bluuebunny/crossref_metadata_2025 huggingface dataset:
ON CAMACHO–SAD'S THEOREM ABOUT THE EXISTENCE OF A SEPARATRIX
Authors: ORTIZ-BOBADILLA L. , ROSALES-GONZALEZ E. , VORONIN S. M.
Published: June 2010

It is proved in Ann. Math. (2)115 (1982) 579–595 that, for any germ of holomorphic nondicritic vector field in (ℂ2, 0), there exists at least one separatrix (invariant analytic curve containing the origin). In Proc. Amer. Math. Soc.125 (1997) 2649–2650 a simple criterion was given to find, at each level of the blow-up, a singular point which leads to an analytical invariant curve. In this paper we prove shortly and strictly combinatorially, the existence of a separatrix, and show that for any germ of holomorphic nondicritic vector field in (ℂ2, 0), there exists at least one separatrix issuing from each connected component of the exceptional divisor of its nice blow-up with nodal corner points deleted.
REPRESENTATION THEORY OF THE STABILIZER SUBGROUP OF THE POINT AT INFINITY IN Diff(S1)
Authors: TANIMOTO YOH
Published: June 2010

The group Diff (S1) of the orientation-preserving diffeomorphisms of the circle S1 plays an important role in conformal field theory. We consider a subgroup B0 of Diff (S1) whose elements stabilize "the point at infinity." This subgroup is of interest for the actual physical theory that lives on the punctured circle, or the real line.

We investigate the unique central extension [Formula: see text] of the Lie algebra of that group. We determine the first and second cohomologies, its ideal structure and the automorphism group. We define a generalization of Verma modules and determine when these representations are irreducible. Its endomorphism semigroup is investigated and some unitary representations of the group which do not extend to Diff (S1) are constructed.
THE CENTRAL OBLIQUE COLLISION EFFICIENCY OF SPHERICAL NANOPARTICLES IN THE BROWNIAN COAGULATION
Authors: WANG YUMING , LIN JIANZHONG , FENG YU
Published: June 2010

The central oblique collision efficiency of spherical nanoparticles in the Brownian coagulation is studied. A new model of central oblique collision between two spherical nanoparticles is proposed to build equations which are solved to get the collision efficiency for the monodisperse dioctyl phthalate nanoparticle with diameter changing from 100 to 800 nm in the presence of Van der Waals force and elastic deformation force. The calculated results are in agreement with the experimental data qualitatively. The results show that the interparticle elastic deformation force cannot be neglected when dealing with particle Brownian coagulation. The collision efficiencies for the central normal collision and central oblique collision are different obviously. A set of new formulas relating central oblique collision efficiency to particle diameter is put forward.
COMPARISON OF DIFFERENT DAILY STREAMFLOW SERIES IN US AND CHINA, UNDER A VIEWPOINT OF COMPLEX NETWORKS
Authors: TANG QIANG , LIU JIE , LIU HONGLING
Published: June 2010

The daily streamflow series of three rivers are analyzed from the view of complex networks, i.e. the Yangtze River in China, the Umpqua River and the Ocmulgee River in the United States. We construct networks from these series by using the visibility graph algorithm respectively. The degree distribution and accumulative degree distribution are investigated. We find that the degree distribution of the Umpqua River series network, the Ocumlgee River series network and the subsequence of the Yangtze River series network can be better fitted by stretched exponential distribution (SED), although the degree distribution curves of these networks in a log–log plot have a linear part. Moreover, the slope α of the linear part and parameters μ in SED have significant meaning in the research of streamflow series properties.
EFFICIENCY DYNAMICS ON SCALE-FREE NETWORKS WITH COMMUNITIES
Authors: QI XIN , SHAO ZHI-GANG , QI JI , YANG LEI
Published: June 2010

The simple efficiency model is developed on scale-free networks with communities to study the effect of the communities in complex networks on efficiency dynamics. For some parameters, we found that the state of system will transit from a stagnant phase to a growing phase as the strength of community decreases.
APPROXIMATE CONTROLLABILITY OF SECOND-ORDER STOCHASTIC DIFFERENTIAL EQUATIONS WITH IMPULSIVE EFFECTS
Authors: SAKTHIVEL RATHINASAMY , REN YONG , MAHMUDOV N. I.
Published: June 2010

Many practical systems in physical and biological sciences have impulsive dynamical behaviors during the evolution process which can be modeled by impulsive differential equations. In this paper, the approximate controllability of nonlinear second-order stochastic infinite-dimensional dynamical systems with impulsive effects is considered. By using the Holder's inequality, stochastic analysis and fixed point strategy, a new set of necessary and sufficient conditions are formulated which guarantees the approximate controllability of the nonlinear second-order stochastic system. The results are obtained under the assumption that the associated linear system is approximately controllable.
INTEGRABLE HAMILTONIAN HIERARCHIES ASSOCIATED WITH THE EQUATION OF HEAT CONDUCTION
Authors: ZHANG YUFENG , TAM HONWAH , MEI JIANQIN
Published: June 2010

