Three closely associated arthropleurid trackways, Diplichnites cuithensis, from the Lower Carboniferous of Fife, Scotland, exhibit signs of interaction between track-makers. An extra file of footprints is found on the downslope side of two trackways (A and C), the upslope side of another (B). These additional files of footprints suggest that either: each trackway resulted from two arthropleurids of different sizes walking in tandem, matching their footprints exactly on one side for some distance; or that one arthropleurid was partially mounted on the back of another producing the three parallel files. It is here argued that the latter is correct and that this represents evidence of mating behaviour in arthropleurids.
{"title":"Mating trackways of a fossil giant millipede","authors":"M. Whyte","doi":"10.1144/sjg2017-013","DOIUrl":"https://doi.org/10.1144/sjg2017-013","url":null,"abstract":"Three closely associated arthropleurid trackways, Diplichnites cuithensis, from the Lower Carboniferous of Fife, Scotland, exhibit signs of interaction between track-makers. An extra file of footprints is found on the downslope side of two trackways (A and C), the upslope side of another (B). These additional files of footprints suggest that either: each trackway resulted from two arthropleurids of different sizes walking in tandem, matching their footprints exactly on one side for some distance; or that one arthropleurid was partially mounted on the back of another producing the three parallel files. It is here argued that the latter is correct and that this represents evidence of mating behaviour in arthropleurids.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"54 1","pages":"63 - 68"},"PeriodicalIF":0.7,"publicationDate":"2018-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-013","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44567327","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}
Paige E. dePolo, S. Brusatte, T. Challands, D. Foffa, D. Ross, Mark Wilkinson, Hong-yu Yi
Middle Jurassic dinosaur fossils are exceedingly rare, but new discoveries from the Isle of Skye, Scotland, are beginning to fill this gap. We here describe a new dinosaur tracksite found in the Lealt Shale Formation (Bathonian) of the Great Estuarine Group at Rubha nam Brathairean (Brothers' Point) on Skye. The site preserves an abundance of small sauropod manus and pes prints and several isolated and broken medium-to-large tridactyl footprints. The main site occurs on a single horizon of shaley limestone that formed in a lagoonal environment. The sauropod tracks are tentatively assigned to the ichnotaxon Breviparopus due to the narrow gauge of the trackways, the digital characteristics of the pes, and the ratio of heteropody observed between the manus and the pes. A theropod trackmaker is inferred for some of the tridactyl impressions with several indicative of the ichnotaxon Eubrontes. This new site strengthens the inference, originally based on a previously discovered locality near Duntulm Castle (Duntulm Formation) in northern Skye, that sauropods habitually spent time in lagoons during the Middle Jurassic. Supplementary material: The photogrammetric model of track BP2_40 and associated metadata and photographs are available at https://doi.org/10.6084/m9.figshare.c.4046390
中侏罗世恐龙化石极为罕见,但苏格兰斯凯岛的新发现正开始填补这一空白。我们在这里描述了在斯凯岛ruha nam Brathairean (Brothers’Point)的Great estuary Group的Lealt页岩组(Bathonian)中发现的一个新的恐龙足迹。该遗址保存了大量小型蜥脚类恐龙的手印和足印,以及一些孤立的、破碎的中型到大型三趾类恐龙脚印。主要场地位于单一水平的泥质石灰岩上,形成于泻湖环境中。根据足迹的狭窄范围、足趾的数字特征以及手足与足趾之间异足的比例,初步将这些蜥脚类动物的足迹归属于短爪目。在一些三趾动物的足迹中推断出兽脚亚目足迹的痕迹,其中有几个表明了鱼分类单元的特征。这个新的遗址加强了先前的推断,该推断最初是基于先前在斯凯北部Duntulm城堡(Duntulm组)附近发现的地点,即中侏罗纪时期蜥脚类动物习惯在泻湖中生活。补充资料:轨道BP2_40的摄影测量模型以及相关的元数据和照片可在https://doi.org/10.6084/m9.figshare.c.4046390上获得
