Links between wave forcing,offshore islands and a macro‐tidal headland‐bound bay beach

Profiles were analysed in conjunction with wave climate to assess offshore island influences on an embayed beach at Tenby, Wales. Time series analyses showed medium and short‐term beach oscillation, with volume exchanges between zones lagging by up to six months. Dominant southerly and southwesterly waves caused sub and low tidal longshore drift from south towards north, while less frequent southeasterly waves generated counter drift. Modelled inshore breaking waves had less energy than offshore ones and the former behaved differently between the low and high tidal zones (spring tidal range of 7 · 5 m). Variations in wave direction from directly behind the islands resulted in reduced wave heights and statistical analyses agreed with wave model results. These were correlated to morphological change and it was concluded that offshore islands change wave dynamics and modify the morphology of embayed beaches in their lee. Consequently, this work provides significant new insights into offshore island influences, shoreline behaviour and especially tidal setting Copyright © 2013 John Wiley & Sons, Ltd.     

Anisotropic elastic full‐waveform inversion of walkaway vertical seismic profiling data from the Arabian Gulf

Borehole seismic addresses the need for high‐resolution images and elastic parameters of the subsurface. Full‐waveform inversion of vertical seismic profile data is a promising technology with the potential to recover quantitative information about elastic properties of the medium. Full‐waveform inversion has the capability to process the entire wavefield and to address the wave propagation effects contained in the borehole data—multi‐component measurements; anisotropic effects; compressional and shear waves; and transmitted, converted, and reflected waves and multiples. Full‐waveform inversion, therefore, has the potential to provide a more accurate result compared with conventional processing methods. We present a feasibility study with results of the application of high‐frequency (up to 60 Hz) anisotropic elastic full‐waveform inversion to a walkaway vertical seismic profile data from the Arabian Gulf. Full‐waveform inversion has reproduced the majority of the wave events and recovered a geologically plausible layered model with physically meaningful values of the medium.     

A new perceived reality: Thomas Harriot's Moon maps

Allan Chapman considers the impact of the first telescopic observation of the heavens, made by the Englishman Thomas Harriot in July 1609.     

A cascade of magmatic events during the assembly and eruption of a super-sized magma body

We use comprehensive geochemical and petrological records from whole-rock samples, crystals, matrix glasses and melt inclusions to derive an integrated picture of the generation, accumulation and evacuation of 530 km³ of crystal-poor rhyolite in the 25.4 ka Oruanui supereruption (New Zealand). New data from plagioclase, orthopyroxene, amphibole, quartz, Fe–Ti oxides, matrix glasses, and plagioclase- and quartz-hosted melt inclusions, in samples spanning different phases of the eruption, are integrated with existing data to build a history of the magma system prior to and during eruption. A thermally and compositionally zoned, parental crystal-rich (mush) body was developed during two periods of intensive crystallisation, 70 and 10–15 kyr before the eruption. The mush top was quartz-bearing and as shallow as ~3.5 km deep, and the roots quartz-free and extending to >10 km depth. Less than 600 year prior to the eruption, extraction of large volumes of ~840 °C low-silica rhyolite melt with some crystal cargo (between 1 and 10%), began from this mush to form a melt-dominant (eruptible) body that eventually extended from 3.5 to 6 km depth. Crystals from all levels of the mush were entrained into the eruptible magma, as seen in mineral zonation and amphibole model pressures. Rapid translation of crystals from the mush to the eruptible magma is reflected in textural and compositional diversity in crystal cores and melt inclusion compositions, versus uniformity in the outermost rims. Prior to eruption the assembled eruptible magma body was not thermally or compositionally zoned and at temperatures of ~790 °C, reflecting rapid cooling from the ~840 °C low-silica rhyolite feedstock magma. A subordinate but significant volume (3–5 km³) of contrasting tholeiitic and calc-alkaline mafic material was co-erupted with the dominant rhyolite. These mafic clasts host crystals with compositions which demonstrate that there was some limited pre-eruptive physical interaction of mafic magmas with the mush and melt-dominant body. However, the mafic magmas do not appear to have triggered the eruption or controlled magmatic temperatures in the erupted rhyolite. Integration of textural and compositional data from all available crystal types, across all dominant and subordinate magmatic components, allow the history of the Oruanui magma body to be reconstructed over a wide range of temporal scales using multiple techniques. This history spans the tens of millennia required to grow the parental magma system (U–Th disequilibrium dating in zircon), through the centuries and decades required to assemble the eruptible magma body (textural and diffusion modelling in orthopyroxene), to the months, days, hours and minutes over which individual phases of the eruption occurred, identified through field observations tied to diffusion modelling in magnetite, olivine, quartz and feldspar. Tectonic processes, rather than any inherent characteristics of the magmatic system, were a principal factor acting to drive the rapid accumulation of magma and control its release episodically during the eruption. This work highlights the richness of information that can be gained by integrating multiple lines of petrologic evidence into a holistic timeline of field-verifiable processes.     

