Lateral variations in tectonic style across cross-strike discontinuities: an example from the Central Apennines belt (Italy)     

Sara Satolli  Paolo Pace  Mauro Gabriele Viandante  Fernando Calamita 《International Journal of Earth Sciences》2014,103(8):2301-2313

In foreland thrust belts, abrupt lateral changes in tectonic style, structural–stratigraphic features, and topography usually occur across cross-strike faults. The Central Apennines of Italy offer an exceptional scenario of lateral variations in tectonic setting. Here, the Sangro Volturno oblique thrust ramp (SVOTR) represents the outer thrust front of the Pliocene–Quaternary foreland thrust system, confining southward the axial culmination of the orogen that occurs in the Central Apennines. We present an interpretation of the Pliocene–Quaternary evolution of this cross-strike fault through an integrated dataset including structural-geological mapping and subsurface onshore seismic reflection profiles. The interpretation of the structural framework is augmented by the analysis of low-temperature thermochronometers from 32 new sites extending across the subsurface transverse structure. As evidenced by seismic line interpretation, the localization and development of the SVOTR have been influenced by inherited extensional faults within a positive inversion tectonics context. The regional distribution of the maximum paleotemperature values across the SVOTR constrains the original extent of the allochthonous thrust sheet over all its hanging-wall and footwall blocks. The Pliocene–Quaternary thrusting and inversion of SVOTR caused the strong hanging-wall uplift, which brought to the complete erosion of the allochthonous units and the exhumation of the Adria units. The integrated analysis of low-temperature thermochronometers and structural evidence as applied in the study case can define the role of major cross-strike discontinuities in foreland thrust belts, by constraining and verifying their tectonics inversion significance and the amount of related exhumation.  相似文献   

Zinc and sulfur isotope variation in sphalerite from carbonate-hosted zinc deposits,Cantabria, Spain   总被引：2，自引：0，他引：2  

Jan Pašava  Fernando Tornos  Vladislav Chrastný 《Mineralium Deposita》2014,49(7):797-807

We studied zinc and sulfur isotopes and the chemical composition of sphalerite samples from Picos de Europa (Aliva mine) and sphalerite and hydrozincite samples from La Florida mine, two carbonate-hosted Mississippi Valley-type (MVT) deposits located in northern Spain; despite being close, they are hosted in carbonatic rocks of different ages, Lower Carboniferous and Lower Cretaceous, respectively. The two generations of sphalerite at Picos de Europa show different δ⁶⁶Zn values (stage 1 sphalerite +0.24 per mil and stage 2 sphalerite from ?0.75 to +0.08 per mil). Both generations also differ in the sulfur isotope composition (stage 1 has δ³⁴S?=?+6.6 and stage 2 has δ³⁴S?=??0.9 to +2.9 per mil) and the chemical composition (stage 1 sphalerite, compared to stage 2 sphalerite, is significantly enriched in Pb, As, Mn, Sb, slightly enriched in Ag, Ni, and Cu and depleted in Co, Ga, Tl, Te, Ge, and Sn). We suggest that Zn isotope fractionation was controlled predominantly by pH and T changes. High Zn isotope values reflect rapid precipitation of sphalerite from higher-temperature acidic fluids that carried Zn mostly as chloride species after interaction with carbonate rocks while lower Zn isotope values most likely resulted from a longer precipitation process from fluid at higher pH and decreasing T that carried dominantly Zn sulfide species. At La Florida, sphalerite samples show light ⁶⁶Zn-depleted signatures with δ⁶⁶Zn values from ?0.80 to ?0.01 per mil (mostly between ?0.80 and ?0.24 per mil) and δ³⁴S values from +10.7 to +15.7 per mil without any relationship between the δ⁶⁶Zn and δ³⁴S values. Here, the variation in Zn isotope values is interpreted as related to mixing of fluids from two reservoirs. The Zn was carried by a single deep-seated and higher T (~250–320 °C) fluid, and precipitation took place after mixing with a connate S-rich fluid in a system with mH₂S?>?mZn²⁺ as a result of change in pH, T, and Zn predominant species. The light δ⁶⁶Zn accompanied by heavy δ³⁴S values resulted from fractionation of Zn aqueous sulfides at near-neutral pH and decreasing T. Hydrozincite samples show much heavier δ⁶⁶Zn values (+0.21 to +0.33 per mil), consistent with fractionation during supergene processes.  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   

Adaptive capacity in Tanzanian Maasailand: Changing strategies to cope with drought in fragmented landscapes     

Mara J. Goldman  Fernando Riosmena 《Global Environmental Change》2013,23(3):588-597

This study examines the ways in which the adaptive capacity of households to climatic events varies within communities and is mediated by institutional and landscape changes. We present qualitative and quantitative data from two Maasai communities differentially exposed to the devastating drought of 2009 in Northern Tanzania. We show how rangeland fragmentation combined with the decoupling of institutions and landscapes are affecting pastoralists’ ability to cope with drought. Our data highlight that mobility remains a key coping mechanism for pastoralists to avoid cattle loss during a drought. However, mobility is now happening in new ways that require not only large amounts of money but new forms of knowledge and connections outside of customary reciprocity networks. Those least affected by the drought, in terms of cattle lost, were those with large herds who were able to sell some of their cattle and to pay for private access to pastures outside of Maasai areas. Drawing on an entitlements framework, we argue that the new coping mechanisms are not available to all, could be making some households more vulnerable to climate change, and reduce the adaptive capacity of the overall system as reciprocity networks and customary institutions are weakened. As such, we posit that adaptive capacity to climate change is uneven within and across communities, is scale-dependent, and is intimately tied to institutional and landscape changes.  相似文献   

