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41.
Mark K. Reagan Julian A. Pearce Katerina Petronotis Renat R. Almeev Aaron J. Avery Claire Carvallo 《International Geology Review》2017,59(11):1439-1450
International Ocean Discovery Program (IODP) Expedition 352 recovered a high-fidelity record of volcanism related to subduction initiation in the Bonin fore-arc. Two sites (U1440 and U1441) located in deep water nearer to the trench recovered basalts and related rocks; two sites (U1439 and U1442) located in shallower water further from the trench recovered boninites and related rocks. Drilling in both areas ended in dolerites inferred to be sheeted intrusive rocks. The basalts apparently erupted immediately after subduction initiation and have compositions similar to those of the most depleted basalts generated by rapid sea-floor spreading at mid-ocean ridges, with little or no slab input. Subsequent melting to generate boninites involved more depleted mantle and hotter and deeper subducted components as subduction progressed and volcanism migrated away from the trench. This volcanic sequence is akin to that recorded by many ophiolites, supporting a direct link between subduction initiation, fore-arc spreading, and ophiolite genesis. 相似文献
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Katerina BARTOSOVA Susanne GIER J. Wright HORTON Jr. Christian KOEBERL Dieter MADER Henning DYPVIK 《Meteoritics & planetary science》2010,45(6):1021-1052
The ICDP–USGS Eyreville drill cores in the Chesapeake Bay impact structure reached a total depth of 1766 m and comprise (from the bottom upwards) basement‐derived schists and granites/pegmatites, impact breccias, mostly poorly lithified gravelly sand and crystalline blocks, a granitic slab, sedimentary breccias, and postimpact sediments. The gravelly sand and crystalline block section forms an approximately 26 m thick interval that includes an amphibolite block and boulders of cataclastic gneiss and suevite. Three gravelly sands (basal, middle, and upper) are distinguished within this interval. The gravelly sands are poorly sorted, clast supported, and generally massive, but crude size‐sorting and subtle, discontinuous layers occur locally. Quartz and K‐feldspar are the main sand‐size minerals and smectite and kaolinite are the principal clay minerals. Other mineral grains occur only in accessory amounts and lithic clasts are sparse (only a few vol%). The gravelly sands are silica rich (～80 wt% SiO2). Trends with depth include a slight decrease in SiO2 and slight increase in Fe2O3. The basal gravelly sand (below the cataclasite boulder) has a lower SiO2 content, less K‐feldspar, and more mica than the higher sands, and it contains more lithic clasts and melt particles that are probably reworked from the underlying suevite. The middle gravelly sand (below the amphibolite block) is finer‐grained, contains more abundant clay minerals, and displays more variable chemical compositions than upper gravelly sand (above the block). Our mineralogical and geochemical results suggest that the gravelly sands are avalanche deposits derived probably from the nonmarine Potomac Formation in the lower part of the target sediment layer, in contrast to polymict diamictons higher in the core that have been interpreted as ocean‐resurge debris flows, which is in agreement with previous interpretations. The mineralogy and geochemistry of the gravelly sands are typical for a passive continental margin source. There is no discernible mixing with marine sediments (no glauconite or Paleogene marine microfossils noted) during the impact remobilization and redeposition. The unshocked amphibolite block and cataclasite boulder might have originated from the outer parts of the transient crater. 相似文献
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Katerina Polychronopoulou Athanasios Lois Deyan Draganov 《Geophysical Prospecting》2020,68(1):232-253
As the global need for mineral resources is constantly rising and the exploitable concentrations of these resources tend to become increasingly complex to explore and exploit, the mining industry is in a constant quest for innovative and cost-effective exploration solutions. In this context, and in the framework of the Smart Exploration action, an integrated passive seismic survey was launched in the Gerolekas bauxite mining site in Central Greece. A passive seismic network, consisting of 129 three-component short-period stations was installed and operated continuously for 4 months. The acquired data permitted detection of approximately 1000 microearthquakes of very small magnitude (duration magnitude ranging between –1.5 and 2.0), located within or at a very close distance from the study area. We use this microseismicity as input for the application of passive seismic interferometry for reflection retrieval, using the body waves (P- and S-wave coda) of the located microearthquakes. We retrieve by autocorrelation zero-offset virtual reflection responses, per component, below each of the recording stations. We process the acquired results using reflection processing techniques to obtain zero-offset time and depth sections, both for P- and for S-waves. In the context of the present work, we evaluate one of the acquired depth sections, using an existing seismic line passing through the Gerolekas passive seismic network, and we perform forward modelling to assess the quality and value of the acquired results. We confirm that passive seismic reflected-wave interferometry could constitute a cost-effective and environmentally friendly innovative exploration alternative, especially in cases of difficult exploration settings. 相似文献
