bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial variability in soil moisture as predicted from airborne thematic mapper (ATM) data
Authors: Davidson Donald A. , Watson Alistair I.
Published: February 2007

In the first part of this project, the extent to which moisture content of alluvial soils could be predicted from imagery derived from an airborne thematic mapper (ATM) was investigated. From sampling done on the same day as the flight, it was found that digital numbers derived from the thermal channel (waveband 11) were strongly correlated with gravimetric moisture content. From sampling three fields of contrasting land cover, the relationship between waveband 11 values and moisture content was found to be independent of land cover type. Spatial variation in waveband 11 values and thus moisture content were related to palaeochannel patterns on the alluvial land. This was investigated by deriving variograms for long transects from each of the three investigated fields. The range and sills of the variograms are shown to express the nature and pattern of palaeochannels. By the application of such geostatistical techniques, high resolution imagery can thus be used to quantify palaeochannel characteristics on alluvial land.
Effects of soil moisture dynamics on slope failure at Hyrum Reservior, Utah
Authors: O'Neill Michael P. , McDonnell Jeffrey J.
Published: February 2007

Field observations of shoreline conditions at Hyrum Reservoir, Utah, were conducted during the summers of 1991 to 1993. A process of bluff retreat is described for a multiple‐layered bluff environment of sand and clay layers. Failure is initiated by wetting and drying of clay sediments, which produces horizontal cracks within bluff material. These cracks appear to penetrate to a depth of approximately 100‐150 mm before initiating vertical cracking in the sediments. The vertical cracks are propagated by continued drying of the surface sediment, ultimately leading to failure of the bluff material. The physical dimensions of sediment blocks succumbing to this mechanism range from a few hundred millimetres up to 3 m on a side, with a depth of approximately 100‐150 mm. The mechanism described here appears to operate optimally when the supply of subsurface moisture is abundant and nearly continuous throughout the spring and early summer. Reservoir draw‐down, large capillary fringe effects in the bluff and periodic wetting from upslope undrained hollows are the dominant moisture controls at this site. Moisture delivery to the face is strongly influenced by anisotropy of saturated hydraulic conductivity in the alternating clay and sand layers and related differences in sediment texture.
Aeolian sediment flux decay: Non‐linear behaviour on developing deflation lag surfaces
Authors: Neuman Cheryl Mckenna , Nickling W. G.
Published: February 2007

Wind tunnel simulations of the effect of non‐erodible roughness elements on sediment transport show that the flux ratio q/qs, shear velocity U*, and roughness density λ are co‐dependent variables. Initially, the sediment flux is enhanced by kinetic energy retention in relatively elastic collisions that occur at the roughness element surfaces, but at the same time, the rising surface coverage of the immobile elements reduces the probability of grain ejection. A zone of strong shearing stress develops within 0·03 to 0·04 m of the rough bed because of a relative straightening of velocity profiles which are normally convex with saltation drag. This positive influence on fluid entrainment is opposed by declining shear stress partitioned to the sand bed. Similarly, because the free stream velocity Uf is fixed while U* increases, velocity at height z and particle momentum gain from the airstream decline, leading eventually to lower numbers of particles ejected on average at each impact. When the ratio of the element basal area to frontal area σ is approximately equal to 3·5, secondary flow effects appear to become significant, so that the dimensionless aerodynamic roughness parameter Z0/h and shear stress on the exposed sand bed Ts decrease. It is at this point that grain supply to the airstream and saltation drag appear to be significantly reduced, thereby intensifying the reduction in U*. The zone of strong fluid shear near the bed dissipates.
Hydrological model of peat‐mound form with vertically varying hydraulic conductivity
Authors: Armstrong Adrian C.
Published: February 2007

The form of raised peat mires can be considered to reflect the form of the saturated water mound. Ingram (1982) calculates this form from hydraulic considerations, but assumes a uniform hydraulic conductivity throughout the profile. Here, the form of the mire is calculated for non‐uniform, depth‐dependent hydraulic conductivity of the peat deposit. Although requiring more computational effort, the alternative model may offer a more appropriate description of the structure of the peat mire.
Lichens: Lichenometric dating of diachronous surfaces
Authors: McCarroll Danny
Published: February 2007

This paper describes software to accompany McCarroll, D. 1993. ‘Modelling late‐Holocene snow‐avalanche activity: incorporating a new approach to lichenometry’, Earth Surface Processes and Landforms 18, 527–539; and McCarroll, D., Matthews, J. A. and Shakesby, R. A. 1995. ‘Late‐Holocene snow‐avalanche activity in southern Norway: interpreting lichen‐size‐frequency distributions using an alternative to simulation modelling’, Earth Surface Processes and Landforms 20, 465–471.
Orthogonality of modal bases in hp finite element models
Authors: Prabhakar V. , Reddy J. N.
Published: February 2007

