Scottish Journal of Geology最新文献

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"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":null,"pages":null},"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}

{"title":"Notes on the brachiopod species from the Silurian of the Pentland Hills described by Lamont (1978)","authors":"Y. Candela, D. Harper, W. R. B. Crighton","doi":"10.1144/sjg2016-003","DOIUrl":"https://doi.org/10.1144/sjg2016-003","url":null,"abstract":"Four Silurian brachiopod species from the Pentland Hills, previously ignored or designated nomina dubia, require some recognition on the basis of material identified in the collections of the National Museum of Scotland and a closer scrutiny of the published work with respect to the guidelines of the International Commission of Zoological Nomenclature.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2017-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46598456","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}

{"title":"Addenda to the record of machaeridian shell plates in the Wether Law Linn Formation (Late Llandovery), Pentland Hills, Scotland","authors":"Y. Candela, W. R. B. Crighton","doi":"10.1144/sjg2016-006","DOIUrl":"https://doi.org/10.1144/sjg2016-006","url":null,"abstract":"Additional machaeridian specimens from the Wether Law Linn Formation (Telychian) have increased our knowledge of this poorly recorded but abundant group in the Pentland Hills, located a few kilometres SE of Edinburgh. A new type of anterior outer shell plate is described and is compared with material previously described from the same horizon and locality. Moreover, a new species of Plumulites is established on the basis of a disarticulated but close association of shell plates.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2017-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/sjg2016-006","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44760512","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}

{"title":"Reply to Discussion on ‘The Neoproterozoic to Mid-Devonian evolution of Scotland: a review and unresolved issues’ Scottish Journal of Geology, 51, 5–30","authors":"J. Dewey, I. Dalziel, R. J. Reavy, R. Strachan","doi":"10.1144/SJG2016-015","DOIUrl":"https://doi.org/10.1144/SJG2016-015","url":null,"abstract":"In the first paragraph of his discussion of our paper, Burton sets up his definition of what he thinks should have been the structure and purpose of our paper, his opinion of what a review should be and then complains that we did not follow his definition. We reject his definition, having defined our purpose in the abstract of our review. We were invited to write a short review of the Precambrian–Lower Palaeozoic tectonic history of Scotland. We structured the review around the topics that interest us; the paper was not, and could not be, an in-depth review of the opinion of everyone who had published relevant data and ideas on the topics covered in the paper. Our purpose, in the space allotted, was to present an overview review rather than a lengthy document argued in detail with references to everyone who had published on the topic. A full detailed analysis and review of the kind suggested would have been far too long for the Scottish Journal of Geology. The purpose of the paper is stated in the abstract and the last paragraph of the summary. There was no conscious effort to exclude Bluck's work; his work did not feature in our review, just as that of many hundreds of geologists who have also written on the subject. Several people who reviewed the manuscript, including the referees, made no mention of the absence of references to Bluck's published work, and it simply did not occur to us as we wrote it. We regret that this has caused offence. In our short review, we outlined our views and did not try to include and argue against all the different opinions with which we disagree. To have done so would have quadrupled the reference list and at least doubled the length of the paper. The whole Highland Border issue has been argued interminably for ages (often in the Scottish Journal of Geology) and, in the end, the consensus was against Bluck's views (e.g. Henderson et al. 2009). There is no point in bringing up arguments just to shoot them down; we do not see that as a positive legacy to Bluck, whose work in fluvial sedimentology was superb.","PeriodicalId":49556,"journal":{"name":"Scottish Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.7,"publicationDate":"2016-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1144/SJG2016-015","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"64033589","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}