Longitudinal dispersion processes in the upper tamar estuary

Measurements of velocity, salinity, and suspended solids concentration have been used to investigate the intra-tidal variation of vertical and transverse shear-induced dispersion. For the study research the interaction of the longitudinal density gradient and vertical shear during the early part of the ebb tide accounted for much of the net longitudinal dispersion of solute landward. The same mechanism also is shown to lead to a net particulate transport landward. The landward flux, however, takes place during the flood tide. The field data are also used to elucidate the tidally averaged tidal pumping mechanism.     

A window to the operation of microplate tectonics in the Tethys Ocean: the geochemistry of the Samothrace granite,Aegean Sea

Summary The island of Samothrace, northeastern Aegean Sea, consists of five main geological units: (i) A basement unit consisting of low grade metamorphic rocks (metapelites, marbles, metavolcanic rocks, and a metaconglomerate); (ii) an ophiolitic complex with K-Ar hornblende date of 154 ± 7 and 155 ± 7 Ma; (iii) A granite intrusion with biotite K-Ar dates of 14.5 ± 0.3 and 14.5 ± 0.5 Ma, and a contact metamorphic event dated at 40.9 + 2.2 Ma; (iv) a unit of Cenozoic volcanic rocks: orogenic volcanism apparently occurred in two cycles with Upper Eocene tholeiitic to calc-alkaline volcanic rocks and post-Eocene high-K andesites to trachytes. (v) Quaternary clastic sedimentary rocks which occur around the peripheral parts of the island. The granitic intrusion is predominantly a hornblende-biotite granite, granodiorite or quartz monzonite, with porphyritic variants and mafic enclaves. The pluton is cut by granophyre, aplite and rare granodioritic veins. All lithological units of the Samothrace intrusion show smooth and continuous major element trends and similar chondrite- and Ocean Ridge Granite-normalized incompatible element profiles. ORG-normalized incompatible element contents of Hf, Zr, Sm are explained with fractionation close to the normalizing values Y and Yb contents combined with high K/Yb ratios; Rb and Th are significantly enriched relative to Nb and Ta. In Y-Nb and Rb-SiO₂ space most samples of the Samothrace granite, plot in the volcanic arc and the syn-collisional granite fields. In Y + Nb-Rb space they are equally distributed within and transgress these two domains. The geochemical and regional data suggest a subduction or collision environment but biotite mineral data do not support a collisional setting for magma genesis. The Samothrace granite was probaby associated with a post-collisional domain after the closure of the Axios section of the Tethys Ocean.

---

Ein Einblick in das Wirken von Mikroplattentektonik in der Tethys—Die Geochemie des Samothrake Granites, Agäisches Meer

Zusammenfassung Die Insel Samothrake in der nordöstlichen Ägäis besteht aus fünf geologischen Haupteinheiten: (i) einem schwach metamorphen Basement (Metapelite, Marmore, Metavulkanite und Metakonglomerate); (ii) einem ophiolithischem Komplex, der mit K-Ar Datierungen an Hornblende ein Alter von 154 ± 7 und 155 ± 7 Ma ergab; (iii) ein granitischer Intrusionskörper mit K-Ar Altern an Biotit von 14.0 ± 0.3 und 14.5 ± 0.5 Ma und einem kontaktmetamorphen Ereignis, das mit 40.9 ± 2.2 Ma datiert ist; (iv) eine Abfolge känozoischer Vulkanite, wobei der orogene Vulkanismus offensichtlich in zwei Zyklen ablief mit tholeiitischen bis kalkalkalischen Vulkaniten im oberen Eozän und high-K Andesiten bis Trachyten im post-Eozän; (v) quartären klastischen Sedimentgesteinen, die im Randbereich der Insel auftreten. Die Granitintrusion setzt sich hauptsächlich aus Hornblende-Biotitgraniten, Granodioriten oder Quarzmonzoniten mit teilweise porphyrischen und mafischen Enklaven enthaltenden Varietäten zusammen. Der Pluton wird von Granophyren, Apliten und seltener von granodioritischen Gängen durchschlagen. Alle lithologischen Einheiten der Samothrake Intrusion zeigen kontinuierliche Hauptelementtrends und ähnliche Chondrit und ORG-normalisierte inkompatible Elementprofile. Die Gehalte an den inkompatiblen Elementen Hf, Zr, Sm sind sehr ähnlich denen von ozeanischen Graniten (ORG). Die niedrigen Y und Yb-Gehalte und die hohen K/Yb Verhältnisse werden durch Fraktionierung erklärt. Rb und Th sind signifikant angereichert im Vergleich zu Nb und Ta. In Y-Nb und Rb-SiO₂ Diagrammen plotten die meisten Proben des Samothrake Granites im Feld der vulkanischen Inselbogen- und Synkollisionsgranite. Im Y + Nb-Rb Diagramm zeigt sich eine gleichmäßige und überlappende Verteilung. Die geochemischen und regionalen Daten weisen auf einen Subduktions- oder Kollisionsbereich hin, obwohl die Biotitzusammensetzungen nicht für eine Bildung der Magmen in einem Kollisionsbereich sprechen. Die Bildung des Samothrake Granites steht möglicherweise mit post-Kollisionstektonik nach dem Schließen der Axioszone in der Tethys in Zusammenhang.