In this paper, we exploit orthogonality of modal bases (SIAM J. Sci. Comput. 1999; 20:1671–1695) used in hp finite element models. We calculate entries of coefficient matrix analytically without using any numerical integration, which can be computationally very expensive. We use properties of Jacobi polynomials and recast the entries of the coefficient matrix so that they can be evaluated analytically. We implement this in the context of the least‐squares finite element model although this procedure can be used in other finite element formulations. In this paper, we only develop analytical expressions for rectangular elements. Spectral convergence of the L2 least‐squares functional is verified using exact solution of Kovasznay flow. Numerical results for transient flow over a backward‐facing step are also presented. We also solve steady flow past a circular cylinder and show the reduction in computational cost using expressions developed herein. Copyright © 2007 John Wiley & Sons, Ltd.
A stabilized finite element method for shape optimization in low Reynolds number flows
Authors: Srinath D. N. , Mittal S.
Published: February 2007

A gradient‐based optimization procedure based on a continuous adjoint approach is formulated and implemented for steady low Reynolds number flows. A stabilized finite element formulation is proposed to solve the adjoint equations. The accuracy of the gradients from the adjoint approach is verified against the ones computed from a simple finite difference procedure. The validation of the formulation and its implementation is carried out via flow past an elliptical bump whose eccentricity is used as a design parameter. Shape design studies for the elliptical bump are then carried on with a more complex 4th order Bézier parametrization of the bump. Results for, both, optimal design and inverse problems are presented. Using different initial guesses, multiple optimal shapes are obtained. A multi‐objective function with additional constraints on the volume and the drag coefficient of the bump is utilized. It is seen that as more constraints are added to the objective function the design space is constrained and the multiple optimal shapes become progressively similar to each other. The study demonstrates the usefulness of this tool in obtaining multiple engineering solutions to a given design problem and also providing a framework to impose multiple constraints simultaneously. Copyright © 2007 John Wiley & Sons, Ltd.
A partially linear tree‐based regression model for assessing complex joint gene–gene and gene–environment effects
Authors: Chen Jinbo , Yu Kai , Hsing Ann , Therneau Terry M.
Published: February 2007

The success of genetic dissection of complex diseases may greatly benefit from judicious exploration of joint gene effects, which, in turn, critically depends on the power of statistical tools. Standard regression models are convenient for assessing main effects and low‐order gene–gene interactions but not for exploring complex higher‐order interactions. Tree‐based methodology is an attractive alternative for disentangling possible interactions, but it has difficulty in modeling additive main effects. This work proposes a new class of semiparametric regression models, termed partially linear tree‐based regression (PLTR) models, which exhibit the advantages of both generalized linear regression and tree models. A PLTR model quantifies joint effects of genes and other risk factors by a combination of linear main effects and a non‐parametric tree ‐structure. We propose an iterative algorithm to fit the PLTR model, and a unified resampling approach for identifying and testing the significance of the optimal “pruned” tree nested within the tree resultant from the fitting algorithm. Simulation studies showed that the resampling procedure maintained the correct type I error rate. We applied the PLTR model to assess the association between biliary stone risk and 53 single nucleotide polymorphisms (SNPs) in the inflammation pathway in a population‐based case‐control study. The analysis yielded an interesting parsimonious summary of the joint effect of all SNPs. The proposed model is also useful for exploring gene–environment interactions and has broad implications for applying the tree methodology to genetic epidemiology research. Genet. Epidemiol. © 2007 Wiley‐Liss, Inc.
A spatial probit model for fine‐scale mapping of disease genes
Authors: De Iorio Maria , Verzilli Claudio J.
Published: February 2007

We present a novel statistical method for linkage disequilibrium (LD) mapping of disease susceptibility loci in case‐control studies. Such studies exploit the statistical correlation or LD that exist between variants physically close along the genome to identify those that correlate with disease status and might thus be close to a causative mutation, generally assumed unobserved. LD structure, however, varies markedly over short distances because of variation in local recombination rates, mutation and genetic drift among other factors. We propose a Bayesian multivariate probit model that flexibly accounts for the local spatial correlation between markers. In a case‐control setting, we use a retrospective model that properly reflects the sampling scheme and identify regions where single‐ or multi‐locus marker frequencies differ across cases and controls. We formally quantify these differences using information‐theoretic distance measures while the fully Bayesian approach naturally accommodates unphased or missing genotype data. We demonstrate our approach on simulated data and on real data from the CYP2D6 region that has a confirmed role in drug metabolism. Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
One degree of freedom for dominance in indirect association studies
Authors: Chapman Juliet , Clayton David
Published: February 2007

Usual tests of association using tag single nucleotide polymorphisms (SNPs) assume that the alleles of the causal locus act additively and that these alleles are then predicted indirectly via a set of tag SNPs. In the presence of strong dominance effects this model is not correct and an extra term needs to be included, which uses the tag SNPs to predict the heterozygosity of the causal locus. Assuming this scenario of a strong dominance effect, we present an appropriate test statistic and investigate how much power, if any, we gain by adding this single degree of freedom for dominance.Genet. Epidemiol. 2007. © 2007 Wiley‐Liss, Inc.
New quaternary sections in liverpool
Authors: Cummins W. A.
Published: February 2007

Sections temporarily exposed in pits near Chatham Street are described. They reveal a late Glacial and Postglacial peat succession resting on boulder clay and overlying the Trias.
Aspects of the evolution of the drainage pattern of north‐east wales the evidence of upper erosion surfaces
Authors: Wilkinson H. R. , Gregory S.
Published: February 2007

