J. Daly, M. Flowerdew, Martin J. Whitehouse, E. Badenszki
A geochronological and isotopic study grounded by field observations is presented on the southern-most Lewisian orthogneisses of Iona, southwest Scotland. Syenitic orthogneisses in western Iona and granodioritic orthogneisses in the east have yielded indistinguishable SIMS U-Pb zircon c . 2710 Ma protolith ages, among the youngest recorded from the Lewisian. Whole-rock Sm-Nd and zircon Lu-Hf data indicate largely juvenile Neoarchaean crustal additions. Based on this evidence, a north-south trending mylonite zone separating eastern and western Iona is unlikely to be a terrane boundary. Extensive reworking during the “late Laxfordian” deformational event between 1779-1753 Ma (bracketed between pre-tectonic migmatisation and post-tectonic granitic pegmatite intrusion) likely corresponds to accretion of the Rhinns Complex to the Nuna/ Columbia supercontinent. Zircon Lu-Hf data indicate that late Laxfordian melts were largely derived from the Neoarchaean orthogneisses. K-feldspar Pb isotope ratios in the orthogneisses have likely been reset during late Laxfordian metamorphism while those in a post-tectonic syenitic pegmatite, with a U-Pb zircon age of 1688 ± 8 Ma are considered to be original and consistent with an exotic source. Correlation of the Iona Lewisian with Coll and Tiree is possible but the younger age of the Iona orthogneisses does not support correlation with the Rona terrane.
{"title":"Palaeoproterozoic (late “Laxfordian”) reworking of juvenile Neoarchean Lewisian orthogneisses, Iona, Inner Hebrides, Scotland.","authors":"J. Daly, M. Flowerdew, Martin J. Whitehouse, E. Badenszki","doi":"10.1144/sjg2024-005","DOIUrl":"https://doi.org/10.1144/sjg2024-005","url":null,"abstract":"\u0000 A geochronological and isotopic study grounded by field observations is presented on the southern-most Lewisian orthogneisses of Iona, southwest Scotland. Syenitic orthogneisses in western Iona and granodioritic orthogneisses in the east have yielded indistinguishable SIMS U-Pb zircon\u0000 c\u0000 . 2710 Ma protolith ages, among the youngest recorded from the Lewisian. Whole-rock Sm-Nd and zircon Lu-Hf data indicate largely juvenile Neoarchaean crustal additions. Based on this evidence, a north-south trending mylonite zone separating eastern and western Iona is unlikely to be a terrane boundary. Extensive reworking during the “late Laxfordian” deformational event between 1779-1753 Ma (bracketed between pre-tectonic migmatisation and post-tectonic granitic pegmatite intrusion) likely corresponds to accretion of the Rhinns Complex to the Nuna/ Columbia supercontinent. Zircon Lu-Hf data indicate that late Laxfordian melts were largely derived from the Neoarchaean orthogneisses. K-feldspar Pb isotope ratios in the orthogneisses have likely been reset during late Laxfordian metamorphism while those in a post-tectonic syenitic pegmatite, with a U-Pb zircon age of 1688 ± 8 Ma are considered to be original and consistent with an exotic source. Correlation of the Iona Lewisian with Coll and Tiree is possible but the younger age of the Iona orthogneisses does not support correlation with the Rona terrane.\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141805342","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}
Two malacostracan crustacean genera are described from the Langsettian (upper part of the Bashkirian, Lower Pennsylvanian) of the Scottish Coal Fields in the Midland Valley of Scotland. One is the youngest occurrence of Tealliocaris Peach, 1908 and was found at Polkemmet Colliery near Whitburn. It is recognised as a new species, Tealliocaris elliotti , based on the presence of eight spines on its scaphocerites and lateral convergent carinae of the telson. The other crustacean is a unique specimen from the Ardenrigg Colliery at Wester Bracco, North Lanarkshire in similar shales of Langsettian age. There are no distinguishing characters preserved that would identify it as a new species, but it can be placed in Palaeocaris Meek and Worthen, 1865 based on the well preserved features of the tail fan. This is the first record of this genus in Scotland, although specimens of Minicaris brandi Schram, 1979 from the Namurian (Serpukhovian, Upper Mississippian) shales of Bearsden are now here also considered to be a species of Palaeocaris .