{"title":"A sauropod-dominated tracksite from Rubha nam Brathairean (Brothers’ Point), Isle of Skye, Scotland","authors":"Paige E. dePolo, S. Brusatte, T. Challands, D. Foffa, D. Ross, Mark Wilkinson, Hong-yu Yi","doi":"10.1144/sjg2017-016","DOIUrl":"https://doi.org/10.1144/sjg2017-016","url":null,"abstract":"Middle Jurassic dinosaur fossils are exceedingly rare, but new discoveries from the Isle of Skye, Scotland, are beginning to fill this gap. We here describe a new dinosaur tracksite found in the Lealt Shale Formation (Bathonian) of the Great Estuarine Group at Rubha nam Brathairean (Brothers' Point) on Skye. The site preserves an abundance of small sauropod manus and pes prints and several isolated and broken medium-to-large tridactyl footprints. The main site occurs on a single horizon of shaley limestone that formed in a lagoonal environment. The sauropod tracks are tentatively assigned to the ichnotaxon Breviparopus due to the narrow gauge of the trackways, the digital characteristics of the pes, and the ratio of heteropody observed between the manus and the pes. A theropod trackmaker is inferred for some of the tridactyl impressions with several indicative of the ichnotaxon Eubrontes. This new site strengthens the inference, originally based on a previously discovered locality near Duntulm Castle (Duntulm Formation) in northern Skye, that sauropods habitually spent time in lagoons during the Middle Jurassic. Supplementary material: The photogrammetric model of track BP2_40 and associated metadata and photographs are available at https://doi.org/10.6084/m9.figshare.c.4046390","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"54 1","pages":"1 - 12"},"PeriodicalIF":0.7,"publicationDate":"2018-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-016","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41576847","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}
L. Bullock, J. Parnell, Magali Perez, A. Boyce, J. Feldmann, J. Armstrong
Carboniferous coals of the Ayrshire Coalfield are enriched in selenium (Se) relative to average UK and world compositions, substituting for sulphur in pyrite. Greenburn surface mine coals are characterized by syngenetic concretionary pyrite (c. 15% total area), occurring as bedding-parallel banding, and later-formed (epigenetic) cross-cutting pyrite in cleats (c. 9% total area). In these, sulphur isotope compositions for both syngenetic and epigenetic pyrite include isotopically light and heavy variants, suggesting diagenetic and hydrothermal fluid formation. Late/post-Visean cleat-filling pyrite is enriched in Se (up to 266 ppm) compared to the earlier-formed material (Se up to 181 ppm). Anomalous Se may have been sourced from near-by sulphidic Dalradian metamorphic rocks. Initial Se sequestration is associated with syngenetic pyrite mineralization, absorbed from seawater and pore waters, with additional Se introduced from fluids mobilized during epigenetic pyrite formation. Cleats from local brittle fracturing provided channels for fluid flow and a locus for precipitation of comparatively high-Se pyrite. Permian dolerite intrusions may have provided an enrichment source and/or fluid distribution mechanism. The Se concentrations of the Greenburn coals relate to multi-stage mineralization, with cleat-filling pyrite showing the highest Se content, and highlight the potential for high Se in similarly altered and fractured coal deposits worldwide. Supplementary material: LA-ICP-MS maps for Fe, Se, Ag, As, Cu, Hg, Pb and Te for Greenburn coal samples from seams 9300 Lime and 6900 Burnfoot Bridge are available at https://doi.org/10.6084/m9.figshare.c.3967860
艾尔郡煤田石炭系煤相对于英国和世界的平均成分富含硒(Se),取代了硫铁矿中的硫。绿本露天矿煤的特征为同生块状黄铁矿(约占总面积的15%),呈顺层平行带状分布,后期形成的(后生的)横切黄铁矿在理块中形成(约占总面积的9%)。其中,同生和表生黄铁矿的硫同位素组成均有轻同位素和重同位素变化,提示成岩和热液流体形成。与早期形成的材料(硒含量高达181ppm)相比,晚期/后visean清晰充填的黄铁矿富含硒(高达266ppm)。异常硒可能来源于附近的硫化物变质岩。初始的硒固存与同生黄铁矿矿化有关,从海水和孔隙水中吸收硒,并从表生黄铁矿形成过程中动员的流体中引入额外的硒。局部脆性压裂产生的裂隙为流体流动提供了通道,并为相对高硒黄铁矿的沉淀提供了场所。二叠系白云岩侵入可能提供了富集源和/或流体分布机制。Greenburn煤的硒含量与多阶段成矿作用有关,其中以填空型黄铁矿的硒含量最高,突出了世界范围内类似蚀变和破碎型煤层的高硒潜力。补充材料:从煤层9300 Lime和6900 Burnfoot Bridge获取的Greenburn煤样品的Fe, Se, Ag, As, Cu, Hg, Pb和Te的LA-ICP-MS图可在https://doi.org/10.6084/m9.figshare.c.3967860上获得