Putative Meteoritic Craters in Río Cuarto (Central Argentina) Interpreted as Eolian Structures     

Cione  Alberto L.  Tonni  Eduardo P.  San Cristóbal  Jorge  Hernández  Pedro J.  Benítez  Adrián  Bordignon  Fernando  Perí  Jorge A. 《Earth, Moon, and Planets》2002,91(1):9-24

Ten oblong aligned depressions in the Río Cuarto area (provincia de Córdoba, Argentina) were supposed to be the result of very-low-angle Holocene meteoroid impacts. However, we consider that authors that studied the structures did not demonstrated their extraterrestrial origin. We suggest that an eolian origin for the structures of Río Cuarto is more likely. Actually, these landforms integrate large systems of similar deflation/accumulation geoforms aligned according to predominant winds during different periods.  相似文献   

Using time‐domain reflectometry to characterize shallow solute transport in an oak woodland hillslope in northern California,USA     

Chris G. Campbell  Masoud Ghodrati  Fernando Garrido 《水文研究》2002,16(15):2921-2940

The natural heterogeneity of water and solute movement in hillslope soils makes it difficult to accurately characterize the transport of surface‐applied pollutants without first gathering spatially distributed hydrological data. This study examined the application of time‐domain reflectometry (TDR) to measure solute transport in hillslopes. Three different plot designs were used to examine the transport of a conservative tracer in the first 50 cm of a moderately sloping soil. In the first plot, which was designed to examine spatial variability in vertical transport in a 1·2 m² plot, a single probe per meter was found to adequately characterize vertical solute travel times. In addition, a dye and excavation study in this plot revealed lateral preferential flow in small macropores and a transport pattern where solute is focused vertically into preferential flow pathways. The bypass flow delivers solute deeper in the soil, where lateral flow occurs. The second plot, designed to capture both vertical and lateral flow, provided additional evidence confirming the flow patterns identified in the excavation of the first plot. The third plot was designed to examine lateral flow and once again preferential flow of the tracer was observed. In one instance rapid solute transport in this plot was estimated to occur in as little as 3% of the available pore space. Finally, it was demonstrated that the soil anisotropy, although partially responsible for lateral subsurface transport, may also homogenize the transport response across the hillslope by decreasing vertical solute spreading. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

The effect of human use of sandy beaches on developmental stability of Talitrus saltator (Montagu, 1808) (Crustacea, Amphipoda). A study on fluctuating asymmetry     

Sandra Barca-Bravo  María J. Servia  Fernando Cobo  & Marcos A. Gonzalez 《Marine Ecology》2008,29(S1):91-98

In recent years, there has been an increasing intensity of human use of coastal areas in Galicia (NW Spain). Actually, there is great concern about rapid and unplanned urban and industrial development on certain locations, as this can generate adverse impacts on those areas. In this study, we selected three sandy beaches along the Galician coast (Chanteiro, Insuela and Valieros) facing different levels of anthropic pressure, and we analysed Talitrus saltator individuals with the aim of elucidating whether anthropogenic pressures on beaches such as tourism or pollution have an influence on the incidence of morphological developmental alterations in sandhoppers in the field. Specifically, levels of fluctuating asymmetry were selected as indicators of environmental stress. Results of two sampling dates (May and September) show that individuals collected at the most touristy and polluted beach were those showing the highest asymmetry values, although results were only statistically significant for samples collected during spring. Results are in accordance with the hypothesis that beach management and pollution reduce symmetry in sandhoppers living in altered beaches.  相似文献   

Modeling spatial landslide susceptibility in volcanic terrains through continuous neighborhood spatial analysis and multiple logistic regression in La Ciénega watershed,Nevado de Toluca,Mexico     

Castro-Miguel  Rutilio  Legorreta-Paulín  Gabriel  Bonifaz-Alfonzo  Roberto  Aceves-Quesada  José Fernando  Castillo-Santiago  Miguel Ángel 《Natural Hazards》2022,113(1):767-788

Natural Hazards - Little study has been done on the effect of the pixel neighborhood information when modeling landslide susceptibility using multiple logistic regression (MLR). The present...  相似文献   

Erratum to: Carl Christian Tscherning: a scientific adventure in Geodesy     

Fernando Sansò  Michael G. Sideris 《Journal of Geodesy》2015,89(8):837-837

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Volcanism–sedimentation interaction in the Campo de Calatrava Volcanic Field (Spain): a magnetostratigraphic and geochronological study     

Antonio Herrero-Hernández  Francisco Javier López-Moro  José Luis Gallardo-Millán  Ángel Martín-Serrano  Fernando Gómez-Fernández 《International Journal of Earth Sciences》2015,104(1):103-122

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