bluuebunny/crossref_metadata_2025_split huggingface dataset:
Precambrian—Cambrian boundary and correlation from southwestern and central part of Spain
Authors: Liñán E. , Palacios T. , Perejón A. 
Published: May 2009

AbstractThis paper comprises the first palaeontological correlation between the Upper Proterozoic–Lower Cambrian Series of Ossa-Morena, Luso-Oriental-Alcúdica and Galaico-Castellana Zones of the Iberian Peninsula.The authors show the palaeontological events on acritarchs, stromatolites, cyanophyta, soft-bodied metazoa, trilobites, archaeocyathans and skeletal microfossils from three representative sequences of the above mentioned zones and discuss the position of the Precambrian–Cambrian boundary in the sequences. The Sierra de Córdoba general Series (Ossa-Morena Zone) has an erosive discontinuity between the rocks with the first record of Cambrian metazoan activity (Skolithossp.,Monomorphichnussp.,Phycodes pedumandRusophycussp.) and the rocks with a palynological association (Bavlinella faveolata, Protosphaeridium flexosum, Trachisphaeridiumsp., aff.Octoedryxium truncatum, Phycomicetes? sp. and cf.Ooidiumsp.) which suggests a Lower–Middle Vendian age. For this reason we suggest that the Precambrian–Cambrian boundary be placed at this unconformity.The upper part of the Sierra de Guadalupe Series (Luso-Oriental-Alcúdica Zone) includes detrital beds withPhycodes pedum, Planolitessp. andTreptichnussp. which are also the first record of Cambrian metazoan activity. In the middle part of the sequences, acritarchs attributed to the genusMicrhystridiumare found at the top of the Calcareous Beds. This is taken to indicate an early Cambrian age. Vendotaenids andBavlinella faveolataare found in abundance, thus indicating a Late Vendian age for the middle part of this unit. Thus, we propose the Precambrian–Cambrian boundary be located in the upper part of the Calcareous Beds.In the Rio Uso Series (Galaico-Castellana Zone), the Azorejo Sandstones containRusophycusgr.radwanskii, Planolitessp. andGordiasp. Trace fossils produced by trilobite-like arthropoda (Monomorphichnus) have been cited in the upper part of the underlying Pusa Shales. Moreover,Octoedryxium truncatumandBavlinella faveolataare found in the lower part of this unit which suggest that the Precambrian–Cambrian boundary could be situated in the Pusa Shales.Calcareous microfossils related to annelid polychaetes are found associated with Upper Vendian acritarchs in the Calcareous Beds of Sierra de Guadalupe. They are the oldest record of skeletal metazoa in the Spanish Series.The medusoids found are associated with a Vendian flora and they are also the oldest non-skeletal metazoa record known in the Iberian Peninsula.
Microfossils and small shelly fossils from the Lower CambrianHyolithesLimestone at Nuneaton, English Midlands
Authors: Brasier M. D. 
Published: May 2009

AbstractThe Lower Cambrian sequence at Nuneaton is outlined, paying particular attention to the 2 m thick Home Farm Member (including theHyolithesLimestone) and its faunal succession at the type locality, Woodlands Quarry, Hartshill. There follows the first modern description and illustration of microfossils and small shelly fossils from this member. Of thirty-two species covered here, twenty are described and illustrated from Nuneaton for the first time and eight of these are new records. The varied fauna includes phosphatic and calcareous microproblematica (especiallyColeoloides typicalis), protoconodonts, agglutinated foraminifera, cap-shaped molluscs, primitive bivalves, hyoliths, inarticulate brachiopods and sponges. The fauna has affinity with fossils in the top Tommotian to lower Atdabanian rocks from Siberia and China, from the Baltic area and the belt from southeast Newfoundland to Massachusetts.
A revised age and correlation for the topmost Sholeshook Limestone Formation (Ashgill) of South Wales
Authors: Price D. 
Published: May 2009

SummaryThe age of the youngest part of the Sholeshook Limestone Formation is reconsidered in the light of recent advances in knowledge of Ashgill trilobite faunas. A low Rawtheyan (Zone 5) age is suggested and correlations are proposed with Ashgill rocks in the SW Berwyns and with part of the Swindale Limestone Formation of Cross Fell. The Cautleyan/Rawtheyan boundary is a level at which faunal changes are sufficiently pronounced to permit reliable and precise correlation.
New evidence on the vertebrate fauna, stratigraphy and palaeobotany of the interglacial deposits at Swanton Morley, Norfolk
Authors: Coxon P. , Hall A. R. , Lister A. , Stuart A. J. 
Published: May 2009

