Louis P. Howell, B. Besly, Surika Sooriyathasan, S. Egan, G. Leslie
Local seismic and borehole-based mapping of the Carboniferous Pennine Coal Measures and Warwickshire Group successions in the Canonbie Coalfield (SW Scotland) provides evidence of repeated episodes of positive inversion, syn-depositional folding and unconformities. A Duckmantian (Westphalian B) episode of NE–SW transpression is recognized, based on onlapping seismic reflector geometries against NE-trending positive inversion structures and contemporaneous NNE-trending syn-depositional growth folding. The basin history thus revealed at Canonbie is at variance with generally accepted models in neighbouring northern England that imply subsidence was due to post-rift thermal subsidence during late Carboniferous times. A late Westphalian–Stephanian unconformity recognized within the Warwickshire Group succession signifies NW–SE, c. 10% local basin shortening during a time of major shortening in the late Carboniferous Variscan foreland, contradicting suggestions that maximum Variscan shortening had negligible impact on Carboniferous basins in northern Britain. Local inversion structures appear to have strongly influenced local late Westphalian–Stephanian depocentres. In this respect, the Variscan foreland at Canonbie may have resembled a ‘broken’ foreland system. Variations in crustal rheology, fault strength and orientation, and mid-crustal detachments are suggested to have played important roles in determining strain localization and the nature of Westphalian–Stephanian depocentres in the Canonbie Coalfield.
{"title":"Seismic and borehole-based mapping of the late Carboniferous succession in the Canonbie Coalfield, SW Scotland: evidence for a ‘broken’ Variscan foreland?","authors":"Louis P. Howell, B. Besly, Surika Sooriyathasan, S. Egan, G. Leslie","doi":"10.1144/sjg2020-007","DOIUrl":"https://doi.org/10.1144/sjg2020-007","url":null,"abstract":"Local seismic and borehole-based mapping of the Carboniferous Pennine Coal Measures and Warwickshire Group successions in the Canonbie Coalfield (SW Scotland) provides evidence of repeated episodes of positive inversion, syn-depositional folding and unconformities. A Duckmantian (Westphalian B) episode of NE–SW transpression is recognized, based on onlapping seismic reflector geometries against NE-trending positive inversion structures and contemporaneous NNE-trending syn-depositional growth folding. The basin history thus revealed at Canonbie is at variance with generally accepted models in neighbouring northern England that imply subsidence was due to post-rift thermal subsidence during late Carboniferous times. A late Westphalian–Stephanian unconformity recognized within the Warwickshire Group succession signifies NW–SE, c. 10% local basin shortening during a time of major shortening in the late Carboniferous Variscan foreland, contradicting suggestions that maximum Variscan shortening had negligible impact on Carboniferous basins in northern Britain. Local inversion structures appear to have strongly influenced local late Westphalian–Stephanian depocentres. In this respect, the Variscan foreland at Canonbie may have resembled a ‘broken’ foreland system. Variations in crustal rheology, fault strength and orientation, and mid-crustal detachments are suggested to have played important roles in determining strain localization and the nature of Westphalian–Stephanian depocentres in the Canonbie Coalfield.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2020-007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41446707","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}
Vertebrate fossils are extremely rare below the Achanarras fish beds and equivalent strata in northern Scotland. Here we describe the cheiracanthid acanthodians from the lowest Middle Devonian of this region, comprising partial articulated specimens and squamation patches of two species Cheiracanthus flabellicostatus and C. brevicostatus. Both species were previously only known as isolated scales from the eastern Baltic and Russia. The stratigraphic range of the two species in Scotland extends up into the Achanarras equivalent fish beds in the Moray Firth.