Using a 4-dimensional Lie algebra g, an isospectral Lax pair is introduced, whose compatibility condition is equivalent to a soliton hierarchy of evolution equations with three components of potential functions. Its Hamiltonian structure is obtained by employing the quadratic-form identity proposed by Guo and Zhang. In order to obtain explicit Hamiltonian functions, a detailed computing formula for the constant appearing in the quadratic-form identity is obtained. One type of reduction equations of the hierarchy is also produced, which is further reduced to the standard equation of heat conduction. By introducing a loop algebra of the Lie algebra g, we obtain a soliton hierarchy with an arbitrary parameter which can be reduced to the previous equation hierarchy obtained, whose quasi-Hamiltonian structure is also worked out by the quadratic-form identity. Finally, we extend the Lie algebra g into a higher-dimensional Lie algebra so that a new integrable Hamiltonian hierarchy, which comprise integrable couplings, is produced; its reduced equations in particular contain two arbitrary parameters.
CALCULATION OF THEORETICAL ISOTROPIC COMPTON PROFILE FOR MANY PARTICLE SYSTEMS
Authors: ALZUBADI ALI A. , ALBAYATI KHALIL H.
Published: June 2010

Theoretical isotropic (spherically symmetric) Compton profiles (ICP) have been calculated for many particle systems' He , Li , Be and B atoms in their ground states. Our calculations were performed using Roothan–Hartree–Fock (RHF) wave function, HF wave function of Thakkar and re-optimized HF wave function of Clementi–Roetti, taking into account the impulse approximation. The theoretical analysis included a decomposition of the various intra and inter shells and their contributions in the total ICP. A high momentum region of up to 4 a.u. was investigated and a non-negligible tail was observed in all ICP curves. The existence of a high momentum tail was mainly due to the electron–electron interaction. The ICP for the He atom has been compared with the available experimental data and it is found that the ICP values agree very well with them. A few low order radial momentum expectation values 〈pn〉 and the total energy for these atomic systems have also been calculated and compared with their counterparts' wave functions.
YIELD DESIGN HOMOGENIZATION METHOD FOR COMPACTION OF MONOSIZED SPHERICAL POWDERS
Authors: ANOUAR BENABBES , LARBI SIAD , LUC DORMIEUX , LIU WING KAM
Published: June 2010

The compaction of a package of monosized spherical solid grains by rate-independent plasticity deformation is examined in this paper through the use of both yield design homogenization method and finite element simulation. Both modes of compaction, isostatic and closed die, are considered. In this study, the arrangement of powder consists of hexagonal array of identical spherical grains touching each other in its initial state. During the compaction process the response of the powder compacts is monitored in terms of behaviors of appropriate representative unit cells subject to axisymmetrical loading conditions. The kinematic approach of the yield design homogenization method has been used to determine external estimates of macroscopic strength criteria of powders at various stages of compaction. The obtained upper bound estimates are based on consideration of discontinuous incompressible velocity fields satisfying conditions of homogeneous strain rate. The shapes and sizes of the macroscopic yield surfaces are determined at various stages of compaction and it has been found that they depend upon the loading history as well as the relative density of the compact. Finite element simulations similar to those of Ogbonna N. and Fleck N. A. [1995] "Compaction of an array of spherical particles," Acta Metall. Mater.43(2), 603–620. have also been performed in order to (i) obtain the deformation modes as well as the evolution of the deformation mechanism of the powder compact during the whole process of compaction; (ii) derive the evolution of contact sizes between adjacent grains; (iii) examine the dependence of the macroscopic yield surface upon the degree of compaction, using the "yield probing technique" Gurson, A. L. and Yuan, D. W. [1995] A Material Model for a Ceramic Powder Based on Ultrasound, TRS Bend Bar, and Axisymmetric Triaxial Compression Test Results (ASME, New York), pp. 57–68, and (iv) validate, to some extent, the results provided by the kinematic approach.
DEFORMATION OF CLOSED-CELL FOAMS INCORPORATING THE EFFECT OF INNER GAS PRESSURE
Authors: XU ZHI MIN , ZHANG WEI XU , WANG T. J.
Published: June 2010

The objective of this work is to numerically investigate the elastic–plastic deformation of closed-cell foams incorporating the effect of inner gas pressure. Both body-centered cubic (BCC) and face-centered cubic (FCC) arrangements of pores are considered in analysis. It is seen that the inner gas pressure has a significant effect on the plastic deformation of closed-cell foams, which is different for the foams with different microstructures and is discussed in detail. The inner gas pressure results in the asymmetry of uniaxial tensile-compressive stress–strain curves and the nominal Poisson's ratio. It is shown that the inner gas pressure makes the yield surface move to the negative direction of the hydrostatic axis in the plane of equivalent and hydrostatic stresses, and the moving distance is equal to the magnitude of inner gas pressure in the foams. Moreover, a new yield function incorporating the effect of inner gas pressure is developed for closed-cell foams. The material constants in the yield function depend on the microstructures of the foams.
SINGULAR PERTURBATION APPROACH TO MAXIMUM PRINCIPLE FORMULATION OF VISCOUS INCOMPRESSIBLE FLUID FLOW
Authors: MATSUBA IKUO
Published: June 2010

A method for the solution of viscous incompressible flow based on the Pontryagin's maximum principle is presented. By minimizing the cost function that ensures the continuity condition, an explicit control law for the pressure is derived with the help of an adjoint variable satisfying the adjoint differential equation and certain terminal conditions. Employing the singular perturbation method, the first-order equation is found to give the well-known pressure stabilization technique in the mixed finite element method. The implementation of the present method is presented in a simple example that shows that the approximate solution indeed approaches uniformly to the exact solution for large time.
ON POST-IMPACT ANGULAR VELOCITIES AND RESULTANT IMPULSES WITH RANK-DEFICIENT JACOBIAN MATRICES USING NEWTON IMPACT LAW
Authors: MU XIUPING , WU CHRISTINE QIONG
Published: June 2010

