bluuebunny/crossref_metadata_2025_split huggingface dataset:
Floodplain palaeosols of the Cenomanian Dunvegan Formation, Alberta and British Columbia, Canada: Micromorphology, pedogenic processes and palaeoenvironmental implications
Authors: McCarthy Paul J. , Plint A. Guy 
Published: April 2008

Abstract
Floodplains represent both sedimentological and pedological entities that record a unique blend of potential environmental indicators in the rock record. Because floodplains develop in aggradational environments with a high preservation potential, they preserve a detailed record of the local pedosedimentary history. Assemblages of micromorphological features present in floodplain palaeosols record, with a high degree of temporal and spatial resolution, specific pedological processes that operated under particular environmental conditions. Detailed micromorphological analyses of floodplain deposits, in conjunction with their regional distribution, are required for accurate palaeoenvironmental reconstruction of these environments.

Micromorphological features are described from floodplain palaeosols in the Upper Cretaceous (Cenomanian) Dunvegan Formation in northwestern Alberts and northeastern British Columbia, Canada. The palaeosols developed on low-lying and generally poorly drained floodplains during a time when the tectonic subsidence rate was very low. High-frequency fluctuations in base level were superimposed upon this tectonic signature, resulting in at least seven phases of valley cutting and the corresponding development of mature interfluve palaeosols. The major pedogenic processes operating were clay illuviation, redox processes, precipitation of soluble salts (primarily FeCO
3
) and pedoturbation. Palaeopedological features in the Dunvegan Formation are consistent with features developed in modern cool temperate soils with a non-seasonal precipitation distribution, such as Brunisols and Luvisols. The presence of embedded grain argillans, compound silt-clay coatings and rounded aggregates suggests at least the possibility of limited frost penetration in inland soils. Floodplains of the mid-Cretaceous Dunvegan Formation (palaeolatidude
c.
65°N) record evidence for cool temperate conditions that supports other palaeobotanical and sedimentological evidence for cool Cretaceous palaeoclimates at high latitudes.
Nature and distribution of heavy minerals in the Natal Group, South Africa
Authors: Liu K. W. 
Published: April 2008

Abstract
The author provides an example of heavy minerals concentrated in floodplain sediments. Nine types of heavy mineral have been found in fluvial sediments of the Ordovician Natal Group, South Africa, among which ilmenite is the most abundant. These heavy minerals are concentrated mainly in the Eshowe and Inanda Formations of the succession, and vary in content from 1.6 to 20.1% (average contents of 3.86% and 4.18%, respectively). This is in contrast to the shallow-marine Kranskloof and Dassenhoek Members, with average contents of only 1.14% and 1.27%, respectively. Host rocks of the heavy minerals are mainly arkose and lithic arkose, with subordinate subarkose. Grain-size analysis shows that heavy mineral rich beds are composed mostly of fine to medium size sand and are better sorted than the host rocks. The main depositional environments for the heavy minerals are branched or braided channels, rather than the main channel, as the moderate hydrodynamic regime is more favourable for the accumulation of fine to medium arenaceous heavy minerals. Palaeogeography and mineral assemblages confirm that the main provenance of the heavy minerals lay to the north of the depositional basin, namely, the Archaean Kaapvaal Craton, with the Natal Structural and Metamorphic Province as a supplementary source.
Euler deconvolution methods used to determine the depth to archaeological features
Authors: Murdie Ruth E. , Styles Peter , Upton Paula , Eardley Phil , Cassidy Nigel J. 
Published: April 2008

Abstract
Field techniques, instrumentation and data processing for geophysical location of archaeological remains are now at such a standard that clear maps of the subsurface detail are readily obtainable. Magnetic gradiometry and resistivity plots are widely used to locate diverse features such as walls, ditches and burial areas. However, information concerning the depth to these features is not often extracted from such plots and would be useful in planning any following excavation. Here we use Euler deconvolution methods, on a reasonably high-resolution magnetic gradiometer data set, to determine the depth to a buried Romano-British villa at the Wroxeter archaeological site. The interpretation of these depth estimates is compared to GPR sections taken over the same site.
Geochemistry of ballast granites from Brouage and La Rochelle, France: evidence for medieval to post-medieval trade with Falmouth, Cornwall, and Donegal, Ireland
Authors: Lazareth Claire E. , Mercier Jean-Claude C. 
Published: April 2008

