bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Burkinian orogenic cycle, precursor of the Eburnian orogeny in West Africa
Authors: Lemoine S. , Tempier P. , Bassot J. P. , Caen‐Vachette M. , Vialette Y. , Touré S. , Wenmenga U. 
Published: February 2007

AbstractIn the best known areas of the West African craton structural, petrographic, and geochronological data provide a distinction between two separate units of the Lower Proterozoic in West Africa. A lower unit was metamorphosed from low to medium grade around 2170 Ma by horizontal shearing. This unit is mainly composed of dominantly basic bimodal magmatic rocks, and some trondhjemitic to tonalitic anatectic gneisses, and locally mesozonal mica schists known in Ivory Coast as the ‘Kounoukou formation’ which has been dated as 2183 Ma old. An upper unit, which frequently begins with polygenic conglomerates, also shows important bimodal vulcanism, but in contrast to the lower unit is dominantly silicic. This unit is affected by lower grade conditions of metamorphism and is weakly deformed. These two units correspond to the classic Eburnian I/Eburnian II succession. However, a clearer distinction is possible, with the recognition of two successive orogenic cycles. In the basal part of each of the two units a major episode of tholeiitic magmatism is evidence for separate periods of lithospheric thinning and fracturing. This was followed by the deposition of various lithological sequences, then by one or more tectonometamorphic events. Later uplift led to the emplacement of anorogenic subvolcanic granitic massifs which are displayed occasionally as ring complexes.This suggests that ‘Eburnian I’ is actually an independent orogenic cycle appearing in the West African formations between 2400 and 2150 Ma, for which we propose the name ‘Burkinian cycle’. This cycle has affected the lower magmatic and sedimentary formations, which we designate Dabakalian. This implies a restricted time span for the Eburnian cycle from 2100–2150 to 1800 Ma.The stratigraphic term ‘Birimian’ is applied to the sedimentary and magmatic formations of the upper unit.This scheme proposed for the Lower Proterozoic in West Africa is probably applicable to other Lower Proterozoic terranes in Africa.
Typology, evolution, and origin of the Kerguelen Plutonic Series, Indian Ocean: A review
Authors: Giret André 
Published: February 2007

AbstractThe Kerguelen Islands (6,500 km2) are the third largest oceanic archipelago after Iceland and Hawaii. One of their most remarkable geological features is the existence of several igneous complexes thought to represent the deep levels of volcano‐plutonic structures of which the upper part has been eroded. These plutonic bodies have ring shapes with diameters ranging from 1 to 15 km. The oldest (39–23 Ma) have transitional petrological features while the youngest (26 Ma–Recent) are typically alkaline. This sequence is also observed in the surrounding flood‐basalts. Both the basalts and the plutonic rocks have a mantle origin. The alkaline plutonic suites evolve towards silica‐over or undersaturated rock types depending on whether they are located to the west or to the east of a NNW–SSE boundary. The divergence in alkaline trends may be related to magmatic differentiation or linked to the evolution of two different initial magmas, one being mid‐alkaline and the other high‐alkaline. In both hypotheses fluids, particularly H2O, play a major role.
Granitoid suites
Authors: Whitten E. H. T. 
Published: February 2007

AbstractThe concept of suites within granitoid batholiths must be treated with extreme caution, especially when petrogenic interpretation of identified suites is involved (e.g. infrastructural control of granitoid suite composition). Without stated, necessary, and sufficient operational definitions of the parameters (and their weighting) used in suite definition, suite/s should be avoided.
Analcime: A characteristic authigenic phase of andean alluvium, northern chile
Authors: Hartley Adrian , Flint Stephen , Turner Peter 
Published: February 2007

