bluuebunny/crossref_metadata_2025_split huggingface dataset:
Caledonian and related events in Scotland
Authors: Bluck B. J. 
Published: November 2011

ABSTRACTThe Scottish Caledonides, sited near the triple-junction between Laurentia, Amazonia and Baltica, is divided into at least five discrete blocks, each with a history incompatible with that of the block now lying adjacent to it. With the exception of the Hebridian margin, with its extensional Torridonian basins and Cambrian passive margin sequence, all blocks have undergone terrane-scale movements. The Moine, Central Highland Division and the bulk (if not all) of the Grampian Group have shared a common regional metamorphism, involving thickening and uplift, atc. 800 Ma andc. 450–480 Ma. This is incompatible with their being in the extensional regime that appears to characterise much of Neoproterozoic Laurentia. They, along with the polymetamorphic Dalradian block, now replace a region of passive margin and an unknown width of attendant Iapetus oceanic crust. These metamorphic blocks are grossly out-of-place.The Midland Valley is a severely contracted block of ancient crust, once fringed by extensive oceanic basins to the N and S. An Ordovician–Devonian arc was founded on this older craton, and supplied sediment to basins on either side of it. This arc, during its Lower Palaeozoic life, matured, finally to yield relatively quartz-rich sediment, but was re-activated during the Devonian. An arc, similar to that of the Midland Valley, also supplied sediment to the Southern Uplands. Metamorphic debris in the Southern Uplands had a provenance in either this arc-basement or in a basement somewhere along the orogen. No metamorphic detritus in the Highland Border Complex has yet been demonstrated to have a Dalradian source.Much of Scotland was assembled in a strike-slip regime. Evidence for strike-slip tectonics can be seen from the Late Proterozoic through to the Devonian. In periods of transtension, basins opened to accumulate sediment; in periods of transpression, those sediments were compressed and uplifted to yield sediments to successor basins. In the Neoproterozoic, during the phase of transpression, the basins were buried and metamorphosed, but during the Palaeozoic the basins were at a much higher level and escaped metamorphism.A substantial volume of the Neoproterozoic–Palaeozoic sediment that accumulated in Scotland was derived from two orogens, both of which were sited some distance away. During the Neoproterozoic, the Grenville orogen was the main source, and in later (Devonian) time sediment accumulated in Scotland from the major, Late Palaeozoic continent–continent collision of Greenland–Scandinavia. These two external sources were augmented by a substantial contribution of sediment supplied from the Midland Valley arc or its lateral equivalent and by mild uplifts within the Scottish basements.
Progress in describing Ordovician siliceous biodiversity from the Southern Uplands (Scotland, U.K.)
Authors: Danelian Taniel , Floyd James D. 
Published: November 2011

ABSTRACTLeaching of Ordovician cherts from the Southern Uplands using dilute hydrofluoric acid has yielded numerous radiolaria, sponge spicules and a few conodonts. Although many of the radiolaria have suffered intense recrystallisation, it nevertheless proved possible to extract for SEM examination some examples with exquisitely preserved micro-structure. Despite this, the radiolaria have not proved sufficient, on their own, to answer the outstanding biostratigraphical question of one continuous or two separate episodes (Arenig and Llanvirn/Caradoc) of chert sedimentation in the Southern Uplands. This is partly because the biostratigraphy of Lower Palaeozoic radiolaria is still quite poorly known. A new radiolarian species, Protoceratoiciskum clarksoni Danelian, has been identified and described from cherts in the Crawford area. In addition, the distinctive sponge species Konyrium varium Nazarov & Popov, has also been found for the first time in Southern Uplands cherts. This new occurrence, in deep-water sediments, suggests a much wider habitat for this unusual sponge. Amongst the few conodont elements extracted, one can be identified as probably belonging to the genus Periodon.
Low-grade metamorphism in the Scottish Southern Uplands terrane: deciphering the patterns of accretionary burial, shearing and cryptic aureoles
Authors: Merriman R. J. , Roberts B. 
Published: November 2011