Abstract

Determination of the geographical origin of exotic ballast boulders found in various archaeologically dated constructions of medieval and post-medieval age along European shores provides evidence for early commercial sea links. However, ballast often consists of common granites. Some are identified here by combining multiple geochemical tools which support a first-degree classification into two groups, muscovite-bearing (with or without biotite) or muscovite-free (with biotite as the only mica), each one showing a remarkably very narrow and distinct range in mineral compositions. This suggests a single locality for the origin of each type of granites. Indistinguishable muscovite-bearing facies are found in La Rochelle and Brouage, with one representative sample geologically dated at 274 ± 6 Ma. In agreement with the evidence from bulk-rock and phase chemistry which are similar to those of the Carnmenellis intrusion, Cornwall, this geological age strongly supports early commercial sea links with nearby Falmouth, at least from the end of the 14th to the middle of the 16th century. For the muscovite-free granites found in Brouage in a different site dated
c.
1650, similar investigations and a 393 ± 9 Ma geological age, strongly suggest ballast loading north of Ros Eoghain Point, Ireland, and direct trade with nearby Donegal.
Zinc isotope fractionation in liquid brass (Cu-Zn) alloy: potential environmental and archaeological applications
Authors: Budd Paul , Lythgoe Paul , McGill Rona A. R. , Pollard A. Mark , Scaife Brett 
Published: April 2008

Abstract

A preliminary study of zinc isotope fractionation in brass melting suggests that the process can be modelled by simple Rayleigh fractionation. Brass melting experiments at 1100°C followed by quadrupole ICP-MS isotope ratio measurements of the resulting alloys suggest that the model is appropriate and that a useful approximation of the fractionation factor (α) is 1.0064. The data indicate that the change in isotope ratio of the residual liquid alloy would be measurable for zinc losses by evaporation of more than about 30 wt.%. It is unlikely that measurements at the precision of the current study (∼0.55‰amu
−1
) would be sufficient to distinguish between the two principal historical brass-making processes, although more precise measurement using a multi-collector ICP-MS probably would be. The experimental data also suggest that zinc vapour evolving during the evaporation of the first few per cent of the metal will be significantly fractionated (∼1.5‰amu
−1
) with respect to the liquid. This might provide a basis to distinguish between environmental zinc from high-temperature industrial processes and that derived from natural and manufactured product sources.
Granitic melt viscosities
Authors: Dingwell Donald B. 
Published: April 2008

Abstract
The viscosities of granitic melts play a crucial role in controlling the kinetics and dynamics of magma transport including generation, segregation, ascent, differentiation and emplacement. No general theory of liquid viscosity has been successfully applied to date to the description of granitic melt viscosities. The approach in the earth sciences so far has been empirical and experiments designed to measure the viscosity of granitic melts have made considerable progress in improving our picture of the composition-, temperature- and pressure-dependence of granitic melt viscosities. This chapter summarizes the recent progress in parameterizing the viscosity of granitic melts with respect to the most important compositional variables such as alkali/aluminium ratio, silica content, water content, anorthite content. The pressure-dependence of granitic melt viscosities is very slight. The temperature-dependence, in contrast, is a very strong and non-linear function of the reciprocal absolute temperature (i.e. non-Arrhenian). Indirect determinations of the viscosity of granitic melts have also contributed substantial information on the composition-, pressure- and temperature-dependence of melt viscosity. These measurements are particularly useful where direct viscosity determinations are difficult or impossible to perform. The outlook for a more complete picture of granitic melt viscosities in the next years is excellent. The combination of several factors, including conceptual advances in the quantitative understanding of relaxation in silicate melts, experimental advances in the measurement of viscosity of silicate melts, and the identification in the experimental studies to date of the areas of investigation where the effort should be concentrated in the future, give reason to expect a more or less complete picture, fully adequate for the purposes of modelling the dynamics of granitic magmas, in the near future.
Geometry of granite emplacement in the upper crust: contributions of analogue modelling
Authors: Román-Berdiel Teresa 
Published: April 2008

