Photoelectric lightcurves and rotation periods of the asteroids 46 Hestia and 115 Thyra

Results of photoelectric observations of the asteriods 46 Hestia and 115 Thyra, performed in a cooperative program between the Torino and Table Mountain Observatories, are presented. The rotation periods and the maximum amplitudes are: P_syn = 21^h.0.4 ± 0^h.01, Amplitude = 0.12 mag and P_syn = 7^h.241 ± 0.^h.001, Amplitude = 0.20 mag, for Hestia and Thyra, respectively. The multiple-scattering factors, Q, inferred from the phase relation data are 0.054 ± 0.003 and 0.058 ± 0.002 for Hestia and Thyra, respectively. The low value obtained for Thyra disagrees with the mean one given by Bowell and Lumme (1979, in Asteroids (T. Gehrels, Ed.), pp. 132–169. University of Arizona Press, Tucson) for S-type asteroids.     

Oxygenation of shallow marine environments and chemical sedimentation in Palaeoproterozoic peritidal settings: Frere Formation,Western Australia

The Palaeoproterozoic Frere Formation (ca 1.89 Gyr old) of the Earaheedy Basin, Western Australia, is a ca 600 m thick succession of iron formation and fine‐grained, clastic sedimentary rocks that accumulated on an unrimmed continental margin with oceanic upwelling. Lithofacies stacking patterns suggest that deposition occurred during a marine transgression punctuated by higher frequency relative sea‐level fluctuations that produced five parasequences. Decametre‐scale parasequences are defined by flooding surfaces overlain by either laminated magnetite or magnetite‐bearing, hummocky cross‐stratified sandstone that grades upward into interbedded hematite‐rich mudstone and trough cross‐stratified granular iron formation. Each aggradational cycle is interpreted to record progradation of intertidal and tidal channel sediments over shallow subtidal and storm‐generated deposits of the middle shelf. The presence of aeolian deposits, mud cracks and absence of coarse clastics indicate deposition along an arid coastline with significant wind‐blown sediment input. Iron formation in the Frere Formation, in contrast to most other Palaeoproterozoic examples, was deposited almost exclusively in peritidal environments. These other continental margin iron formations also reflect upwelling of anoxic, Fe‐rich sea water, but accumulated in the full spectrum of shelf environments. Dilution by fine‐grained, windblown terrigenous clastic sediment probably prevented the Frere iron formation from forming in deeper settings. Lithofacies associations and interpreted paragenetic pathways of Fe‐rich lithofacies further suggest precipitation in sea water with a prominent oxygen chemocline. Although essentially unmetamorphosed, the complex diagenetic history of the Frere Formation demonstrates that understanding the alteration of iron formation is a prerequisite for any investigation seeking to interpret ocean‐atmosphere evolution. Unlike studies that focus exclusively on their chemistry, an approach that also considers palaeoenvironment and oceanography, as well the effects of post‐depositional fluid flow and alteration, mitigates the potential for incorrectly interpreting geochemical data.     

Wavelet correlation filter for wide-angle seismic data

A new filtering technique for single‐fold wide‐angle reflection/refraction seismic data is presented. The technique is based on the wavelet decomposition of a set of adjacent traces followed by coherence analysis. The filtering procedure consists of three steps. In the first, a wavelet decomposition of traces into different detail levels is performed. In the second, the coherence attributes for each level are evaluated by calculating cross‐correlation functions of detail portions contained in a space–time moving window. Finally, the filtered traces are obtained as a weighted reconstruction of the trace details. Each weight is obtained from the coherence‐attributes distribution estimated in a proper interval. A sequence of tests is then conducted in order to select possible optimum or unsuitable wavelet bases. The efficiency of the filter proposed was assessed by calculating some properly designed parameters in order to compare it with other standard de‐noising techniques. The proposed method produced a clear signal enhancement in high‐density wide‐angle seismic data, thus proving that it is a useful processing tool for a reliable correlation of seismic phases.     

Assessing reference conditions and physico-chemical status according to the European Water Framework Directive: a case-study from the Basque Country (Northern Spain)

The European Water Framework Directive requires the development of new and accurate methodologies, addressing the assessment of the physico-chemical status of transitional and coastal waters; these are considered by the Directive as the supporting elements for the final evaluation of the Ecological Quality Status.

This contribution develops new approaches in the determination of the physico-chemical status, solving some problems detected in previous contributions, i.e.: (a) fitting the classification of water bodies and typologies, by means of the stretching of the typologies, according to the natural salinity gradient of types; (b) defining reference conditions, based upon the new approach to typologies, (c) proposing accurate multivariate methodologies, in determining the physico-chemical status of the transitional and coastal waters, based upon the defined typologies and references; and (d) discussion of the results obtained by reference to methodological aspects and water quality evolution in the Basque Country, Spain (as a case-study), during the last decade.     