The upper erosion surfaces of North‐east Wales are plotted and the evolution of the drainage system is traced. A warped and wasted envelope surface of Eocene age is recognized. There is evidence of a late Miocene peneplain at an elevation ranging from 2,200 to 1,800 feet. Into this have been cut numerous valley levels of Pliocene age from which the initial drainage of the Proto‐Dee can be reconstructed and its subsequent break‐up traced.
Notes on the faults of the bala district
Authors: Bassett D. A.
Published: February 2007

In a recent re‐survey of the Bala District the following sets of minor faults have been recognised: two sets of pre‐cleavage, strike‐slip faults which are apparently related to a number of small shear zones and which have no known equivalents in adjoining areas; a complementary system of post‐cleavage, strike‐slip faults which are correlated with similar faults in other parts of North Wales; a set of post‐cleavage, dip‐slip faults probably younger than the complementary ones; and a set of oblique‐slip faults parallel to the main Bala Fault and presumably of the same age.
Hillhouse coastal deposits in South Lancashire
Authors: Gresswell R. Kay
Published: February 2007

Recent borings have provided considerable additional information in connection with the post‐glacial evolution of south‐west Lancashire. The position of the Hillhouse coastline in the area between Hundred End and Holmeswood (previously surmised) has now been determined, and the estuary of the extended river Yarrow confirmed. The boundary between Shirdley Hill Sand and Down‐holland Silt beach deposits is more exactly known than heretofore, and the positions of overlap of these deposits are studied. The overlying peat is divided into different types in accordance with the physical conditions prevailing during the period of its formation, and the distribution of forestal remains is mapped. Intervening river Alt alluvium is found in the district east of Formby.
Recent advances in micropalæontology
Authors: Cummings Robert H.
Published: February 2007

Current opinions as to the status of micropalæontology are reviewed against its historical development in an attempt to form a realistic concept, whilst significant developments in the palæontology of the various biological groups which lie within the scope of this technological activity, are summarised throughout the post‐war period.
The “Geological Population” as a framework for analysing numerical data in geology
Authors: Krumbein W. C.
Published: February 2007

The amount of numerical data in geology has increased markedly during the past several decades. The numbers arise from field and laboratory measurements on rocks and fossils, as well as from controlled laboratory experimentation on geological processes. Much of the numerical data represents sample observations on larger classes of objects or events about which inferences and predictions are made from the observational data. These larger classes constitute geological populations. In this framework of population and sample, modern probability and statistical methods provide the essential means for expressing generalizations and predictions at specified levels of reliability.
Review of some contributions of experimental studies to petrology
Authors: Mackenzie W. S.
Published: February 2007

A brief review of experimental studies on the micas and the feldspars is followed by a discussion of some applications of phase equilibrium studies in the system NaAlSi3O8KAlSi3O8SiO2H2O to the problem of the origin of granites.
Palæomagnetism
Authors: Clegg J. A.
Published: February 2007

The results of numerous palæomagnetic measurements made on rocks during the past decade have been interpreted according to various schemes based upon either or both of the assumptions of polar wandering and the relative movements of continents. Recently, however, certain criticisms have been directed against this approach and a new analysis has been made to reassess the available information, relying on as few preconceptions as possible about the eventual explanation of the data. It can be demonstrated that for older rocks there is a well defined deviation of the measured remanent magnetic vectors from the present geomagnetic field, which increases progressively with geological age. For the four continents in which the results are best attested this deviation shows a systematic trend, and some genuine phenomenon is established. A combination of polar wandering together with continental drift provides an explanation of the results to date. On the other hand, on the present evidence, the possibility cannot be ignored that the observed effects may be due to strong multipolar components in the ancient magnetic field of the earth: alternatively it is conceivable although improbable that they can be explained by some widespread geological activity such as tectonic stresses of continental extent. The most plausible conclusion appears to be that continental drift has taken place, and on this tentative assumption the magnitudes of the land movements can be estimated from the data now available.
Sequences in Hominoid evolution
Authors: Weiner J. S.
Published: February 2007

In the generally accepted mammalian classification, the higher Primates including Man are classified as follows:—

Suborder ANTHROPOIDEA

Superfamily CEBOIDEA

Superfamily CERCOPITHECOIDEA

Superfamily HOMINOIDEA

Family Pongidae (Genera Hylobates, Pongo, Pan, Gorilla

Family Hominidae (Genera

Extinct genera.

Australopithecus,

Pithecanthropus, Homo.

This is of course primarily a taxonomic scheme. How far is it also an evolutionary scheme and what are the probable phyletic relationships, particularly within the Hominoidea? There are two questions of particular importance: (a) What is the relationship of pongid to hominid, is it one of common ancestry? (b) If so, what is the nature of this common ancestral stage?

We can answer these questions quite conveniently by looking in turn first at the hominid evolutionary sequence and then at the pongid sequence.
The case against a lower palaeozoic geosyncline in Wales
Authors: Boswell P. G. H.
Published: February 2007

The author contends that we are in danger of spoiling further a term which has been, in its time, of great service in geology, if we describe as geosynclinal the Lower Palaeozoic rocks in Wales.