Abstract
Granite emplacement in the brittle crust can be modelled by means of the injection of a Newtonian fluid (low-viscosity silicone putty) into sandpacks. This paper describes dynamically scaled analogue models of granite intrusions in the upper crust under different tectonic regimes. Experiments analyse three boundary conditions: (1) static conditions, with different rheological profiles (single sand-layer system, two-layer silicone-sand system, three-layer sand-silicone-sand system and five-layer sand-silicone-sand-silicone-sand system), (2) extensional regime, including gravitational sliding and divergent basal plate, with both mobile and fixed velocity discontinuities and (3) strike-slip regime, induced by two mobile basal plates. The results obtained indicate that: (1) a soft level between two competent units is necessary for laccolith formation—the critical thickness of the soft layer necessary for laccolith formation decreases with increasing depth, (2) when there are two soft layers in the brittle crust, laccolith emplacement occurs in the deeper soft level, even when this is thin and the overburden does reach its critical thickness, (3) in extensional regimes the geometry of intrusions is mainly controlled by normal faults and at the same time intrusions determine the location of faults within the cover and (4) in strike-slip zones intrusions are elongate and their long axis tends to track the principal stretching direction associated with the strike-slip regime. Some natural examples of granitic bodies were considered to test the applicability of experimental results.
A multidisciplinary approach combining geochemical, gravity and structural data: implications for pluton emplacement and zonation
Authors: Hecht L. , Vigneresse J. L. 
Published: April 2008

Abstract
Granitic pluton emplacement and zonation are controlled, among others, by regional deformation and the rate of magma supply. The latter has consequences for the disposition of successively emplaced, more chemically evolved, batches of magma. Our general interpretation is based on a multidisciplinary approach combining field observations, gravity data, internal structures and geochemical variations. Magma feeders are identified in the plutons as the deepest zones, inferred from gravity measurements, when they also correspond to vertical lineations. Correlation of the root zone location with compositional zoning indicate how the magma evolved during emplacement. Two case studies of Hercynian granite plutons illustrate the interpretations: the normally zoned Cabeza de Araya pluton (Spain), and the multiphase Fichtelgebirge pluton (Germany) which displays both normal and reverse zoning. It is proposed that reverse zoning reflects discontinuous magma injection due to a tectonic rate slower than the rate of magma supply. Conversely, normal zoning can occur when magma injection is continuous in time, with successive magma batches entering within not yet crystallized magma. The two case studies illustrate how the understanding of compositional zoning and emplacement of granitic plutons can be improved by multidisciplinary approaches combining classical and modern techniques.
Contrasts in morphogenesis and tectonic setting during contemporaneous emplacement of S- and I-type granitoids in the Eastern Lachlan Fold Belt, southeastern Australia
Authors: Trzebski R. , Lennox P. , Palmer D. 
Published: April 2008

Abstract
Integrative gravity and structural modelling of Ordovician-Silurian granitoids in the Eastern Lachlan Fold Belt (southeastern Australia) revealed contrasts in emplacement mode and deformation style between coeval S- and I-type granites. The NNE-SSW directed contraction during the Benambran event of the Lachlan Orogen caused dextral movement along two major strike-slip faults (Carcoar Fault/Copperhannia Thrust) and simultaneous formation of both transtensional pull-apart and transpressional shear zones. The geometry and deformation style of the plutons and country rock, their spatial relationship at depth to adjacent faults and the structural history of both the granites and country rocks suggest a genetic linkage between magma emplacement and synmagmatic deformation. Synchronously, the Carcoar Granodiorite was emplaced into a transtensional pull-apart structure and the Barry Granodiorite and Sunset Hills Granite intruded transpressional shear zones. The I-type Carcoar and Barry granites are square to tabular, wedge-shaped bodies exhibiting a weak deformation; whereas the S-type Sunset Hills Granite is an elongated, tabular to sheet-like pluton showing a moderate deformation degree. The contrasts in 3D shape, emplacement mode and deformation style between the I- and S-type granites are due to differences in nearfield stress regime, geometry of the emplacement sites, intrusion level with respect to thermal and rheological conditions, and in their response to deformation. This response is in part controlled by the proportion of resistant/non-resistant minerals in the granite and host rock. This study demonstrates that distinctive emplacement modes can operate simultaneously in different parts of a fault system under contrasting deformation conditions.
Origin of megacrysts in granitoids by textural coarsening: a crystal size distribution (CSD) study of microcline in the Cathedral Peak Granodiorite, Sierra Nevada, California
Authors: Higgins Michael D. 
Published: April 2008