ABSTRACTSystematic studies of metapelitic grade linked with the geological re-survey of the Southern Uplands have been used to generate a contoured metamorphic map currently covering nearly two-thirds of the terrane. These studies, based on approximately one pelite sample per 2·5 km2, have used XRD measurements of clay mineral reaction progress, particularly illite crystallinity, to delineate zones of diagenesis and low-grade metamorphism in the imbricated Ordovician and Silurian strata. The regional pattern revealed by metapelitic zonal sequences does not agree with earlier observations that grade increases across the strike, from SE to NW. Instead, the map shows considerable variations in metamorphic trends, including patterns of grade increasing from older into younger strata, indicative of accretionary burial. Other patterns identified include those generated by high strain rates in the Moniaive Shear Zone (MSZ), and by extensive low-temperature cryptic aureoles associated with late granitic intrusions. The present pattern is the result of uplift that generated normal movement on reactivated thrust faults and differential block movement on NW-trending faults.Regional metamorphic patterns were generated by burial and underplating in an accretionary thrust stack. Subduction was initiated in the early Caradoc and probably ceased in the early Wenlock. Metapelitic patterns suggest that two levels of accretion are exposed in the terrane. Strata accreted to the toe of the prism and stacked above the décollement zone are typically at late diagenetic grade. Underplated strata below the décollement are typically at anchizonal grades with moderate to well-developed slaty cleavage. Coherent thrust-bounded tracts of strata at both levels were rotated and buried to produce a syntectonic depth-controlled pattern of meta-morphism. Shear zone metamorphism at depths of 12 km or more was probably confined to the underplated lower level of the thrust stack, and Devonian granitic intrusions were also emplaced mainly within the underplated strata.
Geochemical characteristics and geotectonic setting of early Ordovician basalt lavas in the Ballantrae Complex ophiolite, SW Scotland
Authors: Smellie J. L. , Stone P. 
Published: November 2011

ABSTRACTThe consensus of several geochemical studies is a polygenetic origin for the basic volcanic sequence within the Ballantrae Complex ophiolite. This overall agreement masks differences of opinion regarding local geochemical interpretation, the possible correlation of structurally isolated lava tracts, and the degree of structural imbrication responsible for the juxtaposition of the various lava types. Newly acquired data (XRF, INAA, ICP-MS) provide the best evidence yet obtained for the presence of a MORB component and establish a wider distribution for primitive tholeiitic basalts with plate-margin characteristics than had been previously reported. The two principal within-plate sequences (well established from extensive coastal outcrop) are geochemically indistinguishable, with one considered to be the deeper water equivalent of the other. Lithofacies and geochemical similarities encourage correlation of some inland and sparsely exposed examples of within-plate basalt with the well-exposed coastal sequences, and all of this lava type may have originated from a single, ocean island volcano. The diversity of outcrops formed in within-plate and plate-margin geotectonic settings is combined within a dynamic reconstruction of a Tremadoc to Arenig arc-trench system with an active back-arc spreading region. The new reconstruction reconciles for the first time all of the known geochemical and published isotopic age evidence.
Geochronological studies of the Bohemian massif, Czechoslovakia, and their significance in the evolution of Central Europe
Authors: van Breemen O. , Aftalion M. , Bowes D. R. , Dudek A. , Mísař Z. , Povondra P. , Vrána S. 
Published: November 2011