{"title":"Cheiracanthid acanthodians from the lower fossil fish-bearing horizons (Eifelian, Middle Devonian) of the Orcadian Basin, Scotland","authors":"C. Burrow, M. Newman, J. D. Den Blaauwen","doi":"10.1144/sjg2020-006","DOIUrl":"https://doi.org/10.1144/sjg2020-006","url":null,"abstract":"Vertebrate fossils are extremely rare below the Achanarras fish beds and equivalent strata in northern Scotland. Here we describe the cheiracanthid acanthodians from the lowest Middle Devonian of this region, comprising partial articulated specimens and squamation patches of two species Cheiracanthus flabellicostatus and C. brevicostatus. Both species were previously only known as isolated scales from the eastern Baltic and Russia. The stratigraphic range of the two species in Scotland extends up into the Achanarras equivalent fish beds in the Moray Firth.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2020-006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46363666","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 Hecke orbit conjecture plays an important role in understanding the geometric structure of Shimura varieties. First postulated by Chai and Oort in 1995, the Hecke orbit conjecture predicts that prime-to-p Hecke correspondences on mod p reductions of Shimura varieties characterize the foliation structure formed by Oort's central leaves. In other words, every prime-to-p Hecke orbit is Zariski dense in the central leaf containing it. Roughly speaking, a central leaf is the locus in a Shimura variety consisting of all points whose corresponding Barsotti-Tate groups belong to a fixed geometric isomorphism class. On the other hand, the prime-to-p Hecke orbit of a closed point x is the (countable) set consisting of all points y such that there is a prime-to-p quasi-isogeny from x to y. In 2005, Chai and Yu proved the Hecke orbit conjecture for Hilbert modular varieties, followed by a proof for Siegel modular varieties by Chai and Oort in the same year. The major purpose of the present work is to generalize the method of Chai and Oort to Shimura varieties of PEL type. We show that the Hecke orbit conjecture holds for points in certain irreducible components of Newton strata under our assumptions.
{"title":"On The Hecke Orbit Conjecture for PEL Type Shimura Varieties","authors":"L. Xiao","doi":"10.7907/SJG9-0688.","DOIUrl":"https://doi.org/10.7907/SJG9-0688.","url":null,"abstract":"The Hecke orbit conjecture plays an important role in understanding the geometric structure of Shimura varieties. First postulated by Chai and Oort in 1995, the Hecke orbit conjecture predicts that prime-to-p Hecke correspondences on mod p reductions of Shimura varieties characterize the foliation structure formed by Oort's central leaves. In other words, every prime-to-p Hecke orbit is Zariski dense in the central leaf containing it. Roughly speaking, a central leaf is the locus in a Shimura variety consisting of all points whose corresponding Barsotti-Tate groups belong to a fixed geometric isomorphism class. On the other hand, the prime-to-p Hecke orbit of a closed point x is the (countable) set consisting of all points y such that there is a prime-to-p quasi-isogeny from x to y. In 2005, Chai and Yu proved the Hecke orbit conjecture for Hilbert modular varieties, followed by a proof for Siegel modular varieties by Chai and Oort in the same year. The major purpose of the present work is to generalize the method of Chai and Oort to Shimura varieties of PEL type. We show that the Hecke orbit conjecture holds for points in certain irreducible components of Newton strata under our assumptions.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42893953","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}
Serena Tarlati, S. Benetti, S. L. Callard, C. Ó. Cofaigh, P. Dunlop, A. Georgiopoulou, R. Edwards, K. V. Van Landeghem, M. Saher, R. Chiverrell, D. Fabel, S. Moreton, S. Morgan, C. Clark
