5 resultados para Eastern Hemisphere

em AMS Tesi di Dottorato - Alm@DL - Università di Bologna


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This volume is a collection of the work done in a three years-lasting PhD, focused in the analysis of Central and Southern Adriatic marine sediments, deriving from the collection of a borehole and many cores, achieved thanks to the good seismic-stratigraphic knowledge of the study area. The work was made out within European projects EC-EURODELTA (coordinated by Fabio Trincardi, ISMAR-CNR), EC-EUROSTRATAFORM (coordinated by Phil P. E. Weaver, NOC, UK), and PROMESS1 (coordinated by Serge Bernè, IFREMER, France). The analysed sedimentary successions presented highly expanded stratigraphic intervals, particularly for the last 400 kyr, 60 kyr and 6 kyr BP. These three different time-intervals resulted in a tri-partition of the PhD thesis. The study consisted of the analysis of planktic and benthic foraminifers’ assemblages (more than 560 samples analysed), as well as in preparing the material for oxygen and carbon stable isotope analyses, and interpreting and discussing the obtained dataset. The chronologic framework of the last 400 kyr was achieved for borehole PRAD1-2 (within the work-package WP6 of PROMESS1 project), collected in 186.5 m water depth. The proposed chronology derives from a multi-disciplinary approach, consisting of the integration of numerous and independent proxies, some of which analysed by other specialists within the project. The final framework based on: micropaleontology (calcareous nannofossils and foraminifers’ bioevents), climatic cyclicity (foraminifers’ assemblages), geochemistry (oxygen stable isotope, made out on planktic and benthic records), paleomagnetism, radiometric ages (14C AMS), teprhochronology, identification of sapropel-equivalent levels (Se). It’s worth to note the good consistency between the oxygen stable isotope curve obtained for borehole PRAD1-2 and other deeper Mediterranean records. The studied proxies allowed the recognition of all the isotopic intervals from MIS10 to MIS1 in PRAD1-2 record, and the base of the borehole has been ascribed to the early MIS11. Glacial and interglacial intervals identified in the Central Adriatic record have been analysed in detail for the paleo-environmental reconstruction, as well. For instance, glacial stages MIS6, MIS8 and MIS10 present peculiar foraminifers’ assemblages, composed by benthic species typical of polar regions and no longer living in the Central Adriatic nowadays. Moreover, a deepening trend in the paleo-bathymetry during glacial intervals was observed, from MIS10 (inner-shelf environment) to MIS4 (mid-shelf environment).Ten sapropel-equivalent levels have been recognised in PRAD1-2 Central Adriatic record. They showed different planktic foraminifers’ assemblages, which allowed the first distinction of events occurred during warm-climate (Se5, Se7), cold-climate (Se4, Se6 and Se8) and temperate-intermediate-climate (Se1, Se3, Se9, Se’, Se10) conditions, consistently with literature. Cold-climate sapropel equivalents are characterised by the absence of an oligotrophic phase, whereas warm-temeprate-climate sapropel equivalents present both the oligotrophic and the eutrophic phases (except for Se1). Sea floor conditions vary, according to benthic foraminifers’ assemblages, from relatively well oxygenated (Se1, Se3), to dysoxic (Se9, Se’, Se10), to highly dysoxic (Se4, Se6, Se8) to events during which benthic foraminifers are absent (Se5, Se7). These two latter levels are also characterised by the lamination of the sediment, feature never observed in literature in such shallow records. The enhanced stratification of the water column during the events Se8, Se7, Se6, Se5, Se4, and the concurring strong dilution of shallow water, pointed out by the isotope record, lead to the hypothesis of a period of intense precipitation in the Central Adriatic region, possibly due to a northward shift of the African Monsoon. Finally, the expression of Central Adriatic PRAD1-2 Se5 equivalent was compared with the same event, as registered in other Eastern Mediterranean areas. The sequence of substantially the same planktic foraminifers’ bioevents has been consistently recognised, indicating a similar evolution of the water column all over the Eastern Mediterranean; yet, the synchronism of these events cannot be demonstrated. A high resolution analysis of late Holocene (last 6000 years BP) climate change was carried out for the Adriatic area, through the recognition of planktic and benthic foraminifers’ bioevents. In particular, peaks of planktic Globigerinoides sacculifer (four during the last 5500 years BP in the most expanded core) have been interpreted, based on the ecological requirements of this species, as warm-climate, arid intervals, correspondent to periods of relative climatic optimum, such as, for instance, the Medieval Warm Period, the Roman Age, the Late Bronze Age and the Copper Age. Consequently, the minima in the abundance of this biomarker could correspond to relatively cooler and more rainy periods. These conclusions are in good agreement with the isotopic and the pollen data. The Last Occurrence (LO) of G. sacculifer has been dated in this work at an average age of 550 years BP, and it is the best bioevent approximating the base of the Little Ice Age in the Adriatic. Recent literature reports the same bioevent in the Levantine Basin, showing a rather consistent age. Therefore, the LO of G. sacculifer has the potential to be extended to all the Eastern Mediterranean. Within the Little Ice Age, benthic foraminifer V. complanata shows two distinct peaks in the shallower Adriatic cores analysed, collected hundred kilometres apart, inside the mud belt environment. Based on the ecological requirements of this species, these two peaks have been interpreted as the more intense (cold and rainy) oscillations inside the LIA. The chronologic framework of the analysed cores is robust, being based on several range-finding 14C AMS ages, on estimates of the secular variation of the magnetic field, on geochemical estimates of the activity depth of 210Pb short-lived radionuclide (for the core-top ages), and is in good agreement with tephrochronologic, pollen and foraminiferal data. The intra-holocenic climate oscillations find out in the Adriatic have been compared with those pointed out in literature from other records of the Northern Hemisphere, and the chronologic constraint seems quite good. Finally, the sedimentary successions analysed allowed the review and the update of the foraminifers’ ecobiostratigraphy available from literature for the Adriatic region, thanks to the achievement of 16 ecobiozones for the last 60 kyr BP. Some bioevents are restricted to the Central Adriatic (for instance the LO of benthic Hyalinea balthica , approximating the MIS3/MIS2 boundary), others occur all over the Adriatic basin (for instance the LO of planktic Globorotalia inflata during MIS3, individuating Dansgaard-Oeschger cycle 8 (Denekamp)).