SummaryThe stratigraphy and palaeobotany of new in situ exposures of interglacial deposits at Swanton Morley, Norfolk are described. These organic sediments, which probably accumulated in a river back channel, are shown to cover pollen zones Ib to IIb of the Ipswichian interglacial. Macroscopic plant fossils include a new record for Trapa natans from subzone Ip IIb. Vertebrate remains from the new excavations, and from previous finds, have been pollen-dated. The Ip IIa fauna, the first recorded from this subzone, includes Emys orbicularis, small mammals including Microtus oeconomus, and some large mammals. Hippopotamus amphibies is recorded from early zone Ip III. Of particular interest are hazelnuts gnawed by Apodemus, and large mammal bones damaged by Crocuta.
Resolution of the age structure of the detrital zircon populations of two Lower Cretaceous sandstones from the Weald of England by fission track dating
Authors: Hurford A. J. , Fitch F. J. , Clarke A. 
Published: May 2009

AbstractModes in the frequency of distribution of fission track ages obtained from detrital zircon grains may prove characteristic of individual sandstone bodies, supporting the identification of the sources from which a particular flow of sedimentary detritus was derived and thus allowing new inferences to be made concerning palaeogeography. A computer program has been written and used to identify modes in the zircon fission track age distribution within two Lower Cretaceous sandstone samples from the Weald of southern England. Pronounced modes appear in one rock around 119 Ma, 160 Ma, 243 Ma and 309 Ma and in the other around 141 Ma, 175 Ma, 257 to 277 Ma and 394 to 453 Ma. The geological implications of these quite dissimilar zircon age spectra are discussed. It is concluded that they support the palaeogeographical models of Allen (1981) and indicate that the provenance of the first sample, from the Top Ashdown Sandstone member at Dallington in East Sussex, was almost entirely southerly, while that of the second, from the Netherside Sand member at Northchapel in West Sussex, was more varied, but predominantly westerly and northerly.
The genusBiplanispiraUmbgrove (Foraminiferida) and its occurrence in India
Authors: Samanta Bimal K. 
Published: May 2009

AbstractBiplanispiraUmbgrove is closely related toPellatispiraBoussac, from which it probably arose by the subdivision of the median chambers by the rapidly expanding marginal crest and the development of planispirally arranged secondary chambers on both sides of the peripheral flange. The genus appears to be polyphyletic, its species having been derived from different representatives ofPellatispira. Illustrated records ofBiplanispiraare confined to the region between eastern India and Eua, Tonga, and the genus appears to be restricted to the middle and upper parts of the Upper Eocene. In the Upper Eocene of the Garo Hills, eastern India, it is represented byB. hoffmeisteri(Whipple) and in the Andaman Islands byB. mirabilis(Umbgrove). This is the first record of the genus from mainland India.
Deformational behaviour of migmatites and problems of structural analysis in migmatite terrains
Authors: McLellan Eileen 
Published: May 2009

AbstractAn understanding of the response of migmatites to deformation is crucial to an interpretation of their structures, and in anatectic and intrusive migmatite terrains due consideration must be given to the modification of deformation processes imposed by melts. In partially molten systems containing more than 30% melt the classical theories of fold formation are inapplicable; the folds produced are of the ‘viscous fold’ type. Their geometry is unpredictable and may mimic structures due to refolding; this is particularly true at very high degrees of melting where flow of melt carrying rafts of solids begins. Failure to distinguish ‘viscous folds’ from the products of refolding will lead to errors in interpreting the structural and metamorphic history of an area, and to consequent misinterpretation of the true structural relations between geometrically complex high-grade and more regularly deformed low-grade areas.
Thermal metamorphism of the Silurian strata of the Oslo region, assessed by conodont colour
Authors: Aldridge R. J. 
Published: May 2009