{"title":"Multi-stage pyrite genesis and epigenetic selenium enrichment of Greenburn coals (East Ayrshire)","authors":"L. Bullock, J. Parnell, Magali Perez, A. Boyce, J. Feldmann, J. Armstrong","doi":"10.1144/sjg2017-010","DOIUrl":"https://doi.org/10.1144/sjg2017-010","url":null,"abstract":"Carboniferous coals of the Ayrshire Coalfield are enriched in selenium (Se) relative to average UK and world compositions, substituting for sulphur in pyrite. Greenburn surface mine coals are characterized by syngenetic concretionary pyrite (c. 15% total area), occurring as bedding-parallel banding, and later-formed (epigenetic) cross-cutting pyrite in cleats (c. 9% total area). In these, sulphur isotope compositions for both syngenetic and epigenetic pyrite include isotopically light and heavy variants, suggesting diagenetic and hydrothermal fluid formation. Late/post-Visean cleat-filling pyrite is enriched in Se (up to 266 ppm) compared to the earlier-formed material (Se up to 181 ppm). Anomalous Se may have been sourced from near-by sulphidic Dalradian metamorphic rocks. Initial Se sequestration is associated with syngenetic pyrite mineralization, absorbed from seawater and pore waters, with additional Se introduced from fluids mobilized during epigenetic pyrite formation. Cleats from local brittle fracturing provided channels for fluid flow and a locus for precipitation of comparatively high-Se pyrite. Permian dolerite intrusions may have provided an enrichment source and/or fluid distribution mechanism. The Se concentrations of the Greenburn coals relate to multi-stage mineralization, with cleat-filling pyrite showing the highest Se content, and highlight the potential for high Se in similarly altered and fractured coal deposits worldwide. Supplementary material: LA-ICP-MS maps for Fe, Se, Ag, As, Cu, Hg, Pb and Te for Greenburn coal samples from seams 9300 Lime and 6900 Burnfoot Bridge are available at https://doi.org/10.6084/m9.figshare.c.3967860","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"54 1","pages":"37 - 49"},"PeriodicalIF":0.7,"publicationDate":"2018-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47250113","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}
M. Krabbendam, J. Ramsay, A. Leslie, P. Tanner, D. Dietrich, Kathryn Goodenough
The Grenville and Caledonian orogens, fundamental to building Laurentia and Baltica, intersect in northern Scotland. The Precambrian Glenelg Inlier, within the Scottish Caledonides, preserves a record of Grenvillian, Knoydartian and Caledonian orogenesis. Based on new mapping and re-interpretation of previous mapping, we present a structural model for the evolution of the Glenelg Inlier. The inlier can be divided into Western Glenelg gneiss comprising orthogneiss with no record of Grenville-age metamorphism, and Eastern Glenelg gneiss with ortho- and paragneiss, affected by Grenvillian eclogite-facies metamorphism. The basement gneisses and their original cover of psammitic, Neoproterozoic Morar Group (Moine) rocks were deformed by three generations of major ductile folds (F1–F3). In medium-strain areas F2 and F3 folds are broadly coaxial and both face to the west; in higher strain areas F2 and F3 folds are oblique to each other. By restoring post-F1 folds and late faults, the Glenelg gneiss inliers are seen to form the core of a major recumbent SSE-facing F1 isoclinal fold nappe – the Proto-Moine Nappe. The upper limb of this nappe is a thick, right-way-up sequence of moderately strained Morar Group rocks whereas the lower, inverted limb comprises intensely deformed, migmatitic Morar Group rocks. Within the constraints of published geochronology, the Proto-Moine Nappe is likely Pre-Caledonian and may have originated during the early Neoproterozoic Knoydartian Orogeny.