{"title":"New malacostracan crustaceans from the Lower Coal Measures (Langsettian, Carboniferous) North Lanarkshire, Scotland","authors":"Neil D. L. Clark","doi":"10.1144/sjg2024-004","DOIUrl":"https://doi.org/10.1144/sjg2024-004","url":null,"abstract":"\u0000 Two malacostracan crustacean genera are described from the Langsettian (upper part of the Bashkirian, Lower Pennsylvanian) of the Scottish Coal Fields in the Midland Valley of Scotland. One is the youngest occurrence of\u0000 Tealliocaris\u0000 Peach, 1908 and was found at Polkemmet Colliery near Whitburn. It is recognised as a new species,\u0000 Tealliocaris elliotti\u0000 , based on the presence of eight spines on its scaphocerites and lateral convergent carinae of the telson. The other crustacean is a unique specimen from the Ardenrigg Colliery at Wester Bracco, North Lanarkshire in similar shales of Langsettian age. There are no distinguishing characters preserved that would identify it as a new species, but it can be placed in\u0000 Palaeocaris\u0000 Meek and Worthen, 1865 based on the well preserved features of the tail fan. This is the first record of this genus in Scotland, although specimens of\u0000 Minicaris brandi\u0000 Schram, 1979 from the Namurian (Serpukhovian, Upper Mississippian) shales of Bearsden are now here also considered to be a species of\u0000 Palaeocaris\u0000 .\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.5,"publicationDate":"2024-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141812848","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 Lealt Shale Formation is known for its superb preservation of aragonitic molluscs. As fish otoliths are primarily composed of aragonite, and because of the semi-stable nature of this polymorph, records of otoliths become increasingly rare in deep time. Therefore, the Lealt Shale Formation provides a window through which to expand knowledge of Middle Jurassic otoliths. A total of 753 otoliths have been collected, representing ten species: three in Archaeotolithus , five in Leptolepis , one Archengraulis and a teleost incertae sedis (juveniles only). Four species are new: Archaeotolithus eiggensis, Archaeotolithus invernizziae, Leptolepis flexuosus and Leptolepis skyensis . Two species remain in open nomenclature and the remaining species are known from the Middle Jurassic of southern England and continental Europe: Archaeotolithus doppelsteini , Leptolepis densus , Leptolepis rotundatus and Archengraulis productus . The Lealt Shale Formation was deposited in a low salinity lagoonal environment with variable freshwater influx and a likely tenuous link to marine waters resulting in a complex palaeosalinity history. The relevance of the specific environment for the composition of the fish fauna as documented by otoliths is discussed. The evolution of the otolith morphospace during the Jurassic is discussed in the light of the new finds.
{"title":"Otoliths from the Lealt Shale Formation, Great Estuarine Group, Middle Jurassic (Bathonian), Inner Hebrides, Scotland","authors":"W. Schwarzhans, Matthew I. Wakefield","doi":"10.1144/sjg2024-002","DOIUrl":"https://doi.org/10.1144/sjg2024-002","url":null,"abstract":"\u0000 The Lealt Shale Formation is known for its superb preservation of aragonitic molluscs. As fish otoliths are primarily composed of aragonite, and because of the semi-stable nature of this polymorph, records of otoliths become increasingly rare in deep time. Therefore, the Lealt Shale Formation provides a window through which to expand knowledge of Middle Jurassic otoliths. A total of 753 otoliths have been collected, representing ten species: three in\u0000 Archaeotolithus\u0000 , five in\u0000 Leptolepis\u0000 , one\u0000 Archengraulis\u0000 and a teleost incertae sedis (juveniles only). Four species are new:\u0000 Archaeotolithus eiggensis, Archaeotolithus invernizziae, Leptolepis flexuosus\u0000 and\u0000 Leptolepis skyensis\u0000 . Two species remain in open nomenclature and the remaining species are known from the Middle Jurassic of southern England and continental Europe:\u0000 Archaeotolithus doppelsteini\u0000 ,\u0000 Leptolepis densus\u0000 ,\u0000 Leptolepis rotundatus\u0000 and\u0000 Archengraulis productus\u0000 .\u0000 \u0000 The Lealt Shale Formation was deposited in a low salinity lagoonal environment with variable freshwater influx and a likely tenuous link to marine waters resulting in a complex palaeosalinity history. The relevance of the specific environment for the composition of the fish fauna as documented by otoliths is discussed. The evolution of the otolith morphospace during the Jurassic is discussed in the light of the new finds.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141100772","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}
E. Heptinstall, J. Parnell, Andrea Schito, Adrian J. Boyce, J. Armstrong, David Muirhead
