Sedimentological and palaeohydrological characterization of Late Pleistocene and Holocene tufa mound palaeolakes using trenching methods in the Spanish Pyrenees

Lakes developed in the inner depressions of tufa mounds are rare geomorphic features and still poorly understood. Sedimentation in this unusual type of endorheic lake with a very restricted catchment area is highly sensitive to environmental and hydrological changes. The Isona tufa mound complex, north-eastern Iberian Peninsula, is associated with the discharge zone of a confined artesian aquifer and comprises 11 tufa mounds consisting of an annular rimstone enclosing a central depression filled with lake deposits. Data gathered from trenches excavated in four palaeolakes located within three different morphostratigraphic units permitted a precise analysis of the geometrical characteristics and stratigraphic relationships of the deposits and provided a sedimentation model for the Late Quaternary infilling of the spring-fed lakes. The work illustrates that trenches allow a precise characterization of the stratigraphic arrangements, lateral facies changes and deformation structures, which are not apparent in studies relying solely on borehole records, and facilitate sampling for dating and geochemical analyses. The five sedimentary facies described represent different evolutionary stages of the lakes, including: (i) carbonate-rich palustrine deposits probably related to periods with strong hydrological seasonality; (ii) massive highly bioturbated organic ooze; (iii) banded organic carbonate-rich facies associated with an increase in the regional effective moisture; (iv) finegrained quartz-rich aeolian/slope-wash sediments; and (v) colluvial facies deposited following the desiccation of the lakes located at higher altitudes. Geochemical and sedimentological analyses of the lacustrine sequences provided information on the palaeohydrological evolution of the Isona tufa mound complex and the palaeoenvironmental conditions of the area over the last 28 ka. Radiometric dating suggests that deposition occurred simultaneously at ca 22 ka in palaeolakes situated at different elevations. A drop in the piezometric level prompted by the opening of springs at lower altitudes probably caused the deactivation of the upper springs and the desiccation of the lakes. Arid conditions prevailed in the area during the Late Glacial and the early Holocene (28·0 to 8·5 ka BP). More humid conditions recorded from 8·5 to 4·2 ka and again since 1·7 ka are in accordance with palaeoenvironmental reconstructions available in the Western Mediterranean since the Last Glacial Maximum

Identifying the boundaries of sinkholes and subsidence areas via trenching and establishing setback distances

One of the most effective mitigation strategies in sinkhole areas is the exclusion of sinkholes and their vicinity to construction. The application of this preventive measure requires precise mapping of the boundaries of the areas affected by subsidence and the establishment of adequate setback distances, which is an important policy issue with significant economic implications. Through the investigation of several buried sinkholes in the mantled evaporite karst of the Ebro Valley by trenching, this work illustrates that the actual extent of the subsidence areas may be much larger than that inferred from surface mapping and geophysical surveys. The objective and accurate subsurface information acquired from trenches on the outer edge of the deformed ground revealed sinkhole radii 2–3 times larger than initially estimated, increasing one order of magnitude the sinkhole area. Trenches can therefore help to reduce mapping uncertainties and the size of setbacks. Moreover, the trenching technique, in combination with geochronological data and retrodeformation analyses, provides critical information on the subsidence phenomena and the characteristics of the sinkholes relevant to hazard assessment. Since recommended setback distances found in the existing literature are highly variable and rather arbitrary, we include a discussion here on the main factors that should be considered when defining setback zones for sinkholes

The application of GPR and ERI in combination with exposure logging and retrodeformation analysis to characterize sinkholes and reconstruct their impact on fluvial sedimentation

This work illustrates the practicality of investigating sinkholes integrating data gathered by ground penetrating radar(GPR), electrical resistivity imaging (ERI) and trenching or direct logging of the subsidence-affected sediments in combination withretrodeformation analysis. This mutidisciplinary approach has been tested in a large paleosinkhole developed during the depositionof a Quaternary terrace on salt-bearing evaporites. The subsidence structure, exposed in an artificial excavation, is located next toPuilatos, a village that was abandoned in the 1970s due to severe subsidence damage. Detailed logging of the exposure revealedthat the subsidence structure corresponds to an asymmetric sagging and collapse paleosinkhole with no clear evidence of recent ac-tivity. The sedimentological and structural relationships together with the retrodeformation analysis indicate that synsedimentary sub-sidence controlled channel location, the development of a palustrine environment and local changes in the channel pattern. GPRprofiles were acquired using an array of systems with different antenna frequencies, including some recently developed shielded an-tennas with improved vertical resolution and penetration depth. Although radargrams imaged the faulted sagging structure and pro-vided valuable data on fault throw, they did not satisfactorily image the complex architecture of the fluvial deposit. ERI showed lowerresolution but higher penetration depth when compared to GPR, roughly capturing the subsidence structure and yielding informationon the thickness of the high-resistivity alluvium and the nature of the underlying low-resistivity karstic residue developed on top ofthe halite-bearing evaporitic bedrock. Data comparison allows the assessment of the advantages and limitations of these comple-mentary techniques, highly useful for site-specific sinkhole risk management

