Exceptional preservation of embryos in the actinopterygian Saurichthys from the Middle Triassic of Monte San Giorgio, Switzerland     

Silvio Renesto  Rudolf Stockar 《Swiss Journal of Geoscience》2009,102(2):323-330

New excavations in the famous Monte San Giorgio area, close to the historical sites where the Cassina beds crop out (Lower Meride Limestone, Early Ladinian), revealed an interesting vertebrate fauna, including several specimens of the actinopterygian fish Saurichthys. Among the prepared specimens, three specimens of Saurichthys contain embryos, and in one example the embryos are preserved with traces of the soft parts, most probably phosphatized musculature. This discovery is of particular relevance because fossil embryos with preserved soft parts are extremely rare. In addition, although viviparity had previously been described for Saurichthys, the new specimens are rather better evidence and add further support to this reproductive mode.  相似文献   

Soil depth reconstruction for the assessment of the susceptibility to shallow landslides in fine-grained slopes   总被引：1，自引：1，他引：0  

Leonardo Cascini  Mariantonietta Ciurleo  Silvio Di Nocera 《Landslides》2017,14(2):459-471

This paper proposes a methodology aimed at reconstructing the maximum thickness mobilized by shallow landslides in fine-grained soils with the aid of geological and geotechnical analyses. The methodology, implemented within a geographic information system (GIS) environment, is composed of two stages for map reconstruction and two stages for map validation. The first stage of map reconstruction is aimed at individuating the soil thickness on the basis of only topographical and geological analyses; the second stage improves the previously obtained map with the aid of morphological and geotechnical analyses that provide a thickness map usable for shallow landslide susceptibility assessment. This map is validated with the aid of both in situ investigations (stage I), and geotechnical models able to back-analyse shallow precipitation-induced landslides over a wide area (stage II). An application of the proposed methodology is provided for a test area of the Calabria region (southern Italy) that is representative of the Catanzaro Strait, where widely diffused shallow landslides in fine-grained soils systematically occur. The results highlight the usefulness and reliability of the geotechnical models when implemented with the aid of a database representative of fine-grained soils while a secondary role is played by in situ investigations that in the test site have been performed only in a few representative and accessible areas.  相似文献   

Cambro-Silurian magmatisms at the northern Gondwana margin (Penninic basement of the Ligurian Alps)   总被引：1，自引：0，他引：1  

Matteo Maino  Laura Gaggero  Antonio Langone  Silvio Seno  Mark Fanning 《地学前缘(英文版)》2019,10(1):315-330

The Early Paleozoic evolution of the northern margin of Gondwana is characterized by several episodes of bimodal magmatism intruded or outpoured within thick sedimentary basins. These processes are well recorded in the Variscan blocks incorporated in the Ligurian Alps because they experienced low temperature Alpine metamorphism. During the Paleozoic, these blocks, together with the other Alpine basements, were placed between the Corsica-Sardinia and the Bohemian Massif along the northern margin of Gondwana. In this framework, they host several a variegated lithostratigraphy forming two main complexes(Complexs I and II) that can be distinguished by both the protoliths and their crosscutting relationships, which indicate that the acidic and mafic intrusives of Complex II cut an already folded sequence made of sediments, basalts and granitoids of Complex I. Both complexes were involved in the Variscan orogenic phases as highlighted by the pervasive eclogite-amphibolite facies schistosity(foliation II). However, rare relicts of a metamorphic foliation at amphibolite facies conditions(foliation I)is locally preserved only in the rocks of Complex I. It is debatable if this schistosity was produced during the early folding event e occurred between the emplacement of Complex I and II e rather than during an early stage of the Variscan metamorphic cycle.New SHRIMP and LA ICP-MS Ue Pb zircon dating integrated with literature data, provide emplacement ages of the several volcanic or intrusive bodies of both complexes. The igneous activity of Complex I is dated between 507 ± 15 Ma and 494 ± 5 Ma, while Complex II between 467 ± 12 Ma and 445.5 ± 12 Ma.The folding event recorded only by the Complex I should therefore have occurred between 494 ± 5 Ma and 467 ± 12 Ma. The Variscan eclogite-amphibolite facies metamorphism is instead constrained between ~420 Ma and ~300 Ma. These ages and the geochemical signature of these rocks allow constraining the Early Paleozoic tectono-magmatic evolution of the Ligurian blocks, from a middleeupper Cambrian rifting stage, through the formation of an Early Ordovician volcanic arc during the Rheic Ocean subduction, until a Late Ordovician extension related to the arc collapse and subsequent rifting of the PaleoThetys. Furthermore, the ~420-350 Ma ages from zircon rims testify to thermal perturbations that may be associated with the Silurian rifting-related magmatism, followed by the subduction-collisional phases of the Variscan orogeny.  相似文献   

Formation of metal and silicate globules in Gujba: a new Bencubbin-like meteorite fall     

Alan E. Rubin  Gregory W. Kallemeyn  Robert N. Clayton  Toshiko K. Mayeda  Alexander B. Verchovsky  Silvio Lorenzetti 《Geochimica et cosmochimica acta》2003,67(17):3283-3298