Their facies and distribution yield no evidence that they were deposited in an elongated trough. At the present day they occupy an almost equidimensional area which is made up of a series of basins of deposition modified by tectonics of the platform type. The “mountains” of Wales (ca. 3000 ft.) are irregularly‐distributed monadnocks on a dissected plateau, and owe their elevation to resistant lavas, fragmental volcanic rocks and basic intrusions. There is no mountain chain of either Caledonian or later age. The rocks are predominantly conglomerates, sandstones, siltstones, mudstones and shales (slates): limestones are thin, scarce and scattered. Ultrabasic intrusives are very rare; and granites insignificant and of doubtful age. No metamorphic rocks (apart from slates) are known younger than Pre‐Cambrian. Shelf and basin facies have been identified at a few horizons and in certain areas, but much work remains to be done in this field. The statement that they are symmetrically distributed, and hence the styling of the geosyncline as the prototype of a new variety, the symmetrical geosyncline, are not warranted.

No deep borings from which information about thicknesses could be obtained have been sunk. Estimates from field evidence show that no great thickness of sediments occurs at any particular locality. Breaks in the succession are numerous and widespread. The method of summating “restored” maximum thicknesses of formations and citing the aggregate is of doubtful value in view of the well‐known tendency for the compensatory thickening and thinning of formations as they are traced laterally. Local occurrences of high dips, steep folding and up‐thrusting are not regarded as evidence of orogenesis. It is therefore concluded that the Welsh region consists of a series of gently‐folded basins, in which the facies, thicknesses, trends and structures vary, situated on the south of the Scoto‐Scandinavian geosyncline.
Recrystallization in microfossiliferous limestones
Authors: Banner F. T. , Wood G. V.
Published: February 2007

The microfauna and microflora of the Lower Miocene limestones of the Darai Complex of Papua have been found to recrystallize in a constant order related to the biological affinities of the fossil genera. This recrystallization is independent of the sparry or micritic nature of the interstitial material.

Dolomitisation also destroys the fossil skeletons in a comparable order except that the coralline algae appear to be relatively more resistant to replacement by dolomite.

Only when the skeletons of the most resistant fossil groups have been recrystallized can the occurrence of interstitial sparry calcite be suspected to have originated from recrystallization of an original micritic matrix. Obliteration of fossil remains by recrystallization presents an additional hazard in the interpretation of biofacies in limestones of this type.
The geology and geomorphology of Los Ajaches, Lanzarote
Authors: Driscoll E. M. , Tinkler K. J. , Hendry G. L.
Published: February 2007

The Los Ajaches area, Lanzarote, Canary Islands consists of a Tertiary volcanic series overlain by Quaternary lava areas. A trachyte outcrop, the only acid volcanic rock on the island, was relocated and mapped during a survey in 1963. Erosion stages at heights of 460, 400, 300, 190 and 100 m, occur in the eastern highlands. The coastal plain has a remarkable raised beach succession at heights of 55,35,25,15,6. and 1 m. This chronological sequence enables a new dating of the Quaternary vulcanism. Certain observations are also made on landform development and correlation with other areas.
Radiospectroscopy of minerals
Authors: Marfunin A. S.
Published: February 2007

A review of data on electron paramagnetic resonance (electron spin resonance), nuclear magnetic resonance and nuclear quadrupole resonance in minerals.
The flandrian sequence of north Wirral (N. W. England)
Authors: Kenna R. J. B.
Published: February 2007

The correlation of borehole logs, together with evidence from temporary exposures, shows the relationship between glacial deposits and the overlying Flandrian strata. The courses of buried channels in‐filled with Flandrian strata have been plotted. Radiocarbon assays and pollen and diatom analyses have mainly been confined to samples taken from near the main lithological boundaries, but some radiocarbon assays have been undertaken on in situ tree stumps and on bone. New thick buried channel sequences are described, and an outline chronology from c. 6420 years BP is proposed for the Flandrian coastal sequence of the North Wirral. The data can be applied to the interpretation of sea‐level change and coastal archaeology.
Depositional history of a muddy sabkha complex in the Sokoto Basin of Nigeria, West Africa
Authors: Alam Mahmood
Published: February 2007

Sedimentological and stratigraphical analysis of the Sokoto Basin has resulted in recognition of four lithostratigraphic units. They are Unit A—siltstone and fine‐grained sandstone; Unit B—shale and marl; Unit C—limestone and calcareous shale; and Unit D—red sandstone. Unit A represents a wadi plain system composed of desert‐alluvial beds; Unit B, a mud‐rich sabkha system; and Unit C, an inner‐shelf carbonate system. A marine transgression from the northwest began in the Maastrichtian and reached its peak in the Palaeocene. After regression in the late Palaeocene, the area was subjected to erosion, followed by fluvial sedimentation of Unit D. Wadi plain beds and mud‐rich sabkha facies of Sokoto Basin are similar to alluvial and coastal mud‐flat deposits in the northwestern Gulf of California and ephemeral stream and tidal‐flat sediments in Gladstone Embayment, Australia.
Depositional environments of the Triassic system in central Saudi Arabia
Authors: Sharief Farooq A.
Published: February 2007

Facies analysis of Triassic rocks in central Saudi Arabia indicates a wide expanse of interfingering siliciclastic and carbonate rocks with some evaporites. Eight distinctive sedimentary facies have been recognized. The distribution of these facies show a systematic gradual change in their presumed depositional environments, laterally as well as vertically.

