Influence of minibasin obstruction on canopy dynamics in the northern Gulf of Mexico     

Naiara Fernandez  Oliver B. Duffy  Frank J. Peel  Michael R. Hudec 《Basin Research》2021,33(1):427-446

In salt‐detached gravity‐gliding/spreading systems the detachment geometry is a key control on the downslope mobility of the supra‐salt sequence. Here, we used regional 3D seismic data to examine a salt‐stock canopy in the northern Gulf of Mexico slope, in an area where supra‐canopy minibasins subsided vertically and translated downslope above a complex base‐of‐salt. If thick enough, minibasins can interact with, and weld to, the base‐of‐salt and be obstructed from translating downslope. Based on the regional maps of the base of allochthonous salt and the base of the supra‐canopy sequence, the key controls on minibasin obstruction, we distinguished two structural domains in the study area: a highly obstructed domain and a highly mobile domain. Large‐scale translation of the supra‐canopy sequence is recorded in the mobile domain by a far‐travelled minibasin and a ramp syncline basin. These two structures suggest downslope translation on the order of 40 km from Plio‐Pleistocene to Present. In contrast, translation was impeded in the obstructed domain due to supra‐canopy bucket minibasins subsiding into feeders during the Pleistocene. As a result, we infer that differential translation occurred between the two domains and argue that a deformation area between two differentially translating supra‐canopy minibasin domains is difficult to recognize. However, characterizing domains according to base‐of‐salt geometry and supra‐canopy minibasin configuration can be helpful in identifying domains that may share similar subsidence and downslope translation histories.  相似文献   

Geochemistry and petrogenesis of two-Pyroxene andesites from Sierra de Gata (SE Spain)     

L. Toscani  G. Venturelli  M. Barbieri  S. Capedri  J. M. Fernandez Soler  M. Oddone 《Mineralogy and Petrology》1990,41(2-4):199-213

Summary The Miocene volcanic suite of Sierra de Gata (Betic Cordillera) is composed of dacites, rhyodacites and rhyolites, besides basaltic andesites and andesites. The latter are very fresh and are the least fractionated rock types; thus they have been investigated in order to put some constraints on the genetic interpretation of the volcanic sequence. These rocks are composed of plagioclase, orthopyroxene, clinopyroxene and magnetite both as phenocrysts and in the groundmass. Olivine and ilmenite occur occasionally. The andesites exhibit orogenic chemical features. They are characterized by very low Ni, Co and Cr contents and show negative Eu anomalies, which support fractionation of mafic phases and plagioclase at depth. The petrogenesis of the andesites, however, cannot be related simply to fractionation processes of a single mafic magma since the lack of good interelemental correlations, the scattering of Sr-isotope ratios and the isotope disequilibrium between the phases conflict with such a simple mechanism. A model which can better explain the petrogenesis of the analyzed andesites considers the intervention of different mafic melts, generated in a heterogeneous mantle and characterized by different chemical and isotopic compositions, which fractionated at depth and concomitantly interacted significantly with the continental crust.

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Geochemie und Petrogenese von Pyroxen-Andesiten der Sierra de Gata (SE Spanien)

Zusammenfassung Die miozäne Vulkanitabfolge der Sierra de Gata (Betische Kordillere) wird von Daciten, Rhyodaciten, Rhyoliten sowie basaltischen Andesiten and Andesiten aufgebaut, letztere sind in einem guten Erhaltungszustand and zeigen die geringste Fraktionierung. Sie wurden daher genauer untersucht, um Aussagen über die Genese dieser Vulkanite machen zu können.Phenokrysten und Grundmasse bestehen aus Plagioklas, Orthopyroxen, Klinopyroxen und Magnetit. Manchmal kommen Olivin und Ilmenit hinzu. Die Geochemie der Andesite folgt typisch orogenen Trends. Sie sind durch sehr niedrige Ni-, Co- und Cr-Gehalte und negative Eu-Anomalien charakterisiert; dies belegt eine Fraktionierung der mafischen Gemengteile und des Plagioklases in der Tiefe. Die petrogenetische Entwicklung der Andesite kann allerdings nicht einfach mit Fraktionierungsprozessen eines einzigen mafischen Magmas erklärt werden. Das Fehlen von Element-Korrelationen, das starke Streuen der Sr-Isotopenverhältnisse und das Isotopenungleichgewicht zwischen den einzelnen Mineralphasen stehen in Widerspruch zu einem derartigen einfachen Modell. Ein Modell, das die Petrogenese der untersuchten Andesite besser erklärt, zieht die Beteiligung verschiedener mafischen Schmelzen-sie bildeten sich in einem heterogenen Mantel und sind durch Unterschiede im Chemismus und ihrer Isotopenzusammensetzung charakterisiert—in Betracht. Dabei kam es zu Fraktionierung dieser Magmen in der Tiefe und zu beträchtlichen Reaktionen mit kontinentalem Krustenmaterial.