AbstractAnalcime (NaAlSi2O6.H2O) forms a characteristic authigenic phase in Andean alluvium of northern Chile. Three stratigraphic units ranging from the lower Cretaceous to the Miocene were studied in order to investigate the presence of analcime in diagenetic assemblages of different ages. The units were deposited in forearc, foreland/back‐arc, and intra‐arc basinal settings.Characteristics of other sedimentary analcime occurrences were examined in order to define conditions favourable for analcime precipitation. Zeolite zonation and evidence for the original presence of volcanic glass, common to many sedimentary analcime occurrences, are absent in the studied units. Analcime precipitation requires a high Na+/H+ ratio, relatively low Si4+/Al3+ activity and low H2O activity.Diagenetic examination of the three stratigraphic units revealed early quartz and feldspar overgrowths, mechanical clay infiltration, and dissolution of labile rock and mineral fragments, particularly intermediate plagioclase (An30–80). Conditions for these processes are favoured by oxidizing groundwater at near neutral pH. Later diagenesis involved the precipitation of analcime, non‐ferroan calcite, quartz, and authigenic clays as the main cementing phases. These formed due to the concentration of oxidizing groundwater and resulted from its continued reaction with detrital feldspars and rock fragments of andesitic and dacitic composition.Analcime precipitation in Andean alluvium resulted from the evolution of saline, alkaline brines under an arid, evaporative climate in closed hydrographic basins with circulating groundwater systems.
Aspects of dinantian sedimentation in the edale basin, north derbyshire
Authors: Gutteridge Peter 
Published: February 2007

AbstractThe Dinantian Edale Basin is located to the north of the Derbyshire carbonate platform and underlies the Upper Carboniferous of the central Pennines. The Edale Basin was thought to be part of a large basin which extended from the Derbyshire carbonate platform to the Askrigg Block. The presence of aggregate grains and ooids in the Alport Borehole suggests that a carbonate platform, possibly located on the Holme structural high, was present underneath the central Pennines. This platform is called the Holme Platform.The Arundian to early Asbian section of the Alport Borehole represents deposition of resedimented shallow‐water carbonates with occasional bioturbated periplatform carbonates and basinal shales on the middle part of a carbonate ramp. Volcaniclastic sediments may have been derived from a volcanic centre within the Edale Basin.A change in sedimentation during the mid‐Asbian to the deposition of basinal shales and distal carbonate turbidites is attributed to starvation of the basin. This may have been caused by a combination of the development of accretionary rimmed carbonate shelves and the repeated emergence of shelf carbonates deposited on surrounding carbonate platforms. The late Asbian/early Brigantian section of the Edale Borehole is interpreted as a distal equivalent of the ‘Beach Beds’ which outcrop at the north margin of the Derbyshire carbonate platform. The ‘Beach Beds’ represent bioclastic turbidites derived from the Derbyshire carbonate platform.Throughout the Brigantian, sedimentation in the Edale Basin was dominated by the deposition of distal carbonate turbidites and basinal shales. Variation of dip through the Alport Borehole indicates the common occurrence of slumps throughout the sequence and the presence of either an angular unconformity or a fault within the early Brigantian section.
Early Devensian interstadial and glacigenic sediments in Gwynedd, North Wales
Authors: Addison K. , Edge M. J. 
Published: February 2007

AbstractRecent excavations at Pen‐y‐bryn, Caernarfon have revealed a series of organic deposits below and within a glacial till of Welsh ice provenance. This paper presents the results of 14C analyses carried out on tree wood and organic peaty muds, together with a description of the site stratigraphy. Pen‐y‐bryn is the first Welsh site from which in situ biogenic deposits directly enclosed by glacigenic sediments and yielding finite radiocarbon dates have been recovered. Radiocarbon, plant macrofossil, palynological, fossil coleopteran and lithostratigraphic evidence suggest that this is the first site in Wales at which at least one Early Devensian interstadial episode followed by an Early Devensian stadial ice advance may be represented. Snowdonian glacier ice appears to have buried some of the organic deposits beneath till and incorporated other organic material within the till before a later advance of Irish Sea ice. This evidence is used to construct a Devensian chronostratigraphy which may involve two glacial stadia rather than a single Late Devensian glaciation.
Ordovician volcanism of the Peloritan Mountains (Sicily): Implications for evolution of Palaeozoic basins in the Calabrian‐Peloritan Arc
Authors: Acquafredda P. , Lorenzoni S. , Lorenzoni E Zanettin 
Published: February 2007