A methodology to assess the spatial configuration of urban systems in Iran from an interaction perspective

The aim of this paper is to develop a methodology for identifying various dimensions of the spatial configuration of urban systems in Iran from an interaction perspective. Through the provision of empirical evidence of different types of flows of people including air passenger flows, passenger flows by bus and car, this paper compares the resulting spatial constellations of these flows through the innovative use of indices to systematically describe and measure five dimensions of an urban system’s spatial configuration that include: (1) centrality and dominance of vertices, (2) network cohesion, (3) network strength, (4) network symmetry, and (5) communities and levels. The findings show that although the spatial configurations of different flows are not the same, all were characterized by having a significant distance within a polycentric urban system due to the primacy of the Tehran metropolis. In regard to passenger flows by car and bus, it was found that for various functional regions, there was a balanced distribution of centrality and urban hierarchy evident in Iran. By contrast, air passenger flows were not able to determine centrality within a national urban hierarchy because of the limited distribution of centers for air travel in Iran at higher levels of spatial organization.     

Heterogenous telescope networks: An introduction

The first Heterogenous Telescopes Network (HTN) conference was held in July 2005. It aimed to bring together software developers, observatory staff and science users with the objective of defining the how and why of developing new ways of doing astronomical observing using geographically distributed and differently instrumented and operated telescopes. The papers included in this volume arise from that conference. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The formation and detection of metal dispersion halos in organic lake sediments

The application of organic-rich lake sediment (gyttja) to exploration geochemistry is discussed. Gyttja was collected from some 42 lake sites in the Red Lake-Uchi Lake volcanic-sedimentary sequences.The existance of free sulphide ion in most gyttja is confirmed and theoretical calculations are used to define the approximate concentrations of sulphide ion which determine whether the accumulation of Cu⁺, Cu²⁺, Zn²⁺ and Fe²⁺ is by metal sulphide precipitation, organic complexing or both. These calculations show that in the sediments collected in this study, the accumulation of copper will probably be by metal sulphide formation, whereas for zinc, organic complexing and possibly sulphide precipitation are likely mechanisms.It is shown that the background concentrations of copper and zinc on a dry matter basis increase with the content of organic matter in the sediment and it is further shown that the quantity of interstitial water in the sediment increases linearly with the organic content. Also it is demonstrated that the organic matter in the sediment is dispersed in the interstitial water in approximately the same concentration irrespective of the sediment composition.On the assumption that copper sulphide colloids are dispersed in the interstitial water of the sediment, it is suggested that the copper content of gyttja should be expressed as μg/g interstitial water for meaningful interpretation. Similarly, the zinc content should be expressed relative to the organic matter content.The ability of reagents to selectively extract only chemically dispersed metals and not silicate lattice metals from gyttja is discussed.Both the analytical procedures and the interpretations are applied to the samples collected.     