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Clusters have increasingly become an essential part of policy discourses at all levels, EU, national, regional, dealing with regional development, competitiveness, innovation, entrepreneurship, SMEs. These impressive efforts in promoting the concept of clusters on the policy-making arena have been accompanied by much less academic and scientific research work investigating the actual economic performance of firms in clusters, the design and execution of cluster policies and going beyond singular case studies to a more methodologically integrated and comparative approach to the study of clusters and their real-world impact. The theoretical background is far from being consolidated and there is a variety of methodologies and approaches for studying and interpreting this phenomenon while at the same time little comparability among studies on actual cluster performances. The conceptual framework of clustering suggests that they affect performance but theory makes little prediction as to the ultimate distribution of the value being created by clusters. This thesis takes the case of Eastern European countries for two reasons. One is that clusters, as coopetitive environments, are a new phenomenon as the previous centrally-based system did not allow for such types of firm organizations. The other is that, as new EU member states, they have been subject to the increased popularization of the cluster policy approach by the European Commission, especially in the framework of the National Reform Programmes related to the Lisbon objectives. The originality of the work lays in the fact that starting from an overview of theoretical contributions on clustering, it offers a comparative empirical study of clusters in transition countries. There have been very few examples in the literature that attempt to examine cluster performance in a comparative cross-country perspective. It adds to this an analysis of cluster policies and their implementation or lack of such as a way to analyse the way the cluster concept has been introduced to transition economies. Our findings show that the implementation of cluster policies does vary across countries with some countries which have embraced it more than others. The specific modes of implementation, however, are very similar, based mostly on soft measures such as funding for cluster initiatives, usually directed towards the creation of cluster management structures or cluster facilitators. They are essentially founded on a common assumption that the added values of clusters is in the creation of linkages among firms, human capital, skills and knowledge at the local level, most often perceived as the regional level. Often times geographical proximity is not a necessary element in the application process and cluster application are very similar to network membership. Cluster mapping is rarely a factor in the selection of cluster initiatives for funding and the relative question about critical mass and expected outcomes is not considered. In fact, monitoring and evaluation are not elements of the cluster policy cycle which have received a lot of attention. Bulgaria and the Czech Republic are the countries which have implemented cluster policies most decisively, Hungary and Poland have made significant efforts, while Slovakia and Romania have only sporadically and not systematically used cluster initiatives. When examining whether, in fact, firms located within regional clusters perform better and are more efficient than similar firms outside clusters, we do find positive results across countries and across sectors. The only country with negative impact from being located in a cluster is the Czech Republic.

