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Selected AbstractsMantle-derived and crustal melts dichotomy in northern Greece: spatiotemporal and geodynamic implicationsGEOLOGICAL JOURNAL, Issue 1 2004Diego Perugini Abstract Two distinct groups of subduction-related (orogenic) granitoid rocks, one Jurassic and the other Tertiary, occur in the area between the Vardar (Axios) Zone and the Rhodope Massif in northern Greece. The two groups of granitoids differ in many respects. The first group shows evolved geochemical characters, it is not associated with mafic facies, and evidence of magmatic interaction between mantle- and crustal-derived melts is lacking. The second group has less evolved geochemical characters, it is associated with larger amount of mafic facies, and magmatic interaction processes between mantle-derived and crustal melts are ubiquitous as evidenced by mafic microgranular enclaves and synplutonic dykes showing different enrichment in K2O, Ti, and incompatible elements. This kind of magmatism can be attributed to the complex geodynamic evolution of the area. In particular, we suggest that two successive subduction events related to the closure of the Vardar and the Pindos oceans, respectively, occurred in the investigated area from Late Jurassic to Tertiary. We relate the genesis of Jurassic granitoids to the first subduction event, whereas Tertiary granitoids are associated with the second subduction. Fluids released by the two subducted slabs induced metasomatic processes generating a ,leopard skin' mantle wedge able to produce mafic melts ranging from typical calc-alkaline to ultra-potassic. Such melts interacted in various amounts with crustal calc-alkaline anatectic melts to generate the wide spectrum of Tertiary granitoids occurring in the study area. Copyright © 2004 John Wiley & Sons, Ltd. [source] Shear wave velocity model of the Santiago de Chile basin derived from ambient noise measurements: a comparison of proxies for seismic site conditions and amplificationGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2010Marco Pilz SUMMARY We determined a high-resolution 3-D S -wave velocity model for a 26 km × 12 km area in the northern part of the basin of Santiago de Chile. To reach this goal, we used microtremor recordings at 125 sites for deriving the horizontal-to-vertical (H/V) spectral ratios that we inverted to retrieve local S -wave velocity profiles. In the inversion procedure, we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements, which were found to vary substantially over short distances in the investigated area. The resulting model was derived by interpolation with a kriging technique between the single S -wave velocity profiles and shows locally good agreement with the few existing velocity profile data, but allows the entire area, as well as deeper parts of the basin, to be represented in greater detail. The wealth of available data allowed us to check if any correlation between the S -wave velocity in the uppermost 30 m (v30S) and the slope of topography, a new technique recently proposed by Wald and Allen, exists on a local scale. We observed that while one lithology might provide a greater scatter in the velocity values for the investigated area, almost no correlation between topographic gradient and calculated v30S exists, whereas a better link is found between v30S and the local geology. Finally, we compared the v30S distribution with the MSK intensities for the 1985 Valparaiso event, pointing out that high intensities are found where the expected v30S values are low and over a thick sedimentary cover. Although this evidence cannot be generalized for all possible earthquakes, it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the Santiago basin. [source] Application of SAR interferometry to a large thrust deformation: the 1999 Mw= 7.6 Chichi earthquake in central TaiwanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2004C. P. Chang SUMMARY Application of the interferometric method to four ERS2-SAR images acquired before and after the 1999 Chichi earthquake has allowed determination of the coseismic surface displacement in the footwall area of the Chelungpu fault. The interferometric results revealed a relative shortening in the round trip distance between the radar antenna and the ground of the footwall side of Chelungpu fault, during the earthquake. This shortening progressively increased from the west to the east and reaches the maximum amount of approximately 26 cm near the central segment of the Chelungpu fault. Our interferometric results have been precisely examined using a dense GPS network in the investigated area. We mapped the GPS coseismic measurements into the radar line of sight and implemented a forward simulation of SAR interferogram from this synthesized result to control our unwrapping performance. In this study, these two observations are compared with a 3-D dislocation model of the fault. Finally, a deformation analysis based on our interferometric result has indicated that a segment with irregular deformation behaviour can be distinguished in the footwall area of the Chelungpu fault. This segment may result from either the influence of inherited basement faults or the presence of a structural terrace that provide local opportunities for superficial deformation. [source] Holocene sedimentation in the Skagerrak interpreted from chirp sonar and core data,JOURNAL OF QUATERNARY SCIENCE, Issue 1 2005Richard Gyllencreutz Abstract High-resolution chirp sonar profiling in the northeastern Skagerrak shows acoustically stratified sediments draping a rough-surfaced substratum. A 32 metre long sediment core retrieved from the survey area encompasses the entire Holocene and latest Pleistocene. The uppermost seismo-acoustic units in the chirp profiles represent Holocene marine sediments. The lowermost unit is interpreted as ice-proximal glacial-marine sediments rapidly deposited during the last deglaciation. The end of ice-proximal sedimentation is