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With 5 Figures  相似文献   

Measurement of the relative composition of the Cosmic-ray iron group with Lexan polycarbonate     

M. Casas  C. Baixeras  A. Vidal-Quadras  M. Ortega  F. Fernandez 《Astrophysics and Space Science》1983,94(2):371-381

Relative abundances for the VH group of Cosmic Radiation (20≤Z≤28) at energiesE≤600 MeV nucl^?1 have been measured by means of plastic detector LEXAN. The stack was exposed to cosmic rays during a 82 hr balloon flight at Sioux Falls (South Dakota) at an average altitude equivalent to 4 g cm^?2 of residual atmosphere. A total number of 1058 events have been analyzed, out of which 675 have been unambiguously identified. Two different discrimination methods have been applied in order to test their influence on final spectra. Extrapolation to the top of the atmosphere has been achieved in the frame of the regular model including an energy loss term that has led to corrections of the order of 60% in the extrapolated abundances. The relative abundances so obtained are in reasonable agreement with those reported by other authors using electronic detectors. Abnormal high abundances of manganese and cobalt can be attributed to wide temperature variations during the registration interval. In spite of the poor mass resolution, a high abundance of⁵⁴Fe has been evidenced, indicating a non-stellar origin for cosmic iron.  相似文献   

Relative rheological evolution of chemically contrasted coeval magmas: example of the Tichka plutonic complex (Morocco)     

Angel N. Fernandez  Dominique R. Gasquet 《Contributions to Mineralogy and Petrology》1994,116(3):316-326

The Tichka plutonic complex presents many unusual structures related to physical interaction between mafic and felsic coeval magmas. In this paper, a rheological approach is used to attempt to understand the various observed structures. After a general presentation of rheological laws and a discussion about the present state of our understanding of the rheology of suspensions, we analyse the main steps of rheological evolution of magmas during crystallization. Taking into account the effect of cooling, increase of silica content and increase of crystallinity on viscosity during thermal evolution of magma, a general rheological diagram is presented. Two main rheological thresholds at about 35% crystallinity (Th₁) and about 65–70% (Th₂), allow us to distinguish three major steps in the rheological behaviour of magmas during cooling. Comparative study of evolution curves for viscosity of coeval mafic (M) and felsic (F) magmas shows that an inversion temperature Ti exists, at which viscosities of both magmas are the same. This point has major petrologic significance because the viscosity ratio (M/F) inverses during cooling when the temperature of magma falls below the Ti point. A model for the evolution of the Tichka magmas during cooling has been derived from the knowledge of the chemical and mineralogical composition of the different rocks representing the original (M) and (F) magmas as well as some hybrid and differentiated samples. Viscosities and crystal fractions of magmas as functions of temperature have been calculated from chemical and mineralogical data. Curves representing the evolution of apparent viscosity of the three initial magmas of the complex are presented. From these vicosity/temperature curves and from the calculted temperatures corresponding to rheological thresholds Th₁ and Th₂ for the different coeval magmas, five main evolution stages are defined. The different structures observed at the contracts between M and F magmas are developed throughout the entire cooling history of the pluton, each structure being related to one of the main evolution stages.  相似文献   

Simultaneous phytoremediation of chromium and phenol by L<Emphasis Type="Italic">emna minuta</Emphasis> Kunth: a promising biotechnological tool     

C. E. Paisio  M. Fernandez  P. S. González  M. A. Talano  M. I. Medina  E. Agostini 《International Journal of Environmental Science and Technology》2018,15(1):37-48