ABSTRACTU–Pb zircon and Rb–Sr whole-rock analyses from various gneisses and plutonie rocks of the Moldanubian and Moravo-Silesian zones and the stable foreland of the Hercynian (Variscan) orogenic belt indicate that most of the crust in Central Europe was first formed during the Cadomian orogeny which straddles the Precambrian–Cambrian boundary. Zircons, however, have a memory of older ages which correspond with those of events known in Fennoscandia. The new radiometrie data are consistent with the stratigraphie record in that they do not provide any evidence for a major early Palaeozoic tectonothermal event between the Cadomian and Hercynian orogenies.Granulites from two localities in the Moldanubian zone yield U–Pb zircon ages of 345 ± 5 Ma; discordant zircon data points indicate that the granulite facies metamorphism was not of long duration. Tectonic units containing these high grade rocks were emplaced amongst amphibolite facies rocks during an event of widespread shearing which has been dated at 341 ± 4 Ma on the basis of a lower U–Pb zircon intercept age from one of the sheared gneisses and 338 ± 3 Ma U–Pb ages from monazites. Rb–Sr muscovite ages of 331 ± 5 Ma from pegmatites axial planar to asymmetrical folds date the last stage of SE-directed simple shear. A Rb–Sr whole-rock isochron of 331 ± 4 Ma from a principal magmatic type of the Central Bohemian pluton confirms the field evidence that the large NE-trending plutons of the Moldanubian zone were emplaced during a late stage of the deformation. The strong disturbance of the U–Pb zircon isotopic system in the sheared gneisses suggests U loss while a high U/Th ratio in monazite from one of these tectonised rocks suggests the simultaneous passage of hydrothermal fluids. Thus a crustal source is indicated for the uranium deposits of the Moldanubian zone.Critical to any plate tectonic model for the development of the Middle European Hercynides was the existence of an ocean in Early Devonian times which separated a North European continent from a South European continent(s). The northward movement of the South European continent over a shallowly-dipping subduction zone and subsequent continental collision can explain the high T–low P metamorphism and the imbricated tectonic style of the Moldanubian zone and adjacent Moravo-Silesian zone along the southeastern Hercynian foreland. The temporal separation of granulites and granites implies distinct conditions of formation and it has been suggested that the plutonism, following on from the imbrication of the Cadomian crust, was initiated by the subduction of wet oceanic sediments.
Susceptibility to weathering of some Scottish rocks and their derived soils
Authors: Smith B. F. L. , Mitchell B. D. , MacKenzie R. C. 
Published: November 2011

ABSTRACTThe susceptibility of rocks to weathering into soils and the subsequent weathering of the solum itself are important both with respect to sediment formation and to agriculture. Residual soils developed on some rock types representative of the major soil associations of NE Scotland have consequently been examined in detail in an attempt to assess the weatherability of both the rocks and the derived soils. Methods based on chemical composition have been supplemented by potential methods related to the production of poorly-ordered aluminosilicate material and to depolymerisation of the silicate framework in the minerals present. In general, there is, as would be expected on the basis of increasing energy supply and increasing entropy, an increase in the amount of monomeric silica towards the surface and this appears to be closely related to the amount and nature of the poorly-ordered aluminosilicate. The results suggest that only the purely chemical methods can currently enable a reasonable assessment to be made of the susceptibility of a rock or soil to further weathering.
Geochemistry of a dismembered metaophiolite complex, Letovice, Czechoslovakia
Authors: Jelínek E. , Pačesová M. , Mísař Z. , Martinec P. , Weiss Z. 
Published: November 2011

ABSTRACTThe origin of a suite of ultrabasic and basic rocks from the Letovice crystalline complex in the eastern part of the Bohemian massif, Czechoslovakia, is discussed on the basis of new geological and geochemical data. Strongly serpentinised spinel peridotites, plagioclase peridotites and pyroxenites, together with metagabbros, amphibolites and minor dykes of metadolerite, make up about 70% of the complex; metasediments, mainly mica schists, make up the remaining 30%. The ultramafic and mafic rocks constitute parts of a dismembered ophiolite considered to have been formed in the Cadomian episode. They show effects of polyphase deformation and were variously metamorphosed under conditions of greenschist to garnet amphibolite fades at 400–600°C and 2–5 kb. Geochemical features of the ultrabasic suite are similar to those of other ophiolite complexes, such as those of Bay of Islands, Oman, Papua, Pindos, Sarmiento and Troodos and are likely to be products of a marginal sea environment.
Iron and manganese oxide minerals in soils
Authors: Chukhrov F. V. , Gorshkov A. I. 
Published: November 2011

ABSTRACTAccurate identification of iron and manganese oxides in soils presents great difficulty because, not only are they always in admixture, but the poor crystallinity of the species present leads to difficulties in interpretation of diffraction patterns. A method involving the combined use of electron microscopy, selected area electron diffraction and electron probe microanalysis on the same crystals gives unambiguous identification. Its application is described in relation to the various iron and manganese oxides found in a set of soils from all parts of the world. The occurrence of hausmannite in soils has been definitely established.
Lower Old Red Sandstone fluvial dispersal systems in the British Isles
Authors: Allen J. R. L. , Crowley S. F. 
Published: November 2011