AbstractThe colours of conodont elements recovered from Silurian limestones in the Oslo region, Norway, range from brown to grey. Samples from the south of the region contain black and grey conodonts, indicative of high palaeotemperatures. There is a general decrease in thermal metamorphism towards the north, with the lowest palaeotemperatures recorded from Toten, Ringsaker and parts of the Ringerike district. There is a close correlation between thermal metamorphism and the proximity of Permian intrusions.
Two new Ordovician graptolites from Bolivia
Authors: Finney S. C. , Branisa L. 
Published: May 2009

AbstractTwo new graptolite species from the Ordovician of Bolivia are described. These species, Maeandrograptus bolivianus n.sp. and Gymnograptus floweri n.sp., were probably contemporaneous with congeners from the Didymograptus hirundo Zone (Lower Ordovician) of Sweden and the lower half of the Glyptograptus teretiusculus Zone (Middle Ordovician) of Baltoscandia, respectively. This is the first report of these genera in the Western Hemisphere.The assignment of a new species to Maeandrograptus necessitated a review and revision of that genus. As revised, it consists of M. schmalenseei Moberg, Didymograptus mobergi Törnquist, and M. bolivianus n.sp. Cymatograptus undulatus is a possible ancestor for this group of species, and an assignment of Maeandrograptus to the Sinograptidae is favoured.
The role of silica and iron oxide mobility in the formation of gold-bearing fluvial sediments in the Proterozoic Mporokoso Basin, northern Zambia
Authors: Andrews-Speed C. P. 
Published: May 2009

AbstractGold-bearing sandstone and conglomerate near the base of the Proterozoic Mporokoso Group were deposited in a braided river system. The detrital sand grade material is mainly of quartz, sericite and haematite, and the pebbles are of vein-quartz, chert, silicic volcanics, quartzose metasediment and jaspilite. The basement rocks presently exposed in the basement are silicic igneous rocks and quartzose metasediments.The petrography of the fluvial sediments suggests that silica and, to a lesser extent, iron oxide were mobile both in the source-area and in the braided river system. Evidence for silica-mobility includes jaspilite pebbles with spherulites and glaebules of chalcedony, abundant vein-quartz pebbles, intra-basinal sandstone pebbles, and the silicification of volcanic pebbles. The detrital haematite in the fluvial sandstone forms pseudomorphs after magmatic magnetite. Authigenic iron oxide occurs in several forms which suggest that iron oxide was mobile in the source-area and in the fluvial sediments. Uranium is locally abundant in basement and sedimentary rocks, cassiterite is a common heavy mineral in the fluvial sediments, and fluorite has been found in the basement.These features may be explained by intense weathering which mobilized both silica and iron. The silica was concentrated near the surface to form silcretes in the basement and later in the overlying fluvial sediments. Hydrothermal convection cells driven by the granites may have carried silica, iron, tin, fluorine and uranium towards the surface before and during the erosion of the igneous basement.
The sedimentology of the South Connemara Group, western Ireland – a possible Ordovician trench-fill sequence
Authors: Ffrench G. D. , Williams D. Michael 
Published: May 2009

AbstractThe stratigraphy of the ?Ordovician South Connemara Group is described. The group is approximately 3 km thick and includes sedimentary and volcanic rocks. The sedimentary elements of the succession include conglomerates, sandstones, shales, cherts and minor limestone breccias. The Lettermullen Formation exhibits the thickest continuous sedimentary sequence in the group. It is divided into five facies: a conglomerate facies, thick sandstone facies, medium sandstone facies, sandstone/siltstone facies, and chert facies. The sedimentary features of these rocks include channelling and grading and are described in terms of Bouma units where applicable. The coarse elements of the formation are thought to represent deposition in, or proximal to, submarine channels feeding a more distal depositional site represented by the finer elements. Igneous rocks of the group include pillowed and non-pillowed lavas, massive amphibolites and minor tuffs often in conformable contact with the sediments. Petrography of conglomerate clasts and sandstones indicates derivation from a continental source area. Palaeocurrent analysis reveals a primary easterly mode with a subsidiary northerly mode. It is suggested that the group exhibits some characteristics of trench-fill sequences and the succession may be related to similar environments within the Southern Uplands accretionary wedge.
Systematic fissuring of a matrix-dominated lodgement till at Church Wilne, Derbyshire, England
Authors: Derbyshire E. , Jones P. F. 
Published: May 2009