Gujba is a coarse-grained meteorite fall composed of 41 vol% large kamacite globules, 20 vol% large light-colored silicate globules with cryptocrystalline, barred pyroxene and barred olivine textures, 39 vol% dark-colored, silicate-rich matrix, and rare refractory inclusions. Gujba resembles Bencubbin and Weatherford in texture, oxygen-isotopic composition and in having high bulk δ¹⁵N values (∼+685‰). The ³He cosmic-ray exposure age of Gujba (26 ± 7 Ma) is essentially identical to that of Bencubbin, suggesting that they were both reduced to meter-size fragments in the same parent-body collision. The Gujba metal globules exhibit metal-troilite quench textures and vary in their abundances of troilite and volatile siderophile elements. We suggest that the metal globules formed as liquid droplets either via condensation in an impact-generated vapor plume or by evaporation of preexisting metal particles in a plume. The lower the abundance of volatile elements in the metal globules, the higher the globule quench temperature. We infer that the large silicate globules also formed from completely molten droplets; their low volatile-element abundances indicate that they also formed at high temperatures, probably by processes analogous to those that formed the metal globules. The coarse-grained Bencubbin-Weatherford-Gujba meteorites may represent a depositional component from the vapor cloud enriched in coarse and dense particles. A second class of Bencubbin-like meteorites (represented by Hammadah al Hamra 237 and QUE 94411) may be a finer fraction derived from the same vapor cloud.  相似文献   

Costanti armoniche e non armoniche delle Maree di Porto Lignano     

Dott. Silvio Polli 《Pure and Applied Geophysics》1947,10(1-2):21-28

Riassunto Porto Lignano si trova fra Trieste e Venezia. Il mareografo riduce nel rapporto 110 e ha uno scorrimento di 72 mm per giorno. Le costanti armoniche sono dedotte col metodo delDoodson da una serie di tre mesi. Le maree sono di tipo prevalentemente semidiurno, in vicinanza alle quadrature diventano diurne. Dalle costanti armoniche si deducono quelle non armoniche. I valori trovati si confrontano con quelli di Trieste e Venezia.

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Summary Porto Lignano is situated between Trieste and Venice. The self-reconding tide gauge have a height ratio 110 and a time scale 7,2 cm/day. The method of analysis adopted for the calculation of harmonic tidal constant is that ofDoodson applied to 3 months. The tides are generally semidiurnal, near the quadrature they becom diurnal. From the harmonic constant are deducted the nonharmonic. The determined values are compared with that of Trieste and Venice.

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Zusammenfassung Porto Lignano liegt zwischen Triest und Venedig. Der selbstregistriende Pegel reduziert im Verhältnis 110 und hat einen Ablauf von 72 mm pro Tag. Die harmonischen Konstanten wurden mit derDoodson Methode von einer dreimonatlichen Reihe berectnet. Die Tiden sind vorwiegend Halbtagsgezeiten, bei den Quadraturen werden sie Eintagstiden. Aus den harmonischen Konstanten wurden die nictharmonischen Konstanten abgeleitet. Die berechneten Werte wurden mit jenen von Triest und Venedig verglichen.

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Lavoro eseguito con il contributo del Consiglio Nazionale delle Ricerche.  相似文献   

New evidence on secondary twinning in albitic plagioclases     

Silvio Capedri 《Contributions to Mineralogy and Petrology》1970,25(4):289-296

Twinnings in albitic partially disordered plagioclases (An%=0–5; 2V variable between +80° and -87°) are described; they show optical-morphological features very similar to those exhibited by secondary twinning in calcic plagioclases. One of the twinning observed shows strong analogies with a phenomenon induced on a partially disordered albite in laboratory experiments (Borg and Heard, 1969). The data give new evidence on the debated existence of secondary twinning in albitic plagioclases.  相似文献   

Mechanical stratigraphy as a factor controlling the development of a sandbox transfer zone: a three-dimensional analysis   总被引：3，自引：0，他引：3  

Antonio Ravaglia  Claudio Turrini  Silvio Seno 《Journal of Structural Geology》2004,26(12):2269-2283

In thrust belts, fold–fault terminations are common features of the structural architecture and can pose complicated problems to unravel, in particular when two or more terminations are in close proximity. Such terminations usually reflect pre-existing attributes. Amongst the many factors, lateral variations in the mechanical stratigraphy can control along-strike geometry and kinematics of fault-related folds.A displacement transfer zone was produced in a compressional sandbox model by means of two adjacent, mechanically different stratigraphic domains. The experiment allowed two discrete chains to develop in the different domains, so that a complex structural setting occurred in the connecting area. Periclinal folds, oblique thrust fronts and oblique ramps developed in the resulting transfer zone. The interaction between periclines in the transfer zone produced lateral culminations in the folded structures. The analysis of displacement across the structural domains revealed that a significant loss of slip along the faults occurred in the relay zone. In this area, imbricate faulting was partially replaced by layer-parallel shortening. A linear relationship appears to exist between the bed length of the thrust sheet and the related fault slip.  相似文献   

