Middle Miocene peralkaline ignimbrites in the Hermosillo region (Sonora, Mexico): Geodynamic implications     

Jesús Vidal Solano  Francisco A. Paz Moreno  Alexander Iriondo  Alain Demant  Jean-Jacques Cochem 《Comptes Rendus Geoscience》2005,337(16):314

Scattered ignimbritic mesas crop out in the Hermosillo region (Sonora, Mexico). These rocks that have been dated at 12.5 Ma (Middle Miocene) have the petrography and chemical characteristics of comendites. Such a flare-up of peralkaline acidic volcanism, after a long period of subduction-related arc volcanism, emphasises an important change in the source of volcanism. It corresponds to the latest stage of continental extension prior to the marine invasion and the development of spreading centres in the Gulf of California. To cite this article: J. Vidal Solano et al., C. R. Geoscience 337 (2005).  相似文献   

Sea Level Pressure Departures in the Mediterranean and their Relationship with Monthly Rainfall Conditions in Israel     

H. Kutiel  S. Paz 《Theoretical and Applied Climatology》1998,60(1-4):93-109

Summary Monthly rainfall conditions in Israel were determined, using data from 12 stations, during 30 years (1961–90). The definition of a month to be dry, normal or wet, was done using standardized rainfall totals. Pressure departures for each of the three rainfall categories for each month of the rainy season, were calculated and mapped. Correlation between rainfall totals at each of the 12 stations and monthly mean sea level pressure at 72 grid points in the area delimited by the 20° W and 50° E meridians and the 20° N and 60° N parallels, was performed. For each month, 12 correlation maps were prepared (one of each station). Similar maps were averaged together to form coherent rainfall regions. At the beginning of the rainy season (October) the rainfall in Israel is sporadic and spotty without a distinctable coherent region. At the end of the rainy season (April) the rainfall is more widespread, forming a large coherent region covering most of the country. Dry rainfall conditions in Israel, were found to be characterized by positive pressure departures in the eastern Mediterranean and over Israel and/or by easterly or southerly circulation over the eastern Mediterranean. Wet rainfall conditions in Israel, were found to be characterized by negative pressure departures in the eastern Mediterranean and over Israel and/or by westerly or northerly circulation over the eastern Mediterranean. Moreover, in many cases dry conditions in Israel, were associated with below normal pressure conditions over central or western Europe, while wet conditions in Israel, with above normal conditions over the same region, thus, reflecting the so-called Mediterranean Oscillation. Finally, normal rainfall conditions are characterized by very slight to negligible pressure departures over the entire Mediterranean and Europe. Received November 18, 1997 Revised March 3, 1998  相似文献   

A GIS-Based Multivariate Statistical Analysis for Shallow Landslide Susceptibility Mapping in La Pobla de Lillet Area (Eastern Pyrenees,Spain)   总被引：22，自引：0，他引：22  

Santacana  Núria  Baeza  Baeza  Corominas  Jordi  De Paz  Ana  Marturiá  Jordi 《Natural Hazards》2003,30(3):281-295

This paper presents a GIS-aided procedure for shallow landslide susceptibility mapping at a regional scale. Most of the input data for the susceptibility assessment have been captured automatically. A total of 13 parameters, related to the slope geometry, have been derived from the digital elevation model (DEM) while vegetation cover and thickness of superficial formations have been obtained from photointerpretation and field work. The susceptibility assessment is based on multivariate statistical techniques (discriminant analysis), which hasbeen tested in a pilot area in La Pobla de Lillet (Eastern Pyreenes, Spain). Theresults obtained using a random sample show that 82% of all the cells, and 90% of cells including slope failures, have been properly classified. A susceptibility map based on the discriminant function has given consistent results. The susceptibilityassessment is very sensitive to the parameters selected. Compared to thetraditional methods, the main advantage of the GIS-aided procedure is the rapidityprovided by the automatic capture of parameters. It also has the capability of coveringlarge areas, and the objectivity and reproducibility of the results. The main drawbackis that, at present, not all regions have DEM accurate enough to cope with small landslides.  相似文献   

Notes on fossil remains from the Early Cretaceous Lohan Cura Formation, Neuquén Province, Argentina     

Agustín G. Martinelli  Alberto C. Garrido  Analía M. Forasiepi  Ernesto R. Paz  Yamila Gurovich 《Gondwana Research》2007,11(4):537-552