The nakhlite meteorites: Augite-rich igneous rocks from Mars

The seven nakhlite meteorites are augite-rich igneous rocks that formed in flows or shallow intrusions of basaltic magma on Mars. They consist of euhedral to subhedral crystals of augite and olivine (to 1 cm long) in fine-grained mesostases. The augite crystals have homogeneous cores of Mg′=63% and rims that are normally zoned to iron enrichment. The core-rim zoning is cut by iron-enriched zones along fractures and is replaced locally by ferroan low-Ca pyroxene. The core compositions of the olivines vary inversely with the steepness of their rim zoning - sharp rim zoning goes with the most magnesian cores (Mg′=42%), homogeneous olivines are the most ferroan. The olivine and augite crystals contain multiphase inclusions representing trapped magma. Among the olivine and augite crystals is mesostasis, composed principally of plagioclase and/or glass, with euhedra of titanomagnetite and many minor minerals. Olivine and mesostasis glass are partially replaced by veinlets and patches of iddingsite, a mixture of smectite clays, iron oxy-hydroxides and carbonate minerals. In the mesostasis are rare patches of a salt alteration assemblage: halite, siderite, and anhydrite/gypsum. The nakhlites are little shocked, but have been affected chemically and biologically by their residence on Earth.Differences among the chemical compositions of the nakhlites can be ascribed mostly to different proportions of augite, olivine, and mesostasis. Compared to common basalts, they are rich in Ca, strongly depleted in Al, and enriched in magmaphile (incompatible) elements, including the LREE. Nakhlites contain little pre-terrestrial organic matter. Oxygen isotope ratios are not terrestrial, and are different in anhydrous silicates and in iddingsite. The alteration assemblages all have heavy oxygen and heavy carbon, while D/H values are extreme and scattered. Igneous sulfur had a solar-system isotopic ratio, but in most minerals was altered to higher and lower values. High precision analyses show mass-independent fractionations of S isotopes. Nitrogen and noble gases are complex and represent three components: two mantle sources (Chas-E and Chas-S), and fractionated Martian atmosphere.The nakhlites are igneous cumulate rocks, formed from basaltic magma at ∼1.3 Ga, containing excess crystals over what would form from pure magma. After accumulation of their augite and olivine crystals, they were affected (to various degrees) by crystallization of the magma, element diffusion among minerals and magma, chemical reactions among minerals and magma, magma movement among the crystals, and post-igneous chemical equilibration. The extent of these modifications varies, from least to greatest, in the order: MIL03346, NWA817, Y000593, Nakhla=Governador Valadares, Lafayette, and NWA998.Chemical, isotopic, and chronologic data confirm that the nakhlites formed on Mars, most likely in thick lava flows or shallow intrusions. Their crystallization ages, referenced to crater count chronologies for Mars, suggest that the nakhlites formed on the large volcanic constructs of Tharsis, Elysium, or Syrtis Major. The nakhlites were suffused with liquid water, probably at ∼620 ma. This water dissolved olivine and mesostasis glass, and deposited iddingsite and salt minerals in their places. The nakhlites were ejected from Mars at ∼10.75 Ma by an asteroid impact and fell to Earth within the last 10,000 years.Although the nakhlites are enriched in incompatible elements, their source mantle was strongly depleted. This depletion event was ancient, as the nakhlites’ source mantle was fractionated while short-lived radionuclides (e.g., ) were still active. This differentiation event may have been core formation coupled with a magma ocean, as is inferred for the moon.     

Marine litter prediction by artificial intelligence

Artificial intelligence techniques of neural network and fuzzy systems were applied as alternative methods to determine beach litter grading, based on litter surveys of the Antalya coastline (the Turkish Riviera). Litter measurements were categorized and assessed by artificial intelligence techniques, which lead to a new litter categorization system. The constructed neural network satisfactorily predicted the grading of the Antalya beaches and litter categories based on the number of litter items in the general litter category. It has been concluded that, neural networks could be used for high-speed predictions of litter items and beach grading, when the characteristics of the main litter category was determined by field studies. This can save on field effort when fast and reliable estimations of litter categories are required for management or research studies of beaches--especially those concerned with health and safety, and it has economic implications. The main advantages in using fuzzy systems are that they consider linguistic adjectival definitions, e.g. many/few, etc. As a result, additional information inherent in linguistic comments/refinements and judgments made during field studies can be incorporated in grading systems.     