ABSTRACTAn evolving pattern of fluvial dispersal responsible for the Lower Old Red Sandstone magnafacies has emerged from a stratigraphical and geographical consideration of palaeocurrent structures, clast lithology and fauna, sandstone composition, and sandstone detrital heavy-mineral assemblages. The evidence suggests that the Post-Ludlow (Downton) and lower Gedinnian rocks formed mainly in the joined Dingle–Shannon and Anglo–Welsh basins, fed from metamorphic complexes in NW Britain or beyond. Contemporaneous sedimentation in the Caledonian basin was restricted to its northeastern end. Later in the Gedinnian, the Dingle–Shannon and Angle–Welsh basins appear to have become separated by the uplift of a broad and extensive belt of mainly Lower Palaeozoic sedimentary and volcanic rocks; included in this belt were outcrops of Post-Ludlow strata representing the earlier stream of metamorphic detritus. Granite intrusion, which reduced the density of and consequently uplifted the crust, occurred widely in the regions dividing and bordering these basins, and may be causally connected with their separation in the Gedinnian. The Caledonian basin appears to have remained a separate feature.
Plant miospores from the Dinantian of Foulden, Berwickshire, Scotland
Authors: Clayton G. 
Published: November 2011

ABSTRACTPlant miospore assemblages obtained from eight beds of the Foulden sequence, ranging from Bed 1 to Bed 17, are basically similar to each other in stratigraphical significance. The presence of Convolutispora circumvallata, Crassispora trychera and Schopfltes claviger and the absence of Lycospora pusilla suggest assignment to the Schopfites claviger-Auroraspora macra (CM) Biozone. This indicates the Courceyan Stage of the British Dinantian and the late Tournaisian (Tn3) of the Belgian Series. Comparable miospore assemblages have been described from Cementstone Group localities elsewhere in Berwickshire, East Lothian, Ayrshire and northern England. Preservation, and lack of marine palynomorphs and scolecodonts, suggest non-marine deposition. The presence of vitrinite fragments and megaspores as well as miospore tetrads suggests little transport before deposition.
Coprolites and ostracods from the Dinantian of Foulden, Berwickshire, Scotland
Authors: Pollard John E. 
Published: November 2011

ABSTRACTCoprolites of four distinct shapes, cylindrical, discoidal, beaded and irregular masses, are described from 11 horizons within Bed 16 of the Foulden sequence. These coprolites are composed of either phosphatic or claystone material, although they have not been analysed mineralogically or chemically. Their producers appear to have been fish, probably both nektonic predators and nekto-benthonic scavengers or detritus feeders.Ostracods are poorly preserved and of two broad types, thick shelled paraparchitids including Shemonaella scotoburdigalensis and thin shelled podocopids, possibly species of Carbonita or Cavellina. This ostracod assemblage represents a conservative ‘carbonaceous fades’ fauna which occurs widely in plant-rich sediments in lower Carboniferous (Courceyan) sequences of northern England and southern Scotland. Other microfauna includes spirorbid worm tubes, fish scales, arthropod cuticle fragments, spat of myalinid bivalves, plant fragments and spores. No significant changes in the vertical distribution of the microfauna could be detected.The microfauna indicates a general fresh to brackish water lacustrine or lagoonal environment possibly with access to quasi-marine conditions.
Arthropod ichnofauna of the Old Red Sandstone at Dunure and Montrose, Scotland
Authors: Walker Elaine F. 
Published: November 2011

ABSTRACTSediments which occur frequently within Lower Devonian andesites of the Midland Valley of Scotland have so far yielded trace fossils in only two areas: Dunure, Ayrshire and Montrose, Angus.Smith (1909) interpreted the trace fossils from Dunure as representing an “Upland Fauna” and he named 23 new ichnogenera. Re-examination of his localities and specimens suggests that the environment was a shallow ephemeral lake and when sedimentological and preservational factors, size, behavioural variation and synonymy are taken into account, only 8 ichnogenera are here considered valid. These are redefined as Siskemia, Stiaria, Danstairia, Keircalia, Stiallia, Isopodichnus (=Archatomia Smith), Mermia and Merostomichnites. The Montrose ichnofauna of 5 ichnogenera includes a large arthropod trackway Mitchellichnus ferrydenensis gen. and sp. nov.The trackways from both localities appear to have been formed by various merostomes, crustaceans and possibly early myriapods. The habitat was essentially aquatic although some arthropods may have been amphibious.
Evolutionary trends and ecology of Mesozoic decapod crustaceans
Authors: Förster Reinhard 
Published: November 2011

