacement mechanisms, timescales and petrogenesis of individual granitic intrusions, to aid understanding of Late Caledonian tectonics. Supplementary material: Supplementary data to this article are available at https://doi.org/10.6084/m9.figshare.c.5941375 Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/cc/SJG-early-career-research","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-04-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48279393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The later Paleoproterozoic (Laxfordian) structural and metamorphic history of the Lewisian Complex can be explained by several major kinematic changes. At c. 1.9 Ga, the neighbouring Archean cratons of Rae, North Atlantic (NAC), Kola and Karelia were isolated from each other and subduction and accretion were active at their margins. At c. 1.85 Ga, during the ‘Early Laxfordian’, the Lewisian, then part of the Nagssugtoqidian orogenic belt, experienced NW–SE-directed tectonic movements attributed to east–west convergence between the Rae Craton and the NAC, probably prompted by collision with Baltica. At c. 1.7 Ga, during the ‘Late Laxfordian’, a major change to north–south convergence produced a combination of NW–SE-trending folds and NW–SE dextral shear zones. The kinematic system changed again after c. 1.6 Ga. The latter two changes may be attributable to the docking of further large cratons as the Nuna supercontinent was assembled. The Lewisian terrane model can be interpreted in terms of the relative movements between two major cratons, Rae and NAC. Sandwiched between them was a third, composed of material partly derived from a juvenile magmatic arc or arcs situated in oceanic crust. The Assynt terrane may be an isolated remnant of the upper-plate NAC, whereas most of the remaining Lewisian outcrop may consist of modified Rae material.
{"title":"A regional explanation for Laxfordian tectonic evolution and its implications for the Lewisian terrane model","authors":"G. Park","doi":"10.1144/sjg2021-020","DOIUrl":"https://doi.org/10.1144/sjg2021-020","url":null,"abstract":"The later Paleoproterozoic (Laxfordian) structural and metamorphic history of the Lewisian Complex can be explained by several major kinematic changes. At c. 1.9 Ga, the neighbouring Archean cratons of Rae, North Atlantic (NAC), Kola and Karelia were isolated from each other and subduction and accretion were active at their margins. At c. 1.85 Ga, during the ‘Early Laxfordian’, the Lewisian, then part of the Nagssugtoqidian orogenic belt, experienced NW–SE-directed tectonic movements attributed to east–west convergence between the Rae Craton and the NAC, probably prompted by collision with Baltica. At c. 1.7 Ga, during the ‘Late Laxfordian’, a major change to north–south convergence produced a combination of NW–SE-trending folds and NW–SE dextral shear zones. The kinematic system changed again after c. 1.6 Ga. The latter two changes may be attributable to the docking of further large cratons as the Nuna supercontinent was assembled. The Lewisian terrane model can be interpreted in terms of the relative movements between two major cratons, Rae and NAC. Sandwiched between them was a third, composed of material partly derived from a juvenile magmatic arc or arcs situated in oceanic crust. The Assynt terrane may be an isolated remnant of the upper-plate NAC, whereas most of the remaining Lewisian outcrop may consist of modified Rae material.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64034176","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Mitten, A. Gough, A. Leslie, S. Clarke, M. Browne
The early Devonian Greywacke Conglomerate Formation of the Lanark Basin, southwestern Midland Valley of Scotland, has been exposed by a new road cut in the Glenbuck area, East Ayrshire, enabling a high-resolution sedimentological analysis of this unusually high-quality section. This study provides a facies analysis of the sedimentary rocks exposed in the Glenbuck area, and comparison with contemporaneous bedrock sections from across the Lanark Basin and adjacent Southern Upland High. Eleven lithofacies are identified, grouped into five associations: aggradational talus cone, progradational talus cone, debris flow lobe, fan surface aqueous-alluvial deposits, and gravel barform deposits. These comprise medial and proximal alluvial fan deposits, controlled by autogenic scour and avulsion along with general fan progradation. Contemporaneous sediments are present around Silurian inliers in the Lanark Basin and adjacent regions of the Southern Upland High. Whilst deposits in the Lanark Basin are genetically similar, contemporaneous deposits of the Southern Upland High preserve a distinctly more angular clast assemblage, indicating textural immaturity relative to those in the Lanark Basin.
{"title":"Facies analysis of the Greywacke Conglomerate Formation, Glenbuck, Scotland","authors":"A. Mitten, A. Gough, A. Leslie, S. Clarke, M. Browne","doi":"10.1144/sjg2021-010","DOIUrl":"https://doi.org/10.1144/sjg2021-010","url":null,"abstract":"The early Devonian Greywacke Conglomerate Formation of the Lanark Basin, southwestern Midland Valley of Scotland, has been exposed by a new road cut in the Glenbuck area, East Ayrshire, enabling a high-resolution sedimentological analysis of this unusually high-quality section. This study provides a facies analysis of the sedimentary rocks exposed in the Glenbuck area, and comparison with contemporaneous bedrock sections from across the Lanark Basin and adjacent Southern Upland High. Eleven lithofacies are identified, grouped into five associations: aggradational talus cone, progradational talus cone, debris flow lobe, fan surface aqueous-alluvial deposits, and gravel barform deposits. These comprise medial and proximal alluvial fan deposits, controlled by autogenic scour and avulsion along with general fan progradation. Contemporaneous sediments are present around Silurian inliers in the Lanark Basin and adjacent regions of the Southern Upland High. Whilst deposits in the Lanark Basin are genetically similar, contemporaneous deposits of the Southern Upland High preserve a distinctly more angular clast assemblage, indicating textural immaturity relative to those in the Lanark Basin.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2022-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41961016","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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