During the last glacial maximum, the British–Irish Ice Sheet (BIIS) extended to the shelf edge in the Malin Sea between Ireland and Scotland, delivering sediments to the Donegal Barra Fan (DBF). Analysis of well-preserved, glacially derived sediment in the DBF provides new insights on the character of the BIIS final deglaciation and palaeoenvironmental conditions at the Younger Dryas. Chaotic/laminated muds, ice-rafted debris (IRD)-rich layers and laminated sand–mud couplets are interpreted as respectively mass transport deposits, plumites and turbidites of BIIS-transported sediments. Peaks in IRD, constrained by radiocarbon dating to after 18 cal ka BP, indicate discrete intervals of iceberg calving during the last stages of deglaciation. Glacially derived sedimentation on the slope occurred until c. 16.9 cal ka BP. This is interpreted as the last time the ice sheet was present on to the shelf, allowing glacial meltwater to reach the fan. Bioturbated and foraminifera-rich muds above glaciomarine sediments are interpreted as interglacial hemipelagites and contourites, with the presence of Zoophycos suggesting restoration of bottom currents at the transition between stadial and interstadial conditions. During the Younger Dryas, Neogloboquadrina pachyderma sinistral abundances and an isolated peak in IRD indicate the temporary restoration of cold conditions and the presence of icebergs in the region. Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/cc/SJG-early-career-research
在最后一次冰期高峰期间，英国-爱尔兰冰盖(BIIS)延伸到爱尔兰和苏格兰之间的马林海大陆架边缘，向多尼戈尔巴拉扇(DBF)输送沉积物。对DBF中保存完好的冰川衍生沉积物的分析为BIIS最终消冰的特征和新仙女木时期的古环境条件提供了新的见解。混沌/层状泥、冰筏碎屑(IRD)富层和层状砂泥联层分别被解释为biis输运沉积物的块体输运沉积、plumites和浊积岩。IRD的峰值受放射性碳测年限制在18 cal ka BP之后，表明在冰川消融的最后阶段，冰山崩解的间隔是离散的。斜坡上的冰川沉积一直持续到约16.9 calka BP。这被解释为最后一次冰原出现在冰架上，允许冰川融水到达风扇。冰川海洋沉积物上的生物扰动和富含有孔虫的泥浆被解释为间冰期半浮游岩和等高岩，植生藻的存在表明在静止和间冰期条件之间的过渡期间底流的恢复。在新仙女木期，厚皮虫sinstral的丰度和IRD的一个孤立高峰表明该地区暂时恢复了寒冷条件和冰山的存在。主题收集:本文是早期职业研究收集的一部分:https://www.lyellcollection.org/cc/SJG-early-career-research
{"title":"Final deglaciation of the Malin Sea through meltwater release and calving events","authors":"Serena Tarlati, S. Benetti, S. L. Callard, C. Ó. Cofaigh, P. Dunlop, A. Georgiopoulou, R. Edwards, K. V. Van Landeghem, M. Saher, R. Chiverrell, D. Fabel, S. Moreton, S. Morgan, C. Clark","doi":"10.1144/sjg2019-010","DOIUrl":"https://doi.org/10.1144/sjg2019-010","url":null,"abstract":"During the last glacial maximum, the British–Irish Ice Sheet (BIIS) extended to the shelf edge in the Malin Sea between Ireland and Scotland, delivering sediments to the Donegal Barra Fan (DBF). Analysis of well-preserved, glacially derived sediment in the DBF provides new insights on the character of the BIIS final deglaciation and palaeoenvironmental conditions at the Younger Dryas. Chaotic/laminated muds, ice-rafted debris (IRD)-rich layers and laminated sand–mud couplets are interpreted as respectively mass transport deposits, plumites and turbidites of BIIS-transported sediments. Peaks in IRD, constrained by radiocarbon dating to after 18 cal ka BP, indicate discrete intervals of iceberg calving during the last stages of deglaciation. Glacially derived sedimentation on the slope occurred until c. 16.9 cal ka BP. This is interpreted as the last time the ice sheet was present on to the shelf, allowing glacial meltwater to reach the fan. Bioturbated and foraminifera-rich muds above glaciomarine sediments are interpreted as interglacial hemipelagites and contourites, with the presence of Zoophycos suggesting restoration of bottom currents at the transition between stadial and interstadial conditions. During the Younger Dryas, Neogloboquadrina pachyderma sinistral abundances and an isolated peak in IRD indicate the temporary restoration of cold conditions and the presence of icebergs in the region. 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":"2020-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2019-010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45741248","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}