AbstractThe palaeontologically dated Ordovician associations of the Peloritan Mountains consist of metasilts, metapelites, calc‐schists and metavolcanic rocks. These rocks form a portion of a terrigenous‐volcanic‐carbonate sequence of Cambro‐Ordovician to Carboniferous age. This Palaeozoic sequence occupies the lower tectonic position in a Variscan orogen, affected by later Alpine deformation. The upper portion of this orogen is formed by low to high grade metamorphic rocks and some rare magmatic rocks.The Ordovician section of the sequence is divisible into a lower part (probably Arenigian), characterized by frequent and extensive within‐plate alkaline metabasalts, and an upper part characterized by metadacites and metarhyolites intercalated with metasediments, commonly carbonates. The chemical characteristics of the metavolcanic rocks and the composition and structure of the metasediments indicate the persistence of tensional conditions during the Lower Ordovician. In contrast, the Upper Ordovician was marked by reducing tension, stagnation of basaltic magmas at different crustal levels, and consequent formation of dacitic and rhyolitic melts by partial melting of the surrounding crust.A comparison of the Ordovician sequences of the Peloritan Mountains with those of the Calabrian Palaeozoic basins shows several geodynamic similarities. Among other circum‐Mediterranean basins, only that of north‐western Bulgaria shows good analogies.
Middle Westphalian plant fossils from the West Cumberland Coalfield, UK
Authors: Thomas B. A. , Cleal C. J. 
Published: February 2007

AbstractTwenty‐six form‐species of plant macrofossils occur in the Coal Measures exposed in the Howgill Head Quarry, Whitehaven, Cumbria, UK. They belong to the Neuropteris semireticulata Subzone in the lower part of the Paripteris linguaefolia Zone, indicating the uppermost Duckmantian. They confirm that the sandstones exposed in this part of the West Cumberland Coalfield are part of the Whitehaven Sandstone Formation, and not a stratigraphically lower unit as previously suggested. The Howgill head fossils represent the only well documented example of a N. semireticulata Subzone assemblage in Britain, although comparable assemblages are known from coeval strata in northern France, Belgium, northern Germany and Poland.
An iron‐bearing wave‐dominated siliciclastic shelf: Facies analysis and palaeogeographic implications (Silurian‐Lower Devonian Sierra Grande Formation, Southern Argentina)
Authors: Spalletti Luis A. 
Published: February 2007

AbstractThe Sierra Grande Formation (Silurian‐Early Devonian) consists of quartz arenites associated with clast supported conglomerates, mudstones, shales and ironstones. Eight sedimentary facies are recognized: cross‐stratified and massive sandstone, plane bedded sandstone, ripple laminated sandstone, interstratified sandstone and mudstone, laminated mudstone and shale, oolitic ironstone, massive conglomerate and sheet conglomerate lags. These facies are interpreted as shallow marine deposits, ranging from foreshore to inner platform environments. Facies associations, based on vertical relationships among lithofacies, suggest several depositional zones: (a) beach to upper shoreface, with abundant plane bedded and massive bioturbated sandstones; (b) upper shoreface to breaker zone, characterized by multistorey cross‐stratified and massive sandstone bodies interpreted as subtidal longshore‐flow induced sand bars; (c) subtidal, nearshore tidal sand bars, consisting of upward fining sandstone sequences; (d) lower shoreface zone, dominated by ripple laminated sandstone, associated with cross‐stratified and horizontal laminated sandstone, formed by translatory and oscillatory flows; and (e) transitional nearshore‐offshore and inner platform zones, with heterolithic and pelitic successions, and oolitic ironstone horizons. Tidal currents, fair weather waves and storm events interacted during the deposition of the Sierra Grande Formation. However, the relevant features of the siliciclastics suggest that fair weather and storm waves were the most important mechanisms in sediment accumulation.The Silurian‐Lower Devonian platform was part of a continental interior sag located between southern South America and southern Africa. The Sierra Grande Formation was deposited during a second order sea level rise, in which a shallow epeiric sea flooded a deeply weathered low relief continent.
The Humphrey Head Borehole: Evidence for Carboniferous vulcanicity and Permian dolomitization in the southern Lake District
Authors: Adams A. E. , Wadsworth W. J. 
Published: February 2007

