Evaluating infiltration losses in a Mediterranean wetland: Las Tablas de Daimiel National Park,Spain

Las Tablas de Daimiel National Park is a series of wetlands which naturally originated from groundwater discharges from the Mancha Occidental aquifer, Spain. Despite the relatively large size of this aquifer, 30 years of intensive groundwater pumping have significantly depleted the water table. As a result, wetlands only remain functional due to artificial inflows. Infiltration loss is therefore a key parameter to evaluate how much water is needed to maintain ecosystem functionality. Although yearly infiltration estimates existed prior to this work, these did not take into account key parameters such as the temporal evolution of the flooded area. This paper presents a more concrete estimate of the average infiltration losses. Infiltration is calculated as the closure term of daily water balances during a period of time where all other elements were known to an acceptable accuracy. A validation mechanism is provided to check the potential utility of the calculated infiltration in wetland management practices. Copyright © 2008 John Wiley & Sons, Ltd.     

The status of artisanal fishing in El Salvador

El Salvador is one of the most environmentally degraded nations in Latin America, but the declining fishing industry is under-studied compared with deforestation and landuse. This paper examines the reactions to fish stock decline of two generations of fishers in La Union, El Salvador on the Golfo de Fonseca, one of the most important fishing areas in Latin America, using face to face interviews and questionaires. Both older (>35 years) and younger (<36 years) fishers supplemented their income with trading, farming and loans from their relatives in the United States. All older fishers reported larger fish catches five and ten years previously than at present. Previously, fishers caught more fish, but significantly more younger fishers than older fishers reported their fathers caught more fish than they did, indicating an increasing gap in fish catches in recent decades. More younger fishers than older fishers had fathers or male kin who were also fishers, indicating young men were less likely to join fishing without a parent or kin already involved. Minorities of both older and younger fishers engaged in supplementary activities. Environmental degradation disuaded fishers from switching to farming or hunting. The findings are similar to findings elsewhere on the decline of fish resources and generational gaps in environmental knowledge, but differ in that some other studies report fewer opportunities for fishers to access alternative or complementary activities. These findings are relevant to Latin American studies, considering the great value of the Golfo de Fonseca to the livelihoods of Central America.     

Définition et datation de la Formation de Venaco (Corse) : dépôt d’origine gravitaire d’âge Priabonien

Priabonian age is highlighted for the first time in Corsica in the Venaco Formation using the presence of specific microfauna (in particular some representatives of Turborotalia cerroazulensis lineage). This silicoclastic formation is mainly represented by coarse facies. It is composed of three members from south to north and from oldest towards youngest: member of Uboli, Cardo and Orsu. The sedimentologic analysis reveals a gravity depositional environment, involving different type of currents. Sedimentologic and chronologic characteristics make the Venaco Formation and the Annot Formation (p.p.) equivalent. Dating the Venaco Fm. brings confirmation that the green schist metamorphism of the Variscan batholith and the related deformation are from the pre-Priabonian period.     

Formation and failure of volcanic debris dams in the Chakachatna River valley associated with eruptions of the Spurr volcanic complex, Alaska

The formation of lahars and a debris avalanche during Holocene eruptions of the Spurr volcanic complex in south-central Alaska have led to the development of volcanic debris dams in the Chakachatna River valley. Debris dams composed of lahar and debris-avalanche deposits formed at least five times in the last 8000–10,000 years and most recently during eruptions of Crater Peak vent in 1953 and 1992. Water impounded by a large debris avalanche of early Holocene (?) age may have destabilized an upstream glacier-dammed lake causing a catastrophic flood on the Chakachatna River. A large alluvial fan just downstream of the debris-avalanche deposit is strewn with boulders and blocks and is probably the deposit generated by this flood. Application of a physically based dam-break model yields estimates of peak discharge (Q_p) attained during failure of the debris-avalanche dam in the range 10⁴<Q_p<10⁶ m³ s⁻¹ for plausible breach erosion rates of 10–100 m h⁻¹. Smaller, short-lived, lahar dams that formed during historical eruptions in 1953, and 1992, impounded smaller lakes in the upper Chakachatna River valley and peak flows attained during failure of these volcanic debris dams were in the range 10³<Q_p<10⁴ m³ s⁻¹ for plausible breach erosion rates.Volcanic debris dams have formed at other volcanoes in the Cook Inlet region, Aleutian arc, and Wrangell Mountains but apparently did not fail rapidly or result in large or catastrophic outflows. Steep valley topography and frequent eruptions at volcanoes in this region make for significant hazards associated with the formation and failure of volcanic debris dams.     