The Lower Triassic Sudair facies represents a widespread regressive condition where the Upper Permian marine conditions gave way to the Lower Triassic with predominantly fine clastic deposits representing a restricted shallow marine shelf. This fine‐grained clastic facies consists mainly of unfossiliferous, laminated or massive, varicoloured shale with some silty shale, siltstone and very fine‐to fine‐grained sandstone. The facies is highly calcareous and gypsiferous in the northern area.

A belt of Middle Triassic rocks of mostly non‐marine sandstone with some shale is present in the southern area passing into mixed siliciclastic‐carbonate facies of continental aspect with some intermittent emergence and nearshore conditions in the central area. This facies grades in the northern area into carbonate‐evaporite facies of restricted to more open marine shelf conditions.

Thick siliciclastic deposits characterize the Upper Triassic Minjur facies, where a uniform repeated fining‐upward sequence of mainly sandstone and some shale developed in a non‐marine environment with some intermittent emergence in the northern area.
The fenestrate bryozoan Septopora carbonaria (Etheridge Jun. 1873a) from the Carboniferous of Great Britain
Authors: Bancroft Adrian J.
Published: February 2007

The Carboniferous fenestrate bryozoan Synocladia carbonaria Etheridge Jun. (1873a) is redescribed. Originally assigned to Synocladia and subsequently diagnosed as a variety of Synocladia biserialis Swallow by Etheridge Jun. (1873b), S. carbonaria is here considered to be a distinct species. Synocladia(?) scotica Young and Young (1878) is conspecific with S. carbonaria, as suggested by Graham (1975). Graham (1975) established the new genus Lanarkopora, naming S. carbonaria and S.(?) scotica in synonomy, with S. carbonaria, the senior synonym, being selected as the type species. Re‐examination of the type material of S. carbonaria and S.(?) scotica has shown that they are referable to the genus Septopora Meek, and Lanarkopora is herein designated a junior synonym of Septopora.
Mohr circles for strain, simplified
Authors: Treagus Susan H.
Published: February 2007

The Mohr circle is a well known representation of two‐dimensional strain. It is commonly used to illustrate strain algebra, or derive a strain ellipse from particular strain data. The established sign convention is positive (anticlockwise) shear strain on the upward ordinate, after Brace. However, in practice, confusion may easily arise from inconsistent conventions in standard text books.

A Mohr‐circle convention is proposed here which represents clockwise shear strain on the upward γ ordinate (i.e. upside‐down). It simplifies the Mohr circle by representing both single and double angles in their natural sense. Single angles may be traced from rock to Mohr circle directly which is not the case for the Brace circle. Deformed brachiopods and stretched belemnites are used to illustrate this simplified Mohr circle.

The pole to the Mohr circle is a useful addition which allows strain data to be represented in their true orientation. The pole method only works on the γ clockwise‐up Mohr circle.

The Mohr circle is useful to demonstrate simple‐shear geometry and algebra. Successive Mohr circles with poles may be used to map strain across a heterogeneous simple‐shear zone.
Lower delta plain interdistributary deposits — An example from the Westphalian of the Lancashire Coalfield, northwest England
Authors: Fielding C. R.
Published: February 2007

A large quarry at Billinge Beacon in Lancashire, northwest England, has provided an excellent exposure of part of the Lower Westphalian A (Upper Carboniferous) Coal Measures sequence which was deposited in a lower delta plain setting. The main horizon exposed, known as the Dyneley Knoll Flags, is interpreted as the proximal reaches of two crevasse‐initiated minor delta complexes, into the lower of which has been incised a sinuous minor distributary channel.

The channel, which was approximately 120 m wide, built a 160 m wide channel belt by limited lateral accretion with time; vertical accretion appears to have been the dominant infilling mechanism. This produced a stacked series of epsilon cross‐strata, made up of rhythmically interbedded sandstone and silty claystone. The peculiar style of infilling of the channel is ascribed to deep incision of the channel into minor delta deposits, and possibly the influence of a seasonal climate.
Mud‐Dominated Storm Deposits From A Lower Carboniferous Ramp
Authors: Simpson John
Published: February 2007

The Lower Carboniferous Pen‐y‐Holt Limestone of South Wales comprises about 300m of interbedded wackestones and lime mudstones.

The wackestones are interpreted as relatively distal ‘turbidite‐like’ storm‐generated deposits and the lime mudstones as background deposits. The storms had a periodicity of about one per 9000–18000 years. They were deposited in a deep‐ramp carbonate environment at least 20–30km from the ancient shoreline and in about 100m water depth, and therefore probably below wave base. The ramp is estimated to have had an average slope angle of 0·5–1·0 degree.