Modeling and trustworthy simulation of impact play an important role in research on robotic contact tasks. Impact dynamic equations, based on Newton impact law, and their solution for planar multi-link robotic collisions have been well developed in literature in the context of determined contact problems. Rank-deficient Jacobian matrices cause the impact equations to be indeterminate. However this issue has not been investigated in previous research. In this paper, the solution for the velocity changes due to impact is proved to be unique in spite of rank-deficient Jacobian matrices and it is solved in a closed form that can be easily employed for simulating robotic system contact states. Furthermore, a set of linear equations with unknown impulses is obtained whereas the impulses can only be solved if extra contact constraints are provided. Two robot collision problems with rank-deficient Jacobian matrices are presented to exemplify the method.
EFFECTS OF BALLOON LENGTH AND COMPLIANCE ON VASCULAR STENT EXPANSION
Authors: CUI F. S. , LEE H. P. , LU C. , CHAI P.
Published: June 2010

Vascular stents are used to dilate arteries that are narrowed or clogged by plaque. However, in-stent restenosis is still one of the major causes of the clinical failure. It is believed that vessel trauma imposed during stent deployment is closely correlated to restenosis. Clinical observations show that the longitudinal and axial geographic miss in pre/post-dilation are responsible for the vessel trauma. The interactions between the stent-strut and the artery are difficult to measure in vivo or clinically and reported results are very limited. A numerical approach that leverages on computing power can provide new insights into the stent implantation process. In this study, the effects of balloon length and compliance that play important roles during stent expansion were investigated. Areas in the vessels with high stress concentrations were identified as these were weaknesses that might have a high possibility of vascular injury. Two different types of numerical models were constructed: a simplified model that considered only the balloon and stent and a more comprehensive model that consisted of the balloon, stent, plaque, and artery. Virtual stent implantation trials were simulated and the phenomena of stent recoil, dogboning and foreshortening were observed and examined. It was found that balloons which were slightly longer than the stent and less compliance would be more likely to eliminate dogboning. Furthermore, a new parameter, namely the Ectropion angle, was introduced to describe the turning effect of the stent end in situations when dogboning could not adequately characterize this phenomenon. The present study could provide guidance for the placement of stents by clinical practitioners.
The Early Palaeozoic geography of Europe
Authors: COCKS L. R. M.
Published: June 2010

In the early Ordovician three main continents are recognized by faunas in Europe, Laurentia (northwest of the closed suture of the Iapetus Ocean), which was tropical; Baltica (north of the general area of the Trans‐European Suture Zone), which was temperate; and Gondwana (south of the TESZ), which was high latitude. As the Ordovician progressed, various terranes separated and drifted away from the Gondwana supercontinent at different times, namely Avalonia (which was probably originally part of Gondwana near South America), Iberia–Armorica, Perunica (Bohemia) and various Alpine fragments. Each terrane developed progressively different faunas as time went by. Avalonia collided with Baltica near the end of Ordovician, confirmed by faunas, tectonics and palaeomagnetism, and subsequently Avalonia–Baltica collided with Laurentia to form Laurussia from the mid‐Silurian to the early Devonian. The Ibero‐Armorica, Perunica and Alpine terranes did not join the European collage until the Devonian. The modern sites of the terrane boundaries bear little direct relationships to the original palaeogeographical boundaries in the Early Palaeozoic.
Vesicles in thick komatiite lava flows, Kambalda, Western Australia
Authors: BERESFORD S. W. , CAS R. A. F. , LAMBERT D. D. , STONE W. E.
Published: June 2010

Traditionally, vesicles have been considered to be rare in komatiites, however, field studies at Kambalda, Western Australia, and critical literature examination suggest that vesicle presence and content in komatiites are grossly underestimated. At Kambalda, vesicles are observed in significant amounts (up to 30%) in internal horizons within komatiite lavas. The vesicular horizons are inferred to represent bubbles frozen in place below the upper crust, during multiple episodes of flow through of bubble‐rich lava. We conclude that vesicle and crystal distribution are compatible with many komatiites being emplaced under laminar flow conditions, analogous to models for basalt lava emplacement.
Structural, mineralogical and petrophysical effects on deep crustal rocks of fluid‐limited polymetamorphism, Western Gneiss Region, Norway
Authors: ENGVIK ANE K. , AUSTRHEIM HÅKON , ANDERSEN TORGEIR B.
Published: June 2010

The Proterozoic banded granulite facies complex of BÅrdsholmen, Western Gneiss Region, Norway (
T
=815–845°C) was locally transformed to eclogite (
T
=455–510°C,
P
>12 kbar) and amphibolite facies rocks (
T
=460°C) during the Caledonian continental collision. The granulite complex consists of mafic two‐pyroxene granulite and leucocratic orthopyroxene+garnet‐bearing layers alternating on a scale from 1 cm to 10 m. The granulite facies rocks change to eclogite facies rocks over centimetre‐scale distances along well defined fluid‐infiltration fronts. The mafic granulite was transformed to omphacite+garnet‐rich eclogites and the leucocratic rocks were converted to quartz+phengite‐rich assemblages with minor garnet and local omphacite. Melange‐like lithologies consisting of mafic lenses of eclogite surrounded by felsic material represent an advanced stage in the process of converting deep crust to eclogite facies. During amphibolitization this melange‐like lithology evolves to a rock where amphibolite lenses and layers are surrounded by granitoid gneiss, a lithology typical of the Western Gneiss Region. The BÅrdsholmen locality illustrates the profound control exerted by fluids on the timing of metamorphism, the structural make up and petrophysical properties such as density and rheology of crustal root zones. Fluid‐induced metamorphism will therefore exert control on the attributes of orogenic belts such as topography and Moho depth and influence the dynamics of collision zones by controlling the time of orogenic collapse and the buoyancy of the subducted crust. We suggest that orogens may develop differently depending on the fluid budget.
New U–Pb ages for Early Ordovician magmatism in Central Spain
Authors: VALVERDE‐VAQUERO P. , DUNNING G. R.
Published: June 2010