Graphite occurs in Neoproterozoic (probable Loch Ness Supergroup) marbles of The Aird, in the Northern Highland Terrane, Scotland. The graphite occurs particularly in association with phlogopite mica, and also with other micas and Mg-chlorite. Although the graphite-phlogopite association is recorded widely elsewhere in mantle-derived rocks, our data suggests graphite at The Aird does not have a mantle origin. The carbon isotopic composition of the graphite ( δ 13 C, 0.4 to -1.6 ‰) indicates graphitisation occurred from a CO 2 -rich fluid associated with decarbonation or devolatilisation reactions of a carbonate-silicate protolith. Graphite-phlogopite bearing marbles in the Aird underwent extensive brecciation and haematite deposition that preceded carbon-rich, mantle-derived (carbonatite) fluids. Pyrite in veins within The Aird marble has a sulphur isotope composition depleted in 34 S (-15.5 to -16.6 ‰), suggesting a biogenic origin. Elsewhere in The Aird and in surrounding fenitised rocks 34 S -enriched pyrite has sulphur isotope compositions between 7.7 to 6.1 ‰, outside the sulphur isotopic composition range of most carbonatite-hosted pyrite, suggesting pyrite veining was likely influenced by crustal fluid-rock interactions. The observations show that if the protolith has a carbonate-silicate composition, a graphite-phlogopite association can form without the need for mantle-derived fluids. Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/topic/collections/early-career-research
{"title":"Graphitisation of Neoproterozoic sedimentary marbles in The Aird, Scottish Highlands","authors":"E. Heptinstall, J. Parnell, Andrea Schito, Adrian J. Boyce, J. Armstrong, David Muirhead","doi":"10.1144/sjg2023-013","DOIUrl":"https://doi.org/10.1144/sjg2023-013","url":null,"abstract":"\u0000 Graphite occurs in Neoproterozoic (probable Loch Ness Supergroup) marbles of The Aird, in the Northern Highland Terrane, Scotland. The graphite occurs particularly in association with phlogopite mica, and also with other micas and Mg-chlorite. Although the graphite-phlogopite association is recorded widely elsewhere in mantle-derived rocks, our data suggests graphite at The Aird does not have a mantle origin. The carbon isotopic composition of the graphite (\u0000 \u0000 \u0000 δ\u0000 \u0000 \u0000 13\u0000 C, 0.4 to -1.6 ‰) indicates graphitisation occurred from a CO\u0000 2\u0000 -rich fluid associated with decarbonation or devolatilisation reactions of a carbonate-silicate protolith. Graphite-phlogopite bearing marbles in the Aird underwent extensive brecciation and haematite deposition that preceded carbon-rich, mantle-derived (carbonatite) fluids. Pyrite in veins within The Aird marble has a sulphur isotope composition depleted in\u0000 \u0000 34\u0000 S\u0000 \u0000 (-15.5 to -16.6 ‰), suggesting a biogenic origin. Elsewhere in The Aird and in surrounding fenitised rocks\u0000 \u0000 34\u0000 S\u0000 \u0000 -enriched pyrite has sulphur isotope compositions between 7.7 to 6.1 ‰, outside the sulphur isotopic composition range of most carbonatite-hosted pyrite, suggesting pyrite veining was likely influenced by crustal fluid-rock interactions. The observations show that if the protolith has a carbonate-silicate composition, a graphite-phlogopite association can form without the need for mantle-derived fluids.\u0000 \u0000 \u0000 Thematic collection:\u0000 This article is part of the Early Career Research collection available at:\u0000 https://www.lyellcollection.org/topic/collections/early-career-research\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140982370","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 base of the Mull Lava Sequence, part of the Palaeogene British Igneous Province, contains a variety of volcanic features, e.g., small-scale filled lava tubes and toes that can be interpreted as large-scale inflated sheets from pāhoehoe lava flows. Here, we re-examine a previously reported unique outcrop found along the coastline of Lon Reudle, Mull, which can be better understood under that conceptual model. The outcrop is composed by multiple layers, with repeating porphyritic, poorly columnar jointed and vesicle-free layers, alternating with vesicle-rich layers with individual vesicles measuring up to 1 m. We reinterpret the outcrop as an individual inflated pāhoehoe lobe with an aggregated total thickness of at least 25 m. The estimated thickness of the upper crust of this lobe is 15 m, as the upper crust would account for 40-60% of the total volume of the flow, while the time required for this upper crust to form is ∼4 years. The alternation between vesicle-rich and vesicle-free layers is likely to be caused by instabilities of the suspended bubbles in the basaltic melt, forming a diapir with abundant evidence of bubble coalescence. Typical Hawaiian pāhoehoe lava flows have thickness of 1-3 metres, while in other flood basalt provinces thickness can reach up to 75-80 metres, suggesting that pāhoehoe structures are scale-independent. This is a key factor to take into account at the time of re-interpreting other lava structures that have been found in the Palaeogene British Igneous Province.
