Long-term hydrological changes in northern Iberia (4.9–0.9 ky BP) from speleothem Mg/Ca ratios and cave monitoring (Ojo Guareña Karst Complex,Spain)     

J. A. Cruz  M. J. Turrero  J. O. Cáceres  A. Marín-Roldán  A. I. Ortega  A. Garralón  L. Sánchez  P. Gómez  M. B. Muñoz-García  R. L. Edwards  J. Martín-Chivelet 《Environmental Earth Sciences》2015,74(12):7741-7753

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Fluids during diagenesis and sulfate vein formation in sediments at Gale crater,Mars          下载免费PDF全文

S. P. Schwenzer  J. C. Bridges  R. C. Wiens  P. G. Conrad  S. P. Kelley  R. Leveille  N. Mangold  J. Martín‐Torres  A. McAdam  H. Newsom  M. P. Zorzano  W. Rapin  J. Spray  A. H. Treiman  F. Westall  A. G. Fairén  P.‐Y. Meslin 《Meteoritics & planetary science》2016,51(11):2175-2202

We model the fluids involved in the alteration processes recorded in the Sheepbed Member mudstones of Yellowknife Bay (YKB), Gale crater, Mars, as revealed by the Mars Science Laboratory Curiosity rover investigations. We compare the Gale crater waters with fluids modeled for shergottites, nakhlites, and the ancient meteorite ALH 84001, as well as rocks analyzed by the Mars Exploration rovers, and with terrestrial ground and surface waters. The aqueous solution present during sediment alteration associated with phyllosilicate formation at Gale was high in Na, K, and Si; had low Mg, Fe, and Al concentrations—relative to terrestrial groundwaters such as the Deccan Traps and other modeled Mars fluids; and had near neutral to alkaline pH. Ca and S species were present in the 10^?3 to 10^?2 concentration range. A fluid local to Gale crater strata produced the alteration products observed by Curiosity and subsequent evaporation of this groundwater‐type fluid formed impure sulfate‐ and silica‐rich deposits—veins or horizons. In a second, separate stage of alteration, partial dissolution of this sulfate‐rich layer in Yellowknife Bay, or beyond, led to the pure sulfate veins observed in YKB. This scenario is analogous to similar processes identified at a terrestrial site in Triassic sediments with gypsum veins of the Mercia Mudstone Group in Watchet Bay, UK.  相似文献   

A textural classification of argillaceous rocks and their durability     

Jordi Corominas  Joan Martínez-Bofill  Albert Soler 《Landslides》2015,12(4):669-687

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Groundwater modelling with limited data sets: the Chari–Logone area (Lake Chad Basin,Chad)          下载免费PDF全文

L. Candela  F. J. Elorza  K. Tamoh  J. Jiménez‐Martínez  A. Aureli 《水文研究》2014,28(11):3714-3727

One of the most important issues for water resource management is developing strategies for groundwater modelling that are adaptable to data scarcity. These strategies are particularly important in arid and semi‐arid areas where access to data is poor and data collection is difficult, such as the Lake Chad Basin in Africa. In the present study, we establish a numerical groundwater flow model and evaluate the effects of dry and wet periods on groundwater recharge in the Chari–Logone area (96 000 km²) of the Lake Chad Basin. Boundary conditions, flow direction, sources, and sinks for the Chari–Logone local model were obtained by revising and remodelling the Lake Chad Basin regional hydrogeological model (508 400 km²) developed by the BRGM (Bureau de Recherches Géologiques et Minières) in the 1990s. The simulated aquifer water level showed good agreement with observed levels. Aquifer recharge is primarily determined by river–aquifer interactions and mostly occurs in the southern section of the study area. In wet years, groundwater recharge also occurs in the N'Djamena area. The approach we adopted provided relevant results and was useful as an initial step in more detailed modelling of the area. It also proved to be a useful method for groundwater modelling in large semi‐arid and arid regions where available data are scarce. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Deep electrical resistivity structure of the northern Gibraltar Arc (western Mediterranean): evidence of lithospheric slab break‐off     

Oriol Rosell  Anna Martí  Àlex Marcuello  Juanjo Ledo  Pilar Queralt  Eduard Roca  Joan Campanyà 《地学学报》2011,23(3):179-186

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A new species of Cloudina from the terminal Ediacaran of Spain     

I. Cortijo  M. Martí Mus  S. Jensen  T. Palacios 《Precambrian Research》2010,176(1-4):1-10

The terminal Ediacaran genus Cloudina includes some of the earliest biomineralized fossils. It consists of a tube formed by stacked funnel-shaped elements, and is usually interpreted as the external skeleton of an early metazoan. Although a number of species have been described within this genus, their distinctiveness remains unclear and they may all belong to the type species, Cloudina hartmannae Germs, 1972. Here we describe the new species Cloudina carinata, from central Spain. C. carinata n. sp. has a distinct morphology characterized by external longitudinal crests, which confer on the tube an irregular polygonal cross-section. The funnels have a thickened apertural rim and a basal, slightly constricted circular opening. Successive funnels appear less deeply imbricated than in previously described material of Cloudina. The evidence of tube disarticulation in the material studied, particularly the abundance of loose funnels, indicates that funnels were secreted as independent elements, not fused to the previous ones. However, they could become fused during the life of the organism through the precipitation of inorganic cements between their walls. Several specimens of C. carinata n. sp. show evidence of asexual reproduction.  相似文献   

