Aperçu synthétique sur la tectonique des Carpates Roumaines

Résumé À la constitution des Carpates Roumaines participent les plissements hercyniens et carpatiques.Les déformations géométriques hercyniennes ont résulté des plissements profonds déterminés par le métamorphisme régional. Elles ont influencé d'une manière de plus en plus atténuée les plissements carpatiques. Pendant le paroxisme mésocrétacé, la tectonique carpatique a engendré des nappes de décollement et des glissements grâce à un simple mécanisme, expliqué par la pesanteur.Les nappes à vergences anticarpatiques se sont formées pendant la phase laramienne. Elles sont également le résultat de la pesanteur associée à l'action de la sous-poussée.Les nappes polygénétiques sont les nappes les plus jeunes et caractérisent les zones du Flysch des Carpates Orientales.Pendant le Tertiaire, une tectonique cassante a prédominé dans les Carpates.

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The Romanian Carpathians consist of three subdivisions, each of them having its tectonical features, namely: Eastern Carpathians, Southern Carpathians and Apuseni Mountains.Their architecture consists of Hercynian and Carpathian foldings. The Hercynian tectonics is due to the deep foldings during the metamorphism which called forth the metanappes. The Hercynian foldings have printed their characters into the Carpathian tectonics and into the evolution of the palaeomesozoical sedimentary zones.During the mesocretaceous phase, the gravitational tectonics develop into the Carpathian realm, generating the gravitational nappes of the Metalliferous Mountains, the Raru-Hsma massif and the Perani Mountains.The overthrusts took place at the surface and are not due to the lateral contraction of the rocks in the depth.The anticarpathian vergences are characteristic for the Laramian nappes.The Flysch tectonics is characterized by polygenetic nappes, formed during a long period and developed all along the chain.The ruptural tectonics developed in the Romanian Carpathians during Tertiary.

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Zusammenfassung Die rumänischen Karpaten lassen sich in drei Einheiten teilen, jede mit ihrer Besonderheit: Ostkarpaten, Südkarpaten und Apuseni-Gebirge. Ihr Bau besteht aus herzynischen und karpatischen Elementen. Die herzynische Tektonik ist die Folge der während der Metamorphose entstandenen Tieffaltungen, welche Metadecken hervorgebracht haben. Die herzynischen Faltungen zeigen sich im karpatischen Bau und in der Ablagerungsgeschichte. Während der mittelkretazischen Faltungsbewegungen hat die Abscherungs- und Fließtektonik das karpatische Gebiet ergriffen und das Entstehen der Schweredecken im Erzgebirge, in den Raru- und Hsma-Massiven sowie im Perani-Gebirge bedingt. Die Decken sind die Folge der in der Nähe der Erdoberfläche ablaufenden Bewegungen und keineswegs des seitlichen Druckes der Tiefgesteine. Die laramischen Decken sind durch antikarpatische Vergenzen charakterisiert und auf die Unterschiebungen der alten Blöcke zurückzuführen. Die Tektonik des Flysches zeichnet sich durch polygenetische Decken aus, die sich während mehrerer Perioden, entlang dem Faltenstreichen, entwickelt haben. Die Bruchtektonik setzte in den rumänischen Karpaten erst während des Neozoikums ein.

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Impact of fertilizer phosphorus application on phosphorus release kinetics in some calcareous soils

Phosphate reactions and retention in the soil are of paramount importance from the perspective of plant nutrition and fertilizer use efficiency. The objective of this work was to study the kinetics of phosphorus (P) desorption in different soils of Hamadan in fertilized and unfertilized soils. Soils were fertilized with 200 mg P kg⁻¹. Fertilized and unfertilized soils were incubated at 25 ± 1°C for 6 months. After that, release of P was studied by successive extraction with 0.5 M NaHCO₃ over a period of 1,752 h. The results showed that phosphorus desorption from the fertilized and unfertilized soils began with a fast initial reaction, followed by a slow secondary reaction. The amount of P released after 1,752 h in fertilized and unfertilized soils ranged from 457 to 762.4 and 309.6 to 586.7 mg kg⁻¹, respectively. The kinetics of cumulative P release was evaluated using the five kinetic equations. Phosphorus desorption kinetics were best described by parabolic diffusion law, first order, and power function equations. Rate constants of these equations were higher in fertilized than unfertilized soils. Results from this study indicate that release rate of P plays a significant role in supplying available P and released P in runoff.     

Real Time Analysis and Forecasting of Strata Caving Behaviour during Longwall Operations

Summary. Discontinuous manual observations and irregular caving characteristics of roof rocks often lead to improper decisions resulting in accidents and production loss. Hence, systematic monitoring of the hanging roof behind the chock shields is necessary for safe and productive mining operations. A real-time application was successfully implemented in an Indian mine for forecasting of hanging roof behaviour to enhance safety and productivity. This paper reports the functioning of real-time TWAP (time weighted average pressure) analysis in the forecasting of hanging roof behaviour in real time.     

