bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scottish Silurian shorelines
Authors: Clarkson Euan N. K. , Harper David A. T. , Taylor Cecilia M. 
Published: November 2011

ABSTRACTThe Silurian inliers of the Midland Valley of Scotland all exhibit a regressive sequence, and despite evident facies differences between inliers, marine successions invariably pass upwards into redbeds of continental origin. Contrasting types of shoreline facies can be seen in different inliers; here the beds in the North Esk Inlier (NEI) are compared with those previously described from Knockgardner. At Knockgardner a high energy coastal environment prevailed, but in the NEI very different conditions can be identified in near-contemporaneous deposits. In the NEI thin sandstones and siltstones of the Reservoir and Deerhope formations are succeeded by the sandstones and conglomeratic beds of the Cock Rig Formation. These are overlain by the marine mudstones of the Wether Law Linn Formation and, at the top of the sequence, the continental redbeds of the Henshaw Formation.The Wether Law Linn Formation is interpreted, on various lines of evidence, as a lagoonal system. Conditions therein were initially fully marine, though within the photic zone, but subsequently the faunas were increasingly influenced by fluctuating salinity, prior to deposition of the redbeds. Such a lagoon would have required an offshore bar impounding it, which is represented by the Cock Rig Formation. These sedimentary rocks, previously interpreted as deposits of a laterally unconfined submarine channel, are now considered to be of shallow water origin. The succession closely conforms to classic models in which shoreface sands, consisting of small cross-bedded packets, are succeeded by tabular sandstone sheets representing foreshore beach deposits. Coarser and thicker beds, with herringbone cross-sets, linguoid ripples and trains of rounded pebbles, are interpreted as the deposits of tidal channels within the barrier complex. The barrier-lagoon system persisted throughout the whole of Cock Rig time and most or all of the time during which the Wether Law Linn Formation was deposited, and was either static or prograded seawards until the lagoon dried up during a final marine regression. The sedimentary and faunal evidence is consistent with this interpretation, and the contrast between the shoreline environments of the NEI and Knockgardner is striking. Brief reference is made to other inliers in the Midland Valley.
Scottish Ordovician ostracodes: a review of their palaeoenvironmental, biostratigraphical and palaeobiogeographical significance
Authors: Williams Mark , Floyd James D. , Miller C. Giles , Siveter David J. 
Published: November 2011

ABSTRACTOstracodes have a wide geographical distribution in the Ordovician of Scotland. They are known from the Southern Uplands, the Girvan district, the Highland Border region and the Inner Hebrides. Overall, more than forty species are recorded. They occur in clastic and carbonate rocks indicative of a range of shallow to deeper marine-shelf environments. Though many of the faunas are allochthonous, broad patterns of ostracode palaeoenvironmental distribution can be elucidated, and elements of the shallow marineLeperditellaand open marineshelfAnisocyamusassociations (previously recorded from N America) are present. Indigenous faunas are absent from the deep marine sediments of the Southern Uplands Northern Belt. Ostracodes are known from the Arenig, Llanvirn, Caradoc and Ashgill series in Scotland; those of the latter two series have widest biostratigraphical value. In the Girvan district the Caradoc species ‘Ctenobolbina’ ventrospinosa, Krausella variata, Balticella deckeriandMonoceratella tereshave correlative value with N America, whilst the Ashgill speciesKinnekullea commaappears to be a locum for theancepsgraptolite Biozone in Britain, Ireland and possibly the eastern Baltic. The ostracodes are of typical Laurentian affinity, but show progressive generic links with the Baltic region during the late Llanvirn–Caradoc interval, and by Ashgill times display species-level links with southern Britain and Ireland. These distributional patterns suggest approaching geographical proximity for the early Palaeozoic continents of Laurentia, Baltica and Avalonia, and the ability of some Ordovician ostracodes to cross the Iapetus Ocean.
New palynological data from the Leinster Lower Palaeozoic massif, southeastern Ireland
Authors: Brück Peter M. , Higgs Kenneth T. , Maziane-Serraj Nadia , Vanguestaine Michel 
Published: November 2011