{"title":"Caledonian and Knoydartian overprinting of a Grenvillian inlier and the enclosing Morar Group rocks: structural evolution of the Precambrian Proto-Moine Nappe, Glenelg, NW Scotland","authors":"M. Krabbendam, J. Ramsay, A. Leslie, P. Tanner, D. Dietrich, Kathryn Goodenough","doi":"10.1144/sjg2017-006","DOIUrl":"https://doi.org/10.1144/sjg2017-006","url":null,"abstract":"The Grenville and Caledonian orogens, fundamental to building Laurentia and Baltica, intersect in northern Scotland. The Precambrian Glenelg Inlier, within the Scottish Caledonides, preserves a record of Grenvillian, Knoydartian and Caledonian orogenesis. Based on new mapping and re-interpretation of previous mapping, we present a structural model for the evolution of the Glenelg Inlier. The inlier can be divided into Western Glenelg gneiss comprising orthogneiss with no record of Grenville-age metamorphism, and Eastern Glenelg gneiss with ortho- and paragneiss, affected by Grenvillian eclogite-facies metamorphism. The basement gneisses and their original cover of psammitic, Neoproterozoic Morar Group (Moine) rocks were deformed by three generations of major ductile folds (F1–F3). In medium-strain areas F2 and F3 folds are broadly coaxial and both face to the west; in higher strain areas F2 and F3 folds are oblique to each other. By restoring post-F1 folds and late faults, the Glenelg gneiss inliers are seen to form the core of a major recumbent SSE-facing F1 isoclinal fold nappe – the Proto-Moine Nappe. The upper limb of this nappe is a thick, right-way-up sequence of moderately strained Morar Group rocks whereas the lower, inverted limb comprises intensely deformed, migmatitic Morar Group rocks. Within the constraints of published geochronology, the Proto-Moine Nappe is likely Pre-Caledonian and may have originated during the early Neoproterozoic Knoydartian Orogeny.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"54 1","pages":"13 - 35"},"PeriodicalIF":0.7,"publicationDate":"2017-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49592463","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 coccosteid nuchal bone from the Middle Devonian Tamme Cliffs locality in Estonia is described as Dickosteus cf. threiplandi, D. threiplandi being a common species in the Middle Devonian of the Orcadian Basin, Scotland. A number of other bones from Tamme Cliffs are also placed in this genus. It is already known that the coccosteids Coccosteus cuspidatus and probably Millerosteus minor are present in both areas. A final coccosteid genus Watsonosteus has been shown previously to also be present in both areas. We can confirm that the sequence of coccosteid genera is the same in both the Orcadian Basin and Estonia and is, from the lowest horizon, Coccosteus–Dickosteus–Millerosteus–Watsonosteus. The coccosteids in Estonia are also associated with other Scottish faunal elements (including co-specific species), such as other placoderms, acanthodians and sarcopterygians. This implies a very close connection between the two areas in the Middle Devonian. Some of the acanthodian species of the Orcadian Basin are also present in Belarus and Severnaya Zemlya, suggesting that other Orcadian Basin forms, including coccosteids may be present at these localities and perhaps elsewhere on the Old Red Sandstone continent. Further investigation may allow a continent-wide correlation at species level across the whole continent.