Unlike other previously described carbonate or siliciclastic storm deposits, the Pen‐y‐Holt Limestone storm deposits are totaly mud‐supported and generally lack internal sedimentary structures, yet contain large bioclasts such as crinoid ossicles. The simultaneous deposition of lime mud and crinoid ossicles from a storm‐generated turbidity current is hydrodynamically untenable. Thin‐section evidence however, suggests that the lime mud may have originally been deposited as peloids which have since been largely destroyed during diagenesis. Peloids and crinoid ossicles, it is suggested, could have been transported by the same current.
Punctuated equilibria between rival concepts of granite genesis in the late 18th, 19th, and early 20th centuries
Authors: Tex E. Den
Published: February 2007

A concise review of concepts dealing with the genesis of granite in the late 18th, 19th, and early 20th centuries is given. Arguments are provided for the repeated recurrence of genetic concepts in an altered form which were separated by periods in which a rival concept was dominant. This type of development may be likened to Eldredge and Gould's (1972) punctuations of biological equilibrium. On the other hand phases of development may be recognized in which rival concepts tend to converge towards a unified content, thus conforming to the ‘tree of knowledge’ hypothesis of Popper (1972). In this context the two metaphors do not appear to be mutually exclusive.
The Coastal Batholith of Peru: The product of rapid recycling of ‘new’ crust formed within rifted continental margin
Authors: Atherton Michael P.
Published: February 2007

The Coastal Batholith of Peru was intruded into ‘new’ Albian crust of the marginal basin, which formed on major continental rifting. The ‘magic switch’ from basalt dominated volcanogenic basinal filling to tonalitic Cordilleran type magmatism is part of a magmatic scenario in which the ‘new crust’ melts on major decompression along megafractures defining the batholith structural lineament. Quantitative modelling of the Icelandic rifting system, which is similar in many respects, indicates basalt melting is likely to produce large amounts of tonalitic to granitic magma. The whole sequence of events leading to batholith formation i.e. extension → subsidence with basin formation → spreading → dyking → splitting → basin filling → gabbro intrusion → compression with partial inversion → cratonization → fracturing and batholith intrusion along the axis of the basin relates to a major cycle of crustal growth.
Magmatic mafic enclaves in granitoids of northern Sierra de Paimán, Argentina
Authors: Lorenc Marek W.
Published: February 2007

Field relationships of three types of granitoids with basic rocks, with different mineralogy and structure are described. Zones of mixed‐type character exist between the several types of granitoids as well as between the granitoids and basic rocks. The distribution of magmatic mafic enclaves (MME) in the granitoids varies widely but the largest concentrations occur in the mixed zones between the granites and basic bodies. The origin of such enclaves is closely related to processes of hybridization and mingling of acid and basic magmas. One of the possible variants of such interaction is the fragmentation and partial hybridization of synplutonic basic dykes.
Intrusion sequences within ore‐bearing granitoid plutons
Authors: Štemprok Miroslav
Published: February 2007

A new database of some 200 granitic bodies throughout the world associated with Sn, W and Mo deposits is analysed with respect to size and petrological characteristics. Most Sn, W and Mo deposits relate to small stocks not exceeding 25 km2. Biotite granites are the most common type of ore‐bearing plutons, while two mica granites are subordinate. There seems to be an upward grading in grain size such that the later, higher members of a suite are the finest grained. Ore‐bearing processes relate to deep evolving differentiation of specialized magmas modified by mantle fluids.
Textural variation and tin mineralization in granites from the main range province of the Southeast Asian Tin Belt
Authors: Pitfield P. E. J. , Teoh L. H. , Cobbing E. J.
Published: February 2007

Textural evolution from coarse K‐feldspar megacrystic granite, through heterogeneous granite porphyry to microgranite corresponds to a sequence of geochemical evolution. It was probably triggered by a sudden loss of pressure, resulting in quenching, fluidization, and disruptive emplacement of the residual melt into the partially or wholly crystalline host granite. It was accompanied by alkali metasomatism, volatile‐fluxing, and hydrothermal alteration, culminating in the formation of greisen bordered vein swarms and massive greisens mineralized with tin and other metals.
Rhaxellid sponge microscleres from the Portlandian of Dorset, UK
Authors: Haslett Simon K.
Published: February 2007

Three previously described species and two new species of rhaxellid microscleres, Rhaxella winspitensis sp. nov. and R. elongata sp. nov., are described from cherts collected from the Cherty Series of the Portlandian of Dorset. The classification of Rhaxella is reviewed, retaining the genus within the family Geodiidae Gray. The results of this study suggest that three time‐dependent rhaxellid assemblages can be recognized which, despite being restricted to certain depositional environments, may have biostratigraphic applications. A Portlandian assemblage described here is species‐rich in comparison with known Oxfordian‐Kimmeridgian assemblages. Bajocian‐Callovian assemblages contain only R. sorbyana. The increased faunal diversity with time is speculatively described by an evolving Rhaxella lineage.
Graptolite dating of Ordovician vulcanicity in the Arenig area, North Wales
Authors: Zalasiewicz Jan
Published: February 2007

Graptolite assemblages of multidens Biozone age have been recovered from mudstones immediately above and below the Llyn Conwy Formation, the local representative of the regionally extensive acid tuffs that mark the end of vulcanicity in the south and east of the Harlech Dome. They include several taxa new to Wales and are markedly different to contemporaneous faunas from the Welsh Borders. One new species, Pseudoclimacograptus isknos, is described.
The West Spitsbergen Fold Belt: The result of Late Cretaceous‐Palaeocene Greenland‐Svalbard convergence?
Authors: Lyberis Nikos , Manby Geoff
Published: February 2007