{"title":"Pāhoehoe lava emplacement in Lon Reudle, Mull.","authors":"Steven N. A. Walker, Joaquín A. Cortés","doi":"10.1144/sjg2023-019","DOIUrl":"https://doi.org/10.1144/sjg2023-019","url":null,"abstract":"The base of the Mull Lava Sequence, part of the Palaeogene British Igneous Province, contains a variety of volcanic features, e.g., small-scale filled lava tubes and toes that can be interpreted as large-scale inflated sheets from pāhoehoe lava flows. Here, we re-examine a previously reported unique outcrop found along the coastline of Lon Reudle, Mull, which can be better understood under that conceptual model. The outcrop is composed by multiple layers, with repeating porphyritic, poorly columnar jointed and vesicle-free layers, alternating with vesicle-rich layers with individual vesicles measuring up to 1 m. We reinterpret the outcrop as an individual inflated pāhoehoe lobe with an aggregated total thickness of at least 25 m. The estimated thickness of the upper crust of this lobe is 15 m, as the upper crust would account for 40-60% of the total volume of the flow, while the time required for this upper crust to form is ∼4 years. The alternation between vesicle-rich and vesicle-free layers is likely to be caused by instabilities of the suspended bubbles in the basaltic melt, forming a diapir with abundant evidence of bubble coalescence. Typical Hawaiian pāhoehoe lava flows have thickness of 1-3 metres, while in other flood basalt provinces thickness can reach up to 75-80 metres, suggesting that pāhoehoe structures are scale-independent. This is a key factor to take into account at the time of re-interpreting other lava structures that have been found in the Palaeogene British Igneous Province.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140674159","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. Webb, T. Torvela, R. Chapman, D. Selby, R. Gooday
The Tomnadashan sulphide deposit, which is located on the southern margin of Loch Tay (Scotland, UK), was mined for copper during the 19 th century. The genetic processes at Tomnadashan remain poorly understood, and the mineralisation has never been dated. To gain an improved understanding of this mineral system, we have dated the molybdenite at Tomnadashan using the Re-Os chronometer. Furthermore, we have contextualised these ages within a paragenetic interpretation. Our results show that the molybdenite is ca. 423-419 Ma, and it occurs early in the paragenesis (the second stage out of six). Based on the paragenesis of molybdenite, this age is likely to reflect the initial Caledonian mineralisation event at Loch Tay. Our new data and literature review suggest that whilst Tomnadashan is a magmatic-related ore deposit, the outcropping porphyry is unlikely to have provided the mineralising fluids associated with the mineralisation. A concealed intrusion or granitic dykes within the porphyry may be the source of the magmatic-hydrothermal fluids. The age data indicate that the Tomnadashan mineralisation is coeval with gold mineralisation at Cavanacaw in Northern Ireland, giving rise to the possibility of a previously unrecognised mid-Silurian magmatic-hydrothermal episode of gold and base metal mineralisation throughout the Grampian Terrane. Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/topic/collections/early-career-research
{"title":"A reinterpretation of the mineralisation processes involved in the formation of the Tomnadashan sulphide deposit, Loch Tay, Scotland, UK","authors":"S. Webb, T. Torvela, R. Chapman, D. Selby, R. Gooday","doi":"10.1144/sjg2023-023","DOIUrl":"https://doi.org/10.1144/sjg2023-023","url":null,"abstract":"\u0000 The Tomnadashan sulphide deposit, which is located on the southern margin of Loch Tay (Scotland, UK), was mined for copper during the 19\u0000 th\u0000 century. The genetic processes at Tomnadashan remain poorly understood, and the mineralisation has never been dated. To gain an improved understanding of this mineral system, we have dated the molybdenite at Tomnadashan using the Re-Os chronometer. Furthermore, we have contextualised these ages within a paragenetic interpretation.\u0000 \u0000 Our results show that the molybdenite is ca. 423-419 Ma, and it occurs early in the paragenesis (the second stage out of six). Based on the paragenesis of molybdenite, this age is likely to reflect the initial Caledonian mineralisation event at Loch Tay. Our new data and literature review suggest that whilst Tomnadashan is a magmatic-related ore deposit, the outcropping porphyry is unlikely to have provided the mineralising fluids associated with the mineralisation. A concealed intrusion or granitic dykes within the porphyry may be the source of the magmatic-hydrothermal fluids. The age data indicate that the Tomnadashan mineralisation is coeval with gold mineralisation at Cavanacaw in Northern Ireland, giving rise to the possibility of a previously unrecognised mid-Silurian magmatic-hydrothermal episode of gold and base metal mineralisation throughout the Grampian Terrane.