Structural and kinematic analysis of the Corredoiras detachment: evidence for early Variscan synconvergent extension in the Ordenes Complex, NW Spain

 An important detachment is described in the allochthonous Ordenes Complex, in the NW Iberian Massif, and its meaning is related to the kinematics of contemporaneous convergent structures. The Corredoiras Detachment (CD) separates a hangingwall unit, characterised by a medium-pressure metamorphic gradient, from a footwall high-pressure and high-temperature unit and an underlying ophiolitic unit. An associated ductile shear zone, nearly 2000 m thick, developed in the lower part of the hangingwall unit, where the Corredoiras Orthogneiss, a Lower Ordovician metagranite, was progressively transformed into augengneisses, mylonitic and ultramylonitic gneisses. The attitude of the stretching and mineral lineation in the mylonites varies due to late refolding at map scale, but the sense of movement can be estimated, being roughly top to the SE. According to crosscutting relationships, the CD developed subsequent to the thrusting of the high-pressure/high-temperature unit onto the ophiolitic unit, and prior to younger extensional detachments, upright folding and strike-slip tectonics. The geometric relationships of the CD with the previous structures in the footwall unit, the subtractive character of the metamorphic gap between its hangingwall and footwall, and the available isotopic data suggest that the CD is an early Variscan, ductile extensional detachment, the movement of which was roughly simultaneous with the onset of thrusting of the allochthonous complexes over their relative autochthon. Received: 17 November 1998 / Accepted: 4 April 1999     

经济型酒店空间扩张模式的国内外比较

中国的经济型连锁酒店经过连续几年的高速发展,正处在规模扩张的十字路口。本文对我国经济型连锁酒店空间扩张模式的现状进行分析,并通过对我国排名前几位的经济型连锁酒店与国内外同类型酒店的扩张模式进行理论和数据实证的比较分析,从而得出我国经济型连锁酒店空间扩张模式应选择的路径,以期为我国经济型连锁酒店的发展模式选择和健康运营提供有益的借鉴和探索。     

Recent trends of extreme precipitation indices in the Iberian Peninsula using observations and WRF model results

Spatial and temporal distributions of the trends of extreme precipitation indices were analysed between 1986 and 2005, over the Iberian Peninsula (IP). The knowledge of the patterns of extreme precipitation is important for impacts assessment, development of adaptation and mitigation strategies. As such, there is a growing need for a more detailed knowledge of precipitation climate change.This analysis was performed for Portuguese and Spanish observational datasets and results performed by the Weather Research and Forecast (WRF) model forced by the ERA-Interim reanalysis. Extreme precipitation indices recommended by the Expert Team for Climate Change Detection Monitoring and Indices were computed, by year and season. Then, annual and seasonal trends of the indices were estimated by Theil-Sen method and their significance was tested by the Mann-Kendal test. Additionally, a second simulation forced by the Max Planck Institute Earth System Model (MPI-ESM), was considered. This second modelling configuration was created in order to assess its performance when simulating extremes of precipitation.The annual trends estimated for the 1986–2005, from the observational datasets and from the ERA-driven simulation reveal: 1) negative statistically significant trends of the CWD index in the Galicia and in the centre of the IP; 2) positive statistically significant trends of the CDD index over the south of the IP and negative statistically significant trends in Galicia, north and centre of Portugal; 3) positive statistically significant trends of the R75p index in some regions of the north of the IP; 4) positive statistically significant trends in the R95pTOT index in the Central Mountains Chain, Leon Mountains and in the north of Portugal.Seasonally, negative statistically significant trends of the CWD index were found in Galicia, in winter and in the south of the IP, in summer. Positive statistically significant trends of the CWD index were identified in the Leon Mountains, in spring, and in Galicia, in autumn. For the CDD index, negative statistically significant trends were seen in Valencia, in the spring, and, in Galicia and Portugal (north and centre), in summer. Positive statistically significant trends of the CDD index were found: in the east of the IP, in the winter; in the Cantabrian Mountain, in the spring; and, in the south of the IP, in summer. Regarding to the R75p index, negative statistically significant trends were found in Galicia, in winter and positive statistically significant trends in the north of Portugal, in spring and in the Central Mountains Chain and north of Portugal, in autumn. For the R95pTOT index, negative statistically significant trends were found over the Sierra Cuenca and Sierra Cazorla, in winter and positive statistically significant trends were found over the Sierra Cebollera, in winter and in Castile-la Mancha region, in spring.The results of the annual and seasonal trends of the extreme precipitation indices performed for observational datasets and the simulation forced by ERA-Interim, are similar. The results obtained for the simulation forced by MPI-ESM are not satisfactory, and can be a source of criticism for the use of simulation forced by MPI-ESM in this type of climate change studies. Even for the relatively short period used, the WRF model, when properly forced is a useful tool due to the similar results of Portuguese and Spanish observational datasets and the simulation forced by ERA-Interim.     

