Facies analyses and volcanic setting of the giant Neves Corvo massive sulfide deposit,Iberian Pyrite Belt,Portugal

In the Iberian Pyrite Belt, volcanic rocks are relatively scarce, accounting for approximately only 25% of the geologic record, with the remaining 75% consisting of sedimentary units. This association is very clear in the host succession to the Neves Corvo massive sulfide deposit in Portugal. The Neves Corvo host succession comprises the products of explosive and effusive rhyolitic eruptions intercalated with mudstone that records a submarine below-wave-base environment and provides precise biostratigraphic age constraints. The first and second volcanic events involved eruptions at local intrabasinal vents. The first event generated thick beds of fiamme breccia that are late Famennian in age. The fiamme were originally pumice clasts produced by explosive eruptions and were subsequently compacted. The second event was the late Strunian (latest Famennian) effusion of rhyolitic lava that was pervasively quench-fragmented. The third and final event is younger than the massive sulfide deposits poorly represented in the mine area and minor compared with the two other events. The integration of biostratigraphic data with the volcanic facies architecture indicates that the Neves Corvo ore deposits are similar in age to the late Strunian rhyolitic lava. Although regionally the Iberian Pyrite Belt is essentially a sedimentary succession, ore formation at Neves Corvo can be closely linked to discrete volcanic events that produced a relatively narrow range of volcanic facies.     

Water Balance and Evapotranspiration Monitoring in Geotechnical and Geoenvironmental Engineering

Among the various components of the water balance, measurement of evapotranspiration has probably been the most difficult component to quantify and measure experimentally. Some attempts for direct measurement of evapotranspiration have included the use of weighing lysimeters. However, quantification of evapotranspiration has been typically conducted using energy balance approaches or indirect water balance methods that rely on quantification of other water balance components. This paper initially presents the fundamental aspects of evapotranspiration as well as of its evaporation and transpiration components. Typical methods used for prediction of evapotranspiration based on meteorological information are also discussed. The current trend of using evapotranspirative cover systems for closure of waste containment facilities located in arid climates has brought renewed needs for quantification of evapotranspiration. Finally, case histories where direct or indirect measurements of evapotranspiration have been conducted are described and analyzed.     

Using Crater Lake chemistry to predict volcanic activity at Poás Volcano,Costa Rica

Monitoring of crater lake chemistry during the recent decline and disappearance of the crater lake of Poás Volcano revealed that large variations in SO₄/Cl, F/Cl, and Mg/Cl ratios were caused by the enhanced release of HCl vapor from the lake surface due to increasing lake temperature and solution acidity. Variation in the concentration of polythionic acids (H₂S_xO₆, x=4–6) was the most reliable predictor of renewed phreatic eruptive activity at the volcano, exhibiting sharp decreases three months prior to the initiation of phreatic eruptions in June 1987. Polythionic acids may offer a direct indicator of changing subsurface magmatic activity whereas chloride-based element ratios may be influenced by surface volatilization of HCl and subsequent recycling of acidic fluids in crater lake volcanoes.     

The structure and function of dry weather mangroves on the Pacific Coast of Central America,with emphasis onAvicennia bicolor forests

Mangrove forests along the Pacific Coast of Central America cover around 4,000 km². Most of this coast is occupied with tropical dry forest mangroves where basal areas range between 6 and 20 m² ha^?1 and canopy heights rarely exceed 20 m. Rainfall and runoff alter structure and floristic composition from site to site. Reproductive phenology and mortality appear to be related to soil water availability.Avicennia bicolor forests reach a density of 4,350 plants that are taller than 0.50 m ha^?1, with 769 trees above 5 cm diameter at breast height A total basal area of 41 m² ha^?1 together with a canopy height of about 23 m place these forests among the most developed in the western hemisphere. Growth rate (0.38 m² ha^?1 yr^?1) is surprisingly high for mangrove forests under a seasonal dry climate.     