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Early Career Research collection available at:\u0000 https://www.lyellcollection.org/topic/collections/early-career-research\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140373925","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 Glencoe caldera is a well-studied example of a caldera system exposed to intermediate depths along the glacially excavated glen. We present a first quantitative assessment of clast-size population and matrix chemistry from the flinty crush rock which occurs on the main ring faults. Size-shape metrics of clasts differ from those of a ‘normal’ pseudotachylite from the Outer Hebrides. Both samples display good power-law clast size populations, once allowance is made for dissolution of a portion of clasts into the melt which contained them, with fractal dimensions of 2.7 and 4.0 respectively for the Outer Hebrides and Glencoe samples respectively. Mass-balance calculations of flinty crush rock matrix chemistry imply an origin by mixing between rhyolite and pseudotachylite which was derived from semipelitic host rock. This means that the flinty crush rock was transported some distance from the point of frictional heating, as previously proposed, since semipelitic rocks are not present at the surface at Stob Mic Mhartuin but are likely to be present at depth. This transport, and mixing with rhyolite magma, would have provided the time and thermal energy for clast dissolution beyond that possible during normal pseudotachylite generation and quenching on fault wall rocks. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7084992
{"title":"Magma mixing between rhyolite and pseudotachylite as the origin for the Glencoe ‘Flinty Crush Rock’","authors":"David P Dobson, Viorela Martinescu","doi":"10.1144/sjg2023-016","DOIUrl":"https://doi.org/10.1144/sjg2023-016","url":null,"abstract":"The Glencoe caldera is a well-studied example of a caldera system exposed to intermediate depths along the glacially excavated glen. We present a first quantitative assessment of clast-size population and matrix chemistry from the flinty crush rock which occurs on the main ring faults. Size-shape metrics of clasts differ from those of a ‘normal’ pseudotachylite from the Outer Hebrides. Both samples display good power-law clast size populations, once allowance is made for dissolution of a portion of clasts into the melt which contained them, with fractal dimensions of 2.7 and 4.0 respectively for the Outer Hebrides and Glencoe samples respectively.\u0000 Mass-balance calculations of flinty crush rock matrix chemistry imply an origin by mixing between rhyolite and pseudotachylite which was derived from semipelitic host rock. This means that the flinty crush rock was transported some distance from the point of frictional heating, as previously proposed, since semipelitic rocks are not present at the surface at Stob Mic Mhartuin but are likely to be present at depth. This transport, and mixing with rhyolite magma, would have provided the time and thermal energy for clast dissolution beyond that possible during normal pseudotachylite generation and quenching on fault wall rocks. \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7084992\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2024-02-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140425001","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}
Two species of the closely-related monobathrid crinoid from the Lower Palaeozoic of Scotland, namely Macrostylocrinus cirrifer Ramsbottom (Upper Ordovician, Katian) and Macrostylocrinus silurocirrifer Brower (Lower Silurian, Telychian), are similar in having elongate, unbranched radices proximally. These were not cirri, as suggested by their names, but were radices which were more or less inflexible, lacking contractile tissues. The function of these radices was uncertain. In the absence of contractile tissues, they could not have been for grasping other upright structures and crinoid do not need help to balance, their posture being maintained by mutable collagenous tissues. It is possible, but unlikely, that they may have acted to direct feeding currents towards the crown. Most probably, in an analogy to the post-Palaeozoic isocrinids, the stem acted like a ‘conveyor belt’, the proximal, radicular and upright part being carried away from the cup as further columnals are inserted, eventually forming a distal, recumbent attachment structure. The elongate radices would have stabilised the dististele, but, unlike isocrinids, the arms of Macrostylocrinus spp. were not adapted for crawling and thus escaping predators. Both M. silurocirrifer (type species) and M. cirrifer are included in Macrostylocrinus ( Scotimacrostylocrinus ) subgen. nov.