The hydrological significance of mountains: a regional case study,the Ebro River basin,northeast Iberian Peninsula

Abstract

This study evaluated the hydrological significance of mountain regions, comparing them with the lowlands of the Ebro River basin (northeast Iberian Peninsula). It was based on records obtained from measuring stations. An altitude of 1000 m above mean sea level was adopted as the criterion for distinguishing between lowland and mountain areas. We analysed 12 sub-basins whose rivers flow directly into the River Ebro, and which covered 66% of the total surface area, 91% of the mountain area and accounted for 77% of total annual runoff. For the River Ebro basin, we found that the mean precipitation depth, the runoff volume per unit of surface area, and the runoff coefficient were all greater in the mountains than in the adjacent lowlands, with respective differences of 70%, 180% and 60%. These results and the particular fragility of the Mediterranean mountain ecosystems confirm the mountain regions of the Ebro basin as strategic zones for hydrological and territorial planning.

Citation López, R. & Justribó, C. (2010) The hydrological significance of mountains: a regional case study, the Ebro River basin, northeast Iberian Peninsula. Hydrol. Sci. J. 55(2), 223–233.     

Hydrochemical characterization of an acid mine drainage-affected reservoir: the Sancho Reservoir,Huelva, southwest Spain

Abstract

The objectives of this study were to discover the relationship between variables in a water reservoir and the hydrochemical variations related to acid mine drainage (AMD), and to describe the horizontal stratification related to vertical salinity and variations in metals present in the region. The information obtained may be used for establishing risk evaluation criteria and to design future remediation strategies, which could be useful for new dams. The hydrochemical characterization was based on a sampling campaign performed in October 2011. A total of 28 samples, at 1-m-deep intervals, were obtained. The hydrogeochemical study of the polluted reservoir shows that the dilution effect is not sufficient to neutralize AMD contributions from mining activity. Sampling carried out from the surface water to the deepest points reveals stratification of the reservoir that allows it to be included in the group of monomictic and holomitic lakes.

Editor D. Koutsoyiannis; Associate editor M.D. Fidelibus     

PEDOGENESIS IN LATE PREHISTORIC INDIAN MOUNDS,UPPER MISSISSIPPI VALLEY

Inceptisols are developed on silt loam, loam, and sandy loam Indian mounds at the Keller Mound Group and Bluff Top Mound in northeastern Iowa. The mounds date to the Allamakee Phase of the Late Woodland Period (ca. 1650–1250 B.P.) and are built with fill obtained from the A, E, and upper B horizons of pre-existing soils (Alfisols). Differences in the morphologic and chemical characteristics of soils on different mounds are attributed to textural differences of the mounds' fill. Coarse-textured mound fill is pedogenically altered at a faster rate than fine-textured fill, but total carbon percentage of the A horizon attains a steady state faster in fine-textured mound fill. Total phosphorus content is used to determine from which horizons of pre-existing soils the specific layers of mound fill originated. Rates and pathways of pedogenesis in mound fill may not provide good analogues for the early stages of soil development in materials that have not undergone previous weathering and subsequent modification by humans. Nevertheless, mound soils are useful benchmarks for some pedologic studies since they provide time lines for evaluating minimum rates for development of argillic and albic horizons, as well as attainment of the Alfisol order.     