Accuracy of CFC groundwater dating in a crystalline bedrock aquifer: Data from a site in southern Sweden

The concentrations of chlorofluorocarbons (CFC-11, CFC-12, and CFC-113) and tritium were determined in groundwater in fractured crystalline bedrock at Finnsjön, Sweden. The specific goal was to investigate the accuracy of CFC dating in such an environment, taking potential degradation and mixing of water into consideration. The water was sampled to a depth of 42 m in three boreholes along an 800-m transect, from a recharge area to a local discharge area. The CFC-113 concentration was at the detection limit in most samples. The apparent recharge date obtained from CFC-11 was earlier than from CFC-12 for all samples, with a difference of over 20 years for some samples. The difference was probably caused by degradation of CFC-11. The CFC-12 dating of the samples ranged from before 1945 to 1975, with the exception of a sample from the water table, which had a present-day concentration. Conclusions about flow paths or groundwater velocity could not be drawn from the CFCs. The comparison between CFC-12 and tritium concentrations showed that most samples could be unmixed or mixtures of waters with different ages, and the binary mixtures that matched the measured concentrations were determined. The mixing model approach can be extended with additional tracers.

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Resumen Precisión en la datación de aguas subterráneas utilizando CFC en un acuífero de rocas cristalinas: datos provenientes de un sitio al sur de Suecia.Se determinaron las concentraciones de clorofluorucarbonos (CFC-11, CFC-12, y CFC-113) y de tritio en aguas subterráneas alojadas en rocas cristalinas fracturadas de Finnsjön, Suecia. El objetivo específico consistió en investigar la precisión de la datación de aguas subterráneas con CFC en este tipo de ambiente, tomando en consideración la degradación potencial y la mezcla de agua. Las muestras de agua se tomaron a una profundidad de 42 m en tres pozos ubicados a lo largo de una línea de 800 m transversal a una zona de recarga y de zona de descarga local. En la mayoría de las muestras se encontró que la concentración de CFC-113 estuvo en el límite de detección. La edad que se estimó en todas las muestras para la recarga aparente en base a CFC-11 fue más joven que la edad proveniente de CFC-12, con una diferencia de más de 20 años para algunas muestras. Esta diferencia fue causada probablemente por la degradación del CFC-11. La datación CFC-12 de las muestras varió de antes de 1945 a 1975, con la excepción de una muestra tomada en el nivel freático, la cual presentó concentración actual. No fue posible obtener conclusiones acerca de las trayectorias de flujo o la velocidad de agua subterránea a partir de los CFCs. La comparación entre las concentraciones de CFC-12 y tritio mostró que la mayoría de las muestras pueden tener composición sencilla o bien consistir de mezclas de aguas de diferentes edades. Esta comparación también permitió determinar las mezclas binarias que corresponden a las concentraciones medidas. Pueden utilizarse trazadores adicionales para ampliar el modelo de mezclas propuesto.

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Résumé Précision de la datation au CFC dans un aquifère rocheux-fracturé: données dun site du sud de la Suède.Les concentrations en chlorofluorocarbones (CFC-11, CFC-12, CFC-113) et entritium ont été déterminées dans leau souterraine dun massif fracturé à Finnsjön en Suède. Le but de cette étude est de mieux cerner la précision de la méthode de datation au CFC dans ce type denvironnement hydrogéologique, tout en considérant déventuels phénomènes de dégradation et de mélange deaux. Leau a été échantillonnée à une profondeur de 42 mètres dans trois forages alignés sur 800 mètres entre une zone de recharge et une zone de déversement. Les concentrations en CFC-113 sont dans la plupart des échantillons à la limite de détection. Pour tous les échantillons, la date de la recharge établie avec le CFC-11 est antérieure à la date établie avec le CFC-12. La différence entre les deux dates peut dépasser 20 ans et sexplique—probablement—par la dégradation du CFC-11. Les dates de recharge de la nappe mesurées au CFC-12 sont comprises entre 1945 et 1975, excepté pour un échantillon qui possède une concentration actuelle. Il nest pas possible de tirer des conclusions concernant la direction des écoulements et la vitesse de leau souterraine. La comparaison entre CFC-12 et tritium montre que des échantillons pourraient être soit le résultat du mélange deaux dâges différents, soit des échantillons non-mélangés. Dans le cas dun mélange binaire, les rapports du mélange composant la concentration mesurée sont déterminés. Lapproche par modèle de mélange peut être étendue à des traceurs additionnels.