ABSTRACTIn southeastern Ireland, the tectonic evolution of the northwestern Avalonian margin is rather poorly understood and only partially constrained. This is because the stratigraphy comprises in the main unfossiliferous turbidites. Nevertheless, some authors have attempted to define ‘terranes’ and ‘tracts’ in the region, aided by several significant Caledonoid-trending structural breaks that can be determined in the field. Palynological work was carried out in the early 1970s and established a range of ages from approximately mid Cambrian to late Silurian, although much of the succession proved barren. In the current study, the Lower Palaeozoic sequences W of the Leinster Granite and in the Slievenamon Inlier to the S have been palynologically re-investigated. Previous work proposed an unbroken succession from lower Ordovician Ribband Group turbidites and volcanics younging westwards conformably into upper Silurian Kilcullen Group sediments. The new study clearly shows that the Ordovician palynomorphs in the older part of the Kilcullen Group are reworked. In fact, there exists a major stratigraphical break between the Ribband Group dated as early Ordovician, Arenig, and the Kilcullen Group which is entirely Silurian, late Llandovery to early Wenlock in age. This major break has a minimum strike length of 150 km and is most likely much longer, extending some hundreds of kilometres SW to Dingle and possibly equating with a similar discontinuity in the Isle of Man to the NE. This break would thus appear to be a major feature within the succession of the northwestern Avalonian margin.
Evidence for metamorphic remagnetisation of upper Precambrian tillite in the Dalradian Supergroup of Scotland
Authors: Stupavsky M. , Symons D. T. A. , Gravenor C. P. 
Published: November 2011

ABSTRACTA conglomerate test using 36 clast cores (76 specimens) from the upper Precambrian Port Askaid Tillite of the Dalradian Supergroup in the Garvellach–Islay region of Scotland shows that the tillite was remagnetised during orogenic activity in Lower Ordovician time. After 550°C thermal demagnetisation, the clast remanence directions give a mean of 155°, 14° (α95—12°). This is similar to the mean from four tillite matrix sites of 162°, 4° (α95—9°) and the mean ‘primary component direction’ of 166°, −12° (α95—6°) previously determined from the interbedded siltstones. This indicates that the matrix and siltstones were also remagnetised. These mean directions give virtual geomagnetic poles after tilt correction that fall within the cluster of British Ordovician poles from rocks in the Caledonian orogen, and thereby indicate a prefolding Ordovician age for the remagnetisation. Thermal demagnetisation studies and observations from polished and thin sections of tillite clast and matrix specimens show that secondary hematite derived from partially to completely altered magnetite is the dominant carrier of the metamorphic remagnetisation. These results show that remanence data from the Port Askaid Tillite cannot be used to support the hypothesis that a worldwide glaciation occurred during the Late Precambrian.
Structural evolution of migmatites in granulite facies terrane: Precambrian crystalline complex of Angul, Orissa, India
Authors: Halden N. M. , Bowes D. R. , Dash B. 
Published: November 2011

ABSTRACTBasic granulites, a variety of gneisses including sillimanite-garnet gneiss (khondalite), charnockite and intruded quartzofeldspathic material make up a migmatite complex showing evidence of polyphase deformation, polymetamorphism and successive neosome emplacement. The heterogeneity of the migmatites is dominantly the result of folding and boudinage rather than igneous activity.Tight to isoclinal folds of the second recognised deformational phase affect lithological layering, granulite facies fabric elements of the first deformational phase and early neosome; they played a major role in the development of the macroscopically heterogeneous nature of the complex and they are also a key structure for correlation. Upright folds of the third deformational phase control the major disposition of lithological units and, together with their axial planar fabric, controlled the uprise of quartzofeldspathic neosome and of volatiles and heat which caused localised ‘charnockitisation’ of sillimanite-bearing gneisses. The effects of semibrittle and brittle deformation, including kink bands, fractures and shears, express late deformational phases during which there was neosome emplacement, some at 854 ± 6 m.y. ago (Rb–Sr muscovite age).
Trilobites from the Ordovician Shihtzupu Formation, Zunyi, Guizhou Province, China
Authors: Zhou Zhiyi , Yin Gongzheng , Tripp Ronald P. 
Published: November 2011