As part of the Glasgow Geothermal Energy Research Field Site (GGERFS) project, intended as a test site for mine-water geothermal heat, the GGC-01 borehole was drilled in the Dalmarnock area in the east of the city of Glasgow, starting in November 2018. It was logged in January 2019 to provide a record of subsurface temperature to 197 m depth, in this urban area with a long history of coal mining and industrial development. This borehole temperature record is significantly perturbed away from its natural state, in part because of the ‘permeabilizing’ effect of past nearby coal mining and in part due to surface warming as a result of the combination of anthropogenic climate change and creation of a subsurface urban heat island by local urban development. Our numerical modelling indicates the total surface warming effect as 2.7°C, partitioned as 2.0°C of global warming since the Industrial Revolution and 0.7°C of local UHI development. We cannot resolve the precise combination of local factors that influence the surface warming because uncertainty in the subsurface thermal properties trades against uncertainty in the history of surface warming. However, the background upward heat flow through the shallow subsurface is estimated as only c. 28–33 mW m−2, depending on choice of other model parameters, well below the c. 80 mW m−2 expected in the Glasgow area. We infer that the ‘missing’ geothermal heat flux is entrained by horizontal flow at depth beyond the reach of the shallow GGC-01 borehole. Although the shallow subsurface in the study area is warmer than it would have been before the Industrial Revolution, at greater depths – between c. 90 and >300 m – it is colder, due to the effect of reduced background heat flow. In future the GGERFS project might utilize water from depths of c. 90 m, but the temperature of the groundwater at these depths is maintained largely by the past effect of surface warming, due to climate change and urban development; it is thus a resource that might be ‘mined’ but not sustainably replenished and, being the result of surface warming rather than upward heat flow, arguably should not count as ‘geothermal’ heat in the first place. Our analysis thus indicates that the GGERFS site is a poor choice as a test site for mine-water geothermal heat. Supplementary material: A summary history of coal mining in the study area is available at: https://doi.org/10.6084/m9.figshare.c.4911495.v2
{"title":"Borehole temperature log from the Glasgow Geothermal Energy Research Field Site: a record of past changes to ground surface temperature caused by urban development","authors":"S. Watson, R. Westaway","doi":"10.1144/sjg2019-033","DOIUrl":"https://doi.org/10.1144/sjg2019-033","url":null,"abstract":"As part of the Glasgow Geothermal Energy Research Field Site (GGERFS) project, intended as a test site for mine-water geothermal heat, the GGC-01 borehole was drilled in the Dalmarnock area in the east of the city of Glasgow, starting in November 2018. It was logged in January 2019 to provide a record of subsurface temperature to 197 m depth, in this urban area with a long history of coal mining and industrial development. This borehole temperature record is significantly perturbed away from its natural state, in part because of the ‘permeabilizing’ effect of past nearby coal mining and in part due to surface warming as a result of the combination of anthropogenic climate change and creation of a subsurface urban heat island by local urban development. Our numerical modelling indicates the total surface warming effect as 2.7°C, partitioned as 2.0°C of global warming since the Industrial Revolution and 0.7°C of local UHI development. We cannot resolve the precise combination of local factors that influence the surface warming because uncertainty in the subsurface thermal properties trades against uncertainty in the history of surface warming. However, the background upward heat flow through the shallow subsurface is estimated as only c. 28–33 mW m−2, depending on choice of other model parameters, well below the c. 80 mW m−2 expected in the Glasgow area. We infer that the ‘missing’ geothermal heat flux is entrained by horizontal flow at depth beyond the reach of the shallow GGC-01 borehole. Although the shallow subsurface in the study area is warmer than it would have been before the Industrial Revolution, at greater depths – between c. 90 and >300 m – it is colder, due to the effect of reduced background heat flow. In future the GGERFS project might utilize water from depths of c. 90 m, but the temperature of the groundwater at these depths is maintained largely by the past effect of surface warming, due to climate change and urban development; it is thus a resource that might be ‘mined’ but not sustainably replenished and, being the result of surface warming rather than upward heat flow, arguably should not count as ‘geothermal’ heat in the first place. Our analysis thus indicates that the GGERFS site is a poor choice as a test site for mine-water geothermal heat. Supplementary material: A summary history of coal mining in the study area is available at: https://doi.org/10.6084/m9.figshare.c.4911495.v2","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42860612","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}