Abstract
Microcline megacrysts in the Cathedral Peak Granodiorite and other parts of the Tuolumne Intrusive Suite were formed by textural coarsening (Ostwald Ripening) of earlier formed crystals. The early-formed crystals nucleated and grew in an environment of increasing undercooling, probably during the ascent of the magma. Emplacement of the magma into warm host rocks promoted textural coarsening. Crystals smaller than a certain size (the critical size) dissolved in the interstitial melt whilst large crystals grew. Microcline was most sensitive to this effect as the magma temperature was buffered close to its liquidus for a long period by the release of latent heat of crystallization. Positive feedback between textural coarsening and magma permeability channelled the flow of interstitial melt to produce a heterogeneous distribution of megacrysts. Megacryst growth was halted when cooling resumed at the end of the intrusive cycle. K-feldspar nucleation was then renewed and K-feldspar crystals grew to form part of the groundmass. It was the particular thermal history of this pluton that promoted textural coarsening—chemically similar plutons that lack megacrysts probably did not have the pause during cooling that was necessary for the development of this texture.
Granitic magma ascent and emplacement: neither diapirism nor neutral buoyancy
Authors: Vigneresse J. L. , Clemens J. D. 
Published: April 2008

Abstract
It is probable that granitic magma ascent does not result from the intrinsic properties of the magmas. Within the uppermost crust, neither the reduced viscosity nor the density contrast between magma and surroundings are themselves sufficient to induce either low-inertia flow (diapirism) or fracture-induced magma propagation (dyking). Igneous diapirism is intrinsically restricted to the lower, ductile crust. Dyking is therefore the most probable ascent mechanism for granitic magmas that reach shallow crustal levels. A neutral buoyancy level in the crust, at which magma ascent should stall, is never observed. This is demonstrated by coeval emplacement of magmas with different compositions and densities, and the negative gravity anomalies measured over many granitic plutons. We suggest that deformation, through strain partitioning, is necessary to magma ascent. Pluton formation is controlled by local structures and rock types rather than by intrinsic magma properties. As a result of its intermittent character, deformation (both local and regional) induces magma pulses, and this may have important consequences for the chemical homogeneity of intruded magmas.
Experiments on granite intrusion in transtension
Authors: Román-Berdiel T. , Aranguren A. , Cuevas J. , Tubía J. M. , Gapais D. , Brun J.-P. 
Published: April 2008

Abstract
Granite intrusion in transtensional regime is modelled by injecting a Newtonian fluid into a sand pack containing a ductile layer. The transtensional regime is obtained using two plastic sheets sliding along two rigid horizontal plates, and diverging from two narrow spaces (two fixed velocity discontinuities). The injection tube is located in a central space between these plates. Both symmetric experiments (when the two sheets were displaced with equal and opposite velocity vectors) and asymmetric experiments (in which only one sheet was displaced) were performed. Transtension was applied with a systematic variation (every 15°) of the divergence angle (α), between 15° and 90°. Experiments showed that: intrusions localize strain from the first stages of deformation; intrusions result in partially conformable laccoliths with bowler-hat geometry in cross-section; intrusions show an important offset towards the mobile basal plate for asymmetric transtensional regime, and are more symmetric and centred on the injection point for symmetric transtensional regime; the geometry of intrusions is controlled by the faults developed in the overburden. The significance of this control depends upon the angle of divergence α. Examples of the Hombreiro and Los Pedroches granites of the Variscan belt of Spain have been addressed to test the applicability of these experimental results.
Salt extrusion at Kuh-e-Jahani, Iran, from June 1994 to November 1997
Authors: Talbot Christopher J. , Medvedev Sergei , Alavi Mehdi , Shahrivar Hassan , Heidari Esmael 
Published: April 2008