In this contribution, we describe an association of fossil remains collected in the locality of Cerro de Los Leones, approximately 8 km southwest of the town of Picún Leufú, Neuquén Province, Argentina, from different levels of the Albian Cullín Grande Member, Lohan Cura Formation. The fossils include pelecypodan (Neocorbicula dinosauriorum, Neocorbicula pehuenchensis, and genus indet.) and gastropodan (Physa wichmanni) molluscs, a mesoeucrocodylian, possible pterosaurs, theropods, and sauropods. The sedimentary environment at Cerro de los Leones is characterized by fluvial deposits corresponding to a sandy meandering fluvial system. The most fossiliferous levels (located in the lower part of the exposed sequence) were developed in a distal flood plain and flood basin areas. Sedimentological and paleopedological features suggest semi-arid conditions during the deposition of the Cullín Grande Member. Despite the fragmentary nature of the specimens described here, the new information provided from the Albian assemblages of the Lohan Cura Formation at the Cerro de Los Leones locality provides a broader panorama of the composition of terrestrial faunas during the Early Cretaceous in Patagonia.  相似文献   

Impact of projected climate change on hydrologic regime of the Upper Paraguay River basin   总被引：1，自引：0，他引：1  

Juan Martín Bravo  Walter Collischonn  Adriano Rolim da Paz  Daniel Allasia  Federico Domecq 《Climatic change》2014,127(1):27-41

We present an assessment of climate change impacts on the hydrologic regime of the 600,000 km² Upper Paraguay River basin, located in central South America based on predictions of 20 Atmospheric/Ocean General Circulation Models (AOGCMs). We considered two climate change scenarios from the Intergovernmental Panel on Climate Change (IPCC) and two 30-years time intervals centered at 2030 and 2070. Projected temperature and precipitation anomalies estimated by the AOGCMs for the study site are spatially downscaled. Time series of projected temperature and precipitation were estimated using the delta change approach. These time series were used as input to a detailed coupled hydrologic-hydraulic model aiming to estimate projected streamflow in climate change scenarios at several control points in the basin. Results show that impacts on streamflow are highly dependent on the AOGCM used to obtain the climate predictions. Patterns of temperature increase persist over the entire year for almost all AOGCMs resulting in an increase in the evapotranspiration rate of the hydrological model. The precipitation anomalies show large dispersion, being projected as either an increase or decrease in precipitation rates. Based on these inputs, results from the coupled hydrologic-hydraulic model show nearly one half of projections as increasing river discharge, and other half as decreasing river discharge. If the mean or median of the predictions is considered, no discernible change in river discharge should be expected, despite the dispersion among results of the AOGCMs that reached +/?10 % in the short horizon and +/? 20 % in the long horizon, at several control points.  相似文献   

Parity and disparity between two Chama oysters: the reproductive biology of the Indo-Pacific C. pacifica Broderip,invasive to the Mediterranean Sea; and C. savignyi Lamy,indigenous to the Red Sea     

Dror Zurel  Uri Gophna  Yehuda Benayahu 《Marine Ecology》2012,33(3):261-271

The Indo-Pacific oyster Chama pacifica Broderip, 1835 (Mollusca, Bivalvia, Chamidae) is rarely found in the Northern Red Sea reefs of Eilat (Gulf of Aqaba), where it is outnumbered by its indigenous congener, Chama savignyi Lamy, 1921. The influx of Eritrean biota from the Red Sea into the Mediterranean Sea via the Suez Canal has led to the formation of massive Chama oyster beds along the Eastern Mediterranean shore. However, unlike the Northern Red Sea, the Eastern Mediterranean Chama beds are dominated by C. pacifica oysters, whereas C. savignyi is absent from this region. In an attempt to understand this difference in their respective distribution, the reproductive biology of both species was compared. Histological analysis of the male and female gonads, monitored monthly from March 2009 to August 2010 in both regions, revealed a similar reproductive cycle, comprising six stages: onset of gametogenesis, advanced gametogenesis, ripe, ready to spawn, spent and sexual rest. Female gonads demonstrated an additional, seventh stage – restoration, coinciding with inferred spawning of ripe gametes. Both species were found to be dioecious spawners, with a single, annual, temperature-dependent inferred spawning period. Chama pacifica was found to reproduce efficiently in maximal Mediterranean seawater temperatures not experienced by the Northern Red Sea Chama populations. This study demonstrates the high invasive potential of an oyster species despite its rarity in its source region.  相似文献   

