Circulation and fertility of waters in Concepcion Bay     

Ahumada B. Ramón  Rudolph G. Anny  Martinez M. Victorino 《Estuarine, Coastal and Shelf Science》1983,16(1):95-105

The spatial and temporal distributions of oxygen, nutrients and pigments in the waters of Concepcion Bay, Chile (36°40′S, 73°01′W) are described for 1978–1979. Analysis of the seasonal fluctuations shows the upwelling of water poor in oxygen and rich in nutrients inside the bay during summer. The upwelled water fertilizes the bay and produces progressive eutrophication, causing mass mortalities, discoloured water and mineralization of organic matter.  相似文献   

Comparison of heat and bromide as ground water tracers near streams   总被引：3，自引：0，他引：3  

Constantz J  Cox MH  Su GW 《Ground water》2003,41(5):647-656

Heat and bromide were compared as tracers for examining stream/ground water exchanges along the middle reaches of the Santa Clara River, California, during a 10-hour surface water sodium bromide injection test. Three cross sections that comprise six shallow (<1 m) piezometers were installed at the upper, middle, and lower sections of a 17 km long study reach, to monitor temperatures and bromide concentrations in the shallow ground water beneath the stream. A heat and ground water transport simulation model and a closely related solute and ground water transport simulation model were matched up for comparison of simulated and observed temperatures and bromide concentrations in the streambed. Vertical, one-dimensional simulations of sediment temperature were fitted to observed temperature results, to yield apparent streambed hydraulic conductivities in each cross section. The temperature-based hydraulic conductivities were assigned to a solute and ground water transport model to predict sediment bromide concentrations, during the sodium bromide injection test. Vertical, one-dimensional simulations of bromide concentrations in the sediments yielded a good match to the observed bromide concentrations, without adjustment of any model parameters except solute dispersivities. This indicates that, for the spatial and temporal scales examined on the Santa Clara River, the use of heat and bromide as tracers provide comparable information with respect to apparent hydraulic conductivities and fluxes for sediments near streams. In other settings, caution should be used due to differences in the nature of conservative (bromide) versus nonconservative (heat) tracers, particularly when preferential flowpaths are present.  相似文献   

Effects of trace metal and exposure to air on serotonin and dopamine levels in tissues of the mussel Perna perna   总被引：1，自引：0，他引：1  

Almeida EA  Bainy AC  Medeiros MH  Di Mascio P 《Marine pollution bulletin》2003,46(11):1485-1490

We evaluated levels of serotonin (5HT) and dopamine (DOPA) in muscle and digestive glands of the mussel, Perna perna, collected at different times of day; exposed to air for 24 h, followed by re-submersion; and after exposure to different metals. Mussels collected at different periods of day showed little oscillation in 5HT and DOPA levels. Mussels exposed to metals showed significant changes in 5HT and DOPA levels in digestive gland and muscle, as did mussels exposed to air. Our data suggest that analyses of 5HT and DOPA in tissues of mussels could serve as a tool to evaluate the presence and effects of heavy metal contamination in mussels. Care in data interpretation is required, however, since other environmental factors such as exposure of mussels to air (i.e. at low tides) can also cause changes in DOPA and 5HT levels. Additional research is necessary to separate such natural environmental effects from effects of contaminants.  相似文献   

Crustal attenuation in the Southern Andean retroarc (38°–39°30′ S) determined from tectonic and gravimetric studies: The Lonco-Luán asthenospheric anomaly     

Andrs Folguera  Antonio Introcaso  Mario Gimnez  Francisco Ruiz  Patricia Martinez  Cynthia Tunstall  Ezequiel García Morabito  Víctor A. Ramos 《Tectonophysics》2007,439(1-4):129-147