{"title":"Middle Devonian coccosteid (Arthrodira, Placodermi) biostratigraphy of Scotland and Estonia","authors":"M. Newman, J. D. Den Blaauwen, Tormi Tuuling","doi":"10.1144/sjg-2016-012","DOIUrl":"https://doi.org/10.1144/sjg-2016-012","url":null,"abstract":"A coccosteid nuchal bone from the Middle Devonian Tamme Cliffs locality in Estonia is described as Dickosteus cf. threiplandi, D. threiplandi being a common species in the Middle Devonian of the Orcadian Basin, Scotland. A number of other bones from Tamme Cliffs are also placed in this genus. It is already known that the coccosteids Coccosteus cuspidatus and probably Millerosteus minor are present in both areas. A final coccosteid genus Watsonosteus has been shown previously to also be present in both areas. We can confirm that the sequence of coccosteid genera is the same in both the Orcadian Basin and Estonia and is, from the lowest horizon, Coccosteus–Dickosteus–Millerosteus–Watsonosteus. The coccosteids in Estonia are also associated with other Scottish faunal elements (including co-specific species), such as other placoderms, acanthodians and sarcopterygians. This implies a very close connection between the two areas in the Middle Devonian. Some of the acanthodian species of the Orcadian Basin are also present in Belarus and Severnaya Zemlya, suggesting that other Orcadian Basin forms, including coccosteids may be present at these localities and perhaps elsewhere on the Old Red Sandstone continent. Further investigation may allow a continent-wide correlation at species level across the whole continent.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"63 - 69"},"PeriodicalIF":0.7,"publicationDate":"2017-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg-2016-012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45106311","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 only official maps to show a boundary between the Middle Devonian Stromness and Rousay Flagstones on Orkney are those published by the Geological Survey in 1932 and 1935. Since then, the difficulties of defining and locating this boundary have challenged many workers in the Orcadian Lake Basin. In 2015, the introduction of biozones by Uisdean Michie, based on fossil fish, and the recent discovery in Westray of the zone fossils Osteolepis panderi and Thursius pholidotus in a prominent fish bed across the island, has permitted the boundary for the base of the Rousay Formation to be determined in that part of Orkney. It is suggested that other characteristics of the fish bed of this rhythmic cycle of sediments, together with those in adjacent cycles, may be used as a marker for further correlation and mapping across the basin.
{"title":"Demarcation of the boundary between Middle Devonian Upper Stromness Flagstone and Rousay Flagstone formations in Westray, Orkney","authors":"D. Leather","doi":"10.1144/sjg2017-007","DOIUrl":"https://doi.org/10.1144/sjg2017-007","url":null,"abstract":"The only official maps to show a boundary between the Middle Devonian Stromness and Rousay Flagstones on Orkney are those published by the Geological Survey in 1932 and 1935. Since then, the difficulties of defining and locating this boundary have challenged many workers in the Orcadian Lake Basin. In 2015, the introduction of biozones by Uisdean Michie, based on fossil fish, and the recent discovery in Westray of the zone fossils Osteolepis panderi and Thursius pholidotus in a prominent fish bed across the island, has permitted the boundary for the base of the Rousay Formation to be determined in that part of Orkney. It is suggested that other characteristics of the fish bed of this rhythmic cycle of sediments, together with those in adjacent cycles, may be used as a marker for further correlation and mapping across the basin.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"53 - 61"},"PeriodicalIF":0.7,"publicationDate":"2017-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45761886","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 Scottish National Antarctic Expedition (1902 – 04) made the first topographical survey and geological assessment of Laurie Island, one of the South Orkney Islands. The expedition's surgeon and geologist, J. H. H. Pirie, provided competent geological descriptions but these were largely overshadowed by his misidentification of an obscure plant fossil as a graptolite. Erroneous confirmation by eminent British palaeontologists led to Triassic rocks being regarded as Lower Palaeozoic for fifty years. The mistake arose from the familiarity of all concerned with the geology of the Scottish Southern Uplands: they were led astray by the preconception that, as in Scotland, deformed ‘greywacke–shale’ successions would contain Lower Palaeozoic fossils. Other, more successful aspects of the expedition's geological investigations are less well known. Fossils acquired in the Falkland Islands expanded that archipelago's poorly known Devonian brachiopod fauna, but arguably the most important palaeontological discovery lay unrecognized for ten years. A limestone block dredged from the bed of the Weddell Sea contained Early Cambrian archaeocyath fossils which, had they been promptly identified, would have been the first record of this important Antarctic palaeofauna. Instead, the Weddell Sea material complemented fossils recovered on the opposite, Ross Sea side of the Antarctic continent during Shackleton's British Antarctic Expedition (1907 – 09).