An integrated approach to investigate saline water intrusion and to identify the salinity sources in the Central Godavari delta, Andhra Pradesh, India

The Central Godavari delta is located along the Bay of Bengal Coast, Andhra Pradesh, India, and is drained by Pikaleru, Kunavaram and Vasalatippa drains. There is no groundwater pumping for agriculture as wells as for domestic purpose due to the brackish nature of the groundwater at shallow depths. The groundwater table depths vary from 0.8 to 3.4 m and in the Ravva Onshore wells, 4.5 to 13.3 m. Electrical Resistivity Tomography (ERT) surveys were carried out at several locations in the delta to delineate the aquifer geometry and to identify saline water aquifer zones. Groundwater samples collected and analyzed for major ions for assessing the saline water intrusion and to identify the salinity origin in the delta region. The results derived from ERT indicated low resistivity values in the area, which can be attributed to the existence of thick marine clays from ground surface to 12–15 m below ground level near the coast and high resistivity values are due to the presence of coarse sand with freshwater away from the coast. The resistivity values similar to saline water <0.01 Ω m is attributed to the mixing of the saline water along surface water drains. In the Ravva Onshore Terminal low resistivity values indicated up coning of saline water and mixing of saline water from Pikaleru drain. The SO ₄ ^?2 /Cl^?and Na⁺²/Cl^?ratios did not indicate saline water intrusion and the salinity is due to marine palaeosalinity, dilution of marine clays and dissolution of evaporites.     

Large-scale vertical hydroacoustic structure of the North Atlantic and its seasonal variability

A classification based on the number and types of large-scale acoustic waveguides is proposed for the mean seasonal profiles of sound speed propagation. A scheme for North Atlantic zoning, using typical curves of the sound speed vertical distribution, is given. The channel axis's position is shown not to depend on the water mass haline properties, being controlled by the temperature field vertical stratification.Translated by Vladimir A. Puchkin.     

Site response studies in Agartala Urban agglomeration

A systematic investigation using digital microearthquake recorders with short period SS-1 seismometers, covering 76 sites in and around Agartala city, has been carried out for site response (SR) studies in the area. In the northern part of the area, SR varies from 1.15 to 1.85 corresponding to peak frequency 0.76 to 0.93 Hz where soil is mostly semi-consolidated and stiffer than recent Quaternary deposits (Haora River formation). In the southern part of the area, SR varies from 1.12 to 2.42 corresponding to peak frequency from 0.71 to 0.85 Hz within the Dupitila formation (early Quaternary). It is observed that estimated SR from H/V increases from edges to middle of the Haora River valley and impedance contrast fallows the similar trend. This reflects that site response by H/V is influenced by impedance contrast, whereas computed amplification from 1-D model shows opposite trend. The maximum amplification at fundamental frequency of resonance, 1.04 Hz estimated from H/V by near to BH-7, is 2.5 times greater than the impedance contrast/ratio derived from 1-D model for same location. Relationship between resonance frequency and depth was obtained by applying quarter wavelength and Bard (2000) methodologies, which shows linearity, whereas H/V shows its nonlinearity characteristic in soil across the valley part of Haora River. Shear wave velocities, and subsequently, SPT index and factor of safety (by cyclic stress approach) were estimated from geotechnical parameters. Vs30 and site response data were used in this study for getting a first hand information about soil stiffness condition in the area. The estimation of SPT index and factor of safety could be a useful tool for delineating liquefied and none liquefied zones at various depth levels, especially where water table exists at a very shallow level. The expected liquefiable zone was observed at depths varying from 6–25 m beneath the soil bearing zones where percentage of fines is estimated to be more than 35% for the area. This knowledge about subsurface soil characteristics will be useful for the civil engineers/city planners, which can be taken into account at the time of constructing earthquake-resistant structures in the area.     

Lava tube shatter rings and their correlation with lava flux increases at Kīlauea Volcano,Hawai‘i

Shatter rings are circular to elliptical volcanic features, typically tens of meters in diameter, which form over active lava tubes. They are typified by an upraised rim of blocky rubble and a central depression. Prior to this study, shatter rings had not been observed forming, and, thus, were interpreted in many ways. This paper describes the process of formation for shatter rings observed at Kīlauea Volcano during November 2005–July 2006. During this period, tilt data, time-lapse images, and field observations showed that episodic tilt changes at the nearby Pu‘u ‘Ō‘ō cone, the shallow magmatic source reservoir, were directly related to fluctuations in the level of lava in the active lava tube, with periods of deflation at Pu‘u ‘Ō‘ō correlating with increases in the level of the lava stream surface. Increases in lava level are interpreted as increases in lava flux, and were coincident with lava breakouts from shatter rings constructed over the lava tube. The repetitive behavior of the lava flux changes, inferred from the nearly continuous tilt oscillations, suggests that shatter rings form from the repeated rise and fall of a portion of a lava tube roof. The locations of shatter rings along the active lava tube suggest that they form where there is an abrupt decrease in flow velocity through the tube, e.g., large increase in tube width, abrupt decrease in tube slope, and (or) sudden change in tube direction. To conserve volume, this necessitates an abrupt increase in lava stream depth and causes over-pressurization of the tube. More than a hundred shatter rings have been identified on volcanoes on Hawai‘i and Maui, and dozens have been reported from basaltic lava fields in Iceland, Australia, Italy, Samoa, and the mainland United States. A quick study of other basaltic lava fields worldwide, using freely available satellite imagery, suggests that they might be even more common than previously thought. If so, this confirms that episodic fluctuation in lava effusion rate is a relatively common process at basaltic volcanoes, and that the presence of shatter rings in prehistoric lava flow fields can be used as evidence that such fluctuations have occurred.