---

---

With 7 Figures     

Estimation of sedimentary thickness in the Godavari basin

A major portion of the southern part of the Indian subcontinent is classified as a stable continental region. However, a few segments in this region are punctuated by rifts and shear zones that are seismically active. The Godavari rift that sutures the eastern Dharwar and the Bastar cratons is one such region, prone to seismic hazard. Estimation of the sedimentary thickness in these seismically active regions assumes importance since locales of thick and soft sediments are vulnerable to destruction due to surface waves generated by earthquakes. In the present study, data from five broadband seismological stations are utilized to estimate the average sedimentary thickness of the Godavari region using the difference in travel times of the direct S and converted Sp phases from local earthquakes. The thickness of sediments varies between 0.32 and 4.32 km. Also, the site-specific response in terms of the fundamental resonance frequency and the corresponding amplifications are estimated using the well-established Nakamura technique. The predominant frequencies are in the range of 1.3–4.61 Hz, and the amplifications are higher (>1.5) for the stations inside the Godavari basin. Both the thickness and amplification values clearly indicate that the sediments tend to get thicker toward the center of the basin, in good agreement with the geological distribution of the sedimentary units.     

CU Eridani — A suspected variable

Photometric observations of CU Eridani, recently classified as non-variable, indicate it to be a variable star.     

Piloting a network of small telescopes

The Pilot Small Telescope Network (PSTN) is a state‐of the art system of easily replicable and scalable hardware, software, servers, eXtensible Markup Language (XML) protocols, and network middleware connecting and developing a pilot array of robotic telescopes to one another and the user community. The PSTN is a developmental project that will allow growing access to these telescopes, and make available data to faculty, students and others in an environment of collaboration. The underlying goal of the PSTN is to broaden the quantity and quality of astronomical education and research, particularly with a focus on traditionally underserved populations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Astrometry in the Kerr field inPPN approximation

The equation of motion written down using a metric obtained from the Kerr metric allows us to get both the deflection angle of light ray bending by the gravitational field of the Sun and its corresponding time delay. We reproduce the experimental data of Epstein-Shapiro and also it is in accordance with the theoretical results obtained by Brumberget al. (1990) using another approach to this problem.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9–13 November, 1992.     

Pulsation,rotation and sunspot cycle

A suggestion is made that the periods for solar pulsation, solar rotation, and sunspot cycle may be closely related one to another.     

Rough water as a spawning stimulus in some Trochid and Turbinid gastropods

Adults of three species of common intertidal gastropods, Melagraphia aethiops, Zediloma atrovirens, and Lunella smaragda, were collected from Waitemata Harbour, Auckland (36° 51 S, 174° 47 E) and brought to the laboratory, where several methods of artificial spawning were attempted throughout the year. The one successful method, involving vigorous water movement around ripe adults, induced them to release gametes during their respective spawning seasons, and was equally effective in the natural habitat. Larval stages were found in the plankton only during periods of on‐shore wind speeds greater than 10 knots, with which their presence was correlated, rather than with tides, lunar cycles, or sea temperatures.