AbstractIn south Cumbria, Permo‐Triassic breccias and conglomerates (‘brockram’) are exposed only at Rougholme Point on the Cartmel peninsula. In 1973 the Institute of Geological Sciences Humphrey Head borehole penetrated 257 m of brockram before entering probable Upper Carboniferous sediments. The brockram consists of pebbles of carbonate, chert and basalt in a matrix of haematite‐stained quartz sand. Carbonate and chert fragments were derived from the upper part of the Carboniferous Limestone sequence exposed today nearby. Basalt clasts were derived from lavas, which appear to have cooled in a subaqueous environment, at least in part. They were locally derived and are the only certain evidence for Carboniferous volcanic activity in south Cumbria. As volcanic fragments increase in abundance towards the base of the borehole they must have been derived from the top of the succession being eroded and are probably of Brigantian age.Carbonate fragments were dolomitized soon after incorporation in the brockram, probably by saline fluids derived from the evaporative Zechstein Sea. The dolomitization was incomplete, leaving remnant limestone cores to clasts which were subsequently dissolved. The resultant vugs were infilled by dolomite, calcite and gypsum cements, which have been partially weathered from outcropping brockram, leaving hollow pebbles.
Mantle‐derived heat recorded by conodont colour alteration in the Carboniferous of the Isle of Man
Authors: Swift A. 
Published: February 2007

AbstractA range of colour alteration index (CAI) values between 3.0 and 6.0 is recorded for conodont elements recovered from the Arundian to Brigantian (Dinantian, Lower Carboniferous) sequence around Castletown, Isle of Man. Mantle‐derived heat, channelled through the Caledonian South Barrule pluton, is proposed as the major cause of these elevated values. A lower CAI of 2.5 is obtained from elements recovered from a borehole sunk into the concealed Namurian (Upper Carboniferous) deposits near Shellag Point; the Glen Mona pluton acted as the medium for mantle‐derived heat in this instance. The CAI values which may have been established during a late Dinantian volcanic episode around Castletown were overprinted by the greater effects of heat emanating from the South Barrule pluton. The record of CAI 6.0 for a sample taken from the immediate vicinity of a dyke indicates a high level of very localized CAI elevation in the early Tertiary.
Structural arcuation in the Berwyn Hills, North Wales
Authors: Awan M. A. , Woodcock N. H. 
Published: February 2007

AbstractNew mapping has better defined the well known arc in Acadian (late Caledonian) structures centred in the Berwyn Hills. This arc, convex to the north‐west and about 20 km across, is defined by the strikes of bedding and cleavage and the trends of fold hinges. In contrast, a mineral lineation within the cleavage has a north‐north‐westerly plunge throughout the arc. It approximates to the long (X) axes of measured strain ellipsoids. A primary origin for the arcuation is implied by this consistency, by the absence of secondary cleavages and by opposing senses of fold transection across the arc. The new data favour the hypothesis of shortening of the Lower Palaeozoic cover against and over a pre‐existing basement high inferred from geophysical data and from metamorphic and sedimentary facies.
Low pressure‐high temperature metamorphism in the Vredefort Dome, South Africa: Anticlockwise pressure‐temperature path followed by rapid decompression
Authors: Gibson R. L. , Wallmach T. 
Published: February 2007