Felsic orthogneisses occur widely in the Ollo de Sapo Domain of the Central Iberian Zone, most of which were previously considered to represent a Precambrian basement to the Palaeozoic sequences of this domain. However, new U–Pb dating across the Berzosa‐Riaza shear zone (Sierra de Guadarrama, Central Spain) indicates an Early Ordovician age for the most representative types of orthogneisses in the eastern part of the Ollo de Sapo Domain. Dated rocks include the volcaniclastic Cardoso gneiss (480±2 Ma); from the low–medium‐grade hanging wall; the Riaza gneiss (468
−8
+16
Ma, mylonitic granite) in the Berzosa‐Riaza shear zone; three types of ‘leucogneiss’ (Buitrago gneiss; 488
−8
+10
Ma, megacrystic granite; 482
−11
+14
Ma, aplitic vein; and 482
−8
+9
Ma, gneissic leucogranite); and the La Morcuera granitic augen gneiss (477±4 Ma) in the high‐grade footwall. The new age of the Cardoso gneiss brackets to the Mid–Late Arenig, the so‐called Early Ordovician Sardic unconformity, characteristic of the Central Iberian Zone. These new ages suggest that the broadly coeval volcanism and plutonism were closely associated with the Sardic events, and that these orthogneisses were part of a felsic magmatic belt which extended along the Ollo de Sapo Domain of the Central Iberian Zone. This magmatic belt is interpreted to have been active during the Early Ordovician break‐up of the peri‐Gondwanan margin of the Iapetus Ocean.
Geometry and origin of a polygonal fault system
Authors: WATTERSON J. , WALSH J. , NICOL A. , NELL P.A.R. , BRETAN P.G.
Published: June 2010

A fault array in South Australia, interpreted from a 3D onshore seismic survey, shows fault traces on the lowermost mapped horizon of a shale‐dominated sequence which outline polygonal cells averaging 1.4 km in diameter. The cell boundaries coincide approximately with the downward terminations and near convergence of conjugate pairs of normal faults. The pattern becomes less spatially ordered on higher horizons where faults still show a near‐isotropic strike distribution. Maximum throws,
c.
 80 m, occur
c.
 400 m above the downward terminations of the faults. The faults have a systematic geometric relationship with folds, with anticlines in the mutual hanging walls of fault pairs and broader footwall synclines that define the shallow dish forms of the polygons. Polygon boundaries coincide with anticlinal ridges on the interface between the faulted sequence and an underlying 35 m thick low velocity, low density, overpressured layer. Although the pattern of ridges defining the polygon boundaries is strikingly similar to experimental spoke and hub patterns formed at the boundaries between viscous materials with density inversion, the data do not exclude the possibility of lateral extension.
Three‐dimensional preservation of a non‐biomineralized arthropod in concretions in Silurian volcaniclastic rocks from Herefordshire, England
Authors: ORR PATRICK J. , BRIGGS DEREK E. G. , SIVETER DAVID J. , SIVETER DEREK J.
Published: June 2010

Three‐dimensional preservation of a non‐biomineralized arthropod occurs in carbonate concretions in a volcaniclastic deposit from the Wenlock Series of Herefordshire, England. Specimens are preserved in calcite that co‐precipitated with framboids and polyhedra of pyrite. The texture of the calcite indicates that it is a void infill. It forms a cast of the external surface of the arthropod, having precipitated after decay of even the most recalcitrant biological tissues. Incorporation of the fossils into concretions ensured their long term preservation but was not, at least in most examples, responsible for preventing potential collapse and occlusion of voids in the interval between the decay of tissues and the precipitation of calcite. The precipitation and/or accumulation of clay minerals adjacent to specimens during decay was important in this process, as were possibly the geotechnical properties of the ash itself. Limited dolomitization of the calcite around the edges of the fossils and in the matrix of the concretion occurred at a later stage.
Biomarkers in a Lower Jurassic concretion from Dorset (UK)
Authors: KIRIAKOULAKIS K. , MARSHALL J. D. , WOLFF G. A.
Published: June 2010

