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171.
Bernardi Mara S. Africa Pasquale C. de Falco Carlo Formaggia Luca Menafoglio Alessandra Vantini Simone 《Mathematical Geosciences》2021,53(8):1781-1812
Mathematical Geosciences - Recent advances in satellite technologies, statistical and mathematical models, and computational resources have paved the way for operational use of satellite data in... 相似文献
172.
Gariano S. L. Verini Supplizi G. Ardizzone F. Salvati P. Bianchi C. Morbidelli R. Saltalippi C. 《Natural Hazards》2021,106(3):2207-2225
Natural Hazards - Analyses of historical records of landslides and climate variables are useful tools to search for correlations between damaging landslide events and their triggers. In this work,... 相似文献
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Daniel Ariztegui María Martha Bianchi Julieta Masaferro Eric Lafargue Frank Niessen 《第四纪科学杂志》1997,12(4):333-338
Several high-resolution continental records have been reported recently in sites in South America, but the extent to which climatic variations were synchronous between the northern and southern hemispheres during the Late-glacial–Holocene transition, and the causes of the climatic changes, remain open questions. Previous investigations indicated that, east of the Andes, the middle and high latitudes of South America warmed uniformly and rapidly from 13 000 14C yr BP, with no indication of subsequent climate fluctuations, equivalent, for example, to the Younger Dryas cooling. Here we present a multiproxy continuous record, radiocarbon dated by accelerated mass spectroscopy, from proglacial Lake Mascardi in Argentina. The results show that unstable climatic conditions, comparable to those described from records obtained in the Northern Hemisphere, dominated the Late-glacial–Holocene transition in Argentina at this latitude. Furthermore, a significant advance of the Tronador ice-cap, which feeds Lake Mascardi, occurred during the Younger Dryas Chronozone. This instability suggests a step-wise climatic history reflecting a global, rather than regional, forcing mechanism. The Lake Mascardi record, therefore, provides strong support for the hypothesis that ocean–atmosphere interaction, rather than global ocean circulation alone, governed interhemispheric climate teleconnections during the last deglaciation. © 1997 John Wiley & Sons, Ltd. 相似文献
176.
Arianna Secchiari Alessandra Montanini Delphine Bosch Patrizia Macera Dominique Cluzel 《地学前缘(英文版)》2020,11(1):37-55
The New Caledonia ophiolite(Peridotite Nappe)consists primarily of harzburgites,locally overlain by mafic-ultramafic cumulates,and minor spinel and plagioclase lherzolites.In this study,a comprehensive geochemical data set(major and trace element,Sr-Nd-Pb isotopes)has been obtained on a new set of fresh harzburgites in order to track the processes recorded by this mantle section and its evolution.The studied harzburgites are low-strain tectonites showing porphyroclastic textures,locally grading into protomylonitic textures.They exhibit a refractory nature,as attested by the notable absence of primary clinopyroxene,very high Fo content of olivine(91-93 mol.%),high Mg#of orthopyroxene(0.91-0.93)and high Cr#of spinel(0.44-0.71).The harzburgites are characterised by remarkably low REE concentrations(<0.1 chondritic values)and display"U-shaped"profiles,with steeply sloping HREE(DyN/YbN=0.07-0.16)and fractionated LREE-MREE segments(LaN/SmN=2.1-8.3),in the range of modern fore-arc peridotites.Geochemical modelling shows that the HREE composition of the harzburgites can be reproduced by multi-stage melting including a first phase of melt depletion in dry conditions(15%fractional melting),followed by hydrous melting in a subduction zone setting(up to 15%-18%).However,melting models fail to explain the enrichments observed for some FME(i.e.Ba,Sr,Pb),LREE-MREE and Zr-Hf.These enrichments,coupled with the frequent occurrence of thin,undeformed films of Al2 O3,and CaO-poor orthopyroxene(Al2O3=0.88-1.53 wt.%,CaO=0.31-0.56 wt.%)and clinopyroxene with low Na2 O(0.03-0.16 wt.%),Al2 O3(0.66-1.35 wt.%)and TiO2(0.04-0.10 wt.%)contents,point to FME addition during fluid-assisted melting followed by late stage metasomatism most likely operated by subductionrelated melts with a depleted trace element signature.Nd isotopic ratios range from unradiogenic to radiogenic(-0.80<εNdi≤+13.32)and negatively correlate with Sr isotopes(0.70257≤87Sr/86Sr≤0.70770).Pb isotopes cover a wide range,trending from DMM toward enriched,sediment-like,compositions.We interpret the geochemical signature displayed by the New Caledonia harzburgites as reflecting the evolution of a highly depleted fore-arc mantle wedge variably modified by different fluid and melt inputs during Eocene subduction. 相似文献
177.