AbstractPelitic metasediments of the Witwatersrand Supergroup in the Vredefort Dome contain textural evidence for a two‐stage metamorphic history. The pressure‐temperature (P‐T) path derived for the rocks indicates that they were subjected to a high geothermal gradient (≈40°C km‐1), mid‐amphibolite facies, Mla metamorphic event concomitant with thickening of the overlying upper crust. Peak temperatures of 570–600°C were reached during Mla at depths of 14–16 km. After initial isobaric cooling following Mla, the rocks experienced rapid exhumation during a high strain rate deformation event associated with the formation of the dome. This event led to the development of abundant pseudotachylite and a brittle cleavage in these rocks. These features are overgrown. together with the Mla assemblages, by a low P M1b paragenesis comprising microporphyroblastic cordierite+biotite. Estimated P‐T conditions during Mlb were < 3.5 kbar, ≈500–;530°C.The two‐stage P‐T path is incompatible with existing contact metamorphic and diapiric models that have attempted to link the mid‐amphibolite facies metamorphism with the formation of the Vredefort Dome. Instead, it indicates that the doming event occurred some time after the peak of a regional low P‐high T metamorphic event, during cooling of the terrain. Given an age of 2.02 Ga for the doming event, the Mla event is attributed to a widespread magmatic‐thermal event on the Kaapvaal Craton that accompanied the formation of the Bushveld Complex at 2.05–2.06 Ga. The Mlb event developed in response to the localized exhumation of deep parts of this terrain while the crustal geotherm was still elevated (≈30°C km‐1). The association, elsewhere in the dome, of pseudotachylite with shock metamorphic features generated at pressures in excess of 20–120 kbar indicates that exhumation was accomplished by the impact of a large meteorite into the terrain.
Molecular markers of extracellular matrix remodeling in glioblastoma vessels: Microarray study of laser‐captured glioblastoma vessels
Authors: Pen Ally , Moreno Maria J. , Martin Joel , Stanimirovic Danica B. 
Published: February 2007

AbstractGlioblastoma multiforme (GBM) are the most malignant and vascularized brain tumors. The aberrant vascular phenotype of GBM could be exploited for diagnosis or therapeutic targeting. This study identified new molecular markers of GBM vessels, using a combination of laser capture microdissection (LCM) microscopy, RNA amplification, and microarray analyses to compare vessels from nonmalignant human brain and GBM tumors. Forty‐two genes were differentially expressed in GBM vessels compared to nonmalignant brain vessels. Validation of differentially expressed genes was performed by literature mining, Q‐PCR, and immunohistochemistry. Among the differentially expressed genes, only 64% were previously associated with vessels, angiogenesis, gliomas, and/or cancer. The upregulation of genes encoding secreted extracellular proteins IGFBP7 and SPARC was confirmed by Q‐PCR in LCM‐captured vessels. Whereas SPARC and IGFBP7 protein were absent in nonmalignant brain vessels, a distinct immunoreactivity patterns were observed in GBM sections whereby SPARC was strongly expressed in perivascular cells adjacent to GBM vessels while GBM endothelial cells were immunostained for IGFBP7. IGFBP7 immunoreactivity was also detected on the abluminal side of GBM vessels deposited between strands of vascular basal lamina. The study discerns unique molecular characteristics of GBM vessels compared with nonmalignant brain vessels that could potentially be used for diagnostic or therapeutic purposes. © 2007 Wiley‐Liss, Inc.
Dissociation of response inhibition and performance monitoring in the stop signal task using event‐related fMRI
Authors: Chevrier Andre D. , Noseworthy Michael D. , Schachar Russell 
Published: February 2007

AbstractWe examined the neural substrate of motor response inhibition and performance monitoring in the stop signal task (SST) using event‐related functional magnetic resonance imaging (fMRI). The SST involves a go task and the occasional requirement to stop the go response. We posit that both the go and the stop phases of the SST involve components of inhibition and performance monitoring. The goal of this study was to determine whether inhibition and performance monitoring during go and stop phases of the task activated different networks. We isolated go‐phase activities underlying response withholding, monitoring, and sensorimotor processing and contrasted these with successful inhibition to identify the substrate of response inhibition. Error detection activity was isolated using trials in which a stop signal appeared but the response was executed. These trials were modeled as a hand‐specific go trial followed by error processing. Cognitive go‐phase processes included response withholding and monitoring and activated right prefrontal and midline networks. Response withdrawal additionally activated right inferior frontal gyrus and basal ganglia (caudate). Error detection invoked by failed inhibition activated dorsal anterior cingulate cortex (dACC) and right middle frontal Brodmann's area 9. Our results confirm that there are distinct aspects of inhibition and performance monitoring functions which come into play at various phases within a given trial of the SST, and that these are separable using fMRI. Hum Brain Mapp, 2007. © 2007 Wiley‐Liss, Inc.