{"title":"The geological work of the Scottish National Antarctic Expedition, 1902 – 04","authors":"P. Stone","doi":"10.1144/sjg2017-005","DOIUrl":"https://doi.org/10.1144/sjg2017-005","url":null,"abstract":"The Scottish National Antarctic Expedition (1902 – 04) made the first topographical survey and geological assessment of Laurie Island, one of the South Orkney Islands. The expedition's surgeon and geologist, J. H. H. Pirie, provided competent geological descriptions but these were largely overshadowed by his misidentification of an obscure plant fossil as a graptolite. Erroneous confirmation by eminent British palaeontologists led to Triassic rocks being regarded as Lower Palaeozoic for fifty years. The mistake arose from the familiarity of all concerned with the geology of the Scottish Southern Uplands: they were led astray by the preconception that, as in Scotland, deformed ‘greywacke–shale’ successions would contain Lower Palaeozoic fossils. Other, more successful aspects of the expedition's geological investigations are less well known. Fossils acquired in the Falkland Islands expanded that archipelago's poorly known Devonian brachiopod fauna, but arguably the most important palaeontological discovery lay unrecognized for ten years. A limestone block dredged from the bed of the Weddell Sea contained Early Cambrian archaeocyath fossils which, had they been promptly identified, would have been the first record of this important Antarctic palaeofauna. Instead, the Weddell Sea material complemented fossils recovered on the opposite, Ross Sea side of the Antarctic continent during Shackleton's British Antarctic Expedition (1907 – 09).","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"71 - 87"},"PeriodicalIF":0.7,"publicationDate":"2017-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43298807","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 early history of polymetamorphic basement gneiss complexes is often difficult to decipher due to overprinting by later deformation and metamorphic events. In this paper we integrate field, petrographic and mineral chemistry data from an Archaean tonalitic gneiss xenolith, hosted within a Palaeoproterozoic mafic dyke in the Lewisian Gneiss Complex of NW Scotland to show how xenoliths in dykes may preserve signatures of early tectonothermal events. The Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses of the Lewisian Gneiss Complex are cut by a suite of Palaeoproterozoic (c. 2400 Ma) mafic dykes, the Scourie Dyke Swarm, and both are deformed by later shear zones developed during the upper greenschist- to lower amphibolite-facies Laxfordian event (1740 – 1670 Ma). Detailed field mapping, petrographic analysis and mineral chemistry reveal that a xenolith of TTG gneiss entrained within a Scourie dyke has been protected from amphibolite-facies recrystallization in a Laxfordian shear zone. Whereas the surrounding TTG gneiss displays pervasive amphibolite-facies retrogression, the xenolith retains a pre-Scourie dyke, clinopyroxene-bearing metamorphic assemblage and gneissic layering. We suggest that retrogressive reaction softening and pre-existing planes of weakness, such as the c. 2490 Ma Inverian fabric and gneiss–dyke contacts, localized strain around but not within the xenolith. Such strain localization could generate preferential flow pathways for fluids, principally along the shear zone, bypassing the xenolith and protecting it from amphibolite-facies retrogression. In basement gneiss complexes where early metamorphic assemblages and fabrics have been fully overprinted by tectonothermal events, our results suggest that country rock xenoliths in mafic dykes could preserve windows into the early evolution of these complex polymetamorphic areas. Supplementary material: Electron microprobe analyses and analytical spot locations are available at: https://doi.org/10.6084/m9.figshare.c.3809545