Matthew N. Waters Michael F. Piehler Antonio B. Rodriguez Joseph M. Smoak Thomas S. Bianchi 《Journal of Paleolimnology》2009,42(1):51-64
Lake Mattamuskeet, North Carolina, USA is a large (162 km2) and shallow (mean depth = 1 m) coastal lake, which was significantly modified to support agricultural activities following
European settlement in 1850. Paleolimnological proxies measured on a 400-cm sediment core collected from Lake Mattamuskeet
reveal shifts in organic matter input and primary producer community structure in response to climatic and human impacts on
the lake during the late Holocene. Stratigraphic changes in organic matter content, nutrients, metals, lignin phenols and
photosynthetic pigments were used to divide the sediment core into three intervals. Interval I includes sediment deposited
between A.D. 360–1584 and indicates a clear-water, sand-bottom state with low algal abundance. In addition, the lake catchment
area experienced two significant fires during this interval that were recorded as charcoal layers in the core around A.D.
360 and A.D. 1435 (calibrated 14C AMS dates). Trophic structure changed with the onset of Interval II (A.D. 1584–1860) when total algal abundance increased,
and the primary producer community was comprised primarily of diatoms, chrysophytes, cryptophytes and cyanobacteria. During
this interval there was also an increase in terrestrial organic material input into the lake as well as a shift in plant type
from woody gymnosperms to non-woody angiosperms as determined from lignin data. Sediment deposited in Lake Mattamuskeet following
European settlement (Interval III, A.D. 1860-present) suggests a dramatic increase in organic-matter deposition, metals, primary-producer
abundance and the onset of cyanobacterial dominance. Sedimentary evidence indicates that shallow-water primary producers can
respond rapidly to climate change and human development. 相似文献
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179.
Monica Montefalcone Giancarlo Albertelli Carla Morri Valeriano Parravicini Carlo Nike Bianchi 《Marine pollution bulletin》2009,58(4):515-262
Using the Conservation Index, which measures the proportional amount of dead matte relative to live Posidonia oceanica, we assessed the health of 15 P. oceanica meadows at a regional scale along the coast of Liguria (NW Mediterranean). These areas were characterized by different degrees of anthropization, from highly urbanized sites to marine protected areas. Two different scenarios were identified according to depth: in shallow zones, the health of P. oceanica meadows was related to the degree of anthropization along the coastline. In contrast, in deep zones, most meadows exhibited poor health, independent of both the degree of disturbance and the legal measures protecting the area. Working synergistically with the regional impact of increased water turbidity, local impacts from the coast were recognized as the main causes of the severe regression of most Ligurian P. oceanica meadows. We conclude that marine protected areas alone are not sufficient to guarantee the protection of P. oceanica meadows. We emphasize the need for a management network involving the Sites of Community Interest (SCIs) containing P. oceanica meadows. 相似文献
180.
Evaluation of out‐of‐plane seismic performance of column‐to‐column precast concrete cladding panels in one‐storey industrial buildings 下载免费PDF全文
Andrea Belleri Fabrizio Cornali Chiara Passoni Alessandra Marini Paolo Riva 《地震工程与结构动力学》2018,47(2):397-417
Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of precast cladding panels, typically associated with a connection system not designed to account for displacement and rotation compatibility between the panels and the supporting structure. Experimental investigations were performed in the past to investigate the in‐plane performance of cladding panels and design recommendations have been made accordingly; however, in the case of out‐of‐plane seismic loads, the load demand is commonly evaluated in the design practice by means of formulations for nonstructural components. This paper summarizes the results obtained from parametric analyses conducted to estimate the out‐of‐plane load demand in column‐to‐column cladding panels typical of one‐storey commercial and industrial buildings. Empirical equations suitable for both new and existing panels are proposed and compared with the design equations given in Eurocode 8 and ASCE 7. The paper also considers the effects of the development of plastic hinges at the column base and of the roof flexibility on the load demand in panel‐to‐column connections. The roof flexibility may generate the torsion of the panels; consequently, an analytical procedure to account for such effects is proposed. Finally, general design recommendations are made. 相似文献