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Iberia Africa plate boundary, cross, roughly W-E, connecting the eastern Atlantic Ocean from Azores triple junction to the Continental margin of Morocco. Relative movement between the two plate change along the boundary, from transtensive near the Azores archipelago, through trascurrent movement in the middle at the Gloria Fracture Zone, to transpressive in the Gulf of Cadiz area. This study presents the results of geophysical and geological analysis on the plate boundary area offshore Gibraltar. The main topic is to clarify the geodynamic evolution of this area from Oligocene to Quaternary. Recent studies have shown that the new plate boundary is represented by a 600 km long set of aligned, dextral trascurrent faults (the SWIM lineaments) connecting the Gloria fault to the Riff orogene. The western termination of these lineaments crosscuts the Gibraltar accretionary prism and seems to reach the Moroccan continental shelf. In the past two years newly acquired bathymetric data collected in the Moroccan offshore permit to enlighten the present position of the eastern portion of the plate boundary, previously thought to be a diffuse plate boundary. The plate boundary evolution, from the onset of compression in the Oligocene to the Late Pliocene activation of trascurrent structures, is not yet well constrained. The review of available seismics lines, gravity and bathymetric data, together with the analysis of new acquired bathymetric and high resolution seismic data offshore Morocco, allows to understand how the deformation acted at lithospheric scale under the compressive regime. Lithospheric folding in the area is suggested, and a new conceptual model is proposed for the propagation of the deformation acting in the brittle crust during this process. Our results show that lithospheric folding, both in oceanic and thinned continental crust, produced large wavelength synclines bounded by short wavelength, top thrust, anticlines. Two of these anticlines are located in the Gulf of Cadiz, and are represented by the Gorringe Ridge and Coral Patch seamounts. Lithospheric folding probably interacted with the Monchique – Madeira hotspot during the 72 Ma to Recent, NNE – SSW transit. Plume related volcanism is for the first time described on top of the Coral Patch seamount, where nine volcanoes are found by means of bathymetric data. 40Ar-39Ar age of 31.4±1.98 Ma are measured from one rock sample of one of these volcanoes. Analysis on biogenic samples show how the Coral Patch act as a starved offshore seamount since the Chattian. We proposed that compression stress formed lithospheric scale structures playing as a reserved lane for the upwelling of mantle material during the hotspot transit. The interaction between lithospheric folding and the hotspot emplacement can be also responsible for the irregularly spacing, and anomalous alignments, of individual islands and seamounts belonging to the Monchique - Madeira hotspot.

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Longstanding debates concerning the origin of the Kess Kess Emsian carbonate mounds exposed at Hamar Laghdad Ridge (eastern Anti-Atlas, Morocco) centre around the processes that induced precipitation of carbonate mud and the preservation of steep morphologies. Although in the last years an origin related to hydrothermalism seemed to be more likely, to date the Kess Kess are still considered controversial vent deposits. This study combines in updated research review information from previous work and new detailed field observations coupled with new analytical results to define a consistent framework and some new insight of current knowledge about the origin of these mounds. We obtain a complete minero-petrographic and palaeobiological data set and a detailed geochemical characterization of the different lithologies and facies of the Hamar Laghdad stratigraphic succession, including mounds, and we compared the results with the data from Maïder Basin mounds (Anti-Atlas, Morocco). Our data support the hydrothermal model proposed for the genesis and development of the Kess Kess mounds. The mechanisms linked to the mounds formation and growth are discussed in the light of the new finding of fluid-sediment interaction within a scenario driven by late magmatic fluids circulation. Conical mounds and other fluids related morphologies were also reported from Crommelin crater area (Arabia Terra, Mars). These mounds consist in meter-sized conical buildups hosted in the Equatorial Layered Deposits (ELDs) deposed during a regional groundwater fluid upwelling. Geometries and geological conditions that might have controlled the development of such morphologies were discussed. According to our data the morphological and stratigraphical characteristics of Crommelin area mounds are most consistent with a formation by fluids advection. Then we compare terrestrial and Martian data and examine the geological settings of hydrothermal mound occurrences on Earth in order to describe potential target areas for hydrothermal structures on Mars.

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The analysis of apatite fission tracks is applied to the study of the syn- and post-collisional thermochronological evolution of a vast area that includes the Eastern Pontides, their continuation in the Lesser Caucasus of Georgia (Adjara-Trialeti zone) and northern Armenia, and the eastern Anatolian Plateau. The resulting database is then integrated with the data presented by Okay et al. (2010) for the Bitlis Pütürge Massif, i.e. the western portion of the Bitlis-Zagros collision zone between Arabia and Eurasia. The mid-Miocene exhumation episode along the Black Sea coast and Lesser Caucasus of Armenia documented in this dissertation mirrors the age of collision between the Eurasian and Arabian plates along the Bitlis suture zone. We argue that tectonic stresses generated along the Bitlis collision zone were transmitted northward across eastern Anatolia and focused (i) at the rheological boundary between the Anatolian continental lithosphere and the (quasi)oceanic lithosphere of the Black Sea, and (ii) along major pre-existing discontinuities like the Sevan-Akera suture zone.The integration of both present-day crustal dynamics (GPS-derived kinematics and distribution of seismicity) and thermochronological data presented in this paper provides a comparison between short- and long-term deformation patterns for the entire eastern Anatolia-Transcaucasian region. Two successive stages of Neogene deformation of the northern foreland of the Arabia-Eurasia collision zone can be inferred. (i) Early and Middle Miocene: continental deformation was concentrated along the Arabia-Eurasia (Bitlis) collision zone but tectonic stress was also transferred northward across eastern Anatolia, focusing along the eastern Black Sea continent-ocean rheological transition and along major pre-existing structural discontinuities. (ii) Since Late-Middle Miocene time the westward translation of Anatolia and the activation of the North and Eastern Anatolian Fault systems have reduced efficient northward stress transfer.