Metal binding by humic acids in recent sediments from the SW Iberian coastal area

The concentrations of Cu, Zn, Cr, Ni, Pb, As, Mn and Co were determined by Inductively Coupled Plasma–Mass Spectrometry both in recent sediments from different locations of the Huelva littoral (SW Iberian Peninsula) and in their humic acid (HA) fractions in order to evaluate distribution and binding capacity of those trace elements to HAs. In addition, elemental composition (C, N, S) and δ¹³C values were determined to appraise the sources of organic matter in the area. This study involved the comparison of selected samples taken from different environments including the estuary of the Guadiana River, the main fluvial system of the region, the Tinto and Odiel estuary system and the proximal shelf. Significant positive correlations were found among Cu, Zn, As and Pb in bulk sediments, suggesting a common origin of all of those elements: the mining activities and pyrite deposits located hinterland. On the other hand, results for Cr, Co and Ni pointed to the basic rocks from the low basin of the Guadiana River as their main source. Elemental (C, N) and isotopic (δ¹³C) composition of sediments indicated a significant contribution of autochthonous plankton in coastal shelf sediments, whereas estuarine and riverine sediments showed a major contribution of terrestrial biomass. Geochemical values for their corresponding HAs suggested a greater terrestrial contribution in the sedimentary OM of the coastal shelf sediments than in bulk sediments, which evidenced the influence of coastal currents and sediment fluxes. Humic acids sequester considerable amounts of Cu and Zn contributing to reduce the bioavailability of these contaminants.     

Clay mineralogy as a tool for integrated sequence stratigraphic and palaeogeographic reconstructions: Late Oligocene–Early Aquitanian western internal South Iberian Margin,Spain

The different hydrodynamic behaviour of detrital clay minerals in the marine depositional environment allows assessment of relative sea‐level variations in the sedimentary record. Comparison of smectite and kaolinite:illite (S+K:I) changes with the global sea‐level curves and with the third‐order cycles of the eustatic curve for European basins allows assessment of the influence of global eustasy and local tectonics on sequence stratigraphy. In the South Iberian Margin, sedimentation took place both on open‐marine platforms and in deeper water areas. On this margin during the Late Oligocene to Early Aquitanian, the variations in sedimentation were caused not only by global eustasy but also by compressive tectonics. Correlations were made between the S+K:I cycles and the third‐order cycles for European basins, enabling the definition of four third‐order sedimentary sequences (here called C1, C2, C3, and A1) and two lower‐order sequences within C3 and A1 (here called C3a, C3b, A1a, and A1b) related to tectonic movements. High S+K:I values were observed during episodes of maximum flooding in each sequence and lower‐order sequence and in each succession, enabling changes in palaeocoastal morphology to be considered. Copyright © 2012 John Wiley & Sons, Ltd.     

Interplay of orbital forcing and tectonic pulses in the Cambrian Iberian platform, NE Spain

The stratigraphy of carbonate/shale couplets, cycles and cycle-stacking patterns in a Cambrian shallow water platform (Iberian Chains, NE Spain) are related to sea-level changes driven by orbital forcing and by tectonic pulses. The interplay of both effects can be discriminated in the Iberian fault-controlled platform, in which the tectonic activity can be analysed by accurate and detailed biostratigraphic correlations based on trilobite zonation. The stratigraphic hierarchy of rhythmically interbedded limestones and shales, in two coeval but structurally separated geodynamic settings, yields cycle ratios of 1.44 :1. This ratio is supported by time thickness and spectral analysis, which is based on a graphic method of analysis: the Map of Grey Lines. The cycle ratio seems to be evidence for orbital forcing by obliquity and precession cycles predicted for early Paleozoic time. Carbonate/shale couplets, the smallest rhythmic units recognisable in the field, represent short-term, periodic fluctuations in supply of terrigenous sediments and carbonate productivity of uncertain origin, which could be associated with one of several harmonics of the former orbital cycles. The pulsating tectonic activity was approximated by using a quantitative analysis of tectonically induced subsidence (Shaw method). Recurrence frequencies of tectonic pulses were estimated and dated by biostratigraphy. As a result, tectonic disturbances in the Cambrian Iberian platform show an episodic periodicity comparable to that of orbital eccentricity cycles, which could mask their recognition. Received: 15 November 1999 / Accepted: 9 February 2000