A conceptual framework for the integral management of marine protected areas     

Celia Ojeda-Martínez  Francisca Giménez Casalduero  Just T. Bayle-Sempere  Carmen Barbera Cebrián  Carlos Valle  Jose Luis Sanchez-Lizaso  Aitor Forcada  Pablo Sanchez-Jerez  Pablo Martín-Sosa  Jesús M. Falcón  Fuensanta Salas  Mariagrazia Graziano  Renato Chemello  Ben Stobart  Pedro Cartagena  Angel Pérez-Ruzafa  Fréderic Vandeperre  Elisabeth Rochel  Serge Planes  Alberto Brito 《Ocean & Coastal Management》2009,52(2):89-101

A general conceptual framework for the management of marine protected areas (MPAs) was developed. The driver-pressure-state-impacts-response (DPSIR) framework was used to determine the elements affecting MPAs. The developed evaluation framework helped to select an appropriate suite of indicators to support an ecosystem approach, an assessment of the MPAs functioning and policy decisions. Gaps derived from the management and policy responses in the MPAs were also outlined. It was concluded that the DPSIR framework can help to simplify the complexity of MPA management. This document is a tool for policy makers, scientists and general public on the relevance of indicators to monitor changes and MPAs management.  相似文献   

Structural style of the Malargüe fold-and-thrust belt at the Diamante River area (34°30′–34°50′S) and its linkage with the Cordillera Frontal,Andes of central Argentina     

Martín M. Turienzo 《Journal of South American Earth Sciences》2010,29(3):537-556

The Malargüe fold-and-thrust belt is a thick-skinned belt developed in Miocene-Pliocene times during the Andean orogeny, which together with the Cordillera Frontal constitutes the Andes of central Argentina in the Diamante River area. Detailed field mapping and construction of three regional balanced cross-sections, supported by seismic and well information, constrains the structural style of this Andean region as two basement uplifts in the western and eastern sectors surrounding a central region of thin-skinned deformation. In the west, large basement wedges related to thrust faults developed during Andean compression propagated along favourable horizons (commonly gypsum) into the sedimentary cover. These wedges transferred shortening to the cover rocks producing the thin-skinned structures. There is therefore a close spatial and temporal relationship between basement and cover deformation. In the thin-skinned region, the abundance of shales and salt horizons in the west facilitated the formation of fault-related folds while the more competent units in the east were deformed into duplex and imbricated thrusts. The basement uplift in the eastern sector represents the southern end of the Cordillera Frontal, where the Carrizalito fault placed pre-Jurassic rocks over tertiary synorogenic sediments in the northern area while in the southern region it remained as a blind thrust. A common feature is the development of backthrust systems related to the major east-vergent basement structures. The backthrusts therefore serve to locate basement uplifts where outcrops are absent. Three-dimensional integration of the cross-sections and a structural map at the top of the pre-Jurassic basement show that although the main structures change considerably along strike, the total shortening of each section shows little variation.  相似文献   

Late Mesozoic and Cenozoic palaeomagnetism of Australia–II. Implications for geomagnetism and true polar wander     

Mart Idnurm 《Geophysical Journal International》1985,83(2):419-433

Summary. New palaeomagnetic results from Australia indicate that throughout the Cenozoic era the continent lay further south than suggested by hot-spot data. Moreover, while hot spots give a uniform rate of drift during most of the Cenozoic, the drift rate obtained from apparent polar wander varies considerably.
The discrepancies between the palaeomagnetic and hot-spot results are analysed by comparing the Australian data with those of Europe and the central Pacific. The analysis suggests that the discrepancies are due to: (1) departures of the Earth's magnetic field from the geocentric axial dipole model, and (2), either true polar wander or a non-axial inclined dipole component. It is found that since the mid-Tertiary the dominant non-dipole component has been a quadrupole, and that during this period both the quadrupolar field and the true polar displacement/non-axial dipole component decreased progressively. During the Quaternary, and also at the earliest Tertiary, the non-dipole components appear to have been moderate or small.
The comparison of data sets demonstrates that considerable errors may be incurred when Cenozoic, and presumably earlier, poles from one geographic region are used to derive those of another, widely separated, region. The results also imply that absolute plate velocities estimated from palaeomagnetic data can contain substantial errors, and that hot-spot data may need significant adjustments for true polar wander to yield correct palaeolatitudes.
Finally, the new early Tertiary pole for Australia is used in conjunction with updated early Tertiary poles from other lithospheric plates to reapply the McKenzie test for true polar wander. The results indicate a small true polar displacement since the beginning of the Tertiary. The amount and direction of the displacement, however, differ from those generally obtained from hot-spot data.  相似文献   

A quantitative comparison of vector magnetic field measurement and analysis techniques   总被引：1，自引：0，他引：1  

B. W. Lites  V. Martínez Pillet  A. Skumanich 《Solar physics》1994,155(1):1-27

We make a quantitative comparison between spectral vs filter measurement and analysis techniques for extraction of solar vector magnetic fields from polarimetric data using as a basis the accurately calibrated, high angular resolution Stokes profile data from the Advanced Stokes Polarimeter. It is shown that filter-based measurements deliver qualitative images of the field alignment for sunspots that are visually similar to images derived from the more detailed analysis of the Stokes profiles. However, quantitative comparison with least-squares fits to the full Stokes profiles show that both the strength of the field predicted by the filter-based analysis and its orientation contain substantial errors. These errors are largest for plage regions outside of sunspots, where the field strengths are inferred to be only a fraction of their true values, and errors in the orientation of 40–50° are common. Within sunspots, errors of 20° are commonplace. The greatest source of these errors is the inability of the filter-based measurements to account for the small fill fraction of magnetic fields or, equivalently, scattered light in the instrument, which reduce the degree of polarization. The uncertainties of the full profile fitting methods are also discussed, along with the errors introduced by coarser wavelength sampling of the observed Stokes profiles. The least-squares fitting procedure operates best when the profiles are sampled at least as frequently as one Doppler width of the line.On leave from the Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献