The western retroarc of the Southern Andes between 38° and 40° S is formed by a NNW-elongated ridge not associated with stacked thrust sheets. On the contrary, during the last 4–3 Ma this ridge was affected by extensional deformation, regional uplift and related folding on a very broad scale. Receiver function analysis shows that the drainage divide area and adjacent retroarc lie over an attenuated crust. Expected crustal thickness at these latitudes is around 38 km, whereas in this part of the retroarc the thickness is less than 32 km. The causes for such attenuation have been linked to a moderate steepening of the subducted Nazca plate beneath the South American plate, which is suggested by a westward shift and narrowing of the magmatic arc during the last 4 to 5 Ma. Gravimetric studies show that the upper plate did not react homogeneously to slab steepening, but ancient sutures and lithospheric discontinuities deeply buried under Mesozoic to Cenozoic sequences in the retroarc were locally reactivated. These processes resulted in an asthenospheric anomaly that correlates at the surface with the area of Pliocene to Quaternary doming, widespread extension and three radial troughs. Two of the troughs have accommodated substantial amounts of extension, but the third was probably aborted at an early stage. Moreover, the presence of an anomalous concentration of calderas and large volcanic centers over the proposed asthenospheric anomaly, and their age distribution, may indicate minor migration of the asthenospheric anomaly between 4 and 2 Ma through the western South American plate.  相似文献   

The isotopic composition of oxygen and carbon in the hyaloclastites from the Mt. Iblei volcanic area,Eastern Sicily: A preliminary study     

M. Preite Martinez  B. Turi 《Bulletin of Volcanology》1978,41(3):168-174

Oxygen and carbon isotopic analyses were carried out for some typical submarine volcanic products (a lava flow, a pillow fragment and four hyaloclastite breccias) from the northwestern zone of the Mt. Iblei volcanic complex, eastern Sicily. The δ¹⁸O value of the perental basaltic magma (6.0 ± 0.2‰), estimated from the analyses of some fresh unaltered glassy samples of various type, lies in the values range of primary basalts. Appreciably higher δ¹⁸O values, probably due to low-temperature exchanges with sea water, have been found for lava samples and the interior of the pillow fragment. The δ¹⁸O and δ¹³C of the calcites of the groundmass of the hyaloclastite samples, ranging from 30.59 to 33.65 and from ?2.99 to 0.46‰ respectively, are typical of low-temperature marine carbonates. Because calcite is one of the last minerals to form. these results suggest that the hyaloclastites studied formed entirely in a submarine environment. The¹⁸O/¹⁶O ratios recorded in the silicate portions of the matrices of the hyaloclasites (δ¹⁸O=13.99 to 16.61) are interpreted as the result of halmyrolytic processes occurring at temperatures somewhat higher than that of the sea floor.  相似文献   

Multivariate statistical analysis of some recent volcanics from the Central Andes of Southern Peru     

Dr. Marisa Frangipane 《International Journal of Earth Sciences》1978,67(3):953-959

The application of Principal Component and Discriminant analysis to the major and minor oxides of recent volcanics from the Central Andes (S-Peru, N-Chile, Bolivia and Argentina) illustrates a variation in chemical composition related to geographical distribution, mainly in terms of TiO₂ and K₂O. A relationship between chemistry and distance from the Peru-Chile trench, dependent on P, Ti and Sr content of some cenozoic lavas from Southern Peru is also illustrated, by means of Multilinear Standardized Regressions and Partial Correlation analysis.

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Zusammenfassung Die Anwendung zweier statistischer Methoden (Principal Component und Discriminant Analysis) zur Erfassung der Oxidverteilung in den rezenten Vulkaniten der zentralen Anden (S-Peru, N-Chile, Bolivien und Argentinien) hat gezeigt, daß die Variation der chemischen Zusammensetzung, hauptsächlich bei TiO₂ und K₂O, abhängig von der geographischen Position der Ausbruchzentren ist.Eine Beziehung zwischen Geochemie und Entfernung vom Peru-Chile Tief-Seegraben für die rezenten Laven in S-Peru wird ferner mit multilinearen standardisierten Regressionen und Korrelationsanalysen, mit Schwerpunkt bei den Elementen P, Ti und Sr, aufgezeigt.

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Resume L'application de deux méthodes statistiques multivariées (Principal Component et Discriminant Analysis) à la distribution des éléments majeurs et mineurs dans les roches volcaniques récentes des Andes centrales (S-Pérou, N-Chili, Bolivie et Argentine) montre une variation de la composition chimique en fonction de la distribution géographique, surtout en ce qui concerne TiO₂ et K₂O.Une relation entre la variation de composition chimique de quelques laves récentes du Pérou du Sud et la distance du fossé océanique du Pérou-Chili est aussi montrée, à l'aide des Regressions Multilinéaires Standardisées et de l'Analyse de Corrélation partielle. Cette relation concerne spécialment les teneurs en P, Ti et Sr des laves étudiées.