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This paper presents techniques for studying the influence of the atmospheric variables for the explanation of ozone concentrations. A methodology is described for separating the different time scale components in time series of ozone, namely, the global-term component which describes the long and seasonal variations, and the synoptic-scale component. We prove that the decomposition of the time series of ozone and other atmospheric variables is essential for the analysis. The results indicate that solar radiation is the only main factor between all the atmospheric variables for the global and the synoptic-scale component of the ozone time series. Most of the total variance of ozone can be explained by the atmospheric variables, which makes possible the precise estimation of human effect on ozone. In case the solar radiation data are not available, lagged temperature can be used as a supplement of solar radiation. 相似文献
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Bernd Wagner Paul Tauber Alexander Francke Niklas Leicher Steven A. Binnie Aleksandra Cvetkoska Elena Jovanovska Janna Just Jack H. Lacey Zlatko Levkov Katja Lindhorst Katerina Kouli Sebastian Krastel Konstantinos Panagiotopoulos Arne Ulfers Dušica Zaova Timme H. Donders Andon Grazhdani Andreas Koutsodendris Melanie J. Leng Laura Sadori Mirko Scheinert Hendrik Vogel Thomas Wonik Giovanni Zanchetta Thomas Wilke 《Boreas: An International Journal of Quaternary Research》2023,52(1):1-26
Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. 26Al/10Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at c. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a−1 between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake. 相似文献
47.
Trepekli Katerina Balstrøm Thomas Friborg Thomas Fog Bjarne Allotey Albert N. Kofie Richard Y. Møller-Jensen Lasse 《Natural Hazards》2022,113(1):423-451
Natural Hazards - In this study, we present the first findings of the potential utility of miniaturized light and detection ranging (LiDAR) scanners mounted on unmanned aerial vehicles (UAVs) for... 相似文献
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Sharp-interface (or interface) flow models with Dupuit-Forchheimer approximation are widely used to assess, to first order, an aquifer’s vulnerability to seawater intrusion (SWI) and to evaluate sustainable management options for coastal groundwater resources at the screening level. Recognising that interface flow models overestimate SWI, corrections have been proposed to account for the neglected mixing and also for the outflow through a finite gap. These corrections, however, were introduced in the context of specific studies and may not be generally applicable as proposed. The interface model is revisited, placing its corrections in the context of variable-density flow (VDF) theory, by expressing them in terms of the dimensionless parameters governing VDF in schematised (aspect ratio?=?thickness/length) homogeneous confined coastal aquifers: the coupling parameter (α), a Péclet number (Pe), and the dispersivities ratio (rα). Interfaces are compared to the 50%-salinity lines of VDF numerical solutions and regression equations are developed for estimating the outflow gap and for correcting the length of the interface (terminating with a blunted edge); the dispersion correction, which modifies the interface curvature, is restated with a variable exponent. The corrections for dispersion and for the interface length appear to be the most effective; an outflow gap is important only at small α values (strong advection relative to vertical flow due to density differences). These concepts are applied successfully to calculate the interface position in the lowermost confined sub-unit of the Coastal Plain aquifer of Israel, as an estimate of SWI. 相似文献
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Igor Brovchenko Julia Kanarska Vladimir Maderich Katerina Terletska 《Acta Geophysica》2007,55(1):47-55
New three-dimensional numerical non-hydrostatic model with a free surface that was designed for modelling the bottom and bank
stability subjected by ship propeller jets is presented. Unlike all known models, it describes three-dimensional fields of
velocities generated by ship propellers, turbulence intensity and length scale in the given domain of arbitrary bottom and
coastal topography. Results of simulations are compared with the laboratory experiments. 相似文献