Late Holocene evolution of Tiber river delta and geoarchaeology of Claudius and Trajan Harbor,Rome     

Carlo Giraudi  Cristiana Tata  Lidia Paroli 《Geoarchaeology》2009,24(3):371-382

This study provides new information on the evolution of the Tiber delta during the late Holocene, and describes the record of sedimentation in the Port of Claudius and Trajan. The Tiber flowed into the Tyrrhenian Sea in the area of the Port of Claudius and Trajan between the 8th and 5th centuries B.C. The harbor basins excavated by the Romans during the 1st and 2nd centuries A.D. were filled with sediments containing saltwater fauna, then brackish‐water fauna, and finally by alluvial and marsh deposits. The Port of Claudius and Trajan was silted in as a consequence of episodes of alluviation that correlate with environmental events, possibly triggered by global climate changes. © 2009 Wiley Periodicals, Inc.  相似文献   

Editorial Appreciation     

John Leibacher  Cristina H. Mandrini  Lidia van Driel-Gesztelyi  Michael S. Wheatland 《Solar physics》2017,292(1):19

We are pleased to acknowledge, with sincere thanks, the following referees who supported the community by refereeing articles for Solar Physics during 2016.  相似文献   

High-Performance Parallel Solver for Integral Equations of Electromagnetics Based on Galerkin Method     

Mikhail Kruglyakov  Lidia Bloshanskaya 《Mathematical Geosciences》2017,49(6):751-776

A new parallel solver for the volumetric integral equations (IE) of electrodynamics is presented. The solver is based on the Galerkin method, which ensures convergent numerical solution. The main features include: (i) memory usage eight times lower compared with analogous IE-based algorithms, without additional restrictions on the background media; (ii) accurate and stable method to compute matrix coefficients corresponding to the IE; and (iii) high degree of parallelism. The solver’s computational efficiency is demonstrated on a problem of magnetotelluric sounding of media with large conductivity contrast, revealing good agreement with results obtained using the second-order finite-element method. Due to the effective approach to parallelization and distributed data storage, the program exhibits perfect scalability on different hardware platforms.  相似文献   

Petrogenesis of main group pallasite meteorites based on relationships among texture,mineralogy, and geochemistry     

Seann J. McKibbin  Lidia Pittarello  Christina Makarona  Christopher Hamann  Lutz Hecht  Stepan M. Chernonozhkin  Steven Goderis  Philippe Claeys 《Meteoritics & planetary science》2019,54(11):2814-2844

Main group pallasite meteorites are samples of a single early magmatic planetesimal, dominated by metal and olivine but containing accessory chromite, sulfide, phosphide, phosphates, and rare phosphoran olivine. They represent mixtures of core and mantle materials, but the environment of formation is poorly understood, with a quiescent core–mantle boundary, violent core–mantle mixture, or surface mixture all recently suggested. Here, we review main group pallasite data sets and petrologic characteristics, and present new observations on the low‐MnO pallasite Brahin that contains abundant fragmental olivine, but also rounded and angular olivine and potential evidence of sulfide–phosphide liquid immiscibility. A reassessment of the literature shows that low‐MnO and high‐FeO subgroups preferentially host rounded olivine and low‐temperature P₂O₅‐rich phases such as the Mg‐phosphate farringtonite and phosphoran olivine. These phases form after metal and silicate reservoirs back‐react during decreasing temperature after initial separation, resulting in oxidation of phosphorus and chromium. Farringtonite and phosphoran olivine have not been found in the common subgroup PMG, which are mechanical mixtures of olivine, chromite with moderate Al₂O₃ contents, primitive solid metal, and evolved liquid metal. Lower concentrations of Mn in olivine of the low‐MnO PMG subgroup, and high concentrations of Mn in low‐Al₂O₃ chromites, trace the development and escape of sulfide‐rich melt in pallasites and the partially chalcophile behavior for Mn in this environment. Pallasites with rounded olivine indicate that the core–mantle boundary of their planetesimal may not be a simple interface but rather a volume in which interactions between metal, silicate, and other components occur.  相似文献   