Coral Cover Change Associated to El Niño, Eastern Pacific, Costa Rica, 1992–2001

Abstract. Changes in live and dead coral cover were documented at three localities off the Costa Rican central Pacific coast first in 1992 during the aftermath of the 1991–1992 El Niño; again in the period between 1994 and 1995, and last in January 2001. Recovery of coral communities after the 1991–1992 El Niño was expressed by a significant increase (～40 %) in 1994 of live coral cover at one locality (Manuel Antonio). A subsequent decrease (～50 %) in response to the very strong 1997–1998 episode was recorded at Manuel Antonio and Ballena, mainly due to partial tissue mortality of branching (Pocillopora spp.) and massive (Porites lobata) corals. Mortality of entire colonies associated to that event was scarce and confined to branching and nodular (Psammocora stellata) corals. This species was not found at one locality (Cambutal) in the 2001 survey and it is presumed locally extinct. The recovery of this coral and others will depend on recruits from surviving colonies in deeper waters and other coral communities in the vicinity. Within sites at a given locality, contrasting results in live coral cover variability were found. This is partially due to distinct coral assemblages, coral growth, physical exposure to tidal regime, and, related to the latter, variable duration and intensity of the warming event. In general, predominant meteorological conditions at the studied area are conducive to solar radiation (UV) stress during El Niño years and are related to changes in the atmosphere‐ocean interactions in response to the warming events.     

Inorganic nitrogen in coral reef sediments

Representative profiles of inorganic nitrogenous species dissolved in interstitial waters of coral reef sands are presented. Ammonium is the dominant nitrogenous species in these pore waters with concentrations of up to 40 μm. Nitrate is present but in lower concentrations. Nitrite is found only occasionally in trace amounts. Computations of diffusive fluxes and inferences concerning microbial activity are derived from the profile structures. Computed flux rates of nitrogenous species from the sediment to the water column range between 0.75 and 1.37 μM m⁻¹ h⁻¹. These inputs may represent a significant source of recycled nitrogen to the primary producers of the coral reef ecosystem.     

Lithological control of land subsidence induced by groundwater withdrawal in new urban AREAS (Granada Basin,SE Spain). Multiband DInSAR monitoring

Ground subsidence in the southeastern border of the Granada Basin (SE Spain) has been studied using remote sensing techniques. Over the last decades, the region has experienced a huge urban expansion, which has caused a substantial increase in water supply requirements. Water needs are exclusively met by groundwater by means of numerous pumping wells, which exploit a confined detrital aquifer of alluvial fan deposits with a heterogeneous facies distribution. A general piezometric level decline (up to 50 m) has been recorded in the aquifer during the past 30 years that has induced the generation of a subsiding area with oval shape oriented WNW‐ESE just where the new urban areas and pumping wells are located. Subsidence has been monitored by exploiting synthetic aperture radar (SAR) images from ENVISAT (2003–2009) and Cosmo‐SkyMed (2011–2014). A new approach, which combines A‐DInSAR and small‐area persistent scatterer interferometry (PSI) analysis, has been applied obtaining a good accuracy regarding temporal and spatial dimension of the subsidence. ENVISAT data (2003–2009) reveal subsidence rates up to 10–15 mm/year, and Cosmo‐SkyMed (2011–2014) values slightly lower; up to 10 mm/year. Temporal variations in the subsidence velocity are in accordance with the rainfall pattern and piezometric fluctuations in the aquifer. The sector with highest rates of subsidence does not correspond to the area with more intense groundwater exploitation but to the area with greater presence of clays in the confining layer of the aquifer. There is a clear lithological control in the spatial distribution of the ground subsidence. This work integrates detailed geological and hydrogeological data with differential SAR interferometry monitoring with the aim to better understand subsidence processes in detrital aquifers with small‐scale heterogeneity. Copyright © 2016 John Wiley & Sons, Ltd.     

Forchheimer and added mass effects in the flow towards a well

In this note, we examine the flow towards a well in a confined aquifer in the presence of an interaction force defined by the sum of three terms, namely, a Darcy term (linear in the velocity), a Forchheimer term (quadratic in the velocity), and an added‐mass term (linear in the acceleration). We obtain the exact dynamic solution for the piezometric head distribution around the well and investigate the relative importance of the non‐Darcian terms. Copyright © 2013 John Wiley & Sons, Ltd.