ABSTRACTTwenty-seven species assigned to 20 genera of trilobites are described from Feilaishi in Guizhou Province, the type section of the Shihtzupu Formation in S W China. They occur in association with a sparse graptolite fauna includingGlyptograptus teretiusculus. Eleven taxa are recorded here for the first time. Much new morphological information is provided regarding previously known species and 3 lectotypes are selected. The trilobites are largely endemic and indicate a quiet and comparatively shallow water environment
Chemical, physical and mineralogical characteristics of some Turkish soils derived from volcanic material
Authors: Güzel N. , Wilson M. J. 
Published: November 2011

ABSTRACTThe chemical, physical and mineralogical characteristics of five soil profiles developed on volcanic material on the Anatolian plateau of Turkey have been studied. The soils, which are mainly Entisols, have high pH values in the range 7·5 to 8·0, low amounts of organic matter (usually <1·0%), low available water capacities and a low to medium ability to sorb phosphate. The soil parent materials are basalts and tuffs which often contain large proportions of volcanic glass. Weathering of this material in the prevailing semi-arid climate results in the development of a smectite-dominated clay fraction with small amounts of kaolinite. The smectite usually yields anomalously high X-ray spacings, probably due to interstratification and absorption of interlamellar material. The characteristics of the Anatolian soils are in marked contrast to those of Andepts which have formed on similar parent materials in humid, temperate climates.
Diagenetic pyrite formation and sulphur isotope fractionation associated with a Westphalian marine incursion, northern England
Authors: Love L. G. , Coleman M. L. , Curtis C. D. 
Published: November 2011

ABSTRACTPyrite textures are described and illustrated and stable S-isotope data are presented from the Alton (Gastrioceras listen) marine horizon of the Westphalian Lower Coal Measures, from sections near Penistone in central northern England, with the object of relating the paragenetic sequence of pyrite formation to the conditions of sediment deposition and diagenesis. The earliest diagenetic pyrite is dispersed as framboidal and related textures. It is followed in the marine shale, coal and ganister by more localised but more intense pyrite deposition and replacement in a variety of textures. Most of this is precompactional in age, but some, together with pyrite in veinlets and cleat, is postcompactional. Marcasite is rare and mainly late. δ34S ratios range between −35·31‰ and +20·39‰. There is a definite trend from lighter values (−1·15 ± 6·47‰) in the marine part of the sequence to much heavier values (+12·73 ± 7·66‰) in the sediment below the coal. This allows the relationship of the earliest pyrite deposition in the coal-peat and ganister to the chemistry of their own depositional fresh water to be seen but then relates the main pyrite deposition to the influx of the marine-water sulphate of the Alton horizon, and shows the penetration of this influence downward into the coal-peat and its seat-bed.
Regional framework and geodynamic evolution of the Indus-Tsangpo suture zone in the Ladakh Himalayas
Authors: Thakur V. C. 
Published: November 2011

ABSTRACTThe Indus-Tsangpo suture and its adjoining tectonic zones are well displayed in the Ladakh Himalayas where four tectonic zones have been distinguished, viz. the Zanskar, Indus suture, Shyok suture and Karakoram zones. The Zanskar zone is made up of Precambrian basement of the Zanskar crystalline complex and overlying Phanerozic sediments including Upper Palaeozoic volcanic rocks of the Zanskar Supergroup; they form the northern margin of the Indian plate. The Indus suture zone consists of a remnant of tectonised oceanic lithosphere represented by the Shergol melange and the Nidar complex with a former volcanic arc indicated by the volcanogenic Dras and Khardung formations and the Ladakh plutonic complex. The Shyok suture zone does not represent a tectonic repetition of the Indus suture; it is interpreted as a relic of a back-arc basin. The Karakoram plutonic complex appears to be genetically related to the Ladakh plutonic complex; both were generated from the subducting Indian oceanic plate. It is proposed that the boundary between the Indian and Eurasian plates does not lie along the Indus and Shyok sutures, but is located further N at the junction of Central Pamir (Alpine-Himalayan) and North Pamir (Hercynian).
Metamorphic development of cordierite-amphibole rocks and mica schists in the vicinity of the Outokumpu ore deposit, Finland
Authors: Treloar P. J. , Koistinen T. J. , Bowes D. R. 
Published: November 2011

