bluuebunny/crossref_metadata_2025_split huggingface dataset:
Petrochemistry of metamorphosed pillows, and the geochemical status of the amphibolites (Proterozoic) from the Sirohi district, Rajasthan, India
Authors: Bhattacharyya P. K. , Mukherjee A. D. 
Published: May 2009

AbstractRelic pillows in the middle Proterozoic amphibolites, occurring in the Sirohi Road–Abu Road tract of Rajasthan, India exhibit contrasted mineral assemblages from core to rim – mimetic after the crystalline core, the zone of incipient crystallization, and the rim of the original pillows. The major element distribution pattern across the pillows indicates exchange of Na–Al for Ca (Mg, Fe) in an inner reaction zone, surrounding the core and in the inner margin of the rim, and Fe–Al exchange for Ca–Si at the outer margin of the rim.Despite such exchanges around the rims, these pillows have retained their initial geochemical characteristics internally and thus have largely acted as closed systems during post-emplacement metamorphism. Mineral parageneses indicate that the contrasted mineral assemblages could evolve from domainal characters of the co-existing fluids, the compositions of which were only buffered by the reacting minerals during regional metamorphism.The major, minor and trace element contents of the pillows and of amphibolites of diverse petrographic character in the region further establish that the pillow interiors and the massive amphibolites were least modified during metamorphism(s), and represent oceanic tholeiites. Their average 2300 ppm K, 4.5 ppm Rb, 150 ppm Sr, along with the K/Rb and K/Sr ratios of 510 and 15 respectively resemble that of the low K-tholeiites, occurring nearest to the trenches in modern island arcs. On the other hand, the higher values of 17300 ppm K, 4.9 ppm Rb, and 210 ppm Sr of the banded and the schistose amphibolites indicate that they were contaminated in various magnitudes by oceanic sediments.
Ferruginous vernadite in an Indian Ocean ferromanganese nodule
Authors: Ostwald J. 
Published: May 2009

AbstractSelect area electron diffraction and microanalysis of the optically dark component of a ferromanganese nodule from the South East Indian Ocean Manganese Field indicate that this is composed of a random stratification of crystallites of vernadite MnO2. (R2O, RO, R2O3)x. yH2O, where R represents elements such as K, Ba, Na, Ca, Mg, and a disordered hydrated iron oxide, possibly ferrihydrite 5Fe2, O3. 9H2O or feroxyhyte δ′-FeOOH. Whether the dark component is an irregular mixed-layer hybrid mineral or a layered accumulation resulting from epitaxy of the above phases is uncertain.
New diminutive camerate crinoids from the Ludlow of Oklahoma
Authors: Frest T. J. , Strimple H. L. 
Published: May 2009

SummaryTwo new camerate crinoids from the Henryhouse (Ludlow) of Oklahoma are evolutionarily convergent on monocyclic inadunates. The prokopicrinid Nanicrinus (new) has a calyx consisting only of three basals (small basal in EA interrary) and five radials. The anal opening is bordered by two radials. Praedicticrinus (new) is a hirneacrinid with anal X as the sole interradial plate participating in the calyx and small basal located in DE interray. Assignment to the Camerata is based largely on presumed phylogenetic relationships. The similar-appearing Permian genera Plesiocrinus, Eutelecrinus, Metaeutelecrinus (new) and Paraeutelecrinus (new) are probable prokopicrinid homeomorphs derived from platycrinitid ancestors. They are assigned to the new family Eutelecrinidae. Adaptation of the definition of homeomorphy utilized by Chauff & Klapper (1978) is advocated for supposed paleontologic cases.
The large-scale structure of the Earth's crust beneath southern Britain
Authors: Whittaker A. , Chadwick R. A. 
Published: May 2009

AbstractRecently acquired deep seismic reflection profiles recorded to 12 s two-way travel time in southern Britain suggest that the crust beneath this area is commonly divisible, vertically, into three zones.These zones, based upon seismic character, can be related to structural or tectonic units. They comprise an upper zone of cover rocks of various ages, a middle zone of folded and thrust rocks, and a lower zone tentatively identified as metamorphic or crystalline basement. A sketch crustal profile from Dorset to Yorkshire summarizes the data and illustrates the distribution of the zones.
The significance of the proximal end ofCryptograptus tricornis(Carruthers) (Graptolithina)
Authors: Strachan I. 
Published: May 2009