SummaryA set of sub-vertical curving fissures in a Pennine-derived lodgement till of Wolstonian age is described from Church Wilne near Derby. The fissures are at least 5 m long and curved (radius of curvature c. 3 m) in both vertical and horizontal planes, the concavity facing SE in the direction of regional ice movement. The origin of the structures is considered in the light of a review of modes of formation of structural discontinuities in till. Origins due to stress relief following excavation, desiccation, frost action, direct ice push, ice-core meltout, compaction of the substrate and shear failure are rejected. It is proposed that the fissures were produced by point loading of a frozen till surface by englacial (basal) boulders which provided periodically high compressive stresses and induced tensional failure. Analogous fissures occur in a Devensian lodgement till in the Wirral peninsula in Cheshire. It is concluded that curved fissure sets are localized features of lodgement tills but that they may be quite widely distributed.
Primary bone and dinosaurian physiology
Authors: Reid R. E. H. 
Published: May 2009

AbstractPrimary compact bone is ignored in some recent discussions of claims that dinosaurs were endotherms, but forms the basis of one of the arguments from bone, and part of the basis of another. This paper explains its histology and discusses its possible significance. In dinosaurs the primary compact bone was commonly fibre-lamellar bone, resembling bone seen in many large mammals, and implying a capacity to sustain rapid growth to large sizes. This probably indicates some physiological difference between dinosaurs and modern types of reptiles; but similar bone is present in early therapsids, which were probably not endotherms, and bone with typical reptilian ‘growth rings’ was sometimes formed. Endothermy is also unlikely in most kinds of dinosaurs, if its evolution requires a trend to small sizes; but perhaps they were ‘failed endotherms’.
Kinetics of pyrope megacryst reactions in ascending basaltic magma – relevance to high-pressure magmatic crystallization at Elie Ness, East Fife
Authors: Donaldson Colin H. 
Published: May 2009

AbstractThe rates of resorption of pyrope in basaltic melt and of pyrope decomposition to pyroxene + melt at pressures below the stability of garnet are used to examine the proposition (Chapman, 1976) that pyrope megacrysts in the Elie Ness neck began ascent from the mantle at 1300–1450°C. Both reactions are extremely rapid at these temperatures and yet the petrographic evidence is that neither occurred. Either the transporting magma cooled extremely rapidly during ascent (> 30000 °/h) or, more likely, was considerably cooler than previously proposed. Water was a significant constituent of the magma, and a crystallization temperature for the garnet of as little as 1000 °C is possible, based on existing phase–equilibria data.
Facies variations in peralkaline ash-flow tuffs from the Kenya Rift Valley
Authors: Leat P. T. 
Published: May 2009

AbstractTwo late Quaternary ash-flow tuffs erupted as single flow units from the Menengai caldera volcano, Kenya, show marked facies variations. Dense welding of the tuffs close to source may have been promoted by their peralkaline trachyte compositions. Coarse, near-vent breccias are partly welded and were emplaced as lithic-rich parts of the body of pyroclastic flows. Non-welded tuff forms the bulk of the outflow sheets which include valley-fill deposits up to 520 m above the present caldera rim, indicating ash-flow generation by collapse of moderately high eruption columns. The flows overran varied topography which controlled development of ash-flow tuff facies. On hilly terrain, the flows became turbulent and separated into a lithic-rich, rapidly deposited part and a fine-grained lithic-and crystal-poor part which was subsequently deposited farther from source. Caldera walls belonging to an earlier caldera probably formed a major barrier to the spread of the second ash-flow from its site of collapse. There are many similarities in the facies variations in these peralkaline tuffs and subalkaline tuffs. Differences in welding characteristics and the shape of ash particles reflect the lower viscosity of peralkaline magma.
Morne Patates volcano, southern Dominica, Lesser Antilles
Authors: Wadge G. 
Published: May 2009

AbstractMornes Patates is the youngest volcano in Dominica occupying a depression on the southwestern flank of a larger stratovolcano, Morne Plat Pays. Within the depression an arcuate ridge, apparently of acid andesite lavas, has been cored and largely buried by the explosive emplacement of two acid andesite domes and their associated pyroclastic deposits, mainly block-and-ash flow deposits. A basaltic scoria horizon, exposed on the northern side of the depression, has a14C age of 28450 ± 1500 years B.P. and is not seen on the volcano itself, which suggests that the domes and pyroclastic rocks are younger than this. A14C age of 450 ± 90 years B.P. from a block-and-ash flow deposit from the Morne Patates dome apparently confirms this and the youthful morphology also suggests a young age. The angular shape of the depression and the steep submarine slopes are consistent with an origin as a lateral gravity slide rather than a caldera collapse. Vigorous fumarolic activity and swarms of local earthquakes suggest that magma exists at depth (several kilometres) beneath the Morne Patates–Morne Plat Pays area.
The Ordovician–Silurian boundary at Keisley, northern England
Authors: Wright A. D. 
Published: May 2009

