Search results for "Rift"
showing 10 items of 526 documents
Geochemistry, petrogenesis and tectonic setting of the Samothraki mafic suite, NE Greece: Trace-element, isotopic and zircon age constraints
2009
Abstract The Samothraki mafic suite in the north-eastern Aegean Sea, Greece, is an ‘in situ’ magmatic complex comprising gabbros, sparse dykes and basalt flows and pillows cut by late dolerite dykes. We have determined the age of the complex by SHRIMP zircon geochronology of a gabbro as 159.9 ± 4.5 Ma (i.e. Oxfordian; early Late Jurassic), which precludes any correlation with the so-called Lesvos ophiolite further south (253.1 ± 5.6 Ma; Latest Permian). Six distinct, hitherto unrecognised, geochemical groups have been identified among the basalts and dolerites of the Samothraki mafic suite on the basis of trace-element and Nd–Sr isotopic characteristics. All groups show the presence of an e…
Chemical composition of modern and fossil hippopotamid teeth and implications for paleoenvironmental reconstructions and enamel formation – Part 2: A…
2012
Abstract. For reconstructing environmental change in terrestrial realms the geochemistry of fossil bioapatite in bones and teeth is among the most promising applications. This study demonstrates that alkaline earth elements in enamel of Hippopotamids, in particular Ba and Sr are tracers for water provenance and hydrochemistry. The studied specimens are molar teeth from Hippopotamids found in modern and fossil lacustrine settings of the Western Branch of the East African Rift system (Lake Kikorongo, Lake Albert, and Lake Malawi) and from modern fluvial environments of the Nile River. Concentrations in enamel vary by ca. two orders of magnitude for Ba (120–9336 μg g−1) as well as for Sr (9–21…
Brittle reactivation of ductile shear zones in NW Namibia in relation to South Atlantic rifting
2015
Rifting has occurred worldwide along preexisting mobile belts, which are therefore thought to control rift orientation on a large scale. On a smaller scale, shear zones within mobile belts are reactivated as rift faults. In NW Namibia, shear zones of the Neoproterozoic Kaoko Belt run subparallel to the present-day continental passive margin and are inferred to have been reactivated during the opening of the South Atlantic Ocean. However, the extent of this reactivation and the influence of the reactivated shear zones on South Atlantic rifting are largely unknown. A combined remote sensing and field study was conducted to quantify offsets that are a direct function of shear zone reactivation…
Petrology and geochemistry of submarine volcanism in the Sicily Channel Rift
2006
Submarine magmatism in the Sicily Channel Rift began in the early Pliocene and lasted until almost 200 yr ago. We present here petrological and geochemical data on volcanic rocks dredged from Graham and Nameless banks and Pantelleria seamounts in the Pelagian sector of the Sicily Channel Rift. Petrological evidence suggests that the ascent of magmas to the surface was relatively rapid, probably through channels superimposed over the major tectonic discontinuities of the Rift. Major and trace element data indicate an ocean island basalt affinity for Graham and Nameless bank alkaline lavas and a depleted tholeiitic signature for one Pantelleria seamount, which had a shallower mantle source. S…
Geochemical evolution of rift magmas by progressive tapping of a stratified mantle source beneath the Ross Sea Rift, Northern Victoria Land, Antarcti…
1995
Abstract Source compositions of Neogene-Quaternary volcanic rocks from the McMurdo Volcanic Group of the Ross Sea Rift in Northern Victoria Land, Antarctica are constrained by NdSrPb isotopes and trace element ratios in near-primary basalts. The rocks erupted along the western rift margin (Victoria Land Basin) and the western rift shoulder (Transantarctic Mountains). Near-primary basalts show no evidence of crustal contamination, suggesting that their initial NdSrPb isotopes reflect the composition of their mantle sources. The initial isotope ratios of near-primary basalts range from about 87 Sr 86 Sr = 0.70281 to 0.70504 and 143 Nd 144 Nd = 0.51269 to 0.51291 (ϵNd(t) = 1.3–5.5). The 20…
The Lefkada barrier and beachrock system (NW Greece) — Controls on coastal evolution and the significance of extreme wave events
2012
Abstract The Lefkada–Preveza coastal zone, NW Greece, is characterised by an active barrier system and related extensive beachrock sequences. Besides the gradual coastal processes of longshore drift and spit evolution, the presence of active tectonics and the occurrence of tsunamis have been documented in previous studies and are part of the coastal geomorphological system. In this paper, we present the results of detailed multi-proxy sedimentological and geomorphological investigations carried out along the northern part of the barrier system and in back-beach positions. Our findings suggest that extreme wave events contributed to coastal and environmental changes and involved temporary br…
Beyond budgeting since inception: what is the status?
2017
Master's thesis Business Administration BE501 - University of Agder 2017 The Beyond Budgeting idea as developed by Hope and Fraser (1997) has been in existence for almost twenty years, yet, the research community still has divergent views on whether the concept is a better management accounting tool for organizations’ management control system or not. Also, whether it has received attention in research community like other management accounting tools such as Traditional Budgeting and Balanced Scorecard. On this notion, this study is developed to investigate the status of the research discourse on the concept to gain relevant knowledge. Inspired by Scapens and Bromwich (2001) and built on Ac…
Genetic relationships between sympatric and allopatric Coregonus ciscoes in North and Central Europe
2021
Abstract Background Sympatric speciation along ecological gradients has been studied repeatedly, in particular in freshwater fishes. Rapid post-glacial ecological divergence has resulted in numerous endemic species or ecologically distinct populations in lakes of the temperate zones. Here, we focus on the Baltic cisco (Coregonus albula) complex, to study the genetic similarity among two pairs of sympatric autumn- and spring-spawning populations from post-glacial German Lakes Stechlin and Breiter Luzin. For comparison, we included a similar pair of sympatric populations from the Swedish Lake Fegen. We wanted to explore potential genetic similarities between the three sympatric cisco populati…
Crossing Borders. Concepts and Practices for a New Planetary Dimension
2020
The essay takes into account some categories and practices of colonial relations by considering both domination and subjectification processes and handles the concept of border and the complex dynamics of crossing, mobility, diaspora, and hybridization. The critical analysis of the hierarchical order of the world highlights the ways in which the relations between non-homogeneous elements produce conflict and assimilation practices, but also contaminations and inclusion. By assuming the "colonial" as a precarious concept, the essay stresses the discursive aspects of dominion but also the government, counter-conducts, and resistances, without forecloses the persistence of the epistemological …
Large eddy simulation model for wind-driven sea circulation in coastal areas
2013
Abstract. In the present paper a state-of-the-art large eddy simulation model (LES-COAST), suited for the analysis of water circulation and mixing in closed or semi-closed areas, is presented and applied to the study of the hydrodynamic characteristics of the Muggia bay, the industrial harbor of the city of Trieste, Italy. The model solves the non-hydrostatic, unsteady Navier–Stokes equations, under the Boussinesq approximation for temperature and salinity buoyancy effects, using a novel, two-eddy viscosity Smagorinsky model for the closure of the subgrid-scale momentum fluxes. The model employs: a simple and effective technique to take into account wind-stress inhomogeneity related to the …