AbstractYoung stages isolated from limestone from Girvan indicate that the first two thecae had unsclerotized walls but apertural rings showing that they opened downwards beside the sicula. The development can thus be matched with that ofGlossograptusand the two families Glossograptidae and Cryptograptidae merged. The recognition of downward-opening thecae inC. tricornisallows the earlier speciesC. schaeferito be more easily accommodated in the genus. Relationships in the family are reviewed.
Isolated pods of subaqueous welded ash-flow tuff: a distal facies of the Capel Curig Volcanic Formation (Ordovician), North Wales
Authors: Howells M. F. , Campbell S. D. G. , Reedman A. J. 
Published: May 2009

AbstractAcidic welded tuffs of the Capel Curig Volcanic Formation were deposited from ash-flows that transgressed from a proximal subaerial to a distal submarine environment. Isolated pods of welded tuff enveloped by marine sediments represent a distal facies of the formation deposited beyond the limits of the continuous ash-flow tuff sheets. Various mechanisms for the separation of the tuff pods from a parent flow are discussed and it is concluded that it is most likely that the formation of the pods was due to disruption of a subaqueous ash-flow during transport rather than by downslope collapse at the front of a previously deposited ash-flow tuff sheet.
Electron microscope analysis of zoned dolomite rhombs in the Jet Rock Formation (Lower Toarcian) of the Whitby area, U.K.
Authors: Pye K. 
Published: May 2009

AbstractZoned dolomite rhombs which occur in the organic-rich Jet Rock Formation (Toarcian) of northeast England have been studied using backscattered scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray microanalysis. The rhombs, which are 5–20 μm in size, are variable in chemical composition, but many consist of a dolomite core surrounded by a zone of ferroan dolomite, ankerite or ferroan calcite. Zoned rhombs occur in early-diagenetic calcite-cemented concretions and layers as well as dispersed throughout the shales. Distributional and textural evidence suggests that they formed mainly by primary precipitation from pore fluids within the zone of bacterial sulphate reduction. The ferroan outer zones probably formed after burial below the sulphate reduction zone when insufficient H2S was available to react with all the Fe2+in solution.
Lithostratigraphy of the Red and Norwich Crags of the Aldeburgh–Orford Area, south-east Suffolk
Authors: Zalasiewicz J. A. , Mathers S. J. 
Published: May 2009

AbstractRecent investigations indicate that three distinct lithostratigraphical units can be recognized in the Red and Norwich Crag deposits of the area around Aldeburgh and Orford, Suffolk. These effectively represent a refinement of a stratigraphy originally suggested by Prestwich in 1871. A lowermost coarse-grained shelly sand, the Red Crag Formation, rests on an eroded London Clay surface and is banked against the Pliocene Coralline Crag. The Red Crag Formation passes upwards into a fine-grained generally unfossiliferous well-sorted sand, the Chillesford Sand Member, which overlaps the Red Crag Formation to rest directly on the Coralline Crag. The Chillesford Clay Member is regarded as the lateral equivalent of the upper Chillesford Sand Member, the two members together comprising the Norwich Crag Formation in this area. Sections that have been zoned palaeontologically may be integrated into this lithostratigraphical framework. These indicate that the Red Crag Formation correlates with the Pre-Ludhamian Stage, and the Chillesford Sand Member and the Chillesford Clay Member correlate with the Bramertonian Stage. Type sections are established for the three units described.
A Lancefieldian graptolite from the Lake District
Authors: Rushton A. W. A. 
Published: May 2009

AbstractLargeDictyonemaspecies, includingD. pulchellumT. S. Hall, have been collected from beds in the Uldale Fells (northern Lake District), below strata yieldingDidymograptus protobalticusMonsen. They suggest the presence there of graptolitic beds transitional from Lancefieldian to Bendigonian in age (approximately Tremadoc-Arenig) and suggest that the area may yet provide an internationally correlatable base to the Arenig Series in Britain.
Geochemical evidence for the emplacement of the Whin Sill complex of northern England
Authors: Thorpe R. S. , Macdonald R. 
Published: May 2009

AbstractThe Whin Sill comprises a major quartz tholeiite sill of late Carboniferous age underlying an area of c. 5000 km2 and with a volume of c. 200 km3, associated with contemporaneous dykes emplaced within Carboniferous sedimentary rocks in northeast England. New trace element analyses of chilled margins, sill interiors and dykes indicate that the Whin Sill complex magmas show significant chemical variations in terms of the relatively stable trace elements Th, Ce, Y, Zr, Nb and Ni. These data indicate that the complex was fed by a large number of compositionally distinct magma pulses, and that certain of the dykes may have formed feeder channels for the sill. The chemical characteristics of the sill and dyke samples are consistent with derivation by extensive polybaric fractional crystallization of olivine tholeiite magma derived by partial melting of compositionally heterogeneous mantle peridotite and/or crustal contamination of mantle-derived magmas.
The thrust structures of southern Assynt, Moine thrust zone
Authors: Coward M. P. 
Published: May 2009

