Implications of a combined biostratigraphic and palaeomagnetic study of the Umbrian Maiolica Formation     

Simonetta Cirilli  Péter Márton  Luigi Vigli 《Earth and Planetary Science Letters》1984,69(1):203-214

The study of a 275.5 m thick section of white, pelagic limestones occupying the valley of the Fonte del Giordano river on the southern slope of Mt. Montagnola has yielded a biostratigraphically controlled clear magnetic reversal pattern after thermal cleaning. The magnetic stratigraphy of the lower 131 m of the section (Calpionellid zones) is correlatable with the M-sequence of oceanic magnetic anomalies between M-19 and M-14. The reversal stratigraphy of the upper 81.5 m of the section (Radiolaria zone) has also been tied to the oceanic polarity time scale by making linear interpolation for a missing 63 m thickness underneath it.Besides the Fonte del Giordano section two Berriasian outcrops each with a different bedding attitude were studied at Gubbio and near Cagli for tectonic tilt test giving positive results. The mean palaeomagnetic pole position for the Late Jurassic/Early Cretaceous after bedding correction is: Φ = 19.1°, Λ = 288.2°, k = 148.7, α₉₅ = 10.2° (N = 3), confirming the presence of a large swing in the polar path, a common behaviour of apparent polar wandering for the peri-Adriatic region during this time.  相似文献   

Magmatic character and geotectonic setting of some tertiary-quaternary Italian volcanic rocks: Orogenic,anorogenic and «Transitional» association — A review     

P. di Girolamo 《Bulletin of Volcanology》1984,47(3):421-432

Discrimination functions based on major element distribution (Pearce, 1976) can be used to define the different basalt types of the Tyrrhenian and Perityrrhenian areas in an attempt to clarify their geodynamic significance.The future Tyrrhenian and Perityrrhenian areas have been affected since Oligocene by either compressional (subduction related) or transitional processes which produced well-defined orogenic and anorogenic magmas. A local development of «transitional» magma types, characteristic of «anomalous» volcanic arcs, also occurred with geochemical features that are intermediate between within-plate and orogenic magmas.The eruption of orogenic rock suites (calcalkaline, shoshonitic and leucite-bearing rocks) took place along the Apennine border on the east and southeast of the Tyrrhenian basin from Upper Miocene to Quaternary (Aeolian and neighbouring seamounts; Campania; Latium; Capraia Island). Absence of spatial zonation and interlayering of products with a various potassic character are the peculiar features of these rocks that appear to be originated from a heterogeneous and variously metasomatized mantle source by the influx of fluids (H₂O andLile enrichment) from the subduction zone affecting the Apennine-Maghrebides collisional front during Tertiary times.In the central Tyrrhenian area oceanic tholeiitic magmatism and creation of a new oceanic crust occurred from Upper Miocene. This activity was probably accomplished by Lower Pliocene when a within-plate volcanism produced the seamounts of the Batial Plain (Magnaghi, Vavilov, base of the Marsili Smts.).Etna and Ustica volcanisms occurring along the Perityrrhenian border on the south and west the Aeolian volcanism respectively, show geochemical characteristics that are transitional between anorogenic and orogenic magmas which could indicate some influence of fluids subduction-related to their mantle sources.The complex magmatic situation of the Tyrrhenian and Perityrrhenian areas may be caused by magma-producing events either from unmodified (anorogenic) or variously modified mantle sources (transitional to orogenic) depending on their proximity to and influenced by the Cainozoic subduction zone which developed along the Apennines-Maghrebides collisional front.  相似文献   

Caractérisation géométrique et cinématique des structures liées aux phases compressives de l'Éocène au Quaternaire inférieur en Tunisie : exemple de la Tunisie nord-orientale     