To be or not to be oxidized: A case study of olivine behavior in the fusion crust of ureilite A 09368 and H chondrites A 09004 and A 09502     

Lidia Pittarello  Akira Yamaguchi  Julia Roszjar  Vinciane Debaille  Christian Koeberl  Philippe Claeys 《Meteoritics & planetary science》2019,54(7):1563-1578

Meteorite fusion crusts are quenched melt layers formed during meteoroid atmospheric entry, mostly preserved as coating on the meteorite surface. Antarctic ureilite Asuka (A) 09368 and H chondrites A 09004 and A 09502 exhibit well preserved thick fusion crusts, characterized by extensive olivine crystallization. As olivine is one of the major components of most meteorites and its petrologic behavior is well constrained, it can be roughly considered as representative for the bulk meteorite. Thus, in this work, the evolution of olivine in fusion crusts of the above‐listed selected samples is investigated. The different shape and chemistry of olivine crystallized in the fusion crust, both as overgrown rim on relic olivine clasts and as new crystals, suggest a general temperature and cooling rate gradient. The occurrence of reverse and oscillatory zoning in individual olivine grains within the fusion crust suggests complex redox reactions. Overall, the investigated fusion crusts exhibit a general oxidation of the relatively reduced initial material. However, evidence of local reduction is preserved. Reduction is likely triggered by the presence of carbon in the ureilite or by overheating during the atmospheric entry. Constraining these processes provides a potential analog for interpreting features observed in cosmic spherules and micrometeorites and for calibrating experiments and numerical models on the formation of fusion crusts.  相似文献   

Solar Physics Memoir Series Reinstituted     

Ed Cliver  Lidia van Driel-Gesztelyi 《Solar physics》2010,267(2):233-234

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Cathodoluminescence as a tool to discriminate impact melt,shocked and unshocked volcanics: A case study of samples from the El'gygytgyn impact structure          下载免费PDF全文

Lidia Pittarello  Julia Roszjar  Dieter Mader  Vinciane Debaille  Philippe Claeys  Christian Koeberl 《Meteoritics & planetary science》2015,50(11):1954-1969

El'gygytgyn (Chukotka, Arctic Russia) is a well‐preserved impact structure, mostly excavated in siliceous volcanic rocks. For this reason, the El'gygytgyn structure has been investigated in recent years and drilled in 2009 in the framework of an ICDP (International Continental Scientific Drilling Program) project. The target rocks mostly consist of rhyodacitic ignimbrites and tuffs, which make it difficult to distinguish impact melt clasts from fragments of unshocked target rock within the impact breccia. Several chemical and petrologic attempts, other than dating individual clasts, have been considered to distinguish impact melt from unshocked volcanic rock of the targets, but none has proven reliable. Here, we propose to use cathodoluminescence (imaging and spectrometry), whose intensity is inversely correlated with the degree of shock metamorphism experienced by the investigated lithology, to aid in such a distinction. Specifically, impact melt rocks display low cathodoluminescence intensity, whereas unshocked volcanic rocks from the area typically show high luminescence. This high luminescence decreases with the degree of shock experienced by the individual clasts in the impact breccia, down to almost undetectable when the groundmass is completely molten. This might apply only to El'gygytgyn, because the luminescence in volcanic rocks might be due to devitrification and recrystallization processes of the relatively old (Cretaceous) target rock with respect to the young impactites (3.58 Ma). The alteration that affects most samples from the drill core does not have a significant effect on the cathodoluminescence response. In conclusion, cathodoluminescence imaging and spectra, supported by Raman spectroscopy, potentially provide a useful tool for in situ characterization of siliceous impactites formed in volcanic target.  相似文献   

Screening and classification of ordinary chondrites by Raman spectroscopy          下载免费PDF全文

Lidia Pittarello  Kitty Baert  Vinciane Debaille  Philippe Claeys 《Meteoritics & planetary science》2015,50(10):1718-1732