ABSTRACTAnalysed compositions of coexisting phases from cordierite-amphibole-bearing rocks (cordierite-orthoamphibole-cummingtonite-garnet-staurolite-spinel-opaque ores) and mica schists (garnet-staurolite-biotite-muscovite-plagioclase-andalusite-quartz) have been used in conjunction with experimentally determined equilibria to estimate pressures and temperatures of metamorphism for the rocks of the Outokumpu district. The data do not determine a single point in P-T space, but bracket an area such that T ≈ 600 ± 50°C and P ≈ 3·5 ± 1 kb. These conditions represent the maximum temperature attained by the rocks, and the associated sulphide ore bodies, during the Svecokarelian orogeny and are consistent with a regional palaeogeotherm of c. 50°C/km.Assessment of the composition of the coexisting phases in the cordierite-amphibole-bearing rocks, particularly the Fe-Mg-bearing phases, indicates that it is unlikely that either iron or magnesium was mobile during metamorphism and that the equilibrium assemblage represents essentially isochemical metamorphism of a rock composition that predates the metamorphism. A similar genesis is considered likely for the cordierite-anthophyllite rocks of Orijärvi in southern Finland which forms the basis of the classic statement of the magnesium-metasomatism hypothesis.
Hyalotuff deltaic deposits in the Ballantrae ophiolite of SW Scotland: evidence for crustal position of the lava sequence
Authors: Bluck B. J. 
Published: November 2011

ABSTRACTHyalotuff deltaic deposits, a high proportion of volcanogenic sediment and a repeated occurrence of conglomerate with well-rounded clasts constitute evidence for the shallow-water origin of spilitic lavas and volcanogenic sediments in an Ordovician ophiolite at Ballantrae, SW Scotland. One section, >1.5 km thick, shows repeated evidence for a shallow-water origin. This implies accumulation in a subsiding area. In this sense the sequence at Ballantrae is in marked contrast to those found in oceanic islands (hot spots) which are known to grow from deep into shallow water. Neither does it compare well with those from ocean ridges which usually begin in deep water and move, with cessation of vulcanicity, into even deeper water.The lava sequence at Ballantrae compares well with oceanic island-arc and remnant arc deposits where uplift and subsidence is common. This, the occurrence of intermediate and acidic lavas and clasts, and the restricted palaeontological and radiometric ages support an arc-marginal basin origin for the lavas. Diversity in the chemical composition of the lavas may reflect diverse origins within the marginal basin.An upward coarsening sedimentary sequence was built by a hyalotuff delta which formed in front of advancing lava flows. As the lavas advanced over the sediments so a sequence was generated where these sediments have a source in lava flows which were eventually to overlie them.Clasts of tholeiite were derived from lavas which are now spilite. This, together with the presence of spilitic lava clasts and tuff immediately beneath the flow suggests that the spilitisation resulted from metasomatic activity associated with the convective circulation of trapped water, with the lava as a heat source.
New observations on Sawdonia ornata from Scotland
Authors: Rayner R. J. 
Published: November 2011

ABSTRACTRecent collections of Sawdonia ornata have been made from the Strathmore Group which crops out in the Midland Valley of Scotland. The sediments are Lower Devonian, probably Emsian, in age. New morphological features discovered include planar branching of vegetative and fertile axes, abaxial emergences close to branch points and H branching. Well preserved cuticles have permitted reinterpretation of the structure of stornata, rosettes (hair bases), papillae and spines, and striated cuticle is identified as S. ornata. The morphology of sporangia and in situ spores is described. Pyritised axes have revealed details of xylem shape, maturation, changes in the vicinity of branching, tracheidal structure and the arrangement of xylem and cortex in deformed axes.
Chelicerata from the Dinantian of Foulden, Berwickshire, Scotland
Authors: Waterston Charles D. 
Published: November 2011

ABSTRACTA lower Carboniferous limulaceanRolfeia fouldenensisgen. et sp. nov. is described. It is regarded as a sister group ofPaleolimulusand distinguished from it by the presence of fixed opisthosomal spines and by the more primitive outline of the opisthosoma. Both characters could have been derived from belinuroid ancestors, and both were retained in the advanced belinurids and euproopids. The view that limulaceans are more closely related to certain primitive belinuraceans rather than descended from the euproopaceans is thus supported by the new evidence. AlthoughRolfeiawas probably still capable of coaption, it is postulated that, like other limulaceans, it had adopted burial as a form of defence. It is suggested that the primary adaptive function of the fixed opisthosomal spines was to support the body over a soft substrate although they may also have served a defensive role.The occurrence at Foulden of the eurypteridCyrtoctenus peachiStørmer and Waterston is confirmed. The eoscorpiidTrachyscorpio squarrosusKjellesvig-Waering 1984 has been described from Foulden anddisjecta membraofGigantoscorpiocf.willsiStørmer discovered in the recent excavation are described. The type of preservation and adaptive features of the chelicerates would suggest that the eurypterid and scorpion fragments are allochthonous and the xiphosurans probably autochthonous.
Actinopterygian fish from the Dinantian of Foulden, Berwickshire, Scotland
Authors: Gardiner B. G. 
Published: November 2011