{"title":"Dykes as physical buffers to metamorphic overprinting: an example from the Archaean–Palaeoproterozoic Lewisian Gneiss Complex of NW Scotland","authors":"J. MacDonald, C. Magee, K. Goodenough","doi":"10.1144/sjg2017-004","DOIUrl":"https://doi.org/10.1144/sjg2017-004","url":null,"abstract":"The early history of polymetamorphic basement gneiss complexes is often difficult to decipher due to overprinting by later deformation and metamorphic events. In this paper we integrate field, petrographic and mineral chemistry data from an Archaean tonalitic gneiss xenolith, hosted within a Palaeoproterozoic mafic dyke in the Lewisian Gneiss Complex of NW Scotland to show how xenoliths in dykes may preserve signatures of early tectonothermal events. The Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses of the Lewisian Gneiss Complex are cut by a suite of Palaeoproterozoic (c. 2400 Ma) mafic dykes, the Scourie Dyke Swarm, and both are deformed by later shear zones developed during the upper greenschist- to lower amphibolite-facies Laxfordian event (1740 – 1670 Ma). Detailed field mapping, petrographic analysis and mineral chemistry reveal that a xenolith of TTG gneiss entrained within a Scourie dyke has been protected from amphibolite-facies recrystallization in a Laxfordian shear zone. Whereas the surrounding TTG gneiss displays pervasive amphibolite-facies retrogression, the xenolith retains a pre-Scourie dyke, clinopyroxene-bearing metamorphic assemblage and gneissic layering. We suggest that retrogressive reaction softening and pre-existing planes of weakness, such as the c. 2490 Ma Inverian fabric and gneiss–dyke contacts, localized strain around but not within the xenolith. Such strain localization could generate preferential flow pathways for fluids, principally along the shear zone, bypassing the xenolith and protecting it from amphibolite-facies retrogression. In basement gneiss complexes where early metamorphic assemblages and fabrics have been fully overprinted by tectonothermal events, our results suggest that country rock xenoliths in mafic dykes could preserve windows into the early evolution of these complex polymetamorphic areas. Supplementary material: Electron microprobe analyses and analytical spot locations are available at: https://doi.org/10.6084/m9.figshare.c.3809545","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"41 - 52"},"PeriodicalIF":0.7,"publicationDate":"2017-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2017-004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48861438","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}
After a gap of more than a century new mapping has established that the structural framework of the Lewisian Complex southwards from the north coast of Scotland consists of a pattern of shallowly-plunging upright folds with southeasterly trending axial planes resulting from Palaeoproterozoic deformation of the products of Neoarchaean crust formation. The lithologies and structural features are consistent with polyphase tectonothermal deformation at depth, including crustal shortening, of a flat-lying, mantle-derived protolith assemblage that consisted mainly of acidic and some basic igneous sheet-like intrusions and the products of their metamorphism (quartzofeldspathic gneiss and amphibolite) during crust formation. The crustal shortening is represented by penetrative planar and linear fabrics that largely replace those formed earlier in the less competent gneisses. Large-scale upright northeasterly trending folds formed subsequently are both a major feature of the structural framework and a major control of the emplacement of many pegmatite intrusions. Rotation of structural units with respect to one another was associated with the extension along fold axes, the common development of boudinage structures at various scales and the local reversal of the general southeasterly direction of fold plunge to northwesterly.