ABSTRACTThe fossil record of unquestionable decapod remains dates back to Permo Triassic times. Evaluation of all available data from the fossil record, trace fossils and facies reveals various trends within the evolution of Mesozoic decapods, and its relation to their ecology. One of these trends is the protection of the long vulnerable abdomen. The most successful method, gradual reduction and inflection of the abdomen against the ventral cephalothorax, led to the Brachyura. Brachyurans exhibit the broadest spectrum of habitat adaptions.
Lift based mechanisms for swimming in eurypterids and portunid crabs
Authors: Plotnick Roy E. 
Published: November 2011

ABSTRACTThe striking morphological similarity that exists between appendages of the extant portunid crabs, such asCallinectes sapidus, and those of the extinet eurypterids has long been noted. The fifth pair of pereiopods in blue crags and other portunids are modified to form the broad, flat, highly mobile ‘swim paddles.’ A nearly identical modification is seen in the sixth pair of prosomal appendages of many eurypterids. The similarities are due to convergence and not to shared descent.The kinetics of blue crab swimming were studied using high speed films. The animals are capable of slow upwards locomotion (‘hovering’) and rapid sideways swimming. The blue crab paddles apparently act as reciprocating hydrofoils, employing well-understood principles of lift and thrust generation to overcome the animal's weight and drag. Experimental studies indicated that the paddles are capable of producing appreciable amounts of lift. Drag on the body and paddles was also determined. Resxults are similar to those obtained in previous studies of bird and insect flight.The physical principles employed to study blue crab swimming can be applied to the study of eurypterid locomotion. The eurypterid paddles may have functioned as hydrofoils, producing lift and thrust on forestroke and backstroke. Eurypterids were probably highly agile and manoueverable swimmers, capable of hovering and of high speed swimming. This model predicts observed morphological correlates. Predicted morphological correlates of earlier models (often based on analogies withLimulus) were not found.The observed convergence between eurypterids and blue crabs may have resulted from similar functional constraints and parallel phylogenetic histories.
Early Ordovician Dounans Limestone fauna, Highland Border Complex, Scotland
Authors: Ingham J. Keith , Curry Gordon B. , Williams Alwyn 
Published: November 2011

ABSTRACTA diverse, but sparsely distributed silicified fauna of over 30 taxa has been recovered from 7·5 tonnes of acid-etched Lower Ordovician Dounans Limestone from the Highland Border Complex, near Aberfoyle. The 13 trilobite taxa obtained include 3 new formally named species:Distazeris adoceta, Punka aetholiciocorusandIschyrotoma stubblefieldi.Other elements, representingCarolinites, Illaenus, Goniotelina, Sycophantia, Kawina, Heliomeroides, Strotactinus, Ectenonotus, Ceratocephalaand an indeterminate bathyurelline are described under open nomenclature although at least 4 are also probably new and 2 more may be conspecific with previously described species. The brachiopods include representatives ofArchaeorthis, Nothorthis, Orthidium, ?Camerella, Idiostrophia, Orthambonitesand 4 other indeterminate stocks. Gastropods tentatively assigned toMurchisonia, Subulites, Straparollina, MacluritesandCyrtodiscusare described, as are bryozoans, an orthocone, crinoids, andIncertae sedis.This profoundly North American fauna is Late Canadian ( = mid Arenig) in age and equates with the Cassinian Stage: it is key evidence in showing that the Highland Border rocks are not part of the Dalradian Supergroup whose earliest deformations and metamorphism predate the Ordovician. The field relationships of the limestone, together with evidence from derived clasts in Middle Ordovician and Devonian sequences near Girvan in SW Scotland and at Stonehaven in eastern Scotland suggest that it forms part of a widespread sub-Old Red Sandstone carbonate sequence of Early Ordovician age beneath the northern Midland Valley.