marked by a strong reflector, interpreted to have been formed during latest Pleistocene time as a consequence of rapid ice retreat and drastically lowered sedimentation rate. The subsequent distal glacial-marine sediments were deposited with initially high sedimentation rates caused by an isostatic rebound-associated sea-level fall. Based on correlation between the core and the chirp sonar profiles using measured sediment physical properties and AMS 14C dating, we propose a revised position for the Pleistocene/Holocene boundary in the seismo-acoustic stratigraphy of the investigated area. Copyright © 2005 John Wiley & Sons, Ltd. [source] Isotopic climate record in a Holocene stalagmite from Ursilor Cave (Romania)JOURNAL OF QUATERNARY SCIENCE, Issue 4 2002Bogdan Petroniu Onac Abstract The PU-2 stalagmite from Ursilor Cave provides the first dated Romanian isotope record for the Holocene. The overall growth rate of the speleothem was 3.5 cm kyr,1, corresponding to a temporal resolution of 142 y between each isotope analysis. The ,Hendy' tests indicate that isotopic equilibrium conditions occurred during the formation of PU-2, and hence that it is suitable for palaeoclimatic studies. The relationship between ,18O and temperature was found to be positive. This can be interpreted either as rain-out with distance from the west-northwest ocean source of evaporation or shifts in air mass source with changing North Atlantic Oscillation indices. Applying five U,Th thermal ionisation mass spectrometric (TIMS) dates to a 17.5 cm isotope profile (,18O and ,13C) along the stalagmite growth axis enabled a tentative interpretation of the palaeoclimate signal over the past 7.1 kyr. Spikes of depleted isotopic ,18O values are centred near ca. 7, ca. 5.2 and ca. 4 ka, reflecting cool conditions. The record shows two warm intervals between ca. 3.8 and ca. 3.2 ka (the maximum warmth) and from ca. 2 to ca. 1.4 ka, when the ,18O values were less negative than present. The ,Holocene Climate Optimum' spanning the time interval from ca. 6.8 to ca. 4.4 ka is not well expressed in the PU-2 stalagmite. Individual spikes of lighter ,13C are interpreted as indicative of periods of heavy rainfall, at ca. 7, ca. 5.5, and ca. 3.5 ka. The overall trend to lighter ,13C in the PU-2 stalagmite may reflect a gradual decrease in water,rock interaction. The results demonstrate that the effect of North Atlantic oceanic changes extended to the investigated area. Nevertheless, some differences in temporal correlation and intensity of stable isotopic response to these climatic events have been found, but the exact nature of these differences and the underlying mechanism is yet to be determined. Copyright © 2002 John Wiley & Sons, Ltd. [source] Seabed Morphology and Pollution Along the Bagnoli Coast (Naples, Italy): a Hypothesis for Environmental RestorationMARINE ECOLOGY, Issue 2002Tommaso De Pippo Abstract. The interaction of coastal and submarine morphology with the hydrodynamic regimes exerts a control on coastal dynamic processes, conditioning the dispersion of sediments and potential pollutants existing in the area. Thus, the study of such parameters is useful in order to define environmental threats. Within the submerged sector of the Bagnoli coast and particularly in the southern part of the investigated area, there are sediment groups composed of very fine sands located in low-energy zones due to wave refraction and diffraction; they can also be found on the sea bottom and on the man-made structures typical of this zone. These areas show high pollutant levels of N, P, Cu, Fe, Mn, Ni, Pb, Zn, Cd, polyaromatic hydrocarbons (PAHs) and polychlorinated bi-phenyls (PCBs). The northern area, a place of high-energy hydrodynamic processes, also shows high concentration levels of pollutants due to the presence of secondary cell circulation. Morphological research and analysis of textural characteristics of bottom sediments along the Bagnoli coast allowed the actual processes and their evolution in space and time to be defined. It has also been possible to correlate such processes to the seabed morphology system, the wave formations which affect the coast, the complex system of sediment transport, as well as to the man-made interventions in the area. The results of recent chemical analyses of beach sediments and bottom sediments off the Bagnoli coast were also incorporated. They prove the presence of heavy metals, PAHs and PCBs in high and sometimes very high concentrations. Finally, based on the results of research and analyses, a hypothesis for an intervention for environmental restoration has been formulated in order to renaturalise the coast through dredging and treatment of the sand, both on the seabed and on the emerged beach. [source] Multimethodological approach to investigate chamber tombs in the Sabine Necropolis at Colle del Forno (CNR, Rome, Italy)ARCHAEOLOGICAL PROSPECTION, Issue 2 2009Salvatore Piro Abstract Non-destructive geophysical prospecting methods are increasingly used for the investigation of archaeological sites, especially where a detailed physical and geometrical reconstruction of structures is required prior to any excavation work. Often, due to the limited size and depth of an archaeological structure, it may be rather difficult to single out its position and extent because of the generally low signal-to noise (S/N) ratio. This can be overcome by improving data acquisition and processing techniques and integrating different geophysical methods. In this work the results of a multimethodological surveys, used with the aim of detecting sharp discontinuities (boundary of cavities and fractures in the host medium) at the Archaeological Test Site of Sabine Necropolis at Research Area of National Research Council of Rome (Montelibretti, Italy) are shown. For the survey a combination of passive and active methods (magnetic, ground-penetrating radar (GPR), and dipole,dipole geoelectric (DDG)), topographical and three-dimensional laser scanner surveys and