Robert Jameson is generally remembered for championing Neptunist geology (originated by Abraham Werner) during its early nineteenth-century competition with the rival Plutonist theory (initiated by James Hutton). Hutton's ideas prevailed and Jameson's intellectual transition to Plutonism is documented in the surviving notes taken by students who attended his lectures at Edinburgh University: one early record is from 1809, a second record is from c. 1820 and four sets of notes are from the early 1830s. Of the latter four, two have not been previously considered from a geological perspective and prove to be the most revelatory of Jameson's conversion; notes compiled by the Royal Navy surgeon Robert McCormick are particularly comprehensive. Although Jameson attempted to maintain the essentials of Werner's theory for its well-ordered stratigraphy, he progressively adopted a Plutonist approach to more contentious issues such as the origin of granite, veining and mountain building. Jameson used Edinburgh's Salisbury Crags sill for field demonstrations and the students’ notes illustrate his changing views in terms of the origins of this classic geological feature. Of the students whose lecture notes survive, it is only McCormick for whom Jameson appears to have been a lasting geological influence.
{"title":"Robert Jameson's transition from Neptunism to Plutonism as reflected in his lectures at Edinburgh University, 1820–33","authors":"P. Stone","doi":"10.1144/sjg2019-031","DOIUrl":"https://doi.org/10.1144/sjg2019-031","url":null,"abstract":"Robert Jameson is generally remembered for championing Neptunist geology (originated by Abraham Werner) during its early nineteenth-century competition with the rival Plutonist theory (initiated by James Hutton). Hutton's ideas prevailed and Jameson's intellectual transition to Plutonism is documented in the surviving notes taken by students who attended his lectures at Edinburgh University: one early record is from 1809, a second record is from c. 1820 and four sets of notes are from the early 1830s. Of the latter four, two have not been previously considered from a geological perspective and prove to be the most revelatory of Jameson's conversion; notes compiled by the Royal Navy surgeon Robert McCormick are particularly comprehensive. Although Jameson attempted to maintain the essentials of Werner's theory for its well-ordered stratigraphy, he progressively adopted a Plutonist approach to more contentious issues such as the origin of granite, veining and mountain building. Jameson used Edinburgh's Salisbury Crags sill for field demonstrations and the students’ notes illustrate his changing views in terms of the origins of this classic geological feature. Of the students whose lecture notes survive, it is only McCormick for whom Jameson appears to have been a lasting geological influence.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43897735","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}
Only two nominal species of crinoid, the diplobathrid camerates Diabolocrinus craigheadensis Ramsbottom and Diabolocrinus globularis (Nicholson and Etheridge), have been described from the Ordovician (Chatfieldian; Sandbian) Craighead Limestone Formation, Craighead Quarry, near Girvan, Ayrshire. In contrast, columnal morphotaxa are represented by over 20 taxa including those in open nomenclature. Two thecae from Craighead Quarry and referred to Diabolocrinus sp. or spp. preserve features of the stem facet that are similar to specimens referred to Oanducystis (col.) spp. from the same locality. These columnal morphotaxa are synonymized with Diabolocrinus and left in open nomenclature. However, Diabolocrinus is limited to Laurentia, whereas the remaining morphospecies of Oanducystis (col.) Stukalina are limited to Kazakhstan and Estonia.