Cosmogenic Be dating of the Salpausselkä I Moraine in southwestern Finland     

Vincent R. Rinterknecht  Peter U. Clark  Grant M. Raisbeck  Franoise Yiou  Edward J. Brook  Silvio Tschudi  Juha P. Lunkka 《Quaternary Science Reviews》2004,23(23-24):2283-2289

We determined in situ cosmogenic ¹⁰Be ages for nine boulders sampled on the Salpausselkä I (Ss I) Moraine. Previous dating of this moraine indicated that it formed during the Younger Dryas Stadial along the southern margin of the Scandinavian Ice Sheet in southern Finland. Our new exposure ages range from 10.9±1.0 to 13.5±1.2 ¹⁰Be ka, with an error-weighted mean age of 12.4±0.7 ¹⁰Be ka. Our results confirm four previous ¹⁰Be ages obtained 40 km northeast of our sample location. The combined data (n=13) indicate that retreat from the Ss I Moraine occurred at 12.5±0.7 ¹⁰Be ka, in excellent agreement with an age of 12.1 ka for retreat from the Ss I Moraine based on varve chronologies. These results identify the Ss I Moraine as among the best-dated margins associated with Late Quaternary ice sheets.  相似文献   

Cosmic-ray exposure ages of four acapulcoites and two differentiated achondrites and evidence for a two-layer structure of the acapulcoite/lodranite parent asteroid   总被引：1，自引：0，他引：1  

Otto Eugster  Silvio Lorenzetti 《Geochimica et cosmochimica acta》2005,69(10):2675-2685

We determined the He, Ne, and Ar isotopic abundances in the four acapulcoites Dhofar (DHO) 125, DHO 290, DHO 312, and Graves Nunataks 98028, the metal-rich diogenite Northwest Africa (NWA) 1982, and a unique achondrite, NWA 1058, that resembles the acapulcoites in its chemical composition. The noble gases in these meteorites consist of three components: trapped gases, cosmic-ray produced nuclides, and nuclides produced by K, Th, and U decay. The four acapulcoites yield cosmic-ray exposure (CRE) ages in the range of 5.0-5.7 Ma and confirm earlier conclusions concerning break-up of all acapulcoites from a common S-type parent asteroid, possibly in three events 4.9, 5.9, and 14.8 Ma ago. We also discuss the other characteristics (mineralogy, chemistry, formation ages, and oxygen and trapped noble gas isotopes) of all other acapulcoites and their relatives, the lodranites. We propose that the acapulcoite/lodranite parent asteroid had a shell structure similar to that of the H chondrites: The less metamorphosed acapulcoites correspond to the H3 and H4 chondrites and originate from the exterior layers, whereas the more severely metamorphosed lodranites, similar to the H5 and H6 chondrites, represent the inner regions of their parent body. Ungrouped achondrite NWA 1982, probably a diogenite, shows a CRE age of 18.9 ± 2.0 Ma that falls on the major exposure age cluster of the diogenites. The unique achondrite NWA 1058 differs in cosmic-ray exposure age (38.9 ± 4.0 Ma) and in oxygen-isotopic composition from the acapulcoites and lodranites and is probably a winonaite.  相似文献   

Genetic diversity in old populations of sessile oak from Calabria assessed by nuclear and chloroplast SSR     

Antonio LUPINI  Meriem Miyassa ACI  Antonio MAUCERI  Giuseppe LUZZI  Silvio BAGNATO  Giuliano MENGUZZATO  Francesco MERCATI  Francesco SUNSERI 《山地科学学报》2019,(5)

In the framework of forest resources conservation, this study aims to understand the dynamic and the genetic structure of sessile oak forests in Calabria, Italy. Two old populations of sessile oak(Quercus petraea(Mattuschka) Liebl.) from two areas of Sila and Aspromonte massifs in Calabria were analyzed for genetic diversity and population structure based on 6 nuclear simple sequence repeat(nSSR) and 4 chloroplastic SSR(cpSSR) loci. The populations displayed high amount of genetic diversity, which was toughly structured according to their geographical origins. Number of alleles at SSR loci ranged from 11 to 20 with an average of 13.5 per locus. Gene diversity(expected heterozygosity, He) estimates ranged from 0.575 to 0.834 with a mean of 0.749. The observed heterozygosity(Ho) was on average 0.458 ranging from 0.150 to 0.682. Polymorphism information content(PIC) values ranged from 0.625 to 0.865 with an average of 0.787. The analysis of molecular variance(AMOVA) highlighted a significant higher estimated variance within populations compared to among populations. Finally, the analysis of haplotypes by using cpSSR suggested a higher diversification in the population from Sila. Hierarchical clustering analysis grouped the genotypes into two major clusters, which agreed with the geographic origin of populations, and was confirmed by the Discriminant Analysis of Principal Components(DAPC). The first cluster included plants/population from Sila massif, while the second encompassed mostly plants/population sampled in Aspromonte massif. Finally, model-based clustering by STRUCTURE analysis also supported the presence of clear genetic structuring in the collection with two major populations(K=2) supported to PCoA analysis as well. Finally, our data indicated the Aspromonte population as a marginal forest with fragmented distribution suggesting different strategies of preservation than in Sila massif.  相似文献