The onset of the Messinian salinity crisis in the deep Eastern Mediterranean basin   总被引：1，自引：0，他引：1       下载免费PDF全文

Vinicio Manzi  Rocco Gennari  Stefano Lugli  Davide Persico  Matteo Reghizzi  Marco Roveri  B. Charlotte Schreiber  Ran Calvo  Ittai Gavrieli  Zohar Gvirtzman 《地学学报》2018,30(3):189-198

Astronomical tuning of the Messinian pre‐salt succession in the Levant Basin allows for the first time the reconstruction of a detailed chronology of the Messinian salinity crisis (MSC) events in deep setting and their correlation with marginal records that supports the CIESM ( 2008 ) 3‐stage model. Our main conclusions are (1) MSC events were synchronous across marginal and deep basins, (2) MSC onset in deep basins occurred at 5.97 Ma, (3) only foraminifera‐barren, evaporite‐free shales accumulated in deep settings between 5.97 and 5.60 Ma, (4) deep evaporites (anhydrite and halite) deposition started later, at 5.60 Ma and (5) new and published ⁸⁷Sr/⁸⁶Sr data indicate that during all stages, evaporites precipitated from the same water body in all the Mediterranean sub‐basins. The wide synchrony of events and ⁸⁷Sr/⁸⁶Sr homogeneity implies inter‐sub‐basin connection during the whole MSC and is not compatible with large sea‐level fall and desiccation of the Mediterranean.  相似文献   

Soil moisture remote-sensing applications for identification of flood-prone areas along transport infrastructure     

Anna-Klara Ahlmer  Marco Cavalli  Klas Hansson  Alexander J. Koutsouris  Stefano Crema  Zahra Kalantari 《Environmental Earth Sciences》2018,77(14):533

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Water-table and discharge changes associated with the 2016–2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers     

Petitta  Marco  Mastrorillo  Lucia  Preziosi  Elisabetta  Banzato  Francesca  Barberio  Marino Domenico  Billi  Andrea  Cambi  Costanza  De Luca  Gaetano  Di Carlo  Giuseppe  Di Curzio  Diego  Di Salvo  Cristina  Nanni  Torquato  Palpacelli  Stefano  Rusi  Sergio  Saroli  Michele  Tallini  Marco  Tazioli  Alberto  Valigi  Daniela  Vivalda  Paola  Doglioni  Carlo 《Hydrogeology Journal》2018,26(4):1009-1026

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0–6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m³/s, totaling more than 0.1 km³ of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L’Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers.

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Millennial-scale shifts in microtidal ecosystems during the Holocene: dynamics and drivers of change from the Po Plain coastal record (NE Italy)     

Veronica Rossi  Giulia Barbieri  Stefano Claudio Vaiani  Marco Cacciari  Luigi Bruno  Bruno Campo  Marco Marchesini  Silvia Marvelli  Alessandro Amorosi 《第四纪科学杂志》2021,36(6):961-979

Framed into a robust stratigraphic context, multivariate analyses on the Holocene palaeobiological record (pollen, benthic foraminifers, ostracods) of the Po coastal plain (NE Italy) allowed the investigation of microtidal ecosystems variability and driving parameters along a 35-km-long land–sea transect. Millennial-scale ecosystem shifts are documented by coeval changes in the meiofauna, reflecting variations in organic matter–water depth (shallow-marine environments) and degree of confinement-salinity (back-barrier settings). In-phase shifts of vegetation communities track unsteady water-table levels and river dynamics in freshwater palustrine areas. Five environmental–ecological stages followed one another crossing four tipping points that mark changes in relative sea level (RSL), climate and/or fluvial regime. At the culmination of Mediterranean RSL rise, after the 8200 event, remarkable growth of peatlands took place in the Po estuary, while low accumulation rates typified the shelf. At the transgressive–regressive turnaround (~7000 cal a bp ), the estuary turned into a delta plain with tidally influenced interdistributary embayments. River flow regime oscillations after the Climate Optimum (post-5000 cal a bp ) favoured isolation of the bays and the development of brackish wetlands surrounded by wooded peatlands. The youngest threshold (~800 cal a bp ), which led to the establishment of the modern delta, reflects a major avulsion of the Po River.  相似文献   

Wavelet‐based regularization of the extracted topographic index from high‐resolution topography for hydro‐geomorphic applications          下载免费PDF全文

Vahid Nourani  Stefano Zanardo 《水文研究》2014,28(3):1345-1357

High‐resolution topography, e.g. 1‐m digital elevation model (DEM) from light detection and ranging (LiDAR), offers opportunity for accurate identification of topographic features of relevance for hydrologic and geomorphologic modelling. Yet, the computation of some derived topographic properties, such as the topographic index (TI), is characterized by daunting challenges that hamper the full exploration of topography‐based models. Particular problems, for example, arise when a distributed (or semi‐distributed) rainfall–runoff model is applied to high‐resolution DEMs. Indeed, the characteristic dependency between landscape resolution and the computed TI distribution results in the formation of un‐physical, unconnected saturated zones, which in turn cause unrealistic representations of rainfall–runoff dynamics. In this study, we present a methodology based on a multi‐resolution wavelet transformation that, by means of a soft‐thresholding scheme on the wavelet coefficients, filters the noise of high‐resolution topography to construct regularized sets of locally smoother topography on which the TI is computed. While the methodology needs a somewhat arbitrary definition of the wavelet coefficients threshold, our study shows that when the information content (entropy) of the TI distribution is used as a filtering efficiency metric, a critical threshold automatically emerges in the landscape reconstruction. The methodology is demonstrated using 1‐m LiDAR data for the Elder Creek River basin in California. While the proposed case study uses a TOPMODEL approach, the methodology can be extended to different topography‐based models and is not limited to hydrological applications. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A bond contact model for methane hydrate‐bearing sediments with interparticle cementation     