Houcem Mzali  Hédi Zouari 《Comptes Rendus Geoscience》2006,338(10):742-749

During Eocene to Early Quaternary period, three compressive tectonic phases are recognized in Northeast Tunisia: a NW–SE to north–south phase during the Late Eocene, a N120-to-N140 phase in the Late Miocene, and a NW–SE to north–south phase in the Plio-Early Quaternary. The first Eocene phase has built NE–SW folds and remobilised east–west-to-N120 and NE–SW faults with a reverse component. The second Miocene phase is characterized by east–west-to-N120 faults with a normal component and NE–SW folds. The third phase occurred during the Plio-Early Quaternary has edified NE–SW folds associated with east–west-to-N120 dextral reverse strike-slip faults and NE–SW faults with a reverse component. To cite this article: H. Mzali, H. Zouari, C. R. Geoscience 338 (2006).  相似文献   

On the relationship between hydrocarbon migration pathways and carbonate mound occurrence in the Porcupine Basin     

J. Naeth  R. di Primio  B. Horsfield  R. G. Schaefer  B. M. Krooss 《International Journal of Earth Sciences》2007,96(1):199-200

  相似文献   

Occurrence of brominated flame retardants, polycyclic musks, and chlorinated naphthalenes in seal blubber from Antarctica: Comparison to organochlorines     

Alessandra Schiavone  Kurunthachalam Kannan  Yuichi Horii  Silvano Focardi  Simonetta Corsolini 《Marine pollution bulletin》2009,58(9):1415-1419

  相似文献   

The use of taxonomic distinctness indices in assessing patterns of biodiversity in modular organisms   总被引：1，自引：0，他引：1  

Stanislao Bevilacqua  Simonetta Fraschetti  Antonio Terlizzi  & Ferdinando Boero 《Marine Ecology》2009,30(2):151-163

Estimating diversity of modular organisms may be problematic due to actual difficulties in discriminating between 'individuals' and quantifying their abundances. Quantitative data, when available, are collected through methods that could preclude the application of classical diversity indices, making comparisons among studies difficult. Taxonomic distinctness indices, such as the 'Average Taxonomic Distinctness' (Δ⁺) and the 'Variation in Taxonomic Distinctness' (Λ⁺) may represent suitable tools in investigating diversity beyond the simple species number. The potential usefulness of such indices has been explored almost exclusively on unitary organisms, neglecting modular ones. In this study, we employed Δ⁺ and Λ⁺ to analyse patterns of diversity of epiphytic hydroid assemblages living on Cystoseira seaweeds at a hierarchy of spatial scales, along 800 km of rocky coast (SE Italy). ANOVA on species richness and Λ⁺ showed no significant difference in sample diversity at the investigated spatial scales. In contrast, there were significant differences at the scale of 10s of km in Δ⁺. Analyses based on simulations detected significant variations at all spatial scales in Δ⁺. Such findings underline the potential of Δ⁺ in highlighting relevant spatial scales of variation in patterns of hydroid diversity. Our results also suggest that the interplay between natural environmental variations and the complex ecological traits of modular organisms might affect taxonomic distinctness indices. We stress the need for further investigations focusing on modular organisms before any generalizations on the use of taxonomic relatedness measures in examining marine biodiversity can be made.  相似文献   

Seeing through porous media: An experimental study for unveiling interstitial flows          下载免费PDF全文

Simonetta Rubol  Daniele Tonina  Lionel Vincent  Jill A. Sohm  William Basham  Ralph Budwig  Pratixa Savalia  Eva Kanso  Douglas G. Capone  Kenneth H. Nealson 《水文研究》2018,32(3):402-407

