Trace element distribution in annual stalagmite laminae mapped by micrometer-resolution X-ray fluorescence: Implications for incorporation of environmentally significant species   总被引：3，自引：0，他引：3  

Andrea Borsato  Silvia Frisia  Andrea Somogyi  Jean Susini 《Geochimica et cosmochimica acta》2007,71(6):1494-1512

Stalagmite ER78, from Grotta di Ernesto cave in NE Italy displays clear annual lamination consistent with its shallow depth below a forest ecosystem subject to autumnal peaking of water infiltration. Synchrotron radiation scanning micro-X-ray fluorescence analyses of heavy elements at European Synchrotron Radiation Facility beamline ID22, and light elements at ID21, with 1-3 μm resolution has been combined with data from ion microprobe analyses to reveal chemical variability across the visible layers of these annual laminae. A series of elements display a symmetrical peak, centered around the thin, dark layer at the top of each lamina. The peak concentration is ordered Y > Zn, Cu and Pb > P and Br. This hierarchy is thought to reflect the selectivity of transport of these elements, possibly by organic colloids flushed from the soil zone during autumn infiltration. Ion microprobe analysis indicates Na and F also increase, as does H, the latter reflecting increased microporosity. Sr displays a trough around the dark and thin autumn layer implying that its incorporation may be limited by competition with other elements. Mg and S show a different pattern of annual variation and Fe displays none. The trace metals, Br and Y display peak abundance in the early 20th century, which appears to reflect a period of tree-felling rather than a climatic anomaly. The results demonstrate the power of the high spatial resolution and low detection limits of the synchrotron technique, and its ability to produce quantitative maps that allow distinction of layered structure from that of isolated particles, or irregular inhomogeneities.  相似文献   

Palynological biozones and radiometric data at the Carboniferous–Permian boundary in western Gondwana     

Silvia N. Csari 《Gondwana Research》2007,11(4):529-536

Absolute radiometric data obtained recently in Upper Paleozoic basins of South America and Southern Africa are available to constrain the age of some palynological biozones defined in the Western Gondwana. Some dates obtained from Argentina coincide with southern Africa's and are useful to constrain the palynological associations. In this way, the Permian Argentinian Lueckisporites–Weylandites (LW) Biozone is compared with the Lueckisporites virkkiae Biozone of Brazil and Zone 3 of South Africa. On the other hand, the palynofloras from Dwyka (South Africa) are comparable with Argentinian and Brazilian associations recovered near the Carboniferous–Permian boundary. Tuffaceous intervals of the Dwyka Group in South Africa suggest the beginning of that sequence at 307 Ma reaching the 290 Ma at the top. The available palynological, paleoenvironmental and radiometric data from these three western Gondwanan areas are analyzed and compared.  相似文献   

Documentary Evidence on Climate in Sixteenth-Century Europe   总被引：2，自引：0，他引：2  

Christian Pfister  Rudolf Brázdil  Rüdiger Glaser  Mariano Barriendos  Dario Camuffo  Mathias Deutsch  Petr Dobrovolný  Silvia Enzi  Emanuela Guidoboni  Oldřich Kotyza  Stefan Militzer  Lajos Rácz  Fernando S. Rodrigo 《Climatic change》1999,43(1):55-110

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Sédimentologie et paléontologie des paléoenvironnements côtiers rupéliens de la Molasse marine rhénane dans le Jura suisse     

Laurent Picot  Damien Becker  Lionel Cavin  Claudius Pirkenseer  Frédéric Lapaire  Gaëtan Rauber  Peter A. Hochuli  Silvia Spezzaferri  Jean-Pierre Berger 《Swiss Journal of Geoscience》2008,101(2):483-513

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The Late Pleistocene clastic deposits in the Romito Cave,southern Italy: a proxy record of environmental changes and human presence     

Massimiliano Ghinassi  Andrè C. Colonese  Zelia Di Giuseppe  Lisa Govoni  Domenico Lo Vetro  Giulia Malavasi  Fabio Martini  Silvia Ricciardi  Benedetto Sala 《第四纪科学杂志》2009,24(4):383-398

Clastic sediments deposited in caves and rock shelters bear peculiar sedimentological characteristics and have seldom been considered as a high‐resolution proxy record of climatic or environmental changes. The Romito Cave has its entrance at 275 m above sea level, about 25 km from the Tyrrhenian coast of Calabria, southern Italy. New archaeological excavation performed since 2000 has revealed a sedimentary succession spanning the record of Gravettian to Late Epigravettian cultures (Late Pleistocene). The present study focuses on the lower part (2.5 m thick) of the succession, where three main unconformity‐bounded stratigraphic units have been recognised (labelled RM1–3). Each unit consists of water‐lain deposits indicating high‐ to low‐competence flow, capped with anthropogenic deposits. The gradual deactivation and reactivation of the water drainage between 23 475 ± 190 and 16 250 ± 500 cal. a BP is correlated with regional precipitation changes due to the onset of dry climatic conditions of the Last Glacial Maximum. However, the deactivation of cave drainage after the deposition of unit RM3, around 15 400 ± 500 cal. a BP, deviates from the regional hydrological trend of progressively increasing water discharges and is attributed to the drainage cut‐off by probable cave wall collapses. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Star formation and stellar populations across nuclear rings in galaxies     