Textural, petrographic and stable isotopic evidence suggest that a zoned concretion (Birchi Bed, Lower Lias, West Dorset, UK), formed under very shallow burial, with carbonate cement passively filling the pore spaces. The calcitic core of the concretion formed initially, whilst the intermediate and outer edge cements, which are dominated by a dolomite and a calcite respectively, precipitated successively. Mixtures of calcite and dolomite occur in the intermediate zone and outer rim, suggesting initial incomplete cementation and later back‐filling. The enveloping fibrous calcite vein (beef) formed later by displacive crystallization. The concretionary carbonates preferentially preserve labile organic compounds (i.e. unsaturated fatty acids) not found in the surrounding shales. Fatty acid distributions in the concretion are distinct and informative. The presence of 10‐methylhexadecanoic acid provides direct evidence for sulphate‐reducing bacteria in the calcitic core whereas the abundance of unsaturated fatty acids in the concretion as a whole is attributed to localized bacterial production and its early formation. The core probably formed in the sulphate reduction zone, whereas dolomite in the intermediate zone was derived largely from methanogenesis and iron reduction, although direct biomarker evidence for methanogenesis was not found. The outer rim and the fibrous calcite vein probably resulted from ‘late’ bacterial processes, probably including renewed sulphate reduction. The complex biogeochemistry of the sedimentary environment is reflected by the concentrations and distributions of biomarkers and by the detailed petrography. Nevertheless, carbonate concretions can provide a ‘snapshot’ of early diagenesis in ancient mudstones.
Mudrock‐hosted carbonate concretions: a review of growth mechanisms and their influence on chemical and isotopic composition
Authors: RAISWELL R. , FISHER Q. J.
Published: June 2010

Existing interpretations of cement textures and isotopic compositions may significantly under‐estimate the depth and duration of concretionary growth. Minus‐cement porosities can commonly under‐estimate depths of concretionary growth for some, or all, of the following reasons; (i) cements might not passively replace host sediment porosity, (ii) non‐cement carbonate phases (such as replaced bioclastic carbonate) can be significant, (iii) sediment compaction models over‐estimate rates of porosity loss at shallow (<500 m) depths and (iv) cementation can create a framework that prevents compaction and preserves porosity. Cement textures can be used to distinguish two modes of growth; concentric growth, where successive layers of cement are added to the outer surface (radius increases with time), and pervasive growth, where cement crystals grow simultaneously throughout the concretion volume (little or no radius increase with time). Cement textures of siderite concretions are mostly consistent with pervasive growth, but many calcite microsparite concretions show no diagnostic textural features and could grow either concentrically or pervasively. Concretionary cementation, whether concentric or pervasive, occurred such that there was accessible porosity which could be filled by later cements. Pervasive growth in particular is associated with the retention of substantial amounts of porosity which may be filled by chemically and isotopically distinct phases. The resulting chemical gradients across concretions may then reflect variations in the relative proportions of early and later cements more than variations in porewater composition.

Carbon isotope data from modern sediments show that dissolved carbonate in the methanogenic zone has a continuum of values from −30‰ to +15‰, and thus overlaps
13
C‐depleted values normally considered characteristic of sulphate reduction. Many concretions previously thought to have grown entirely during sulphate reduction may therefore have continued cementation during methanogenesis, indicating a deeper and more prolonged cementation history. The necessary carbonate supersaturation for concretionary growth could either occur throughout the porewaters (the equilibrium model), or be generated
in situ
by organic matter decay (the local‐equilibrium model), or created where external fluids are introduced (the fluid‐mixing model).
A new scheme for the very deep geological disposal of high‐level radioactive waste
Authors: GIBB FERGUS G. F.
Published: June 2010

A case is presented for reconsidering deep borehole disposal for high‐level radioactive waste (HLW) in the light of recent discoveries about the hydrogeology and hydrogeochemistry of the continental crust. A new multi‐barrier concept is proposed for very deep, elevated‐temperature disposal of vitrified HLW, spent fuel and ex‐military and other fissile materials which involves melting and recrystallization of a granitic host rock utilizing the heat from the waste. This scheme is fundamentally different from previously proposed borehole disposal scenarios in its key aspects, particularly in utilizing only partial melting and a surviving container. The perceived advantages of the scheme are discussed, in general and in relation to previous deep disposal ideas, particularly from the standpoint of safety. It is concluded that the scheme offers a potentially safer and environmentally more acceptable option for the permanent disposal of high‐level waste.
Stratigraphy of late Palaeocene events in the Middle East: implications for low‐ to middle‐latitude successions and correlations
Authors: SPEIJER ROBERT P. , SCHMITZ BIRGER , LUGER PETER
Published: June 2010

We have investigated the upper Palaeocene stratigraphical record in four sections in Egypt and one in Israel. The sections are arranged on a depth transect across the southern Tethyan margin. In all sections, a δ
13
C excursion and benthic foraminiferal extinctions coincide at a level within planktic foraminiferal Zone P5. In three sections, a bed (sapropelic in two of the deeper profiles) contains extraordinarily transient benthic and planktic foraminifera assemblages. These planktic assemblages are dominated by
Acarinina
and contain rare to common
Morozovella allisonensis
and
Globanomalina luxorensis,
but unusually few other
Morozovella.
The extremely restricted stratigraphical range of
M. allisonensis
to the lower part of the δ
13
C excursion enables: (1) a three‐fold subdivision of Zone P5, (2) accurate correlation to the best sections spanning the δ
13
C excursion in the Atlantic and Pacific and (3) assessment of stratigraphical completeness over the δ
13
C excursion in other (sub)tropical successions. Discontinuities and especially dissolution intervals in many low‐ to middle‐latitude marine successions elsewhere, as in two Middle East sections, preclude an accurate correlation within the lower part of the δ
13
C excursion (=
M. allisonensis
Zone P5b). Three studied sections can provide the best coverage of the sequence of events over the onset and early part of the δ
13
C excursion in the Middle East, but as in most known sections, probably none constitutes a complete upper Palaeocene–lower Eocene record.
Mass origination versus mass extinction: the biological contribution to the Pliensbachian–Toarcian extinction event
Authors: ABERHAN M. , FÜRSICH F. T.
Published: June 2010