Spada: An Array of Spad Detectors For Astrophysical Applications

Astrophysical studies require accurate, sensitive and fast detectors to detect faint sources with high variability. Recently an array of Single Photon Avalanche Diodes (SPAD), SPADA, has been developed. This array is suitable for competitive adaptive optics operations and fast transient image acquisition at a fraction of the current cost of imaging arrays. The fabricated solid-state photon counters are rugged, easily integrated with the optics, free from readout noise, and have very fast frame rates (> 10 kHz, for visible corrections) with nanosecond electronic gating. In this paper, the following are described: the development of silicon monolithic arrays of 60 photon-counters, the detection electronics (based on integrated active quenching circuits for each pixel of the array), the real-time data-processing board implemented into FPGA and some aspects of the mechanical housing.     

Amplification of strong ground motion in the city of Zagreb, Croatia, estimated by computation of synthetic seismograms

A hybrid technique consisting of modal summation and subsequent finite differences modelling is applied for the computation of synthetic accelerograms along a profile crossing the city of Zagreb, the capital of Croatia. Assuming the source geometry is known, the amplification properties of the underlying soil may be determined by comparison of synthetics and their response spectra computed for a bedrock model with the ones obtained under the assumption of a realistic laterally varying local model. The peak ground acceleration is larger by a factor of up to 3.5 than the value obtained for the bedrock model. The amplification of the response spectra is most prominent for frequencies below 2 Hz, and increases sharply to the SW from the mapped fault running through the centre of the city.     

Interval velocity and thickness estimate from wide-angle reflection data

A method to estimate interval velocities and thickness in a horizontal isotropic layered medium from wide-angle reflection traveltime curves is presented. The method is based on a relationship between the squared reflection traveltime differences and the squared offset differences relative to two adjacent reflectors. The envelope of the squared-time versus offset-difference curves, for rays with the same ray parameter, is a straight line, whose slope is the inverse of the square of the interval velocity and whose intercept is the square of the interval time. The method yields velocity and thickness estimates without any knowledge of the overlying stratification. It can be applied to wide-angle reflection data when either information on the upper crust and/or refraction control on the velocity is not available. Application to synthetic and real data shows that the method, used together with other methods, allows us to define a reliable 1D starting model for estimating a depth profile using either ray tracing or another technique.     

The origin of thermal waters from the eastern flank of the Dead Sea Rift Valley (western Jordan)

Thermal waters emerging along the eastern flank of the northernmost part of the Dead Sea Rift Valley close to the Yarmuk river are dilute, Ca–SO₄–(HCO₃) and Na–Cl water types with measured temperatures of 35–60 °C and estimated teperatures, according to silica solubility, of 60–110 °C. They are fed only by present‐day recharged meteoric waters (Wadi Hasa, Al Himma and North Shuna thermal baths) and by meteoric waters contaminated with saline waters (El Ma'in thermal Bath). Although they have been known for a long time, there is still dispute about their origins and the source of heat. On the basis of new chemical and isotopic analyses, the saline waters could represent residual pockets of groundwater in equilibrium with those filling the Dead Sea depression before the last retreat of Lake Lisan at 17–15 kyr bp or with the ancient seawaters of the Sedom Lagoon in the early Pleistocene, in both cases unaffected by significant evaporation processes but chemically and isotopically modified by water/rock interaction.     

Gold and silver metallogeny of the South China Fold Belt: a consequence of multiple mineralizing events?

The South China Fold Belt is part of the South China Block that is interpreted to be the result of multiple tectonic and magmatic events that formed a collage of accreted Proterozoic and Phanerozoic terranes. The Jurassic to early Cretaceous Yanshanian period (180–90 Ma), a time of major tectono-thermal events that affected much of eastern and southeastern China, is of great metallogenic importance in the fold belt. This period is linked to subduction of the Pacific plate beneath the Eurasian continent, and is manifested by voluminous volcano-plutonic activity of predominantly calc-alkaline affinity.The distribution of gold and silver deposits in the South China Fold Belt indicates the presence of two distinct metallogenic provinces. A region of basement uplifts, which are controlled by shear zones and form Neoproterozoic inliers of metamorphosed iron-rich rock types, defines the first province. In this province, orogenic lodes and volcanic-related epithermal deposits represent the more significant precious-metal mineralization. The second province is essentially confined to a belt of Yanshanian felsic–intermediate volcanic and subvolcanic rocks that extends along most of the southeastern China coast in an area known as the Coastal Volcanic Belt. Deposits in the Coastal Volcanic Belt are silver- and/or copper-rich, volcanic-hosted and epithermal in character.The precious-metal metallogeny of the South China Fold Belt is interpreted to have developed in at least three stages: one as a result of collision events, during the Caledonian Orogeny (ca. 400 Ma), the second during the Indosinian Orogeny (ca. 200 Ma) and the third during or soon after the formation of the Yanshanian magmatic belt (Yanshanian Orogeny; 180–90 Ma). The latter was responsible for a hydrothermal event that affected large sections of the belt and its Proterozoic substrate. This may have resulted in the redistribution and enrichment of precious metals from preexisting orogenic gold lodes in Neoproterozoic basement rocks, which are now exposed as windows in zones of tectonic uplift. The Yanshanian hydrothermal activity was particularly widespread in the Coastal Volcanic Belt and resulted in the formation of both low- and high-sulfidation epithermal gold and silver, and locally copper and other base-metal mineralization. It is suggested that the Coastal Volcanic Belt has greater potential for world-class epithermal and porphyry deposits than previously realised.