M. Sarzi  E. L. Allard  J. H. Knapen  L. M. Mazzuca 《Monthly notices of the Royal Astronomical Society》2007,380(3):949-962

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Relating electrical conduction of alluvial sediments to textural properties and pore‐fluid conductivity     

Mauro Mele  Silvia Inzoli  Mauro Giudici  Riccardo Bersezio 《Geophysical Prospecting》2014,62(3):631-645

Electrical conductivity of alluvial sediments depends on litho‐textural properties, fluid saturation and porewater conductivity. Therefore, for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers, it can be useful to characterize the prevailing mechanisms of electrical conduction (electrolytic or shale conduction) according to the litho‐textural properties and to the porewater characteristics. An experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the Po plain (Northern Italy), characterized by different grain‐size distribution, and fully saturated with porewater of variable conductivity. The bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two‐component model, which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample, and with a three‐component model. The latter is based on the two endmember mechanisms, surface and electrolytic conduction, but takes into account also the interaction between dissolved ions in the pores and the fluid‐grain interface. The experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume.  相似文献   

The physical conditions in the BHR71 outflows     

Bérengère Parise  Arnaud Belloche  Silvia Leurini  Peter Schilke 《Astrophysics and Space Science》2008,313(1-3):73-76

Highly-collimated outflows are believed to be the earliest stage in outflow evolution, so their study is essential for understanding the processes driving outflows. The BHR71 Bok globule is known to harbour such a highly-collimated outflow, which is powered by a protostar belonging to a protobinary system. Using the APEX telescope on Chajnantor, we mapped the BHR71 highly-collimated outflow in CO(3-2), and observed several bright points of the outflow in the molecular transitions CO(4-3), CO(7-6), ¹³CO(3-2), C¹⁸O(3-2), CH₃OH(7-6) and H₂CO(4-3). We use an LVG code to characterise the temperature enhancements in these regions. These observations are particularly interesting for investigating the interaction of collimated outflows with the ambient molecular cloud. In our CO(3-2) map, the second outflow driven by IRS2, which is the second source of the binary system, is completely revealed and shown to be bipolar. We also measure temperature enhancements in the lobes. The CO and methanol LVG modelling points to temperatures between 30 and 50 K in the two lobes. The methanol emission in the southern lobe bright knot is barely resolved with the APEX single-dish. ALMA will thus be a central tool to study the shock chemistry in these regions.  相似文献   

Modelling the cosmological co-evolution of supermassive black holes and galaxies – I. BH scaling relations and the AGN luminosity function     

Federico Marulli  Silvia Bonoli  Enzo Branchini  Lauro Moscardini  Volker Springel 《Monthly notices of the Royal Astronomical Society》2008,385(4):1846-1858

We model the cosmological co-evolution of galaxies and their central supermassive black holes (BHs) within a semi-analytical framework developed on the outputs of the Millennium Simulation. This model, described in detail by Croton et al. and De Lucia and Blaizot, introduces a 'radio mode' feedback from active galactic nuclei (AGN) at the centre of X-ray emitting atmospheres in galaxy groups and clusters. Thanks to this mechanism, the model can simultaneously explain: (i) the low observed mass dropout rate in cooling flows; (ii) the exponential cut-off in the bright end of the galaxy luminosity function and (iii) the bulge-dominated morphologies and old stellar ages of the most massive galaxies in clusters. This paper is the first of a series in which we investigate how well this model can also reproduce the physical properties of BHs and AGN. Here we analyse the scaling relations, the fundamental plane and the mass function of BHs, and compare them with the most recent observational data. Moreover, we extend the semi-analytic model to follow the evolution of the BH mass accretion and its conversion into radiation, and compare the derived AGN bolometric luminosity function with the observed one. While we find for the most part a very good agreement between predicted and observed BH properties, the semi-analytic model underestimates the number density of luminous AGN at high redshifts, independently of the adopted Eddington factor and accretion efficiency. However, an agreement with the observations is possible within the framework of our model, provided it is assumed that the cold gas fraction accreted by BHs at high redshifts is larger than at low redshifts.  相似文献   

Ostreopsis cf. ovata (Dinophyta) bloom in an equatorial island of the Atlantic Ocean     

Nascimento SM  França JV  Gonçalves JE  Ferreira CE 《Marine pollution bulletin》2012,64(5):1074-1078

The epi-benthic dinoflagellate Ostreopsis cf. ovata Fukuyo has an increasingly global distribution. In Brazil there are reports of O. cf. ovata along the coast from 8°S to 27°S latitude and blooms have been registered on the Rio de Janeiro coastline. In the current study, an O. cf. ovata bloom is reported at Saint Paul's Rocks (0°55'10″N; 29°20'33″W), between the southern and northern hemispheres. The Archipelago is not inhabited and not subjected to eutrophication, due to isolation, and sustains a number of endemic species. Therefore, blooms of O. cf. ovata may potentially cause demise to trophic chains by affecting marine invertebrates and vertebrates.  相似文献