The Pliensbachian–Toarcian bivalve mass extinction in the Andean Basin of South America is characterized by a sharp drop in species diversity, caused mainly by extinction of endemics, and an extended lag phase. Whilst analysis of community attributes such as guild diversity, number of associations, and species richness of samples constituting associations did not yield any significant changes across the critical interval, rates of origination and extinction of species differed markedly between the various substages of the Early Jurassic. The most prominent feature is the drastic increase in the rate of origination of endemics culminating in the Early Pliensbachian. The time span between the peaks of rate of origination and extinction (5.7 Ma) closely corresponds to the longevity peak of Jurassic endemic bivalves (4–6 Ma). In addition to physico‐chemical changes, we therefore explain the drop in species diversity as a result of the evolutionary dynamics of endemics, characterized by a preceding increase in the origination rate. Global mass extinctions are usually explained by one or more physico‐chemical causes. We suggest that evolutionary factors, in particular species longevities, may substantially contribute to the phenomenon.
Low‐ and high‐frequency sea‐level changes control peritidal carbonate cycles, facies and dolomitization in the Rock of Gibraltar (Early Jurassic, Iberian Peninsula)
Authors: BOSENCE D. W. J. , WOOD J. L. , ROSE E. P. F. , QING H.
Published: June 2010

The Rock of Gibraltar comprises two tectonically separated limbs of an isolated klippe of Liassic Gibraltar Limestone Formation. Both limbs have similar,c. 400 m thick sequences of inner carbonate platform facies arranged in high‐frequency, metre‐scale, shallowing‐upward, peritidal cycles with emergent, caliche caps. Four cycle types are recognized on the basis of vertically repeated successions of different sedimentary structures, lithologies, facies and biota. When compared with other Liassic cycles from fault‐bound platforms of the western Mediterranean region all are found to be of similar scale, facies and cycle type. Likely common origins are through Milankovitch band allocyclicity, or autocyclic tidal flat progradation superimposed on regional subsidence.

Within the Gibraltar Limestone high‐frequency cycles are superimposed on a low‐frequency (third order?) cyclicity that is revealed, through the use of Fischer plots, to control the occurrrence of facies, biota, high‐frequency cycle types and dolomitization. Falling sea‐level and lowstand phases, with reduced accommodation space, are typified by restricted, inner platform facies and cycles and by early reflux dolomitization. Transgressive and highstand phases, with more accommodation space, are characterized by the absence of early dolomites, the incoming of inner platform microfossils (i.e. foraminifera and calcareous algae) and by less restricted marine facies (i.e. oncoids, shelly rudstones, packstones and grainstones).

Fischer plots have demonstrable value in the correlation and analysis of tectonically separated and geographically isolated cyclic sequences that lack prominent marker beds or stratigraphically useful biotas.
Fault activity and sedimentation in a marine rift basin (Upper Jurassic, Wessex Basin, UK)
Authors: NEWELL ANDREW J.
Published: June 2010

Shallow‐marine carbonates and siliciclastics of the Corallian Formation (Oxfordian–Early Kimmeridgian) accumulated on and around an intrabasinal high in the extensional Wessex Basin. Four sequences can be recognized. Sequences 1–3 accumulated under conditions of thermal subsidence on a ramp‐type margin. The initial sequence was siliciclastic. Highstand sedimentation in this sequence reflects the supply of sandy mud from a recently emergent intrabasinal high. During transgression and regression this muddy sediment was reworked into cleaner sandstone bodies by landward or basinward migrating zones of shoreface erosion. Carbonates dominate the second and third sequences when rising sea level increased the area of carbonate production and reduced siliciclastic input. Oolite bodies developed as both transgressive barrier bars and highstand sheets. The forth sequence formed during the activation of major normal faults. This caused the breakdown of the ramp system, and patterns of sediment accumulation were strongly controlled by tectonic subsidence patterns.
Geochemical transitions in the ancestral Iceland plume: evidence from the Isle of Mull Tertiary volcano, Scotland
Authors: CHAMBERS L. M. , FITTON J. G.
Published: June 2010

The Mull Tertiary volcano lies on the eastern edge of the North Atlantic Igneous Province, and was active soon after the initiation of the Iceland plume. Detailed sampling of the Mull lava pile has allowed temporal changes in the mantle source to be determined. A significant change at 700 m above sea level from N‐MORB‐like to ‘Icelandic’ marks the first arrival beneath the region of mantle from the core of the ancestral plume. The earlier basalts represent an outer plume sheath of heated upper mantle. From the initiation of magmatism in Mull, it took 1.9±0.4 Ma for this transition to occur.
Palaeomagnetic constraints on the age of the Red Arch Formation and associated sandstone dykes (Northern Ireland)
Authors: TURNER P. , SHELTON R. , RUFFELL A. , PUGH J.
Published: June 2010

The Red Arch Formation is a continental red bed succession of uncertain age exposed on the northeast coast of Ireland. There are lithological similarities with the Old Red Sandstone of the Highland Border region, although unconformities within the succession, the presence of reworked aeolian sand grains and variations in the induration of the rocks have prompted earlier workers to suggest that the upper part of the succession may be Triassic in age.

This paper reports palaeomagnetic results from the Red Arch Formation. The characteristic magnetizations (ChRMs) are exclusively of reversed polarity and the palaeomagnetic pole position for the sequence bears close comparison with other results from the Old Red Sandstone in Scotland and southern Britain. These poles are regarded as magnetic overprints formed during the Kiaman Superchron because they fall in the Permo‐Carboniferous segment of the apparent polar wander path.