Abstract

Kuh-e-Jahani is one of the largest extrusions of salt currently active in the Zagros mountains. Salt rises from about 4 km below sea level to nearly 1.5 km, above, where, unable to support its own weight, it spreads over the surrounding scenery in a process responsible for present and past allochthonous salt sheets elsewhere. We report vertical movements and apparent horizontal displacements of 43 markers dispersed over this mountain of salt for 4.5 years in three consecutive intervals, the first of 18 months and two others of 12 months. The geometry and inferred flow rate of the salt changed between surveys emphasizing that the gravity spreading is not steady. Our field readings of the dimensions and velocities of the salt at Kuh-e-Jahani are used to tune a simple numerical model and constrain the viscosity of the salt to between 10
16
and 10
17
Pa s
−1
, its rate of surface dissolution to 2–3 cm a
−1
, and its rate of rise out of its orifice at 2–3 m a
−1
for
c.
55 ka. These results imply that vigorous extrusion of salt at Kuh-e-Jahani is probably close to evacuating its deep source and that this mountain will soon begin to waste as salt dissolution overtakes extrusion. This progress report is warranted because our results have significant implications for sophisticated engineering in salt.
Salt tectonics in and around the Nile deep-sea fan: insights from the PRISMED II cruise
Authors: Gaullier Virginie , Mart Yossi , Bellaiche Gilbert , Mascle Jean , Vendeville Bruno C. , Zitter Tiphaine ,   Second Leg Prismed II Scientific Party
Published: April 2008

Abstract
The recent PRISMED II geophysical survey has documented various styles of salt tectonics in and around the Nile deep-sea fan (Eastern Mediterranean Sea). The first main type of salt-related structures comprises listric normal growth faults and grabens, trending roughly perpendicular to the slope line of the Nile Cone. These faults and associated salt structures result from thin-skinned extension, driven by gravity gliding and spreading as a result of sediment loading of the Plio-Quaternary overburden above the Messinian evaporites, which acted as a décollement layer. The second major type of salt structures consists of lineaments that obliquely intersect the continental slope of the Nile deep-sea fan. These structures may have had some strike-slip movement, and salt diapirs grew reactively or were deformed by fault-block movement. In the western distal part of the Nile deep-sea fan, compressional tectonics of the adjacent Mediterranean Ridge caused the formation of a series of salt-cored folds and reverse faults above the Messinian evaporites. In the eastern distal part of the Nile Cone, sediment progradation progressively expelled salt northward, first forming small folds and tight diapirs, then a scarp of 400 m height around the Eratosthenes Seamount, corresponding to the basinward limit of salt deformation.
Influence of extension and compression on salt diapirism in its type area, East Carpathians Bend area, Romania
Authors: Stefanescu Mihai , Dicea Oprea , Tari Gabor 
Published: April 2008

Abstract
The East Carpathians Bend area has a very complex structure characterized by the presence of nappes, their post-tectonic cover and salt diapirs. The salt forming the studied diapirs is Early Miocene (Burdigalian) in age. After its accumulation the salt was more or less continuously involved in alternating extensional and compressional stages that deformed it from its original tabular position to the present-day diapir. Five stages of salt deformation have been established: initial, pre-nappe emplacement, nappe emplacement, post-nappe emplacement and Wallachian. During all of these stages the salt was configured into different shapes: it formed a truncated cone during the initial stage, a mushroom head during the prenappe emplacement stage, and an increasingly more tapered shape with nappe emplacement and during the post-nappe emplacement stages. Finally, it was squeezed out and refashioned by strike-slip faulting during the Wallachian compressional stage of Pleistocene age.