{"title":"On Oanducystis (col.) Stukalina (Crinoidea) from the Craighead Limestone Formation, Girvan district, Ayrshire","authors":"S. Donovan, N. Clark","doi":"10.1144/sjg2019-022","DOIUrl":"https://doi.org/10.1144/sjg2019-022","url":null,"abstract":"Only two nominal species of crinoid, the diplobathrid camerates Diabolocrinus craigheadensis Ramsbottom and Diabolocrinus globularis (Nicholson and Etheridge), have been described from the Ordovician (Chatfieldian; Sandbian) Craighead Limestone Formation, Craighead Quarry, near Girvan, Ayrshire. In contrast, columnal morphotaxa are represented by over 20 taxa including those in open nomenclature. Two thecae from Craighead Quarry and referred to Diabolocrinus sp. or spp. preserve features of the stem facet that are similar to specimens referred to Oanducystis (col.) spp. from the same locality. These columnal morphotaxa are synonymized with Diabolocrinus and left in open nomenclature. However, Diabolocrinus is limited to Laurentia, whereas the remaining morphospecies of Oanducystis (col.) Stukalina are limited to Kazakhstan and Estonia.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2019-022","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41281976","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 aetosaur Stagonolepis robertsoni was the first reptile to be named from the Late Triassic Lossiemouth Sandstone Formation of Morayshire. Its characteristic rectangular armour plates have been reported in isolation and in association with skeletal remains. Here we present for the first time a three-dimensional reconstruction of the armour plates around the tail in association with caudal vertebrae and a chevron, to give direct evidence of the body outline. The caudal vertebral column was surrounded by eight bony osteoderms, paired paramedian dorsal and ventral plates, and a pair of lateral osteoderms on right and left. The tail shape was subcircular, broader than high. The osteoderms overlap like roofing tiles, the posterior margin of each overlapping the osteoderm following behind. The success of these scans suggests that computed tomography scanning could reveal excellent detail of all the Elgin reptiles in the future. Supplementary material: Three-dimensional models of the two fossil specimens are available at: https://doi.org/10.6084/m9.figshare.c.4824183
{"title":"Three-dimensional tomographic study of dermal armour from the tail of the Triassic aetosaur Stagonolepis robertsoni","authors":"E. Keeble, M. Benton","doi":"10.1144/sjg2019-026","DOIUrl":"https://doi.org/10.1144/sjg2019-026","url":null,"abstract":"The aetosaur Stagonolepis robertsoni was the first reptile to be named from the Late Triassic Lossiemouth Sandstone Formation of Morayshire. Its characteristic rectangular armour plates have been reported in isolation and in association with skeletal remains. Here we present for the first time a three-dimensional reconstruction of the armour plates around the tail in association with caudal vertebrae and a chevron, to give direct evidence of the body outline. The caudal vertebral column was surrounded by eight bony osteoderms, paired paramedian dorsal and ventral plates, and a pair of lateral osteoderms on right and left. The tail shape was subcircular, broader than high. The osteoderms overlap like roofing tiles, the posterior margin of each overlapping the osteoderm following behind. The success of these scans suggests that computed tomography scanning could reveal excellent detail of all the Elgin reptiles in the future. Supplementary material: Three-dimensional models of the two fossil specimens are available at: https://doi.org/10.6084/m9.figshare.c.4824183","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2020-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2019-026","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48614809","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}