Sinkholes in hypogene versus epigene karst systems, illustrated with the hypogene gypsum karst of the Sant Miquel de Campmajor Valley, NE Spain

The Garrotxa-Banyoles artesian aquifer system in NE Spain includes zones with epigene and hypogene evaporite karst and sinkhole development. The sinkhole fields related to hypogene evaporite dissolution are associated with the discharge zones of the aquifer, where groundwater from a confined limestone rises traversing an overlying gypsum formation capped by thick marls. This work analyses the sinkhole field developed in the Sant Miquel de Campmajor Valley (SMCV), a discharge area of the aquifer, where a cartographic inventory including 94 sinkholes has been produced. Sinkholes in this hypogene gypsum karst are mainly large caprock-collapse sinkholes rooted in deep-seated cavities generated by interstratal hypogene karstification, as corroborated by an electrical resistivity imaging (ERI) survey. They show a non-clustered distribution within the sinkhole field and the variations in size and density across the area are mainly controlled by the thickness of the marl caprock. The magnitude and frequency relationships of the sinkholes can be modelled with a high goodness of fit with a log-normal function, like in other regions of the world. However, in this deep-seated hypogene system the depressions show much larger dimensions. Potential differences between the sinkholes developed in hypogene and epigene karst environments are discussed, including their distribution with respect to the groundwater flow system, their spatial patterns and dimensions

Resultados preliminaries del uso de piezómetros de cuerda vibrante como herramienta a considerar para el estudio de la generación de deslizamiento en morrenas glaciales

Los depósitos glaciales del tipo morrena, suspendidos en forma de hombrera, yacentes sobre sustratos paleozoicos y terciario, en los valles Pirenaicos, son en su mayor parte inestables a medio y largo plazo. La evolución de estos depósitos desde el mismo momento en que se inició la retirada de los glaciares que los generaron ha sido la de inestabilizarse ya fuese en forma de deslizamientos rotacionales y/o flujos torrenciales. La dinámica de laderas probablemente nunca había interferido como ahora con la actividad humana y muestra de ello son los cada vez más numerosos desastres generados con las lluvias en entornos de montaña. La actividad económica de la última década ha propiciado una descontrolada ocupación del territorio construyendo en zonas históricamente conocidas por la afectación de fenómenos torrenciales. En el Barranc de Erill en la Vall de Boí, en el marco de una proyecto de investigación entre Forestal Catalana, Geobrugg y la UPC para el estudio de la aplicabilidad de las protecciones flexibles frente a flujos torrenciales, se ha instalado en la cabecera de la cuenca sobre depósitos morrénicos 5 piezómetros de cuerda vibrante a distintas profundidades en una misma vertical. Los datos tomados automáticamente cada 6 horas durante los últimos dos años combinados con el registro en la propia cuenca de la precipitación pueden ser de gran utilidad para determinar la relación entre la precipitación y la infiltración en términos de presión de poro efectiva y por ende poder llegar a determinar las condiciones de presión de poro en el momento de la rotura del terreno.Postprint (published version

Time-lapse resistivity analysis of Quaternary sediments in the Midlands of Ireland

Electrical Resistivity Tomography (ERT) data are influenced by a number of factors associated with the subsurface such as porosity, moisture content and lithology; as well as external factors such as rainfall and temperature. Two time-lapse ERT profiles with 5 m and two with 2 m electrode spacings were acquired over a range of Quaternary sediment types encompassing till, esker gravel, glaciofluvial sand and silt and glaciolacustrine silt/clay. Data were collected on a monthly basis during 2006 at a site located in the Midlands of Ireland in order to evaluate the influence of such conditioning factors on the resistivity of the subsurface. Effective recharge, the depth of investigation, the texture and the internal architecture of the different sediment types and temperature variation are the main factors influencing the resistivity seasonal variation. The shallow subsurface (b3 m depth) showed a direct relationship between resistivity variation and effective recharge, whereas, an increasing time-lag between effective recharge and resistivity was recorded at increasing depths. As a result of the time-lag, it was possible to determine the rate of movement of the wetting/drying front for the unconsolidated relatively sorted coarse sediments recorded on the site at 7.8 cm/day. Conversely, poorly sorted and fine sediments show little resistivity variation and the velocity of the wetting front could not be estimated. Other factors influencing the electrical response of the subsurface are the electrode spacing used for data collection and the seasonal temperature variation of the subsurface. Two methods for temperature correction of electrical resistivity data were tested in this study — both gave similar results. Resistivity values recorded in the shallow subsurface (b5 m) show variations of over 15% subsequent to temperature correction. The results illustrate that seasonal temperature changes and their influence on subsurface temperature have to be accounted for in data interpretation and emphasise the potential of this technique for the estimation of the rate of movement of the wetting/drying front in soft sediments