AbstractThe Moine thrust zone of southern Assynt forms part of the northwest margin of the Caledonide belt and has aroused controversy concerning amounts and timing of thrust displacement and sequence of thrust development. Recent mapping shows it to have been a foreland propagating thrust sequence; the uppermost ductile Moine thrust formed first, followed by sequences of imbricates, a major thrust (the Ben More thrust) and then several lower duplex zones. This sequence is clear from new observations that many of the earlier thrusts were folded and/or breached during the development of the underlying structures. A displacement of over 54 km has been estimated for the zone as a whole. An alkaline igneous complex, including the large Borrolan syenite, was intruded during the development of the thrust zone and much of it was carried some 30 km to the west-northwest onto the foreland. Late extensional structures in southern Assynt are an integral part of the Caledonide thrust sequence and probably developed from the collapse of the thrust wedge as it climbed from stronger basement rocks on to a weaker cover sequence on the foreland.
The graptolite biostratigraphy of a Llandovery outlier near Llanystumdwy, Gwynedd, North Wales
Authors: Baker S. J. 
Published: May 2009

SummaryLlandovery strata at Llanystumdwy are described. Ninety graptolite species have been identified enabling the establishment of the following zones:acinaces, cyphus, triangulatus, magnus, leptotheca, convolutus, ?sedgwickii, turriculatusandcrispus.The name Llanystumdwy Mudstone Formation is proposed for previously undescribed mudstones cropping out on the River Dwyfor at Llanystumdwy and includes all strata referable to theacinacestoturriculatuszones. Comparison is made between Llanystumdwy and other areas, notably Northern England and Southern Scotland
The Late Triassic Blue Anchor Formation and the initial Rhaetian marine transgression in south-west Britain
Authors: Mayall M. J. 
Published: May 2009

SummaryThe Blue Anchor Formation of the Upper Trias in south-west Britain is divided into two members. The lower (Rydon Member) was deposited in an evaporitic lacustrine environment whilst the upper (Williton Member) was deposited in a shallow marine environment and represents the initial marine transgression into south-west Britain late in the Triassic Period. Sedimentological and clay mineralogical evidence indicates that the Williton Member is bounded by erosional disconformities and, at present, can only be positively recognised in North Somerset.
Micropalaeontological evidence for land near Cirencester, England, in Forest Marble (Bathonian) times: a preliminary account
Authors: Ware M. , Windle T. M. F. 
Published: May 2009

SummaryAnalysis of a Bathonian ostracod fauna and the microflora from a claypit at Tarlton, Gloucestershire, strongly suggests that land was then nearby. Among the non-marine Ostracoda are cypridacean species similar to lacustrine forms from the French Bathonian. Such an assemblage has not previously been recorded from Britain. The clay is assigned to Bate's revised Bathonian ostracod zone 6, and a palaeogeographical interpretation is offered in terms of recent reconstructions of British Bathonian landmasses.
Columnar sandstone, Island of Bute, Scotland
Authors: Buist D. S. 
Published: May 2009

SummaryA unique columnar sandstone, produced by the thermal metamorphism of an Upper Old Red quartz arenite, is described, from South Bute, together with other examples of similarly altered sediments from nature and industry. The columnar structure probably developed as a result of the emplacement of a basic dyke via a fissure. In view of the relatively large area exhibiting this structure, metamorphic effects must have been amplified by the agency of steam and volatile constituents of the magma, passing up through the fissure.
Comparative geochemistry of pelites from the Moinian and Appin Group (Dalradian) of Scotland
Authors: Lambert R. St. J. , Winchester J. A. , Holland J. G. 
Published: May 2009

SummaryPelitic schists from the Appin Group of the Dalradian Supergroup are all chemically distinct from pelitic schists in the older Moinian Supergroup. In addition, trace-element geochemistry can also discriminate between the individual pelitic schists within the Appin Group, especially those within the Lochaber Subgroup. These differences apparently relate mainly to differences in provenance rather than differences of sedimentary environment, and are sufficiently consistent to offer a means for correlation or identification of pelitic units in areas of the Central Highlands where the stratigraphy is still in dispute.
The Gillbrea Nappe in the Skiddaw Group, Cockermouth, Cumbria, England
Authors: Banham P. H. , Hopper F. M. W. , Jackson J. B. 
Published: May 2009