AbstractThe relationships of the Keisley Limestone, an isolated carbonate mudmound in the Cross Fell Inlier of northern England, have long been problematical with respect both to the other upper Ordovician as well as the Silurian strata of the inlier. Bedded limestones, separated by gaps from the Keisley mudmound below and fromatavusBiozone graptolite shales above, yielded a prolific shelly fauna to Temple in 1968 which he regarded as being of lower Llandovery age. This age is controversial. To try to establish the precise ages of the rock units, the position of the Ordovician–Silurian boundary, and the detailed nature of the changes which took place at this boundary, a critical section was excavated. Bed by bed lithological and faunal collections reveal from beneath the knownatavusoutcrop (a) five bentonite bands, unexpected in the context of northern England, (b) graptolites of bothacuminatusandpersculptusBiozonesabovethe bedded limestones and (c) a similar but distinct assemblage from siltstones associated with these limestones which containsHirnantiaelements. From the palaeontological evidence there is little doubt that the topmost part of the carbonate sequence is of Hirnantian age.
Silurian trench sedimentation in the Southern Uplands, Scotland: implications of new age data
Authors: Kemp A. E. S. , White D. E. 
Published: May 2009

AbstractResults of detailed remapping of the Kirkcudbright area in the Southern Belt of the Southern Uplands of Scotland, together with new palaeontological data, necessitate revision of the regional structure, and re-interpretation of the sedimentary history of the northwest margin of the Lower Palaeozoic lapetus Ocean. On the east side of Kirkcudbright Bay, at least six sediment-ologically and structurally distinct, subvertical tectonic blocks can be distinguished. Recognition of the Raeberry Castle Formation as a Wenlock turbidite sequence, rather than mid- to late Llandovery as previously interpreted, removes the need to postulate the existence of an axial rise and a distinct basin adjacent to the south, in mid- to late Llandovery times.
Microstructure, geochemistry and differentiation of a primary layered teschenite sill
Authors: Martin D.J. 
Published: May 2009

AbstractA 22 m thick primitive, basanitoid sill comprises homogeneous olivine teschenite, overlain by picrite and a rhythmically layered sequence of olivine teschenite, salitic teschenite and syenite. Differentiation occurred in two stages by fractional crystallization, in part from melt residual from formation of picrite. Syenitic blebs and hydrated globules, occurring through the layered sequence, formed by the same mechanism rather than by immiscibility. Endothermic cindering of a small coal seam below the intrusion absorbed heat and steam from the sill, removing volatiles from the lower part and establishing a strong downward heat flux. The picrite was restricted to the upper part of the sill by more rapid cooling of the lower half.
Palaeomagnetism of the Lower Carboniferous Billefjorden Group, Spitsbergen
Authors: Watts D. R. 
Published: May 2009

AbstractPalaeomagnetic data from mid to late Palaeozoic rocks are potentially valuable for testing models of the assembly of Spitsbergen and for determining the palaeo-position of parts of Spitsbergen relative to the major tectonic elements that comprised the Old Red Continent. Fine-grained red sandstones from the Tournaisian to Namurian Billefjorden Group, collected by members of Cambridge Spitsbergen expeditions, were subjected to stepwise chemical and thermal demagnetization. The characteristic magnetization is found in normal and reverse polarities and corresponds to a pole position at 23° S, 332 °E, dp = 5.7°, dm = 10.5°, which is near an early Carboniferous pole computed for the Baltic Shield-Russian Platform (Baltica). When compared to Laurentia (North America) in the context of the revised Mauch Chunk palaeomagnetic study, Spitsbergen falls a few degrees south of the Bullard reconstruction but the error of the determination of the palaeolatitude overlaps with this position. Therefore relative motion between any part of Spitsbergen and Laurentia and Baltica during the Carboniferous is not resolved.