Hadean-archean detrital zircons from Jatulian quartzites and conglomerates of the Karelian craton     

V. N. Kozhevnikov  S. G. Skublov  Yu. B. Marin  P. V. Medvedev  Yu. Systra  V. Valencia 《Doklady Earth Sciences》2010,431(1):318-323

Using local procedures, the new results on the isotope ages and composition of mineral inclusions were obtained for detrital zircons from Paleoproterozoic Jatulian terrigenous quartzites and polymictic conglomerates in Central and Western Karelia. For Eastern Laurasia, signs of the existence of Hadean and ancient Eoarchean matter were found for the first time (zircon grains of 3871 ± 38.6 and 3837 ± 42.1 Ma concordant ages). The multimodal distribution of ages within 3.45−2.61 Ga was revealed. The discovery of the oldest zircon grains provides the conditions for valid global correlations of geological events that determined the deposition and formation of the continental crust of the North Atlantic supercraton.  相似文献   

Late Cretaceous porphyry copper mineralization in Sonora,Mexico: Implications for the evolution of the Southwest North America porphyry copper province   总被引：1，自引：0，他引：1  

Fernando Barra  Victor A Valencia 《Mineralium Deposita》2014,49(7):879-884

Two porphyry Cu-Mo prospects in northern Sonora, Mexico (Fortuna del Cobre and Los Humos) located within the southwestern North American porphyry province have been dated in order to constrain the timing of crystallization and mineralization of these ore deposits. In Fortuna del Cobre, the pre-mineralization granodiorite porphyry yielded an U-Pb zircon age of 76.5?±?2.3 Ma, whereas two samples from the ore-bearing quartz feldespathic porphyry were dated at 74.6?±?1.3 and 75.0?±?1.4 Ma. Four molybdenite samples from Los Humos porphyry Cu prospect yielded a weighted average Re-Os age of 73.5?±?0.2 Ma, whereas two samples from the ore-bearing quartz monzonite porphyry gave U-Pb zircon ages of 74.4?±?1.1 and 74.5?±?1.3 Ma, showing a Late Cretaceous age for the emplacement of this ore deposit. The results indicate that Laramide porphyry Cu mineralization of Late Cretaceous age is not restricted to northern Arizona as previously thought and provide evidence for the definition of NS trending metallogenic belts that are parallel to the paleo-trench. Porphyry copper mineralization follows the inland migration trend of the magmatic arc as a result of the Farallon slab flattening during the Laramide orogeny.  相似文献   

Low-salinity plumes in the oceanic region of the Basque Country     

L. Ferrer  A. Fontán  J. Mader  G. Chust  M. González  V. Valencia  Ad. Uriarte  M.B. Collins 《Continental Shelf Research》2009,29(8):970-984

Low-salinity waters, within the upper layers of the water column, have been observed in the oceanic region of the southeastern limit of the Bay of Biscay (in March, 2007). This contribution assesses the potential role of large surface freshwater discharges from the Adour (France), Nervión, Oria, Deba, Urola, Urumea and Bidasoa (Basque Country) rivers, to explain the presence of these low-salinity waters. Such discharges, within the offshore waters, reached to at least 50 m in depth; likewise, extending over 15–20 km, in the horizontal. This pattern is confirmed by field data collected by offshore buoys, model results, and the analysis of satellite images. The presence of the low-salinity waters is corroborated by numerical simulations, performed by the ROMS (Regional Ocean Modeling System) hydrodynamic model, with the incorporation of river discharges. In order to simulate the freshwater movements and to identify their origin, particles were released at the river mouths and dispersed (by a Lagrangian particle-tracking model, LPTM), supplied by 3-hourly current fields derived from the ROMS model. The plumes of the Nervión, Oria, Urola and Urumea rivers appear to be the main factors contributing to the low-salinity field, at the offshore locations of the buoys. This pattern is related mainly to the prevailing oceano-meteorological conditions, over the period of analysis.  相似文献   

The South China Sea: Prospects for marine regionalism     

Mark J. Valencia 《Marine Policy》1978,2(2):87-104

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Retracking considerations in spaceborne GNSS-R altimetry   总被引：1，自引：0，他引：1  

Hyuk Park  Adriano Camps  Enric Valencia  Nereida Rodriguez-Alvarez  Xavier Bosch-Lluis  Isaac Ramos-Perez  Hugo Carreno-Luengo 《GPS Solutions》2012,16(4):507-518

The European Space Agency Passive Reflectometry and Interferometry System In-orbit Demonstrator (IoD) aims to perform mesoscale altimetric observations by measuring the Global Navigation Satellite System (GNSS) opportunity signals reflected over the sea surface. Altimetry based on GNSS reflectometry (GNSS-R) is significantly affected by satellite motion, since it requires relatively long integration times to reduce noise. We present the impact of the satellite motion on the GNSS-R observables and the need to retrack the waveforms. By using a detailed GNSS-R space mission simulator, the change of delay difference between the direct and the reflected signals during the incoherent averaging of the waveform has been investigated. Their effects on the waveform shape and the altimetric performance are presented comparing the aligned and non-aligned waveforms. Results show that the performance of spaceborne GNSS-R altimeter is seriously degraded without a proper alignment of the waveform samples.  相似文献   

Evaluation of extreme temperature events in northern Spain based on process control charts     

Villeta  M.  Valencia  J. L.  Saá  A.  Tarquis  A. M. 《Theoretical and Applied Climatology》2018,131(3-4):1323-1335