Sandstone dykes that cut the Red Arch Formation on a NNE–SSW and NNW–SSE trend have also been studied palaeomagnetically. The dykes show more steeply inclined ChRMs predominantly of normal polarity. The dykes are therefore interpreted to be post‐Kiaman in age, a conclusion consistent with our structural observations. The age of the dykes cannot be determined precisely because they have also been, at least partially, remagnetized. Lithological and regional geological considerations suggest the dykes are Triassic in age and formed in an extensional stress regime prior to the opening of the North Atlantic. They were remagnetized in Tertiary times, possibly associated with uplift and emplacement of the British Tertiary Igneous Province.
Thermochronology of northern Murihiku Terrane, New Zealand, derived from apatite FT analysis
Authors: KAMP PETER J. J. , LIDDELL IVAN J.
Published: June 2010

Murihiku Terrane is the least deformed of a series of tectonostratigraphic terranes that have been amalgamated to form the basement underlying New Zealand. Apatite fission‐track (FT) thermochronology has been applied to the youngest beds (Late Jurassic, Hettangian–Tithonian Stages) of this terrane, located at Port Waikato in western North Island, which are broadly folded. The apatite FT ages are partially annealed, are younger than their stratigraphic ages, and remarkably, decrease in age upsection. Interpretation and modelling of the maximum palaeotemperatures experienced by the sample horizons and the timing of cooling requires a wedge of Cretaceous sedimentary rocks to have accumulated within the axis of the major fold (Kawhia Syncline). Deposition of Murihiku Terrane sequences continued therefore into the Cretaceous and probably until
c.
 100 Ma. Deposition may have ended as late as 85 ± 10 Ma, when cooling via denudation started. The upper parts of the former succession probably accumulated during folding. In addition, interpretation of the FT data require a marked increase in palaeogeothermal gradient from a subnormal value of 15°C km
−1
during the Late Jurassic, up to
c.
 30°C km
−1
at 85 ± 10 Ma. This is attributed to the termination of subduction along the Pacific margin of Gondwanaland, and a transition to a rift‐transform tectonic setting in western New Zealand during Tasman Sea spreading. The latest Cretaceous–Palaeocene eastward tilting of the Murihiku basement at Port Waikato may have been accommodated on the Taranaki Fault or another coast‐parallel fault; the Waikato Fault probably acted as a transfer fault at that time accumulating a significant amount of throw.
An oxygen and carbon isotopic study of multiple episodes of fluid flow in the Dalradian and Highland Border Complex, Stonehaven, Scotland
Authors: MASTERS R. L. , AGUE J. J. , RYE D. M.
Published: June 2010

The carbon and oxygen systematics of rocks north of Stonehaven, Scotland were studied to provide new constraints on the nature and timing of metamorphic and post‐metamorphic fluid infiltration. Carbon and oxygen isotopic data were collected from carbonated spilites and carbonate‐bearing veins in the Highland Boundary Fault, from Dalradian metacarbonate layers and pervasively carbonated schists, and from three generations of carbonate‐bearing veins, and a quartz porphyry dyke within the Dalradian. Isotopic evidence for syn‐metamorphic fluid infiltration in the Dalradian is preserved in quartz–calcite veins in the upper chlorite zone and in staurolite zone metacarbonates. δ
18
O values for coexisting quartz (δ
18
O
quartz
= 13.6‰) and calcite (δ
18
O
calcite
= 11.6‰) in a vein from the upper chlorite zone are consistent with precipitation of both minerals from a single fluid at
c.
 375°C. Oxygen isotopic data from staurolite zone metacarbonate layers (δ
18
O
calcite
= 10.4 to 12.9‰) suggest major isotopic exchange with an external fluid equilibrated with a quartzo‐feldspathic reservoir, such as the Dalradian metasediments, at metamorphic temperatures. Low, negative carbon isotope data from these metacarbonate layers (δ
13
C
calcite
= −12.4 to −17.7‰) may indicate a component of oxidized organic material in the infiltrating fluid. Post‐metamorphic fluids derived from or equilibrated with a high‐temperature silicate reservoir such as felsic igneous rocks were responsible for precipitation of post‐metamorphic vein carbonate, carbonation of pelitic schists, and alteration of metamorphic feldspar porphyroblasts from Barrow’s famous spotted chloritoid schists in an area geographically associated with several carbonated quartz porphyry dykes. Some veins in the biotite and garnet zones have been conduits for multiple generations of fluid flow. Quartz from this generation of veins preserves a metamorphic isotopic signature (δ
18
O
quartz
= 11.2 to 13.2‰) whereas dolomite and calcite are considered to be post‐metamorphic based on textural evidence and isotopic data indicating extreme oxygen isotopic disequilibrium between vein quartz and carbonate minerals (δ
18
O
dolomite
= 23.7 to 24.2‰, δ
18
O
calcite
= 25.3‰, δ
18
O
quartz
= 11.2 to 13.2‰). Variably depleted carbon isotopes from carbonate minerals in these veins (δ
13
C
dolomite
= −8.1 to −13.4‰, δ
13
C
calcite
= −12.2‰) may reflect input of oxidized organic material in the mineralizing fluid. Isotopic data from carbonate veins and variably carbonated spilites from the Highland Boundary Fault are consistent with hydrothermal alteration of basalts by seawater, which had its carbon isotope systematics modified by addition of magmatic CO
2
and/or oxidation of organic carbon. Such alteration may have occurred on the seafloor or during emplacement in the Highland Boundary Fault.
Continental rift to back‐arc basin: Jurassic–Cretaceous stratigraphical and structural evolution of the Larsen Basin, Antarctic Peninsula
Authors: HATHWAY B.
Published: June 2010