archaeological excavations were used to study the state of conservation of underground tombs. With all geophysical methods a high-resolution data acquisition was adopted with the aim of reconstructing a global vision of the study area. Signal processing and amplitude time-slice representation techniques were used for the analysis of GPR data. The bi-dimensional cross-correlation technique was applied to enhance the S/N ratio of the magnetic data. An example of the integration (both qualitative and quantitative) of these results is presented for a portion of the investigated area in the Sabine Necropolis at Colle del Forno (Rome, Italy). Archaeological excavations were then conducted systematically after completing the geophysical surveys and interpretations (from 2000 to 2006), which confirmed the location and shape of the individual chamber tombs with associated corridors. Copyright © 2009 John Wiley & Sons, Ltd. [source] SHAFT-HOLE AXES FROM SLOVENIA AND NORTH-WESTERN CROATIA: A FIRST ARCHAEOMETRIC STUDY ON ARTEFACTS MANUFACTURED FROM META-DOLERITES*ARCHAEOMETRY, Issue 6 2009F. BERNARDINI A group of Copper Age shaft-hole axes from Caput Adriae (northeastern Italy, western Slovenia and northwestern Croatia) manufactured using meta-dolerite have been analysed for major and trace elements. All the samples show magmatic textures and well recognizable relicts of primary mineralogical phases. Petrographic observations suggest an ophiolitic provenance of the protolithic source(s) while geochemical data indicate that the original magmas originated in a fore arc or pre arc tectonic setting. Strong similarity has been found with several lithotypes from the Banija Ophiolite Complex (Croatia), here indicated as the most probable source area. Considering the available archaeometric data about shaft-hole axes found in northern Italy and Caput Adriae in comparison to those of axe blades discovered in the same area, it emerges that there is a utilization of different rock types, the source of which appears to be quite close to the discovery sites. In the investigated area the shaft-hole axes are largely made from ophiolitic-related rocks which are associated with copper deposits. Consequently there may have been a relation between the localization of the geological sources of shaft-hole axes and the development of metallurgical activities. [source] Genetic structure of the widespread and common Mediterranean bryophyte Pleurochaete squarrosa (Brid.) Lindb. (Pottiaceae) , evidence from nuclear and plastidic DNA sequence variation and allozymesMOLECULAR ECOLOGY, Issue 4 2007MICHAEL GRUNDMANN Abstract The Mediterranean Basin as one the world's most biologically diverse regions provides an interesting area for the study of plant evolution and spatial structure in plant populations. The dioecious moss Pleurochaete squarrosa is a widespread and common bryophyte in the Mediterranean Basin. Thirty populations were sampled for a study on molecular diversity and genetic structure, covering most major islands and mainland populations from Europe and Africa. A significant decline in nuclear and chloroplast sequence and allozyme variation within populations from west to east was observed. While DNA sequence data showed patterns of isolation by distance, allozyme markers did not. Instead, their considerable interpopulation genetic differentiation appeared to be unrelated to geographic distance. Similar high values for coefficients of gene diversity (GST) in all data sets provided evidence of geographic isolation and limited gene flow among populations (i) within islands, (ii) within mainland areas, and (iii) between islands and mainland. Notably, populations in continental Spain are strongly genetically isolated from all other investigated areas. Surprisingly, there was no difference in gene diversity and GST between islands and mainland areas. Thus, we conclude that large Mediterranean islands may function as ,mainland' for bryophytes. This hypothesis and its implication for conservation biology of cryptogamic plants warrant further investigation. While sexually reproducing populations were found all over the Mediterranean Basin, high levels of multilocus linkage disequilibrium provide evidence of mainly vegetative propagation even in populations where sexual reproduction was observed. [source] Effects of Betamethasone Treatment on Central Myelination in Fetal Sheep: An Electron Microscopical StudyANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 2 2008C. Raschke Summary The long-term effect of betamethasone on the myelination of commissural and associational fibres was investigated in fetal sheep. We studied the corpus callosum and subcortical white matter by electron microscopy. Axons were subdivided into classes according to their axonal diameter: class I: ,0.65 ,m; class II: 0.66,0.84 ,m; class III: ,0.85 ,m. Under control conditions, the different functions of the white matter tracts examined were reflected by three morphological criteria: (1) there was a diverse percentage of axonal classes in the investigated areas. In corpus callosum the axons of class II predominate (47.1%). In the subcortical white matter, class I axons with small diameter are in majority (40.8%). (2) In the subcortical white matter more axons are present, with especially large diameter and hence of axonal class III. (3) The axons of subcortical white matter have thicker myelin sheaths than those of the corpus callosum. Betamethasone administration caused a significant decrease of class II axons in the corpus callosum (36.9%). In corpus callosum, axons of all classes present thicker myelin sheaths. Betamethasone administration resulted in a change in the formation of the myelin sheath in the commissural fibres of the corpus callosum but not in the associational fibres of the subcortical white matter. This could be the morphological correlate to behavioral and cognitive changes known to occur in humans after prenatal glucocorticoid treatment. [source] | ||||||||||||||||