North polar trough formation due to in-situ erosion as a source of young ice in mid-latitudinal mantles on Mars

The clockwise spiral of troughs marking the Martian north polar plateau forms one of the planet’s youngest megastructures. One popular hypothesis posits that the spiral pattern resulted as troughs underwent poleward migration. Here, we show that the troughs are extensively segmented into enclosed depressions (or cells). Many cell interiors display concentric layers that connect pole- and equator-facing slopes, demonstrating in-situ trough erosion. The segmentation patterns indicate a history of gradual trough growth transversely to katabatic wind directions, whereby increases in trough intersections generated their spiral arrangement. The erosional event recorded in the truncated strata and trough segmentation may have supplied up to ~25% of the volume of the mid-latitude icy mantles. Topographically subtle undulations transition into troughs and have distributions that mimic and extend the troughs’ spiraling pattern, indicating that they probably represent buried trough sections. The retention of the spiral pattern in surface and subsurface troughs is consistent with the megastructure’s stabilization before its partial burial. A previously suggested warm paleoclimatic spike indicates that the erosion could have occurred as recently as ~50 Ka. Hence, if the removed ice was redeposited to form the mid-latitude mantles, they could provide a valuable source of near-surface, clean ice for future human exploration. © 2021, The Author(s).Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Resultados preliminaries del uso de piezómetros de cuerda vibrante como herramienta a considerar para el estudio de la generación de deslizamiento en morrenas glaciales

Los depósitos glaciales del tipo morrena, suspendidos en forma de hombrera, yacentes sobre sustratos paleozoicos y terciario, en los valles Pirenaicos, son en su mayor parte inestables a medio y largo plazo. La evolución de estos depósitos desde el mismo momento en que se inició la retirada de los glaciares que los generaron ha sido la de inestabilizarse ya fuese en forma de deslizamientos rotacionales y/o flujos torrenciales. La dinámica de laderas probablemente nunca había interferido como ahora con la actividad humana y muestra de ello son los cada vez más numerosos desastres generados con las lluvias en entornos de montaña. La actividad económica de la última década ha propiciado una descontrolada ocupación del territorio construyendo en zonas históricamente conocidas por la afectación de fenómenos torrenciales. En el Barranc de Erill en la Vall de Boí, en el marco de una proyecto de investigación entre Forestal Catalana, Geobrugg y la UPC para el estudio de la aplicabilidad de las protecciones flexibles frente a flujos torrenciales, se ha instalado en la cabecera de la cuenca sobre depósitos morrénicos 5 piezómetros de cuerda vibrante a distintas profundidades en una misma vertical. Los datos tomados automáticamente cada 6 horas durante los últimos dos años combinados con el registro en la propia cuenca de la precipitación pueden ser de gran utilidad para determinar la relación entre la precipitación y la infiltración en términos de presión de poro efectiva y por ende poder llegar a determinar las condiciones de presión de poro en el momento de la rotura del terreno

Quantifying groundwater discharge from different sources into a Mediterranean wetland by using Rn-222 and Ra isotopes