Mingjing Jiang  Fangyuan Zhu  Fang Liu  Stefano Utili 《国际地质力学数值与分析法杂志》2014,38(17):1823-1854

While methane hydrates (MHs) can be present in various forms in deep seabeds or permafrost regions, this paper deals with MH‐bearing sediments (MHBS) where the MH has formed bonds between sand grains. A bond model based on experimentally validated contact laws for cemented granules is introduced to describe the mechanical behavior of the MH bonds. The model parameters were derived from measured values of temperature, water pressure and MH density. Bond width and thickness adopted for each bond of the MHBS were selected based on the degree of MH saturation. The model was implemented into a 2D distinct element method code. A series of numerical biaxial standard compression tests were carried out for various degrees of MH saturation. A comparison with available experimental data shows that the model can effectively capture the essential features of the mechanical behavior of MHBS for a wide range of levels of hydrate saturation under drained and undrained conditions. In addition, the analyses presented here shed light on the following: (1) the relationship between level of cementation and debonding mechanisms taking place at the microscopic level and the observed macro‐mechanical behavior of MHBS and (2) the relationship between spatial distribution of bond breakages and contact force chains with the observed strength, dilatancy and deformability of the samples. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Measurements of rill and gully erosion in Sicily     

Costanza Di Stefano  Vito Ferro 《水文研究》2011,25(14):2221-2227

This article reports the results of a field investigation aimed to characterize the morphology of both rills monitored at Sparacia experimental area and two ephemeral gullies (EGs) located in the Tremamargi basin, Sicily, Italy. At first, the available literature data together with the measurements carried out in this investigation were used to show that the EG length is a key parameter for the estimation of the eroded volume. Then, the comparison among the pairs length and volume corresponding to measured rills, EGs and gullies showed that the exponent of the power relationship is independent of the channelized erosion type (rill, EG and gully), while a different scale factor has to be used for each erosion process. Finally, a single relationship applicable to all channelized erosion processes was deduced applying the dimensional analysis and the self‐similarity theory. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Geophysical investigation of the Sandalp rock avalanche deposits     

Laura Valentina Socco  Denis Jongmans  Daniele Boiero  Stefano Stocco  Margherita Maraschini  Ken Tokeshi  Didier Hantz 《Journal of Applied Geophysics》2010,70(4):277-291

In the study of rock avalanche phenomena, numerical modelling makes use of back analyses of the rock avalanche propagation for calibration of the modelling assumptions and parameters. The back analyses require knowledge of the run-out area boundaries and the thickness distribution of the deposit. Geophysical methods can be applied to retrieve the thickness distribution, but, due to strong heterogeneities and logistic problems they are seldom applied. The aim of this work is to assess the potential of integrated geophysical methods to recognise and characterise a deposit created by two rock avalanches which occurred in the Sandalp valley (Switzerland) in 1996. The topography of the site before and after the rock avalanche is known and can be used as a benchmark. Resistivity tomography, seismic P-wave tomography, and active and passive surface wave analysis have been applied on several profiles deployed both on the rock avalanche deposit and in the surrounding area. Innovative approaches for surface wave analysis based on laterally constrained inversion and multimodal inversion have been applied to the data. A comparison of the results of the geophysical investigations with the topographic benchmark has shown the capability of the geophysical methods to locate the bottom of the deposit in the areas where the contrast with the host sediments properties is significant. In these areas, the deposit has higher resistivities and lower seismic velocities than the underlying materials. In the areas where the deposit is thicker and richer in fine-grained materials the geophysical parameters are not able to discriminate between the rock avalanche deposit and the underlying sediments. As a secondary task, the geophysical methods also allowed the bedrock pattern to be outlined.  相似文献   

The Alps in the Cretaceous: a doubly vergent pre‐collisional orogen     

Stefano Zanchetta  Eduardo Garzanti  Carlo Doglioni  Andrea Zanchi 《地学学报》2012,24(5):351-356

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Early diagenesis in rapidly accumulating sediments on the Alboran slope, ODP site 976     

Stefano M. Bernasconi  Philip A. Meyers  Gerard O’Sullivan 《Geo-Marine Letters》1998,18(3):209-214

The oxidation and reduction that occur during early diagenesis of sediments has been studied in the interstitial waters of a rapidly accumulating sedimentary sequence from the Mediterranean margin of Spain. A series of reactions that are mediated by progressively lower free energy derived from oxidation of organic matter is evident in the sedimentary sequence. Iron and manganese are rapidly reduced. Phosphate and alkalinity maxima at a subbottom depth of 15?m indicate maximal organic matter degradation. Methane first appears at ～20?m subbottom after sulfate is depleted, and its concentrations quickly climb.  相似文献