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31.
Subsidence and thermal history of an inverted Late Jurassic‐Early Cretaceous extensional basin (Cameros,North‐central Spain) affected by very low‐ to low‐grade metamorphism
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Silvia Omodeo‐Salé Ramon Salas Joan Guimerà Robert Ondrak Ramon Mas José Arribas Isabel Suárez‐Ruiz Luis Martinez 《Basin Research》2017,29(Z1):156-174
The Cameros Basin (North Spain) is a Late Jurassic‐Early Cretaceous extensional basin, which was inverted during the Cenozoic. It underwent a remarkable thermal evolution, as indicated by the record of anomalous high temperatures in its deposits. In this study, the subsidence and thermal history of the basin is reconstructed, using subsidence analysis and 2D thermal modelling. Tectonic subsidence curves provide evidence of the occurrence of two rapid subsidence phases during the syn‐extensional stage. In the first phase (Tithonian‐Early Berriasian), the largest accommodation space was formed in the central sector of the basin, whereas in the second (Early Barremian‐Early Albian), it was formed in the northern sector. These rapid subsidence phases could correspond to relevant tectonic events affecting the Iberian Plate at that time. By distinguishing between the initial and thermal subsidence and defining their relative magnitudes, Royden's (1986) method was used to estimate the heat flow at the end of the extensional stage. A maximum heat flow of 60–65 mW/m2 is estimated, implying only a minor thermal disturbance associated with extension. In contrast with these data, very high vitrinite reflectance, anomalously distributed in some case with respect to the typical depth‐vitrinite reflectance relation, was measured in the central‐northern sector of the basin. Burial and thermal data are used to construct a 2D thermal basin model, to elucidate the role of the processes involved in sediment heating. Calibration of the thermal model with the vitrinite reflectance (%Ro) and fluid inclusion (FI) data indicates that in the central and northern sectors of the basin, an extra heat source, other than a typical rift, is required to explain the observed thermal anomalies. The distribution of the %Ro and FI values in these sectors suggests that the high temperatures and their distribution are related to the circulation of hot fluids. Hot fluids were attributed to the hydrothermal metamorphic events affecting the area during the early post‐extensional and inversion stages of the basin. 相似文献
32.
Quantification of the environmental structural risk with spoiling ties: is randomization worthwhile?
R.?PappadàEmail author F.?Durante G.?Salvadori 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(10):2483-2497
Many recent works show that copulas turn out to be useful in a variety of different applications, especially in environmental sciences. Here the variables of interest are usually continuous, being times, lengths, weights, and so on. Unfortunately, the corresponding observations may suffer from (instrumental) adjustments and truncations, and eventually may show several repeated values (i.e., ties). In turn, on the one hand, a tricky issue of identifiability of the model arises, and, on the other hand, the assessment of the risk may be adversely affected. A possible remedy is to adopt suitable randomization procedures: here three different strategies are outlined. The goal of the work is to carry out a simulation study in order to evaluate the effects of the randomization of multivariate observations when ties are present. In particular, it is investigated whether, how, and to what extent, the randomization may change the estimation of the structural risk: for this purpose, a coastal engineering example will be used, as archetypical of a broad class of models and problems in engineering applications. Practical advices and warnings about the use of randomization techniques are hence given. 相似文献
33.
34.
A. Gabàs A. Macau B. Benjumea F. Bellmunt S. Figueras M. Vilà 《Surveys in Geophysics》2014,35(4):983-1002
35.
Assessment of the effects of a marine urban outfall discharge on caged mussels using chemical and biomarker analysis 总被引:1,自引:0,他引:1
de los Ríos A Juanes JA Ortiz-Zarragoitia M López de Alda M Barceló D Cajaraville MP 《Marine pollution bulletin》2012,64(3):563-573
To assess the presence of endocrine disruptors in treated marine outfall discharges and their possible effects, mussels (Mytilus galloprovincialis) were caged in the environmental mixing zone of the outfall of the Santander sanitation system and in one control area. After 30, 60 and 90 days, samples were collected to perform chemical analyses (metals, anionic surfactants, alkylphenols, bisphenol A, phthalates and estrogenic hormones), biomarkers of general stress (lysosomal membrane stability-LMS, histopathology) and biomarkers of endocrine disruption (vitellogenin-like proteins and gonad index). There were no significant differences between outfall and control sites on contaminant levels, except for 4-tert-octylphenol which was higher in the outfall site. Bacteriological counts were higher in the outfall area. No relevant differences in biomarkers were detected between treated and control mussels. A significant reduction in LMS occurred in both groups after 90 days caging, indicating a stress situation possibly related to caging or to post-spawning reproductive state. 相似文献
36.
Giovanni Tecchio Marco Donà Francesca da Porto 《Bulletin of Earthquake Engineering》2016,14(11):3099-3124
Masonry arch bridges are crucial elements in the railway transportation network throughout Europe. Although significant advances in seismic risk assessment of various bridge types have been made by developing fragility curves of generalized classes of structures, there are no comparable tools for masonry arch structures. In this context, this paper presents the construction of seismic fragility curves of single-span masonry bridges according to the limit analysis method. An iterative procedure is implemented to define the capacity curve of the equivalent single degree of freedom system through non-linear kinematic analysis. The process involves determination of the collapse mechanism, calculation of the limit load multiplier, and definition of the thrust line. The intrinsic variability of the seismic action is incorporated with the use of different sets of elastic spectra compatible with EC 8 Type-1 spectrum for various types of soil, with peak ground acceleration varying over the range 0.05–1.5 g. The fragility curves of the generalized classes of single-span masonry bridges are finally obtained from the effective ranges of the main geometric and material parameters affecting arch bridge capacity. 相似文献
37.