The Larsen Basin developed in Jurassic times as a result of continental rifting during the early stages of Gondwana break‐up. Lower‐?Upper Jurassic non‐marine sedimentary and volcanic rocks constitute a syn‐rift megasequence recording initial largely amagmatic extension and subsequent widespread extension‐related silicic volcanism. A succeeding, Kimmeridgian–early Berriasian transgressive megasequence, consisting largely of anoxic‐dysoxic hemipelagic mudstones, is thought to have been deposited during a thermal subsidence phase when relative magmatic quiescence and peak Jurassic eustatic sea levels served to maximize sediment starvation. The fragmentary record for late Berriasian–Barremian times suggests that a ?regressive megasequence may have developed in the earlier part of this period, recording increased sediment yield to the Larsen Basin from the increasingly emergent Antarctic Peninsula arc. Subsequently, strata in the southern, but not the northern, part of the basin underwent relatively intense eastward‐verging deformation, possibly during the formation of a retro‐arc fold‐thrust belt. Where exposed, the lower part of the succeeding Aptian–Eocene megasequence consists of a deep‐marine clastic wedge deposited along the fault‐bounded western basin margin during a phase of arc uplift and related differential subsidence. Following partial basin inversion in Late Cretaceous times, regression took place as reduced basinal subsidence rates allowed shallow marine facies to prograde basinward.
Subsidence and erosion in the Pennine Carboniferous Basin, England: lithological and thermal constraints on maturity modelling
Authors: PEARSON MICHAEL J. , RUSSELL MARIE A.
Published: June 2010

Forward modelling of maturity against vitrinite reflectance and chemical data for a number of onshore boreholes was used to test a range of subsidence and thermal histories for the Pennine Carboniferous Basin. The preferred models suggest maximum palaeotemperatures were reached during late Cretaceous or possibly early Tertiary burial, consistent with the outcome of previous apatite fission‐track studies. Models in which maximum palaeotemperature was attained in the late Carboniferous are considered less likely: rapid burial under a normal heat flow requires an unrealistic thickness of missing late Westphalian strata, whilst high regional heat flow is incompatible with the observed vitrinite reflectance gradients. The lithologies assumed for missing strata have a significant influence on the range of estimates of eroded thicknesses. Preferred estimates of Cenozoic erosion range from around 1.6 km in Mesozoic basinal areas to around 2.8 km within areas of present Carboniferous outcrop.
Death of a sand sea: an active aeolian erg systematically buried by the Etendeka flood basalts of NW Namibia
Authors: JERRAM D. A. , MOUNTNEY N. P. , HOWELL J. A. , LONG D. , STOLLHOFEN H.
Published: June 2010

Here we report on a ‘fossilized’ sand sea that was progressively engulfed by the basal Etendeka flood basalts in NW Namibia. Preserved relict aeolian landforms include transverse barchanoid dunes and isolated barchan dunes. Present‐day preferential erosion of the lava flows exhumes relict aeolian bedforms preserved in the position in which they were migrating at the time of burial (
c.
 133 Ma). A passive eruption style of inflated pahoehoe flows has preserved the bedforms without significant deformation. The sediment interlayers record a decrease in sand supply and a change in palaeowind direction, which may have been driven by the ongoing break‐up of west Gondwana, or may be a direct result of the widespread volcanism itself.
Late Quaternary evolution of a hyperactive rhyolite magmatic system: Taupo volcanic centre, New Zealand
Authors: SUTTON ANDREW N. , BLAKE STEPHEN , WILSON COLIN J.N. , CHARLIER BRUCE L. A.
Published: June 2010

Taupo volcanic centre has been active for
c.
 300 000 years. Since the
c.
 26.5 ka caldera‐forming Oruanui eruption 28 eruptions have occurred from Taupo, varying between 0.1 and >45 km
3
in minimum bulk volume, and with repose periods ranging from
c.
 20 to 6000 years. All magma erupted post‐26.5 ka is compositionally and mineralogically distinct from pre‐Oruanui and Oruanui eruptives, and is inferred to have formed at or after 26.5 ka. Four post‐Oruanui magma types are identified on the basis of whole rock and mineral compositions: one dacitic, forming three eruptions between 20.5 ka and 17 ka, and three subtly distinct rhyolite compositions erupted in discrete periods from 11.8 to 9.95, 7.05 to 2.75 and 2.15 to 1.74 ka. Stepwise compositional variations between, and limited variation within, rhyolite groups suggest emplacement of three petrogenetically separate batches of magma within only 10 000 years. The 15–35 km
3
of magma erupted at 1.77 ka evidently appeared in <10
3
years; this short residence time may have contributed to the lack of zonation within this magma chamber. Taupo is unusual amongst large rhyolite volcanoes in terms of the high frequency of activity since 26.5 ka, rapid stepwise changes in rhyolite compositions, and insignificant differentiation within individual subgroups. These traits are attributed to the combined effects of the extensional arc setting, thermal energy from mafic magma, and the shallow slope of the plagioclase‐saturated rhyolite liquidus.