In modern rivers, vegetation affects hydrological, geomorphological and sedimentological functioning, so extant fluvial systems can provide only partial analogues for those rivers that operated before the evolution of land plants. However, pre-vegetation rivers were the norm for the first 90% of Earth's history and so a better understanding of their sedimentary product can provide insights into both the fundamental underlying mechanisms of river behaviour and the ways in which fluvial processes operated on ancient Earth. In addition to a short review of the history of research into pre-vegetation alluvium, this paper presents a fieldwork-based case study of the later Proterozoic Torridon Group, which contains some of the most extensive and easily accessible exposures of pre-vegetation alluvium worldwide. Three alluvial architectural deposits have been recognized: (1) channel-bedform deposits (c. 80%); (2) barform deposits (c. 20%); and (3) out-of-channel deposits (≪1%). Channel-bedform deposits have erosional bases and most frequently stack vertically to form thick multistorey channel-bedform sequences. The preferential preservation of these deposits, which record the deepest parts of river channels, suggests that channel migration had a dominant control on preservation in the Torridon Group. Less frequently, channel-bedform deposits pass upwards into a genetically related barform deposit. Barform preservation in these instances is interpreted to be due to channel avulsion, which protected the barforms from reworking. Channel-bar thickness, measured from the basal erosional surface of a channel-bedform deposit to the top of its associated barform deposit, indicates minimum water depths of 1.7 to 8.0 m. Downstream-accreting barform deposits are most frequent, but lateral and upstream modes of accretion are also well represented. Dominant southeastward-palaeoflow directions imply that the Torridonian rivers were sourced from the Grenvillian Mountain Belt. The preserved architectural deposits and narrow dispersal of palaeocurrent data are explained by interpreting the Torridon Group as the alluvium of dominantly low-sinuosity rivers, with signatures recording autogenic fluvial adjustments. In the few rare instances where out-of-channel deposits are preserved, they contain fossil evidence for microbial mats, which prove that not all Proterozoic river systems were wholly abiotic. The overall characteristics of the Torridon alluvium, in terms of its ubiquitous highly tabular beds of sand-grade or coarser material, make it an archetypal example of pre-vegetation alluvium as known globally. Thematic collection: This article is part of the SJG Collection on Early-Career Research available at: https://www.lyellcollection.org/cc/SJG-early-career-research
{"title":"Physical and biological functioning in Proterozoic rivers: evidence from the archetypal pre-vegetation alluvium of the Torridon Group, NW Scotland","authors":"W. McMahon, N. Davies","doi":"10.1144/sjg2019-013","DOIUrl":"https://doi.org/10.1144/sjg2019-013","url":null,"abstract":"In modern rivers, vegetation affects hydrological, geomorphological and sedimentological functioning, so extant fluvial systems can provide only partial analogues for those rivers that operated before the evolution of land plants. However, pre-vegetation rivers were the norm for the first 90% of Earth's history and so a better understanding of their sedimentary product can provide insights into both the fundamental underlying mechanisms of river behaviour and the ways in which fluvial processes operated on ancient Earth. In addition to a short review of the history of research into pre-vegetation alluvium, this paper presents a fieldwork-based case study of the later Proterozoic Torridon Group, which contains some of the most extensive and easily accessible exposures of pre-vegetation alluvium worldwide. Three alluvial architectural deposits have been recognized: (1) channel-bedform deposits (c. 80%); (2) barform deposits (c. 20%); and (3) out-of-channel deposits (≪1%). Channel-bedform deposits have erosional bases and most frequently stack vertically to form thick multistorey channel-bedform sequences. The preferential preservation of these deposits, which record the deepest parts of river channels, suggests that channel migration had a dominant control on preservation in the Torridon Group. Less frequently, channel-bedform deposits pass upwards into a genetically related barform deposit. Barform preservation in these instances is interpreted to be due to channel avulsion, which protected the barforms from reworking. Channel-bar thickness, measured from the basal erosional surface of a channel-bedform deposit to the top of its associated barform deposit, indicates minimum water depths of 1.7 to 8.0 m. Downstream-accreting barform deposits are most frequent, but lateral and upstream modes of accretion are also well represented. Dominant southeastward-palaeoflow directions imply that the