Simultaneous Determination of Fluorine,Chlorine, Bromine and Iodine in Six Geochemical Reference Materials Using Pyrohydrolysis,Ion Chromatography and Inductively Coupled Plasma‐Mass Spectrometry

Concentrations of halogens (fluorine, chlorine, bromine and iodine) were determined in six geochemical reference materials (BHVO‐2, GS‐N, JG‐1, JR‐1, JB‐1b, JB‐2). Halogens were first extracted from powdered samples using a pyrohydrolysis technique, then hydrolysis solutions were analysed by ion chromatography for F and Cl and inductively coupled plasma‐mass spectrometry for Br and I. The detection limits in solutions were 100 μg l^?1 for both F and Cl and 10 ng l^?1 for Br and I. Considering the extraction procedure, performed on a maximum of 500 mg of sample and producing 100 ml of pyrohydrolysis solution, detection limits in rock samples were 20 mg kg^?1 for F and Cl and 2 μg kg^?1 for Br and I. The mean analytical errors on the studied composition ranges were estimated at 10 mg kg^?1 for F and Cl, 100 μg kg^?1 for Br and 25 μg kg^?1 for I. The concentration values, based on repeated (generally > 10) sample analysis, were in good agreement generally with published values and narrowed the mean dispersion around mean values. Large dispersions are discussed in terms of samples heterogeneity and contaminations during sample preparation. Basaltic RMs were found to be more suitable for studies of halogen compositions than differentiated rock material, especially granites – the powders of which were heterogeneous in halogens at the 500 mg level.     

An Optimised 1,10‐Phenanthroline Method for the Determination of Ferrous and Ferric Oxides in Silicate Rocks,Soils and Minerals

A precise, accurate and rapid method for the sequential determination of FeO and Fe₂O₃ in rocks, soils and some non‐refractory minerals by 1,10‐phenanthroline spectrophotometry is described. Fe(II) and Fe(III) were leached from the sample (?200 mesh) using a mixture of NH₄HF₂ and H₂SO₄ at 40–80 °C for 10 min on a hot plate. Both Fe(II) and Fe(III) could be conveniently estimated sequentially from the same reaction mixture at the μg g^?1 to percentage level. The method is better than the existing wet chemical methods, including the commonly used Pratt's titrimetric redox method, for Fe(II) and Fe(III) determinations in rock and soil samples in terms of precision, accuracy and rapidity. The throughput of the method was very high; at least forty to fifty samples could be estimated easily in a day. The results obtained compare favourably with those obtained by Pratt's method, as well as for certified/recommended values of a set of eleven certified reference materials having FeO and Fe₂O₃ contents in the range 0.21–14.63% and 0.58–8.48%, respectively. The optimised 1,10 phenanthroline method was found to be accurate to within 0.21% m/m FeO and 0.30% m/m Fe₂O₃ compared with the literature values of the certified reference materials studied.     

The Ordovician Sierras Pampeanas–Puna basin connection: Basement thinning and basin formation in the Proto-Andean back-arc