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— Principal Component, Discriminant Analysis ( , , ) , . . . iO₂, K₂, . - . T Sr

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Evaluating parameter effects in a DEM ‘burning’ process based on land cover data     

Augusto C. V. Getirana  Marie‐Paule Bonnet  Jean‐Michel Martinez 《水文研究》2009,23(16):2316-2325

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Quantifying the seasonal variations in fluvial and eolian sources of terrigenous material to Cariaco Basin,Venezuela     

Aurora C. Elmore  Robert C. Thunell  Richard Styles  David Black  Richard W. Murray  Nahysa Martinez  Yrene Astor 《Journal of South American Earth Sciences》2009,27(2-3):197-210

The varved sediments that accumulate in the Cariaco Basin provide a detailed archive of the region’s climatic history, including a record of the quantity of fluvial and wind-transported material. In this study, we examine the sedimentological characteristics (clay mineralogy and grain size) of both surface sediments and sinking lithogenic material collected from sediment trap samples over a three-year period from 1997 to 2000. Data from biweekly sediment trap samples show a tri-modal particle size distribution, with prominent peaks at 2, 22 and 80 μm, indicating sediment contributions from both eolian and fluvial sources. The clay mineralogy of the water column samples collected from 1997 to 1999 also shows distinctive characteristics of eolian and fluvial material. An examination of surface sediment samples from the Cariaco Basin indicates that the Unare River is the main source of riverine sediments to the eastern sub-basin. By combining these sedimentological proxies, we estimate that ～10% of the terrigenous material delivered to the Cariaco Basin is eolian, while ～90% is fluvial. This represents an annual dust accumulation rate of ～0.59 mg/cm²/yr. Since aerosols are closely linked to climate variability, the ability to quantify paleo-dust fluxes using sedimentological characteristics will be a useful tool for future paleoclimate studies looking at sub-Saharan aridity and latitudinal migration of the Intertropical Convergence Zone.  相似文献   

The 2013 Ibiza Calibration Campaign of Jason-2 and SARAL Altimeters     

F. Frappart  N. Roussel  R. Biancale  J.J. Martinez Benjamin  F. Mercier  F. Perosanz 《Marine Geodesy》2015,38(3):219-232

This study presents the results of the 2013 Ibiza (Western Mediterranean) calibration campaign of Jason-2 and SARAL altimeters. It took place from 14 to 16 September 2013 and comprised two phases: the calibration of the GNSS (Global Navigation Satellite System) buoys to estimate the antenna height of each of them and the absolute calibration to estimate the altimeter bias (i.e., the difference of sea level measured by radar altimetry and GNSS). The first one was achieved in the Ibiza harbor at a close vicinity of the Ibiza tide gauge and the second one was performed at ～ 40 km at the northwest of Ibiza Island at a crossover point of Jason-2 and SARAL nominal groundtracks. Five buoys were used to delineate the crossover region and their measurements interpolated at the exact location of each overflight. The overflights occurred two consecutive days: 15 and 16 September 2013 for Jason-2 and SARAL, respectively. The GNSS data were processed using precise point positioning technique. The biases found are of (?0.1 ± 0.9) and (?3.1 ± 1.5) cm for Jason-2 and SARAL, respectively.  相似文献   

The lithology of Ogallala gravels and hunter‐gatherer procurement strategies along the Southern High Plains eastern escarpment of Texas,USA     

Stance Hurst  Eileen Johnson  Zaneta Martinez McCoy  Doug Cunningham 《Geoarchaeology》2010,25(1):96-121

Ogallala gravels are an important lithic material source for stone tool manufacture across the Great Plains. The lithology of eight gravel sample locations along the eastern escarpment of the Southern High Plains has been examined to quantify the composition and variability in Ogallala deposits. In addition, three Ogallala gravel quarry sites have been analyzed to determine how the lithology of Ogallala gravels influenced procurement and tool production strategies. Results indicate deposits of Ogallala gravels differ in their composition related to their position on the landscape, and the types of rocks vary by size and shape. Investigation of the quarry sites has revealed that the lithology of Ogallala gravels had an impact on testing and the initial stages of lithic reduction. Different rock types, however, may have more of an influence on later stages of tool manufacture at nearby campsites and other locations where Ogallala gravels are not as dense. © 2009 Wiley Periodicals, Inc.  相似文献