The aim of this work was to evaluate the usefulness of Lemna minuta Kunth for the simultaneous removal of Cr(VI) and phenol. The impact of these contaminants on plant growth and some biochemical processes have also been discussed for a better understanding and utilization of this species in the field of phytoremediation. The optimal growth conditions and plant tolerance to Cr(VI) and/or phenol as well as removal were determined. Plants exposed to Cr(VI) and phenol were able to efficiently grow and remove both contaminants at high concentrations (up to 2.5 and 250 mg/L, respectively) after 21 days, indicating that they were resistant to mixed contamination. There were no significant differences between chlorophyll, carotene and malondialdehyde content of treated plants with respect to the controls, which would be due to an efficient antioxidant response. L. minuta showed a higher biomass than control without contaminant when was exposed to low concentrations of Cr(VI), suggesting an hormesis effect. The main removal process involved in chromium phytoremediation would be sorption or accumulation in the biomass. Moreover, our results suggest that phenol could be used as a donor of carbon and energy by these plants. These findings demonstrated that Lemna minuta Kunth might be suitable for treatment of different solutions contaminated with Cr(VI) and phenol, showing a high potential to be used in the treatment of effluents containing mixed contamination.  相似文献   

A short-term predictive system for surface currents from a rapidly deployed coastal HF radar network     

Donald Barrick  Vicente Fernandez  Maria I. Ferrer  Chad Whelan  Øyvind Breivik 《Ocean Dynamics》2012,62(5):725-740

In order to address the need for surface trajectory forecasts following deployment of coastal HF radar systems during emergency-response situations (e.g., search and rescue, oil spill), a short-term predictive system (STPS) based on only a few hours data background is presented. First, open-modal analysis (OMA) coefficients are fitted to 1-D surface currents from all available radar stations at each time interval. OMA has the effect of applying a spatial low-pass filter to the data, fills gaps, and can extend coverage to areas where radial vectors are available from a single radar only. Then, a set of temporal modes is fitted to the time series of OMA coefficients, typically over a short 12-h trailing period. These modes include tidal and inertial harmonics, as well as constant and linear trends. This temporal model is the STPS basis for producing up to a 12-h current vector forecast from which a trajectory forecast can be derived. We show results of this method applied to data gathered during the September 2010 rapid-response demonstration in northern Norway. Forecasted coefficients, currents, and trajectories are compared with the same measured quantities, and statistics of skill are assessed employing 16 24-h data sets. Forecasted and measured kinetic variances of the OMA coefficients typically agreed to within 10–15%. In one case where errors were larger, strong wind changes are suspected and examined as the cause. Sudden wind variability is not included properly within the STPS attack we presently employ and will be a subject for future improvement.  相似文献   

Evaluating the capabilities of the CASI hyperspectral imaging system and Aquarius bathymetric LiDAR for measuring channel morphology in two distinct river environments          下载免费PDF全文

Carl J. Legleiter  Brandon T. Overstreet  Craig L. Glennie  Zhigang Pan  Juan Carlos Fernandez‐Diaz  Abhinav Singhania 《地球表面变化过程与地形》2016,41(3):344-363

Remote sensing is a powerful tool for examining river morphology. This study used detailed field surveys to assess the capability of the CASI hyperspectral imaging system and Aquarius bathymetric LiDAR to measure bed elevations in rivers with disparate optical characteristics. Field measurements of water column optical properties in the clear Snake River, the more complex Blue and Colorado, and highly turbid Muddy Creek were used to calculate depth retrieval precision and dynamic range. Differences in depth of a few centimeters were detectable via passive optical techniques in the clearest stream, but precision was greatly reduced under turbid conditions. The bathymetric LiDAR evaluated in this study could not detect shallow depths or differences in depth smaller than 11 cm owing to the difficulty of distinguishing water surface and bottom returns in laser waveforms. In clear water and with high radiometric resolution, hyperspectral systems such as CASI could detect depths approaching 10 m, but semi‐empirical analysis of the Aquarius LiDAR indicated that maximum detectable depths were of the order of 2–3 m in the clear‐flowing Snake River, and closer to 1 m in the more turbid streams. Turbidity also constrained spectrally based depth retrieval, and depth estimates from the Blue/Colorado were far less reliable than on the Snake. Both sensors yielded positively biased (0.03 m for CASI, 0.08 m for Aquarius) bed elevations on the Snake, with precisions of 0.16–0.17 m. For the Blue/Colorado, mean errors were of the order of 0.2 m, biased shallow for optical data and biased deep for LiDAR, although no Aquarius laser returns were recorded from the deepest parts of these channels; precisions were reduced to 0.29–0.32 m. Both approaches have advantages and limitations, and prospective users must understand the capabilities and constraints associated with various types of remote sensing to ensure efficient use of these evolving technologies. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Obstructed minibasins on a salt-detached slope: An example from above the Sigsbee canopy,northern Gulf of Mexico     