{"title":"Structural framework of the gneiss–amphibolite–pegmatite assemblage of the Lewisian Complex south of Durness, NW Highlands","authors":"D. Findlay, D. Bowes","doi":"10.1144/sjg2016-009","DOIUrl":"https://doi.org/10.1144/sjg2016-009","url":null,"abstract":"After a gap of more than a century new mapping has established that the structural framework of the Lewisian Complex southwards from the north coast of Scotland consists of a pattern of shallowly-plunging upright folds with southeasterly trending axial planes resulting from Palaeoproterozoic deformation of the products of Neoarchaean crust formation. The lithologies and structural features are consistent with polyphase tectonothermal deformation at depth, including crustal shortening, of a flat-lying, mantle-derived protolith assemblage that consisted mainly of acidic and some basic igneous sheet-like intrusions and the products of their metamorphism (quartzofeldspathic gneiss and amphibolite) during crust formation. The crustal shortening is represented by penetrative planar and linear fabrics that largely replace those formed earlier in the less competent gneisses. Large-scale upright northeasterly trending folds formed subsequently are both a major feature of the structural framework and a major control of the emplacement of many pegmatite intrusions. Rotation of structural units with respect to one another was associated with the extension along fold axes, the common development of boudinage structures at various scales and the local reversal of the general southeasterly direction of fold plunge to northwesterly.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"13 - 28"},"PeriodicalIF":0.7,"publicationDate":"2017-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2016-009","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42859161","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}
Prior investigations concur that the granite plutons in Scotland which are most likely to prove favourable for geothermal exploration are the Ballater, Bennachie, Cairngorm and Mount Battock plutons, all of which have heat production values greater than 5 μW m−3. This heat production arises from the significant concentrations of potassium, uranium and thorium in some granite plutons. A new field-based gamma-ray spectrometric survey targeted plutons that were poorly surveyed in the past or near areas of high heat demand. This survey identifies several other plutons (Ben Rhinnes, Cheviot, Hill of Fare, Lochnagar and Monadhliath) with heat production rates between 3 and 5 μW m−3 that could well have geothermal gradients sufficient for direct heat use rather than higher temperatures required for electricity generation. The Criffel and Cheviot plutons are examples of Scottish granites that have concentric compositional zonation and some zones have significantly higher (up to 20%) heat production rates than others in the same plutons. However, the relatively small surface areas of individual high heat-production zones mean that it is unlikely to be worthwhile specifically targeting them. Supplementary material: The full set of heat production data is available at https://doi.org/10.5525/gla.researchdata.302
先前的调查一致认为,苏格兰最有可能被证明有利于地热勘探的花岗岩深成岩体是Ballater、Bennachie、Cairngorm和Mount Battock深成岩体,所有这些岩体的产热值都大于5 μW m−3。这种热量的产生源于一些花岗岩深成岩体中钾、铀和钍的显著浓度。一项新的基于野外的伽马射线光谱测量针对的是过去或高热量需求地区附近调查不力的深成岩体。该调查确定了其他几个热生产率在3-5之间的深成岩体(Ben Rhines、Cheviot、Hill of Fare、Lochnagar和Monadhliath) μW m−3的地热梯度足以直接使用热量,而不是发电所需的更高温度。Criffel和Cheviot深成岩体是具有同心成分分带的苏格兰花岗岩的例子,其中一些区域的产热率明显高于同一深成岩体中的其他区域(高达20%)。然而,单个高温生产区的表面积相对较小,这意味着不太可能有价值专门针对它们。补充材料:完整的热量生产数据可在https://doi.org/10.5525/gla.researchdata.302
{"title":"Ranking the geothermal potential of radiothermal granites in Scotland: are any others as hot as the Cairngorms?","authors":"A. McCay, P. Younger","doi":"10.1144/sjg2016-008","DOIUrl":"https://doi.org/10.1144/sjg2016-008","url":null,"abstract":"Prior investigations concur that the granite plutons in Scotland which are most likely to prove favourable for geothermal exploration are the Ballater, Bennachie, Cairngorm and Mount Battock plutons, all of which have heat production values greater than 5 μW m−3. This heat production arises from the significant concentrations of potassium, uranium and thorium in some granite plutons. A new field-based gamma-ray spectrometric survey targeted plutons that were poorly surveyed in the past or near areas of high heat demand. This survey identifies several other plutons (Ben Rhinnes, Cheviot, Hill of Fare, Lochnagar and Monadhliath) with heat production rates between 3 and 5 μW m−3 that could well have geothermal gradients sufficient for direct heat use rather than higher temperatures required for electricity generation. The Criffel and Cheviot plutons are examples of Scottish granites that have concentric compositional zonation and some zones have significantly higher (up to 20%) heat production rates than others in the same plutons. However, the relatively small surface areas of individual high heat-production zones mean that it is unlikely to be worthwhile specifically targeting them. Supplementary material: The full set of heat production data is available at https://doi.org/10.5525/gla.researchdata.302","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":"53 1","pages":"1 - 11"},"PeriodicalIF":0.7,"publicationDate":"2017-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2016-008","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45004112","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}