{"title":"Functional morphology of the stem in the Lower Palaeozoic crinoid\u0000 Macrostylocrinus\u0000 Hall from Scotland","authors":"Stephen K. Donovan","doi":"10.1144/sjg2023-021","DOIUrl":"https://doi.org/10.1144/sjg2023-021","url":null,"abstract":"\u0000 Two species of the closely-related monobathrid crinoid from the Lower Palaeozoic of Scotland, namely\u0000 Macrostylocrinus cirrifer\u0000 Ramsbottom (Upper Ordovician, Katian) and\u0000 Macrostylocrinus silurocirrifer\u0000 Brower (Lower Silurian, Telychian), are similar in having elongate, unbranched radices proximally. These were not cirri, as suggested by their names, but were radices which were more or less inflexible, lacking contractile tissues. The function of these radices was uncertain. In the absence of contractile tissues, they could not have been for grasping other upright structures and crinoid do not need help to balance, their posture being maintained by mutable collagenous tissues. It is possible, but unlikely, that they may have acted to direct feeding currents towards the crown. Most probably, in an analogy to the post-Palaeozoic isocrinids, the stem acted like a ‘conveyor belt’, the proximal, radicular and upright part being carried away from the cup as further columnals are inserted, eventually forming a distal, recumbent attachment structure. The elongate radices would have stabilised the dististele, but, unlike isocrinids, the arms of\u0000 Macrostylocrinus\u0000 spp. were not adapted for crawling and thus escaping predators. Both\u0000 M. silurocirrifer\u0000 (type species) and\u0000 M. cirrifer\u0000 are included in\u0000 Macrostylocrinus\u0000 (\u0000 Scotimacrostylocrinus\u0000 ) subgen. nov.\u0000","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138980852","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. G. Davidson, N. H. Trewin, J. Armstrong, S. R. Waters
The area known as Lethen Bar and Clune, SE of Nairn, Scotland, is a classic Middle Devonian locality which has yielded nodules or concretions, some of which contain fossil fishes with the highest quality of preservation. The locality was largely centred on farm limestone quarries situated around the perimeter of an isolated outlier of the main fishbed. It was first described in the 19 th century, although the upsurge in collecting fossil fishes only occurred some twelve years after the quarries were first mentioned in the scientific literature. Our knowledge of the provenance of the locality is based on very limited accounts, which have never been scientifically tested; these accounts also contain apparent anomalies that have never been adequately addressed. Based on these anomalies, the author of a paper published in 1983 proposed that the locality had been untraceable since the late 19 th century and that the outcrop was quarried out. In 2005, the present authors recorded the first scientifically detailed stratigraphical section of the fishbed, followed in 2021-2023 by detailed field surveys and by a re-appraisal of the literature. This work has resolved the 19 th century anomalies and enabled us to confirm the locations of old quarries, to give affirmation to two previously unrecognised sites, and to show that the outcrop is still present. Thematic collection: This article is part of the Geology of Scotland collection available at: https://www.lyellcollection.org/topic/collections/geology-of-scotland
{"title":"Dr John Grant Malcolmson and a reconciliation of the Middle Devonian Lethen Bar and Lethen House fish bearing nodule localities","authors":"R. G. Davidson, N. H. Trewin, J. Armstrong, S. R. Waters","doi":"10.1144/sjg2023-011","DOIUrl":"https://doi.org/10.1144/sjg2023-011","url":null,"abstract":"The area known as Lethen Bar and Clune, SE of Nairn, Scotland, is a classic Middle Devonian locality which has yielded nodules or concretions, some of which contain fossil fishes with the highest quality of preservation. The locality was largely centred on farm limestone quarries situated around the perimeter of an isolated outlier of the main fishbed. It was first described in the 19 th century, although the upsurge in collecting fossil fishes only occurred some twelve years after the quarries were first mentioned in the scientific literature. Our knowledge of the provenance of the locality is based on very limited accounts, which have never been scientifically tested; these accounts also contain apparent anomalies that have never been adequately addressed. Based on these anomalies, the author of a paper published in 1983 proposed that the locality had been untraceable since the late 19 th century and that the outcrop was