SummaryNew observations of sedimentary and tectonic structures confirm ‘pre-cleavage’ folding of the Arenig Loweswater Flags and Kirk Stile Slates. A major recumbent fold is thought to have developed by gravity gliding during Arenig-Llanvirnian times.
A trondhjemite vein in the Sulitjelma Gabbro, Norway, and its implications for the age of the Sulitjelma Ophiolite
Authors: Mason Roger 
Published: May 2009

SummaryThe Sulitjelma Gabbro, occurring as a member of the Sulitjelma Ophiolite Complex, and typical of the ophiolite suite in its petrography and geochemistry, is cut by a vein of trondhjemite (plagiogranite). The previous identification of the vein as an offshoot of a continental potassium-rich granite, the Furulund Granite, is wrong. Therefore the Rb-Sr isochron age of 413±34 Ma, obtained from the granite, cannot be taken as the age of intrusion of the Sulitjelma Gabbro.
The use of flexible synthetic rubbers for casts of complex fossils from natural moulds
Authors: Benton M. J. , Walker A. D. 
Published: May 2009

SummarySome commercial silicone (Dow Corning Silastic E, J) and PVC (Dugdale DD 118) synthetic rubbers make excellent casting materials for the production of high-fidelity replicas of fossils from complex natural cavities. The methods described avoid tearing of the cast and damage to the mould.
A Coniacian ammonite from the ‘Top Rock’ in the Chalk of Kent
Authors: Gale A. S. , Woodroof P. B. 
Published: May 2009

SummaryThe occurrence of Barroisiceras within the top bed of the Zone of Holaster planus near Dover in Kent provides the first ammonite evidence for the position of the base of the Coniacian in the Chalk of England. Inoceramus cf. rotundatus occurs ½ m above the ‘Top Rock’.
The Ordovician fauna from the Contaya Formation of eastern Peru
Authors: Hughes C. P. , Rickards R. B. , Williams A. 
Published: May 2009

SummaryThe Ordovician Fauna from the Contaya Formation from the lowlands of eastern Peru is fully described for the first time. The fauna is restricted and consists essentially of brachiopods, trilobites and Graptolites and three new species, the brachiopodTissintia simplex, and the trilobitesAnebolithus tafuri and Porterfieldia contayaensisare described. The fauna is shown to have close affinities with those of central Europe and North Africa.
Interactive processing of satellite images for structural and lithological mapping in northeast Africa
Authors: Berhe S. M. , Rothery D. A. 
Published: May 2009

AbstractInteractive digital processing of multispectral satellite images (Landsat MSS) using principal components transformations and spatial filtering has clarified the position of continuous sutures linking apparently isolated Pan African (late Proterozoic) ophiolites. These have been field-checked and an arrangement of Pan African suture zones is proposed. Spatial filtering has also highlighted faults with various trends which can be related to the late Precambrian tectonics of the Horn of Africa region.
Facies analysis of the Lo Valdés Formation (Tithonian–Hauterivian) of the High Cordillera of central Chile, and the palaeogeographic evolution of the Andean Basin
Authors: Hallam A. , Biró-Bagóczky L. , Perez E. 
Published: May 2009

AbstractFacies descriptions and environmental interpretations are given for outstanding sections of marine Tithonian to Hauterivian strata in the High Cordillera of the central Chilean Andes. Comparisons are made with correlative strata in other regions in Chile, and with the Neuquén Basin of west central Argentina. The rich and partly endemic bivalve fauna, which has strong African affinities, shows no change up the stratigrapic sequence that cannot be related to local facies. Water depth is recognized as the main variable controlling the distribution of the bivalve and ammonite faunas. Utilizing data from both Chile and Argentina, a model is put forward for the late Jurassic to mid Cretaceous sequence whereby the facies distributions are accounted for by the interaction of global sea-level changes and regional tectonics in a shallow back-arc basin.
A polymorphic graptolite from concealed Tremadoc rocks of England
Authors: Rushton A. W. A. 
Published: May 2009

SummaryAbundant specimens from the middle or upper Tremadoc beds in the Napton Fields Borehole, Warwickshire, are referred to one variable species,Kiaerograptus? quasimodosp.nov. Two-stiped forms typical ofKiaerograptusco-exist with ‘one-stiped’ forms in which the first stipe consists only of Th 11. Rare specimens with three primary thecae gave rise to forms with one, two? or three stipes.
The age of the Dinantian (Lower Carboniferous) rocks proved beneath the Kent Coalfield
Authors: Mitchell M. 
Published: May 2009