Classification of ordinary chondrite meteorites generally implies (1) determining the chemical group by the composition in endmembers of olivine and pyroxene, and (2) identifying the petrologic group by microstructural features. The composition of olivine and pyroxene is commonly obtained by microprobe analyses or oil immersion of mineral separates. We propose Raman spectroscopy as an alternative technique to determine the endmember content of olivine and pyroxene in ordinary chondrites, by using the link between the wavelength shift of selected characteristic peaks in the spectra of olivine and pyroxene and the Mg/Fe ratio in these phases. The existing correlation curve has been recalculated from the Raman spectrum of reference minerals of known composition and further refined for the range of chondritic compositions. Although the technique is not as accurate as the microprobe for determining the composition of olivine and pyroxene, for most of the samples the chemical group can be easily determined by Raman spectroscopy. Blind tests with ordinary chondrites of different provenance, weathering, and shock stages have confirmed the potential of the method. Therefore, we suggest that a preliminary screening and the classification of most of the equilibrated ordinary chondrites can be carried out using an optical microscope equipped with a Raman spectrometer.  相似文献   

Pixel correlation searches for O vi in the Lyman α forest and the volume filling factor of metals in the intergalactic medium at z∼ 2–3.5     

Matthew M. Pieri  Martin G. Haehnelt 《Monthly notices of the Royal Astronomical Society》2004,347(3):985-993

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Genesis of the mafic impact melt rock in the northwest sector of the Vredefort Dome,South Africa     

Wolf Uwe Reimold  Natalia Hauser  Alisson Lopes Oliveira  Ana Rita Pereira Maciel  Steven Goderis  Lidia Pittarello  Wencke Wegner  Mario Fischer-Goedde  Christian Koeberl  Vinciane Debaille  Carolinna Silva Maia de Souza 《Meteoritics & planetary science》2023,58(7):907-944

Genesis and emplacement of Vredefort Granophyre, the impact melt rock exposed on the Vredefort Dome, the erosional remnant of the central uplift of the Vredefort impact structure, South Africa, have long been debated. This debate was recently reinvigorated by the discovery that besides the previously known felsic variety of >66 wt% SiO₂, a second, somewhat more mafic phase of <66 wt% SiO₂ occurs along a Granophyre dike on farms Kopjeskraal and Eldorado in the northwest sector of the dome. Two hypotheses have been put forward to explain the genesis and emplacement of this second phase: (1) successive injections of impact melt into extensional fractures opened in the course of central uplift formation/crater modification, with melts of distinct compositions derived from a differentiating impact melt body in the crater, and (2) generation of the more mafic phase as a product of admixture/assimilation of a mafic country rock component, either the so-called epidiorite of possible Ventersdorp Supergroup affiliation or the Dominion Group meta-lava (DGL), to Felsic Granophyre. In the latter model, contamination with mafic country rock would have occurred during downward intrusion and stoping into and below the crater floor. The so-called Mafic Granophyre has previously only ever been sampled on a single site (Farm Kopjeskraal). In this study, samples of Granophyre occurring along the southerly extension of this dike on farm Rensburgdrif, and from a second dike on the Rietkuil property further southwest were investigated by field work, and petrographic, geochemical, and isotopic analysis. The mafic phase indeed occurs in the interior of the dike at Rensburgdrif, and also on Rietkuil. New geochemical and Sr-Nd isotope data support the hypothesis that the Mafic Granophyre composition represents a mixture between Felsic Granophyre and a mafic country rock. A 20% admixture of epidiorite or DGL to Felsic Granophyre provides an excellent match for the chemical composition of the Mafic Granophyre. The Sr-Nd isotope data indicate that this admixture likely involved the epidiorite component rather than DGL. Together with earlier Sr-Nd-Os-Se isotopic data, and other geochemical data, these results further support formation of the Mafic Granophyre by local assimilation/admixture of epidiorite to Felsic Granophyre.  相似文献