The Ordovician Sierras Pampeanas, located in a continental back-arc position at the Proto-Andean margin of southwest Gondwana, experienced substantial mantle heat transfer during the Ordovician Famatina orogeny, converting Neoproterozoic and Early Cambrian metasediments to migmatites and granites. The high-grade metamorphic basement underwent intense extensional shearing during the Early and Middle Ordovician. Contemporaneously, up to 7000 m marine sediments were deposited in extensional back-arc basins covering the pre-Ordovician basement. Extensional Ordovician tectonics were more effective in mid- and lower crustal migmatites than in higher levels of the crust. At a depth of about 13 km the separating boundary between low-strain solid upper and high-strain lower migmatitic crust evolved to an intra-crustal detachment. The detachment zone varies in thickness but does not exceed about 500 m. The formation of anatectic melt at the metamorphic peak, and the resulting drop in shear strength, initiated extensional tectonics which continued along localized ductile shear zones until the migmatitic crust cooled to amphibolite facies P–T conditions. P–T–d–t data in combination with field evidence suggest significant (ca. 52%) crustal thinning below the detachment corresponding to a thinning factor of 2.1. Ductile thinning of the upper crust is estimated to be less than that of the lower crust and might range between 25% and 44%, constituting total crustal thinning factors of 1.7–2.0. While the migmatites experienced retrograde decompression during the Ordovician, rocks along and above the detachment show isobaric cooling. This suggests that the magnitude of upper crustal extension controls the amount of space created for sediments deposited at the surface. Upper crustal extension and thinning is compensated by newly deposited sediments, maintaining constant pressure at detachment level. Thinning of the migmatitic lower crust is compensated by elevation of the crust–mantle boundary. The degree of mechanical coupling between migmatitic lower and solid upper crust across the detachment zone is the main factor controlling upper crustal extension, basin formation, and sediment thickness in the back-arc basin. The initiation of crustal extension in the back-arc, however, crucially depends on the presence of anatectic melt in the middle and lower crust. Consumption of melt and cooling of the lower crust correlate with decreasing deposition rates in the sedimentary basins and decreasing rates of crustal extension.     

Modeling long-period noise in kinematic GPS applications

We develop and test an algorithm for modeling and removing elevation error in kinematic GPS trajectories in the context of a kinematic GPS survey of the salar de Uyuni, Bolivia. Noise in the kinematic trajectory ranges over 15 cm and is highly autocorrelated, resulting in significant contamination of the topographic signal. We solve for a noise model using crossover differences at trajectory intersections as constraints in a least-squares inversion. Validation of the model using multiple realizations of synthetic/simulated noise shows an average decrease in root-mean-square-error (RMSE) by a factor of four. Applying the model to data from the salar de Uyuni survey, we find that crossover differences drop by a factor of eight (from an RMSE of 5.6 to 0.7 cm), and previously obscured topographic features are revealed in a plan view of the corrected trajectory. We believe that this algorithm can be successfully adapted to other survey methods that employ kinematic GPS for positioning.     

The topographic record of The Netherlands 1800–1992 for sale

Abstract

At the end of the eighteenth century, a large-scale map of the Austrian Netherlands and the Prince-Bishopric of Liège was manufactured, covering more or less the current territory of Belgium. The work for this Carte de Cabinet was carried out by artillerists under the guidance of count Joseph de Ferraris, who was commissioned for the task by the Habsburg government. At the time that the map was designed, no modern legend was included. This paper tries to fill that gap by presenting a legend that was constructed more systematically than any of its predecessors. It is based on the structure of the legend of the Topographic Map of Belgium and the CORINE land cover map, making it an easy-to-use tool for modern researchers. The problems encountered during the development of the legend are described, and the link between the Carte de Cabinet and eighteenth-century French cartography as well as with cartographic manuals is also discussed.     

Dynamics of volcanic eruptions: Understanding electric signatures for activity monitoring

Aside common methods as seismology, ground deformation, and geochemistry, electromagnetic and especially electric ones can efficiently be applied for imaging and monitoring active volcanoes and hydrothermal systems that most often control the initial eruptive phase. Surveys and mappings image ground fluids flow, faults systems, and structural interfaces with anomalies up to several hundred of mV. Reiteration of surveys highlights time and spatial evolution. Continuous networks must extend surveys when the activity becomes stronger. Resolution in the data can reach a few microvolts as compared to the tens of millivolts for surveys. Observations made on several volcanoes definitively show that electric signals, up to some tens of millivolts, may appear some hours to a few weeks before ground deformation and seismicity, and are related to some extent to the location of the future activity. These transient signals may have a relationship with those recorded aboard satellites. Both of them appear during the transition period between the “fatigue” and the “dynamical” stages, which announces accelerating and irreversible processes.