Theoretical and Applied Climatology - Extreme climate events have recently attracted the attention of a growing number of researchers because these events impose a large cost on agriculture and...  相似文献   

Reliable Procedure for Molecular Analysis of Airborne Microflora in Three Indoor Environments: An Office and Two Different Museum Contexts     

Carole Gaüzère  Marina Moletta‐Denat  Faisl Bousta  Stéphane Moularat  Geneviève Orial  Sébastien Ritoux  Jean‐Jacques Godon  Enric Robine 《洁净——土壤、空气、水》2013,41(3):226-234

Biological aerosols from air constitute a significant source of exposure to microorganisms in public places. Airborne microorganisms are involved in the development of certain respiratory symptoms, allergies, or infections among users and occupants. Various sampling instruments have commonly been used in aerobiology to collect bacteria and fungi suspended in the air. The objective of this study was to develop a reliable procedure for sampling in indoor public environments presenting different levels of occupancy, airborne bacteria and fungi to be subjected to molecular analysis (bacteria and fungi quantitative PCR, capillary electrophoresis single strand conformation polymorphism fingerprinting). Four different sampling devices were tested in situ in an office building (open‐plan type) and the sampling strategy chosen was tested in two museum contexts. In accordance with the drawbacks involved to our study (quantitative and qualitative aspects, cost, and overcrowding), cyclone device appeared to be most suitable. The results underline the effectiveness of this high‐volume aerosol sampling device for both qualitative and quantitative molecular analysis. Four in situ sampling collections were carried out in 1 day in the Louvre Museum to study quantitative and qualitative variations of airborne bacterial and fungal diversity. The quantitative results revealed a similar order of magnitude for the numbers of both bacteria and fungi. In the Louvre Museum, the samples yielded between 3.7 × 10⁴ and 4.1 × 10⁴ genome equivalent (GE) bacteria/m³ air and between 5.0 × 10⁴ and 5.9 × 10⁴ GE fungi/m³ air and in the Decorative Arts Museum between, 2.1 × 10⁴ and 2.5 × 10⁴ GE bacteria/m³ air and between 1.4 × 10⁴ and 1.7 × 10⁴ GE fungi/m³ air. The results also indicate that the dominant bacterial community displayed a stable structure over a short period of time whereas dominant eukaryotic airborne community appeared more variable.  相似文献   

Changes in daily climate extremes in China and their connection to the large scale atmospheric circulation during 1961–2003     

Qinglong You  Shichang Kang  Enric Aguilar  Nick Pepin  Wolfgang-Albert Flügel  Yuping Yan  Yanwei Xu  Yongjun Zhang  Jie Huang 《Climate Dynamics》2011,36(11-12):2399-2417

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Two hundred years of environmental change in Picos de Europa National Park inferred from sediments of Lago Enol, northern Iberia     

Lourdes L��pez-Merino  Ana Moreno  Manel Leira  Javier Sigr��  Pen��lope Gonz��lez-Samp��riz  Blas L. Valero-Garc��s  Jos�� Antonio L��pez-S��ez  Manola Brunet  Enric Aguilar 《Journal of Paleolimnology》2011,46(3):453-467

We present a study of two short sediment cores recovered from Lago Enol, in the Picos de Europa National Park, Cantabrian Mountains, northern Iberia. We inferred past climate conditions and anthropogenic impacts using geochemical and biological (pollen and diatoms) variables in the dated sequences, in conjunction with temperature and precipitation data collected since 1871 at meteorological stations in the region. The record provides evidence of environmental changes during the last 200 years. At the end of the Little Ice Age (~1800?C1875 AD) the region was characterized by an open landscape. Long-term use of the area for mixed livestock grazing in the mountains, and cultivation of rye during the nineteenth century, contributed to the expansion of grassland at the expense of forest. Warmer temperatures since the end of the nineteenth century are inferred from a change in diatom assemblages and development of the local forest. Socioeconomic transformation during the twentieth century, such as livestock changes related to dairy specialization, planting of non-native trees, mining activities, and management of the national park since its creation in 1918, caused profound changes in the catchment and in the lake ecology. The last several decades (~1970?C2007 AD) of the Lago Enol sediment record are strikingly different from previous periods, indicating lower runoff and increasing lake productivity, particularly since AD 2000. Today, the large number of tourists who visit the area cause substantial impacts on this ecosystem.  相似文献   

Spatial and temporal variability of deep-water algal assemblages in the Northwestern Mediterranean: The effects of an exceptional storm     

Laura Navarro  Enric Ballesteros  Cristina Linares  Bernat Hereu 《Estuarine, Coastal and Shelf Science》2011

There are deep-water populations of the endemic and threatened Mediterranean brown alga Cystoseira zosteroides in the Medes Islands Marine Reserve (NW Mediterranean). Here, the distribution, population structure, individual growth, mortality and recruitment rates of this species over two years are described in relation to the effects of an exceptional storm. We found a high spatial variability in the structure and dynamics of C. zosteroides populations at small geographical scales, suggesting that environmental factors acting at the population level display a key role in population size structure, mortality and recruitment. The elevated mortality rates recorded at some locations (almost 80%) is amongst the highest recorded for perennial algae as a consequence of a single storm, emphasizing the importance of episodic catastrophic events in the maintenance of these deep-water, slow-growing populations. These findings are of particular importance not only to fully understand the ecology of C. zosteroides, but also for its conservation.  相似文献