Oliver B. Duffy  Naiara Fernandez  Frank J. Peel  Michael R. Hudec  Tim P. Dooley  Christopher A.-L. Jackson 《Basin Research》2020,32(3):505-524

Salt-detached gravity gliding/spreading systems having a rugose base-of-salt display complex strain patterns. However, little was previously known about how welding of supra-salt minibasins to the sub-salt may influence both the downslope translation of minibasins on salt-detached slopes and the regional pattern of supra-salt strain. Using a regional 3D seismic reflection data set, we examine a large salt-stock canopy system with a rugose base on the northern Gulf of Mexico slope, on which minibasins both subside and translate downslope. Some minibasins are welded at their bases and others are not. We suggest that basal welds obstruct downslope translation of minibasins and control regional patterns of supra-canopy strain. The distribution of strain above the canopy is complex and variable. Each minibasin that becomes obstructed modifies the local strain field, typically developing a zone of shortening immediately updip and an extensional breakaway zone immediately downdip of the obstructed minibasin. This finding is corroborated by observations from a physical sandbox model of minibasin obstruction. We also find in our natural example that minibasins can be obstructed to different degrees, ranging from severe (e.g., caught in a feeder) to mild (e.g., welded to a flat or gently dipping base-of-salt). By mapping both the presence of obstructed minibasins and the relative degree of minibasin obstruction, we provide an explanation for the origin of complex 3-D strain fields on a salt-detached slope and, potentially, a mechanism that explains differential downslope translation of minibasins. In minibasin-rich salt-detached slope settings, our results may aid: i) structural restorations and regional strain analyses; ii) prediction of subsalt relief in areas of poor seismic imaging; and iii) prediction of stress fields and borehole stability. Our example is detached on allochthonous salt and where the base-of-salt is rugose, with the findings applicable to other such systems worldwide (e.g., Gulf of Mexico; Scotian Margin, offshore eastern Canada). However, our findings are also applicable to systems where the salt is autochthonous but has significant local basal relief (e.g., Santos Basin, Brazil; Kwanza Basin, Angola).  相似文献   

Assessment of global wave models on regular and unstructured grids using the Unresolved Obstacles Source Term     

Mentaschi  Lorenzo  Vousdoukas  Michalis  Montblanc  Tomas Fernandez  Kakoulaki  Georgia  Voukouvalas  Evangelos  Besio  Giovanni  Salamon  Peter 《Ocean Dynamics》2020,70(11):1475-1483

Ocean Dynamics - The Unresolved Obstacles Source Term (UOST) is a general methodology for parameterizing the dissipative effects of subscale islands, cliffs, and other unresolved features in ocean...  相似文献   

Validating the KAGIS black‐box GIS‐based model in a Mediterranean karst aquifer: Case of study of Mela aquifer (SE Spain)          下载免费PDF全文

Javier Valdes‐Abellan  Concepción Pla  Miguel Fernandez‐Mejuto  José Miguel Andreu 《水文研究》2018,32(16):2584-2596

Karst Aquifer GIS‐based model (KAGIS model) is developed and applied to Mela aquifer, a small karst aquifer located in a Mediterranean region (SE Spain). This model considers different variables, such as precipitation, land use, surface slope and lithology, and their geographical heterogeneity to calculate both, the run‐off coefficients and the fraction of precipitation which contributes to fill the soil water reservoir existing above the aquifer. Evapotranspiration uptakes deplete water, exclusively, from this soil water reservoir and aquifer recharge occurs when water in the soil reservoir exceeds the soil field capacity. The proposed model also obtains variations of the effective porosity in a vertical profile, an intrinsic consequence of the karstification processes. A new proposal from the Nash–Sutcliffe efficiency index, adapted to arid environments, is presented and employed to evaluate the model's ability to predict the water table oscillations. The uncertainty in the model parameters is determined by the Generalized Likelihood Uncertainty Estimation method. Afterwards, when KAGIS is calibrated, wavelet analysis is applied to the resulting data in order to evaluate the variability in the aquifer behaviour. Wavelet analysis reveals that the rapid hydrogeological response, typical of a wide variety of karst systems, is the prevailing feature of Mela aquifer. This study proves that KAGIS is a useful tool to quantify recharge and discharge rates of karst aquifers and can be effectively applied to develop a proper management of water resources in Mediterranean areas.  相似文献