We describe a novel inexpensive method, utilizing particle image velocimetry (PIV) and refractive index‐matching (RIM) for visualizing and quantifying the flow field within bio‐amended porous media. To date, this technique has been limited to idealized particles, whose refractive index does not match that of fresh water and thus requires specialized and often toxic or hazardous fluids. Here, we use irregularly shaped grains made of hydrogel as the solid matrix and water as the fluid. The advantage of using water is that it provides, for the first time, the opportunity to study both hydraulic and biological processes, which typically occur in soils and streambeds. By using RIM coupled with PIV (RIM‐PIV), we measured the interstitial flow field within a cell packed with granular material consisting of hydrogel grains in a size range of 1–8 mm, both in the presence and in the absence of Sinorhizobium meliloti bacteria (strain Rm8530). We also performed experiments with fluorescent tracer (fluorescein) and fluorescent microbes (Shewanella GPF MR‐1) to test the capability of visualizing solute transport and microbial movements. Results showed that the RIM‐PIV can measure the flow field for both biofilm‐free and biofilm‐covered hydrogel grains. The fluorescent tracer injection showed the ability to visualize both physical (concave surfaces and eddies) and biological (biofilms) transient storage zones, whereas the fluorescent microbe treatment showed the ability to track microbial movements within fluids. We conclude that the proposed methodology is a promising tool to visualize and quantify biofilm attachment, growth, and detachment in a system closer to natural conditions than a 2D flow cell experiment.  相似文献   

Numerical analysis of wetting-induced instabilities in partially saturated soils under plane strain conditions     

Giada M. Rotisciani  Augusto Desideri  Claudio di Prisco 《国际地质力学数值与分析法杂志》2019,43(10):1867-1884

This paper concerns the hydromechanical stability of partially saturated soils during wetting. The response of a loose silty sand is numerically/theoretically investigated with the main aim of identifying both triggering mechanisms and predisposing factors to instability. This latter is testified by both a rapid increase in the pore water pressure and an unexpected loss of numerical convergence. The study has been conducted at different scales from laboratory tests to boundary value problems, and in both cases, the controllability theory has been employed to both interpret and justify the numerical results.  相似文献   

A stability criterion for elasto‐viscoplastic constitutive relationships          下载免费PDF全文

F. Pisan  C. di Prisco 《国际地质力学数值与分析法杂志》2016,40(1):141-156

In this paper, the onset of mechanical instability in time‐sensitive elasto‐viscoplastic solids is theoretically analyzed at the constitutive level and associated with the occurrence of ‘spontaneous accelerations’ under stationary external perturbations. For this purpose, a second‐order form of Perzyna's constitutive equations is first derived by time differentiation, and a sufficient stability condition is identified for general mixed loading programs. These loading conditions are in fact the most general in both laboratory tests and real boundary value problems, where a combination of certain stress and strain components is known/prescribed. The theoretical analysis leads to find precise stability limits in terms of material hardening modulus. In the case of constitutive relationships with isotropic strain‐hardening, no instabilities are possible while the hardening modulus is larger than the so‐called ‘controllability modulus’ defined for (inviscid) elasto‐plastic materials. It is also shown that the current stress/strain rate may also directly influence the occurrence of elasto‐viscoplastic instability, which is at variance with elasto‐plastic inviscid media. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Optical‐NIR spectra of quasars close to reionization (z ∼ 6)     

V. D'Odorico  G. Cupani  S. Cristiani  R. Maiolino  P. Molaro  M. Nonino  A. Cimatti  S. di Serego Alighieri  F. Fiore  A. Fontana  S. Gallerani  E. Giallongo  F. Mannucci  A. Marconi  L. Pentericci  M. Viel  G. Vladilo 《Astronomische Nachrichten》2011,332(3):315-318

X‐shooter, with its characteristics of resolution, spectral coverage and efficiency, provides a unique opportunity to obtain spectra of the highest‐redshift quasars (z ∼ 6) that will allow us to carry out successful investigations on key cosmological issues, from the details of the re‐ionization process, to the evolution of the first galaxies and AGNs. In this paper, we present the spectra of three z ∼ 6 quasars: one obtained during the commissioning of X‐shooter and two in the context of our ongoing GTO programme. Combining this sample with data in the literature, we update the value of the C IV cosmic mass density in the range 4.5 ≤ z ≤ 5, confirming the constant trend with redshift between 2.5 and 5 (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献