Marianne Holmer Núria Marbà Morgane Lamote Carlos M. Duarte 《Estuaries and Coasts》2009,32(3):456-466
Species of the macroalgae Caulerpa sp. are increasingly being observed in meadows of the endemic Mediterranean seagrass Posidonia oceanica, and in particular Caulerpa taxifolia, has been considered as an invasive species leading to seagrass decline. Studies have so far failed to reveal the underlying
mechanisms of the success of the macroalgae, and here, we examine how biogeochemical changes of the environment associated
to indigenous (Caulerpa prolifera) and non-indigenous (Caulerpa racemosa and C. taxifolia) species affect the habitat of P. oceanica. Two of the species (C. prolifera and C. racemosa) affect the sediment biogeochemical conditions by increasing organic matter pools, microbial activity, and sulfide pools
of the sediments, and limited effects were found for C. taxifolia. Biomass of the macroalgae contributed to the extent of impacts, and high sulfide invasion into the seagrasses and regression
of the meadow were pronounced at the location with the highest Caulerpa biomass. This suggests that Caulerpa invasion contributes to seagrass decline probably because Caulerpa thrives better than the seagrasses in the modified environment. 相似文献
38.
AbstractThe Hilhorst model was used to convert bulk electrical conductivity (σb) to pore water electrical conductivity (σp) under laboratory conditions by using the linear relationship between the soil dielectric constant (εb) and σb. In the present study, applying the linear relationship εb–σb to data obtained from field capacitance sensors resulted in strong positive autocorrelations between the residuals of that regression. We were able to derive an accurate offset of the relationship εb–σb and to estimate the evolution of σp over time by including a stochastic component to the linear model, rearranging it to a time-varying dynamic linear model (DLM), and using Kalman filtering and smoothing. The offset proved to vary for each depth in the same soil profile. A reason for this might be the changes in soil temperature along the soil profile.
Editor D. Koutsoyiannis; Associate editor M.D. Fidelibus 相似文献
39.
Magma plumbing beneath Anak Krakatau volcano, Indonesia: evidence for multiple magma storage regions
B?rje Dahren Valentin R. Troll Ulf B. Andersson Jane P. Chadwick Màiri F. Gardner Kairly Jaxybulatov Ivan Koulakov 《Contributions to Mineralogy and Petrology》2012,163(4):631-651
Understanding magma plumbing is essential for predicting the behaviour of explosive volcanoes. We investigate magma plumbing
at the highly active Anak Krakatau volcano (Indonesia), situated on the rim of the 1883 Krakatau caldera by employing a suite
of thermobarometric models. These include clinopyroxene-melt thermobarometry, plagioclase-melt thermobarometry, clinopyroxene
composition barometry and olivine-melt thermometry. Petrological studies have previously identified shallow magma storage
in the region of 2–8 km beneath Krakatau, while existing seismic evidence points towards mid- to deep-crustal storage zone(s),
at 9 and 22 km, respectively. Our results show that clinopyroxene in Anak Krakatau lavas crystallized at a depth of 7–12 km,
while plagioclase records both shallow crustal (3–7 km) and sub-Moho (23–28 km) levels of crystallization. These magma storage
regions coincide with well-constrained major lithological boundaries in the crust, implying that magma ascent and storage
at Anak Krakatau is strongly controlled by crustal properties. A tandem seismic tomography survey independently identified
a separate upper crustal (<7 km) and a lower to mid-crustal magma storage region (>7 km). Both petrological and seismic methods
are sensitive in detecting magma bodies in the crust, but suffer from various limitations. Combined geophysical and petrological
surveys, in turn, offer increased potential for a comprehensive characterization of magma plumbing at active volcanic complexes. 相似文献
40.
Raquel Vaquer-Sunyer Carlos M. Duarte Gabriel Jordà Sergio Ruiz-Halpern 《Estuaries and Coasts》2012,35(5):1182-1192
Hypoxia is emerging as a major threat to marine coastal biota. Predicting its occurrence and elucidating the driving factors are essential to set successful management targets to avoid its occurrence. This study aims to elucidate the effects of warming on the likelihood of hypoxia. High-frequency dissolved oxygen measurements have been used to estimate gross primary production (GPP), net ecosystem production (NEP) and community respiration (CR) in a shallow macroalgae (Caulerpa prolifera) ecosystem in a highly human-influenced closed Mediterranean bay. Daily averaged GPP and CR ranged from 0 to 1,240.9 and 51.4 to 1,297.3?mmol?O2?m?2?day?1, respectively. The higher GPP and CR were calculated for the same day, when daily averaged water temperature was 28.3?°C, and resulted in a negative NEP of ?56.4?mmol?O2?m?2?day?1. The ecosystem was net heterotrophic during the studied period, probably subsidized by allochthonous organic inputs from ground waters and from the surrounding town and boating activity. Oxygen dynamics and metabolic rates strongly depend on water temperature, with lower oxygen content at higher temperatures. The probability of hypoxic conditions increased at a rate of 0.39?% °C?1 (±0.14?% °C?1). Global warming will increase the likelihood of hypoxia in the bay studied, as well as in other semi-enclosed bays. 相似文献