ISI Document Delivery No.: 022UG Times Cited: 5 Cited Reference Count: 38 Cited References: Ballesteros B.J., 2007, COASTAL AQUIFERS CHA, V23, P549 Beck AJ, 2007, MAR CHEM, V106, P419, DOI 10.1016/j.marchem.2007.03.008 Burnett W.C., 2001, J RADIOANAL NUCL CHE, V69, P21 Burnett WC, 2006, SCI TOTAL ENVIRON, V367, P498, DOI 10.1016/j.scitotenv.2006.05.009 Burnett WC, 2010, J HYDROL, V380, P298, DOI 10.1016/j.jhydrol.2009.11.005 Changnon SA, 1988, J CLIMATE, V1, P1239, DOI 10.1175/1520-0442(1988)0012.0.CO;2 Charette MA, 2007, LIMNOL OCEANOGR, V52, P230 Charette MA, 2003, MAR CHEM, V84, P113, DOI 10.1016/j.marchem.2003.07.001 Charette MA, 2001, LIMNOL OCEANOGR, V46, P465 Cook PG, 2008, J HYDROL, V354, P213, DOI 10.1016/j.jhydrol.2008.63.016 Corbett DR, 1997, J HYDROL, V203, P209, DOI 10.1016/S0022-1694(97)00103-0 De Stefano L., 2004, FRESHWATER TOURISM M de Weys J, 2011, ENVIRON SCI TECHNOL, V45, P3310, DOI 10.1021/es104071r Garcia-Orellana J, 2006, J GEOPHYS RES-ATMOS, V111, DOI 10.1029/2005JD006660 Garcia-Solsona E, 2008, MAR CHEM, V109, P292, DOI 10.1016/j.marchem.2008.02.007 Garcia-Solsona E, 2010, BIOGEOSCIENCES, V7, P2625, DOI 10.5194/bg-7-2625-2010 Garcia-Solsona E, 2008, MAR CHEM, V109, P198, DOI 10.1016/j.marchem.2007.11.006 Hancock GJ, 1996, EARTH PLANET SC LETT, V138, P145, DOI 10.1016/0012-821X(95)00218-2 Kluge T, 2007, HYDROL EARTH SYST SC, V11, P1621 KRABBENHOFT DP, 1990, WATER RESOUR RES, V26, P2445, DOI 10.1029/90WR01135 Macintyre S, 1995, BIOGENIC TRACE GASES, P52 Mejias M, 2008, ENVIRON GEOL, V54, P521, DOI 10.1007/s00254-007-0845-0 Mejias M., 2012, J HYDROL Moore W. 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Mejias, Miguel Zarroca, Mario Rodellas, Valenti/F-3475-2013; Masque, Pere/B-7379-2008 Masque, Pere/0000-0002-1789-320X Spanish Government project EDASMAR [CGL2006-09274/HID]; Consejo de Seguridad Nuclear project [2686-SRA]; MICINN (Spain) [AP2008-03044]; Plan Nacional de I-D+i, Spain [EX2009-0651]; ICREA Academia; Generalitat de Catalunya The authors gratefully acknowledge our colleagues at the Laboratori de Radioactivitat Ambiental for their help and assistance during field work. This project has been funded partially by the Spanish Government project EDASMAR (Ref. CGL2006-09274/HID) and the Consejo de Seguridad Nuclear project 2686-SRA. V.R. acknowledges financial support through a PhD fellowship (AP2008-03044) from MICINN (Spain). Support from a post-doctoral fellowship to E.G.-S. (EX2009-0651; Plan Nacional de I-D+i 2010-2012, Spain) is acknowledged. Support for the research of P.M. was received through the prize ICREA Academia, funded by the Generalitat de Catalunya. 5 ELSEVIER SCIENCE BV AMSTERDAM J HYDROLGroundwater discharge constitutes the main water inflow of many coastal wetlands. Despite the potential of Ra isotopes and Rn-222 as tracers of groundwater discharge, the use of these radionuclides to quantify the groundwater inflow in coastal wetlands has been only scarcely addressed in the literature. The main goal of this study is to evaluate the use of Rn-222 and Ra isotopes to estimate the contribution of distinct groundwater sources into a Mediterranean coastal wetland (the Peniscola marsh, Castello, Spain). The Peniscola marsh is a small shallow wetland nourished by groundwater coming from four different flowpaths: (i) a deep flow from the regional carbonate aquifer of El Maestrat, (ii) a shallow flow and (iii) an intermediate flow, both from the Irta Range and the detritic Vinaros-Peniscola aquifer, and (iv) seawater intrusion. Data on Ra-226, Rn-222 and salinity obtained in summer 2007 revealed that the deep groundwater contribution was 15% of the total water inflow, whereas the shallow and intermediate flow paths represented 32% and 48%, respectively. Seawater accounted only for the remaining 5% inputs to the wetland. Ra isotopes also allowed estimating the marsh water age in 1.2 days. Both the groundwater contributions derived from Rn-222 measurements and the Ra-derived marsh water age agreed well with the direct measurements obtained using propeller flow meters, evidencing the effectiveness of the used methods. An interannual comparison between the estimated groundwater inflow and the precipitation revealed that shallow groundwater flows respond to local precipitation, whereas the deep groundwater flow from the carbonate aquifer is dominated by a constant baseflow. (C) 2012 Elsevier B.V. All rights reserved