quarried out. In 2005, the present authors recorded the first scientifically detailed stratigraphical section of the fishbed, followed in 2021-2023 by detailed field surveys and by a re-appraisal of the literature. This work has resolved the 19 th century anomalies and enabled us to confirm the locations of old quarries, to give affirmation to two previously unrecognised sites, and to show that the outcrop is still present. Thematic collection: This article is part of the Geology of Scotland collection available at: https://www.lyellcollection.org/topic/collections/geology-of-scotland","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139220741","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}
Martín D. Ezcurra, Daniel Marke, Stig A. Walsh, Stephen L. Brusatte
The broadest diversification of early predatory dinosaurs is represented by the ‘coelophysoid-grade’ neotheropods, but their Hettangian–Sinemurian ( c. 191–201 Ma) record is scarce worldwide. More information is needed to shed light on the evolution of this dinosaur group after the end-Triassic mass extinction ( c. 201 Ma). Here we revisit the anatomy and phylogeny of one of these earliest Jurassic neotheropod specimens, an isolated partial tibia from the lower Sinemurian of the Isle of Skye (Scotland) that was previously identified as probably closely related to Liliensternus liliensterni and coelophysids. However, we found that the Skye specimen is positioned in the branch leading to Averostra (Ceratosauria + Tetanurae), in a polytomy with Sarcosaurus woodi from the late Hettangian–lower Sinemurian of central England and a clade composed of Tachiraptor admirabilis and Averostra. The morphology of the Skye specimen is congruent with that of referred specimens of Sarcosaurus woodi , but because it probably represents a skeletally immature specimen, we assign it to cf. Sarcosaurus woodi . The Skye specimen increases the number of averostran-line neotheropod specimens recorded in the Lower Jurassic of Europe and current evidence indicates that these forms, and not coelophysoids, were relatively common in this part of the world at that time. Supplementary material : Character list and dataset for phylogenetic analysis and 3D model of the tibia are available at https://doi.org/10.6084/m9.figshare.c.6863016 Thematic collection: This article is part of the Palaeontology of Scotland collection available at: https://www.lyellcollection.org/topic/collections/palaeontology-of-scotland
{"title":"A revision of the ‘coelophysoid-grade’ theropod specimen from the Lower Jurassic of the Isle of Skye (Scotland)","authors":"Martín D. Ezcurra, Daniel Marke, Stig A. Walsh, Stephen L. Brusatte","doi":"10.1144/sjg2023-012","DOIUrl":"https://doi.org/10.1144/sjg2023-012","url":null,"abstract":"The broadest diversification of early predatory dinosaurs is represented by the ‘coelophysoid-grade’ neotheropods, but their Hettangian–Sinemurian ( c. 191–201 Ma) record is scarce worldwide. More information is needed to shed light on the evolution of this dinosaur group after the end-Triassic mass extinction ( c. 201 Ma). Here we revisit the anatomy and phylogeny of one of these earliest Jurassic neotheropod specimens, an isolated partial tibia from the lower Sinemurian of the Isle of Skye (Scotland) that was previously identified as probably closely related to Liliensternus liliensterni and coelophysids. However, we found that the Skye specimen is positioned in the branch leading to Averostra (Ceratosauria + Tetanurae), in a polytomy with Sarcosaurus woodi from the late Hettangian–lower Sinemurian of central England and a clade composed of Tachiraptor admirabilis and Averostra. The morphology of the Skye specimen is congruent with that of referred specimens of Sarcosaurus woodi , but because it probably represents a skeletally immature specimen, we assign it to cf. Sarcosaurus woodi . The Skye specimen increases the number of averostran-line neotheropod specimens recorded in the Lower Jurassic of Europe and current evidence indicates that these forms, and not coelophysoids, were relatively common in this part of the world at that time. Supplementary material : Character list and dataset for phylogenetic analysis and 3D model of the tibia are available at https://doi.org/10.6084/m9.figshare.c.6863016 Thematic collection: This article is part of the Palaeontology of Scotland collection available at: https://www.lyellcollection.org/topic/collections/palaeontology-of-scotland","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191844","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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