SummaryThe history of research into the Lower Carboniferous rocks of Kent since Dines' 1933 account of the stratigraphy of the coalfield is outlined. Details of the boreholes that have proved Lower Carboniferous are listed, including notes of the significant fossils that have been identified. The age of the Lower Carboniferous rocks is discussed. Two boreholes yielded faunas of Tournaisian age and i4 proved rocks of Holkerian age. No younger Dinantian strata are known from Kent.
The origin and microstructures of metamorphic felsic dykes emplaced during brittle-ductile extension (southeast Sinai)
Authors: Reymer Arthur P. S. 
Published: May 2009

AbstractStructural, petrographic and chemical analyses of a set of northeast-trending quartzofeld-spathic dykes in Wadi Kid area (southeastern Sinai) show that they are the product of anatexis of pelitic rocks. Metamorphic P-T data indicate that anatexis could have occurred only 2 km below the present erosion level. The partial melts intruded into overlying rocks during regional metamorphism along a set of northeast-oriented extensional fractures, thereby recrystallizing and in some cases obtaining tectonite fabrics. The fractures were formed perpendicular to the regional mineral lineation and show that the area was within the deeper parts of the brittle–ductile transition zone. The original depth of the presently exposed crustal level corresponds well with the theoretical and experimentally derived depths of the brittle-ductile transition zone in high heat flow regimes. The emplacement of a granitoid pluton or gneiss dome, possibly of dioritic composition, could be responsible for both melting and tensile fracturing of the overlying rocks.
Interactive processing of satellite images for geological interpretation – a case study
Authors: Rothery D. A. 
Published: May 2009

AbstractInteractive digital processing of satellite images reveals significantly more information than the standard product photographic versions of the same images. Interactively processed images preserve finer details and can show information in areas which appear too dark or too bright on standard product images. This is illustrated by comparisons between both types of image as used in a photogeological interpretation of the tectonics of the Tibetan plateau.
Mid-Cretaceous (Albian-Cenomanian) calcareous nannofossils from Pont du Fahs (northern Tunisia)
Authors: Hojjatzadeh Minoo 
Published: May 2009

SummaryCalcareous nannofossils from mid-Cretaceous (Albian-Cenomanian) sections at Pont du Fahs (northern Tunisia) allow the recognition of three nannofossil zones-the Prediscosphaera cretacea Zone, the Hayesites albiensis Zone, and the Eiffellithus turriseffeli Zone. A comparative study has been made of the nannofossil assemblages from Pont du Fahs and 14 other sites in North Africa, Western Europe, the North Atlantic and United States.
Evolution of a non-resurgent cauldron: the Late Permian Coombadjha Volcanic Complex, northeastern New South Wales, Australia
Authors: McPhie J. 
Published: May 2009

AbstractThe Coombadjha Volcanic Complex is the remnant of a Late Permian cauldron. It is part of an extensive sequence of silicic calc-alkaline volcanics that covers the southeastern portion of the New England Orogen in NSW. The Complex is elliptical, measuring 15 × 24 km, and is outlined by a ring pluton and an arcuate fault. Bedding in the volcanic units of the Complex defines a structural basin, with steep inward dips at the monoclinal rim and gentle to horizontal orientations near the centre. An older group of outflow ignimbrites, lavas, breccias and volcaniclastic rocks at least 1500 m thick, is conformably overlain by more than 500 m of texturally homogeneous, crystal-rich, dacitic ignimbrite. Ignimbrites of the older group are the products of several discrete eruptions from separate vents, all of which were situated outside the Coombadjha area. Silicic lava domes with volcaniclastic aprons, and a tuff ring, mark the positions of local vents active on a small scale during intervals between the emplacement of the outflow ignimbrites. No significant subsidence occurred, nor did a caldera exist at this stage. Cauldron subsidence occurred in response to the large magnitude eruption that produced the crystal-rich ignimbrite. The central cauldron block was lowered at least 2000 m by downwarping and fault displacement, and remained largely intact. There is no evidence for resurgent doming of the cauldron after subsidence, although igneous activity continued with intrusion of an adamellite ring pluton along much of the cauldron margin. The crystal-rich ignimbrite and the ring pluton are similar in composition and may have been successive products of a common magma source that sustained this simple, single cauldron cycle.