Torridonian rivers were sourced from the Grenvillian Mountain Belt. The preserved architectural deposits and narrow dispersal of palaeocurrent data are explained by interpreting the Torridon Group as the alluvium of dominantly low-sinuosity rivers, with signatures recording autogenic fluvial adjustments. In the few rare instances where out-of-channel deposits are preserved, they contain fossil evidence for microbial mats, which prove that not all Proterozoic river systems were wholly abiotic. The overall characteristics of the Torridon alluvium, in terms of its ubiquitous highly tabular beds of sand-grade or coarser material, make it an archetypal example of pre-vegetation alluvium as known globally. Thematic collection: This article is part of the SJG Collection on Early-Career Research 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":"2019-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2019-013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44823736","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. Abrook, I. Matthews, A. Milner, I. Candy, A. Palmer, Rhys G. O. Timms
The Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene. Supplementary material: All raw data associated with this publication: raw pollen counts, charcoal data, Principal Curve and Rate of Change outputs and the age-model output are available at https://doi.org/10.6084/m9.figshare.c.4725269 Thematic collection: This article is part of the ‘Early Career Research’ available at: https://www.lyellcollection.org/cc/SJG-early-career-research
最后一次冰川-冰间过渡（LGIT）是一个气候复杂的时期，千年尺度的气候重组导致了生态系统的变化。除了千年尺度的变化外，在格陵兰岛和欧洲大陆的记录中还观察到了百年尺度的气候事件。这些突发事件对景观和环境的影响目前很难辨别。这在一定程度上与许多研究获得的低时间分辨率以及古环境指标对突变的敏感性有关。我们对奥克尼Quoyloo Meadow进行了高分辨率的孢粉学和木炭研究，并使用主曲线统计方法来帮助揭示生物地层的变化。奥克尼的LGIT植被演替在温德米尔季际和全新世早期表现为开阔草原和Empetrum荒原，在洛蒙德湖体育场表现为开阔草地和蒿属。然而，以开阔地植物群扩张为特征的生态变化的另外三个阶段分别为14.05-13.63、10.94-110.8和10.2 cal ka BP。这些变化的时间受到已知年龄的隐孢子虫的限制。本文通过将Quoyloo Meadow和奥克尼的Crudale Meadow进行比较得出结论，认为温德米尔的两个星际记录都是不完整的，火灾是全新世早期重要的景观控制因素。补充材料：与本出版物相关的所有原始数据：原始花粉计数、木炭数据、主曲线和变化率输出以及年龄模型输出可在https://doi.org/10.6084/m9.figshare.c.4725269专题集：本文是“早期职业研究”的一部分，可访问：https://www.lyellcollection.org/cc/SJG-early-career-research
{"title":"Environmental variability in response to abrupt climatic change during the Last Glacial–Interglacial Transition (16–8 cal ka BP): evidence from Mainland, Orkney","authors":"A. Abrook, I. Matthews, A. Milner, I. Candy, A. Palmer, Rhys G. O. Timms","doi":"10.1144/sjg2019-006","DOIUrl":"https://doi.org/10.1144/sjg2019-006","url":null,"abstract":"The Last Glacial–Interglacial Transition (LGIT) is a period of climatic complexity where millennial-scale climatic reorganization led to changes in ecosystems. Alongside millennial-scale changes, centennial-scale climatic events have been observed within records from Greenland and continental Europe. The effects of these abrupt events on landscapes and environments are difficult to discern at present. This, in part, relates to low temporal resolutions attained by many studies and the sensitivity of palaeoenvironmental proxies to abrupt change. We present a high-resolution palynological and charcoal study of Quoyloo Meadow, Orkney and use the Principal Curve statistical method to assist in revealing biostratigraphic change. The LGIT vegetation succession on Orkney is presented as open grassland and Empetrum heath during the Windermere Interstadial and early Holocene, and open grassland with Artemisia during the Loch Lomond Stadial. However, a further three phases of ecological change, characterized by expansions of open ground flora, are dated to 14.05–13.63, 10.94–10.8 and 10.2 cal ka BP. The timing of these changes is constrained by cryptotephra of known age. The paper concludes by comparing Quoyloo Meadow with Crudale Meadow, Orkney, and suggests that both Windermere Interstadial records are incomplete and that fire is an important landscape control during the early Holocene. Supplementary material: All raw data associated with this publication: raw pollen counts, charcoal data, Principal Curve and Rate of Change outputs and the age-model output are available at https://doi.org/10.6084/m9.figshare.c.4725269 Thematic collection: This article is part of the ‘Early Career Research’ 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":"2019-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47360734","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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