The West Spitsbergen Fold Belt, together with the Eurekan structures of northern Greenland and Ellesmere Island, are suggested to be the result of Late Cretaceous‐Palaeocene intracontinental compressional tectonics. The Late Palaeozoic –Mesozoic rocks of western Spitsbergen are characterized by near‐foreland deformation with ramp‐flat, top‐to‐the east thrust trajectories, whereas structurally higher nappes involving Caledonian complexes are typified by more listric thrusts and mylonite zones. A minimum of 40 km of shortening is estimated for the northern part of the West Spitsbergen Fold Belt. The axial trends in the West Spitsbergen and the North Greenland Eurekan fold belts parallel the principal fault zones which accommodated the separation of Greenland and Svalbard after Chron 25/24. In northern Greenland, north directed Eurekan thrusts associated with mylonites and cleavage formation represent at least 10 km of shortening. Between 50 and 100 km of shortening is estimated for the markedly arcuate Eurekan Fold Belt of Ellesmere Island, but the principal tectonic transport is eastwards. Kinematic reconstructions suggest that Svalbard was linked to North America before the opening of the Eurasian Basin and Norwegian — Greenland Sea. In the Late Cretaceous — Palaeocene interval, the relative motion between Greenland and North America was convergent across the Greenland — Svalbard margin, giving rise to the West Spitsbergen Fold Belt and the Eurekan structures of North Greenland.
Late Cambrian acritarchs and their age constraints on an Ediacaran‐type fauna from the Booley Bay Formation, Co. Wexford, Eire
Authors: Moczydłowska M. , Crimes T. P.
Published: February 2007

Acritarch assemblages have been recovered from the Booley Bay Formation in Duncannon area, Co. Wexford, southeastern Eire. Twelve morpho‐species are described, including the new species Polygonium martinae n. sp., and two informal species Comasphaeridiu n. sp. A and Heliosphaeridium n. sp. B. A new combination, Retisphaeridium brayense (Gardiner and Vanguestaine 1971) comb. nov., is proposed. The relative ages provided by discrete microfossil assemblages and their sequence within the lithological succession suggest that the entire investigated portion of the Booley Bay Formation may be referred to the Upper Cambrian. This biostratigraphic evaluation constrains the age of the recently discovered Ediacaran‐type biota described in Crimes et al. (1995).
New litho‐ and biostratigraphic evidence for a Mid‐Ordovician hiatus in southern central Snowdonia, North Wales
Authors: Smith M. , Rushton A. W. A. , Howells M. F.
Published: February 2007

Detailed mapping and biostratigraphic data provide new evidence of a major break below the base of the Caradoc succession along the northern margin of the Harlech Dome in south central Snowdonia. Within this outcrop the sequence is locally complicated by subsequent tectonic and volcanic events, but undisturbed sections indicate a break of at least 10 Ma between upper Arenig and middle, or upper, Llandeilo strata. The break is greatest between two N‐S trending fracture systems, the Cwm Pennant Fault Zone in the west and Trawsfynydd Fault Zone in the east, which both have a persistent history of reactivation. Between these two fractures neither Llanvirn nor lower Llandeilo strata occur. This contrasts with the thick, and perhaps complete, sequence preserved in the Cadair Idris district on the southern margin of the dome and suggests that, during Llanvirn times, the Harlech Dome formed a major uplifted and tilted block, with a tectonically active northern margin. Subsequently, uplift and tectonism either ceased before, or was overwhelmed by, the ensuing sea‐level rise associated with the gracilis (early Caradoc) transgression. The preservation of ooidal ironstones around the dome suggests that it may have became a large shoal or platformal area at this time. Renewed uplift and erosion along the northern margin of the Harlech Dome during the early Caradoc (gracilis to multidens) led to large‐scale disruption of the stratigraphic succession by mass gravity flow and slumping, overprinting and locally accentuating the effects of the earlier hiatus.
Geomorphological evidence from the Lleyn Peninsula constraining models of the magnitude and rate of isostatic rebound during deglaciation of the Irish Sea Basin
Authors: McCarroll Danny
Published: February 2007

A stepped series of sand and gravel terraces on the Lleyn peninsula of North Wales is used to test the magnitude and rate of isostatic depression required by the recently proposed glacimarine model of deglaciation of the Irish Sea Basin. A relative sea‐level fall of 70 m is required while the ice remained pinned at the north Lleyn coast. Even taking the maximum known rate of isostatic uplift, the margin would have to remain stationary for 1400 years. It seems more reasonable to interpret the Lleyn terraces, and similar features around the Irish Sea Basin, as glacifluvial and glacilacustrine.
Rate and time controls on metamorphic processes
Authors: Vance Derek
Published: February 2007