Carbon dioxide emissions from Specchio di Venere,Pantelleria, Italy     

Mariana P. Jácome Paz  Salvatore Inguaggiato  Yuri Taran  Fabio Vita  Giovanella Pecoraino 《Bulletin of Volcanology》2016,78(4):29

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The role of aluminium in the preservation of microbial biosignatures     

Alan Levett  Emma J. Gagen  Hui Diao  Paul Guagliardo  Llew Rintoul  Anat Paz  Paulo M. Vasconcelos  Gordon Southam 《地学前缘(英文版)》2019,10(3):1125-1138

Demonstrating the biogenicity of presumptive microfossils in the geological record often requires supporting chemical signatures, including isotopic signatures. Understanding the mechanisms that promote the preservation of microbial biosignatures associated with microfossils is fundamental to unravelling the palaeomicrobiological history of the material. Organomineralization of microorganisms is likely to represent the first stages of microbial fossilisation and has been hypothesised to prevent the autolytic degradation of microbial cell envelope structures. In the present study, two distinct fossilisation textures(permineralised microfossils and iron oxide encrusted cell envelopes)identified throughout iron-rich rock samples were analysed using nanoscale secondary ion mass spectrometry(NanoSIMS). In this system, aluminium is enriched around the permineralised microfossils, while iron is enriched within the intracellularly, within distinct cell envelopes. Remarkably,while cell wall structures are indicated, carbon and nitrogen biosignatures are not preserved with permineralised microfossils. Therefore, the enrichment of aluminium, delineating these microfossils appears to have been critical to their structural preservation in this iron-rich environment. In contrast,NanoSIMS analysis of mineral encrusted cell envelopes reveals that preserved carbon and nitrogen biosignatures are associated with the cell envelope structures of these microfossils. Interestingly, iron is depleted in regions where carbon and nitrogen are preserved. In contrast aluminium appears to be slightly enriched in regions associated with remnant cell envelope structures. The correlation of aluminium with carbon and nitrogen biosignatures suggests the complexation of aluminium with preserved cell envelope structures before or immediately after cell death may have inactivated autolytic activity preventing the rapid breakdown of these organic, macromolecular structures.Combined, these results highlight that aluminium may play an important role in the preservation of microorganisms within the rock record.  相似文献   

Global velocity field and bubbles in the blue compact dwarf galaxy Mrk 86     

A. Gil de Paz  J. Zamorano  J. Gallego 《Monthly notices of the Royal Astronomical Society》1999,306(4):975-987

We have studied the velocity field of the blue compact dwarf galaxy Mrk 86 (NGC 2537) using data provided by 14 long-slit optical spectra obtained in 10 different orientations and positions. This kinematical information is complemented with narrow-band ([O  iii ]5007 Å and H α ) and broad-band ( B , V , Gunn r and K ) imaging. The analysis of the galaxy global velocity field suggests that the ionized gas could be distributed in a rotating inclined disc, with projected central angular velocity of Ω=34 km s⁻¹ kpc⁻¹. The comparison between the stellar, H  i and modelled dark matter density profile indicates that the total mass within its optical radius is dominated by the stellar component. Peculiarities observed in its velocity field can be explained by irregularities in the ionized gas distribution or local motions induced by star formation.
Kinematical evidences for two expanding bubbles, Mrk 86–B and Mrk 86–C, are given. They show expanding velocities of 34 and 17 km s⁻¹, H α luminosities of 3×10³⁸ and 1.7×10³⁹ erg s⁻¹, and physical radii of 374 and 120 pc, respectively. The change in the [S  ii ]/H α , [N  ii ]/H α , [O  ii ]/[O  iii ] and [O  iii ]/H β line ratios with the distance to the bubble precursor suggests a diminution in the ionization parameter and, in the case of Mrk 86–B, an enhancement of the shock-excited gas emission. The optical–near-infrared colours of the bubble precursors are characteristic of low‐metallicity star‐forming regions (∼0.2 Z_⊙) with burst strengths of about 1 per cent in mass.  相似文献   

Recent changes in the feeding of cod (Gadus morhua) off the Flemish Cap, Newfoundland 1989-1993   总被引：1，自引：0，他引：1  

Casas  J. M.; Paz  J. 《ICES Journal of Marine Science》1996,53(5):750-756

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