ABSTRACTThe four stem-group neopterygians from Foulden are redescribed: Carboveles ovensi White, Aetheretmon valentiacum White, Strepheoschema fouldenensis White and Fouldenia ottadinica White. Carboveles is shown to be a junior synonym of Phanerosteon Traquair, Fouldenia ottadinica White is synonymised with Styracopterus fulcratus (Traquair), Strepheoschema rhodesi Moy-Thomas with S. fouldenensis White and Aetheretmon whitei Moy-Thomas with A. valentiacum White. The family Strepheoschemidae is erected to comprise Strepheoschema and Aetheretmon, characterised by paired ventral ridge scales in front of the pelvic fins. Cosmoptychius striatus (Agassiz), recorded here from Foulden for the first time, is widespread in the geologically younger Oil Shale Group. The Foulden actinopterygian fauna is identical to that of the Cementstone Group at Coomsdon Burn, Northumberland, although with two additional taxa. Styracopterus fulcratus occurs also at a further two Cementstone Group localities in Scotland.
Palaeoecology of the Dinantian of Foulden, Berwickshire, Scotland
Authors: Clarkson E. N. K. 
Published: November 2011

ABSTRACTThe Foulden Fish Bed was deposited in a semi-permanent brackish water lake on a floodplain between a northerly mountain range and the sea. The lake supported a rich biota mainly of swimming animals (fish and crustaceans) with a benthos of trace fossils only in the earlier and later stages of the lake's development. Xiphosurans are very rare. This biota changed according to the physical conditions of the lake. Salinity, fluctuating according to water level, was a dominant control. Early in the lake's history there was a dominant benthos of euryhaline bivalves; at the same time, large rhizodonts lived in the lake as the top carnivores. Subsequently, crustaceans were the dominant nektobenthos, in a probable brackish-water regime, the rareBairdopspreying on the commonBelotelson; there was a limited infauna. Following this, palaeoniscids abound in the middle part of the sequence, perhaps due to a higher water level but crustaceans are absent at this horizon. During the last stages before final silting-up following a mass-mortality episode, biotic diversity reached a maximum with many fishes and crustaceans and some trace fossils, due to optimal salinity conditions.Comparisons are made with other Carboniferous biotas and with the Jurassic Solnhofen limestone.
Sensory and other superficial structures in living marine Crustacea
Authors: Laverack M. S. , Barrientos Y. 
Published: November 2011

ABSTRACTLiving Crustacea possess many types of sensory receptors that detect environmental signals. These structures allow the speculation that similar organs existed in fossil arthropods and were involved in similar ways in the fossil forms when they were extant.Posture, for example, is difficult to reconstruct in fossils without the understanding that internal proprioceptors monitoring position and movement are crucial in determining the placement of limbs, and the position of the abdomen and other jointed portions of the body. These receptors are associated also with autotomy reflexes through soft cuticle detectors that respond to strain not associated with joints.Many receptors are placed on the outer surface of the animal, the eyes being the most obvious. The eyes receive no attention in this paper, but descriptions are given of a number of different types of setae, serving both mechanical and chemical sensors. The possession of a pore at the apex (or sub-apex) of a seta or setule probably indicates a chemoreceptor function, but its absence does not necessarily indicate a lack of such sensitivity. A range of forms is illustrated.The dorsal organ is a recently discovered structure in decapod larvae. It is composed of a central single gland cell opening via an aperture in the midline just behind the rostrum. It is bounded by four depressions each containing a central ‘nipple’. These prove to be sensors, with ciliated endings (bifid) that end in a highly modified cuticle at the depression nipple. The function is unknown, but it is proposed that it represents an unusual chemoreceptor.