Among the most important controls on metamorphism is the rate at which tectonic processes operate. The purpose of this paper is to review briefly a couple of recent advances in the field of geochronology and metamorphic petrology which have helped to elucidate these processes. Re‐equilibration at high temperatures often eradicates information that might have been recorded by rocks during their prograde and high‐temperature evolution. One of the major advances of recent years has been the recognition of the utility of garnet in preserving information on prograde thermal histories. A case study involving garnet‐bearing rocks from New England is described: In this area, garnet grew during the latter stages of prograde metamorphism and records heating through 100°C during decompression of around 2.5 kbar. Combined with chronological data on garnet cores and rims, which yield a time interval for garnet growth of 10 Ma, these data yield a heating rate of ∼ 10°C Ma‐1 and an exhumation rate of about 1 mm a‐1. Comparison with simple thermal models suggests that the heating rate is too high to be accounted for by simple conductive relaxation. At temperatures appropriate to crustal melting, even garnet re‐equilibrates such that any chronological information is lost. At these grades one approach is to use the extent of diffusional modification of growth zonation profiles to provide time constraints on the process operating. Mn distributions in garnets from the Zanskar Himalaya are used to limit the time available for high‐grade metamorphism. The times obtained of 1–2 Ma are extremely short and require cooling by emplacement of cold upper crustal rocks adiacent to migmatitic rocks.
Ultrametamorphism in Precambrian granulite terranes: Evidence from Mg‐AI granulites and calc‐silicate granulites of the Eastern Ghats, India
Authors: Dasgupta Somnath , Sengupta Pulak
Published: February 2007

High Mg‐Al granulites and calc‐silicate granulites provide evidence for ultra‐high temperatures of metamorphism (ca. 1000°C) at moderate pressures (9–10 kbar) in the Eastern Ghats Belt, India. Lack of proper geochronological data prevents the dating of this extreme metamorphism. High Mg‐Al granulites contain different subsets of mineral assemblages involving spinel, quartz, sapphirine, cordierite, orthopyroxene, garnet and sillimanite coexisting with either rutile‐ilmenite or titanohaematite‐ferrianilmenite. These high Mg‐AI rocks are poor in Zn and Cr, as reflected primarily in the composition of spinel. Evidence of ultra‐high temperature metamorphism comes from (i) textural interpretation of the former coexistence of spinel‐cordierite‐quartz and sapphirine‐quartz and stabilization of the assemblages orthopyroxene‐sillimanite‐cordierite and spinel‐quartz‐sapphirine‐garnet and (ii) the high Al2O3 content of orthopyroxene coexisting with garnet and/or cordierite. Consideration of the sequence of deduced mineral reactions in petrogenetic grids in the system FMAS attests to an anticlockwise P‐T path of evolution for the granulites. In calc‐silicate granulites stabilization of nearly pure meionite and of the wollastonite‐plagioclase‐andradite‐rich garnet, wollastonite‐scapolite‐grandite garnet‐calcite association corroborate high temperatures of metamorphism. Conventional mineralogical geothermobarometry in all the rocks record lower temperatures (maximum 950°C) at 9–10 kbar pressures, attributed to resetting of the mineral compositions during cooling. Following peak metamorphism, the rocks firstly experienced near‐isobaric cooling followed by near‐isothermal decompression. On the basis of the available evidence it appears that non‐extensional lithospheric thinning and/or heat input from basic/enderbitic magma are the causes of such ultra‐high temperature metamorphism on an anticlockwise path in the Eastern Ghats Belt.
Pressure‐temperature‐time paths and the relationship between collision, deformation and metamorphism in the north‐west Himalaya
Authors: Treloar Peter J.
Published: February 2007

Tertiary collision in the NW Himalaya was between the Indian plate and the Kohistan island arc, the leading edge of the Indian plate being subducted beneath the arc along the Main Mantle Thrust (MMT). Porphyroblast‐matrix relationships show that metamorphism within Indian plate cover sediments exposed on the footwall of the MMT was synchronous with ductile shearing which marks the main deformation phase. The P‐T‐t paths, derived from inclusion assemblages and forward modelling of garnet zonation patterns, show that this metamorphism was along a path of increasing pressure. These data are consistent with Indian plate metamorphism occurring during active subduction beneath the Kohistan island arc. Geochronological data date the metamorphic peak as pre‐50 Ma. As initial collision cannot have pre‐dated 65 Ma, there was thus insufficient time for the long time‐scales of metamorphism generally predicted by conductive models of post‐thickening thermal relaxation. The cover sediments show a metamorphic inversion, argued previously as the result entirely of post‐metamorphic thrusting and imbrication. By contrast, basement gneisses exposed beneath the MMT have largely been unaffected by Tertiary metamorphism. The relationship between ductile shearing and metamorphism on the footwall of the MMT during active subduction, and the concentration of the highest metamorphic grades in the stratigraphically youngest rocks, suggests that early Tertiary metamorphism was controlled by dissipative shear heating distributed across the uppermost cover sediments of the subducting Indian plate. This generated a primary, inverted metamorphic sequence shortly after collision, an inversion reinforced by subsequent thrusting associated with accretion of the metamorphic pile onto the base of the over‐riding arc. This conclusion stresses the importance of dissipative shear heating in controlling metamorphism within thrust systems and provides a mechanism by which areas of apparently large regional extent can undergo regional metamorphism over short time‐scales, but in the absence of any magmatic heating.