Inverse modelling using PS‐InSAR data for improved land subsidence simulation in Las Vegas Valley,Nevada

Las Vegas Valley has had a long history of groundwater development and subsequent surface deformation. InSAR interferograms have revealed detailed and complex spatial patterns of subsidence in the Las Vegas Valley area that do not coincide with major pumping regions. This research represents the first effort to use high spatial and temporal resolution subsidence observations from InSAR and hydraulic head data to inversely calibrate transmissivities (T), elastic and inelastic skeletal storage coefficients (S_ke and S_kv) of the developed‐zone aquifer and conductance (CR) of the basin‐fill faults for the entire Las Vegas basin. The results indicate that the subsidence observations from InSAR are extremely beneficial for accurately quantifying hydraulic parameters, and the model calibration results are far more accurate than when using only groundwater levels as observations, and just a limited number of subsidence observations. The discrepancy between distributions of pumping and greatest levels of subsidence is found to be attributed to spatial variations in clay thickness. The Eglington fault separates thicker interbeds to the northwest from thinner interbeds to the southeast and the fault may act as a groundwater‐flow barrier and/or subsidence boundary, although the influence of the groundwater barrier to this area is found to be insignificant. Copyright © 2016 John Wiley & Sons, Ltd.     

Identification of potential subsidence related to pumping in the Almería basin (SE Spain)

Ground subsidence of detrital deposits in the Almería basin (SE Spain) was studied using the remote sensing technique of Differential Interferometry SAR (DInSAR). This basin is one of the most arid in Europe, receiving an average rainfall of 250 mm per year. Over the last 60 years the region has experienced an enormous agricultural and urban expansion, whose water demand has been largely supplied from groundwater, leading to the current situation of overexploitation of water resources. This paper outlines the likely relationship between groundwater abstraction and subsidence. To this end, 34 ERS and Envisat images, taken between 2003 and 2009, were analysed to estimate ground surface deformations, and hence, compared with water table variations measured in a number of piezometers in the basin. The analysis shows a clear parallelism between the variations in piezometric level and deformation of the ground surface. In addition, the zones of greatest subsidence coincide with those areas where groundwater abstractions are concentrated. Subsidence over the examined period varies from 10 to 30 mm, with extreme values as high as 50 mm, which translates to a rate of between 1·7 and 5 mm/year, reaching maximum rates of 8 mm/year at some points. Given such subsidence rates, damage to urban infrastructures are, for the moment, incipient. Copyright © 2011 John Wiley & Sons, Ltd.     

Deep-seated gravitational slope deformation (DSGSD) and slow-moving landslides in the southern Tien Shan Mountains: new insights from InSAR,tectonic and geomorphic analysis

We investigated deep-seated gravitational slope deformation (DSGSD) and slow mass movements in the southern Tien Shan Mountains front using synthetic aperture radar (SAR) time-series data obtained by the ALOS/PALSAR satellite. DSGSD evolves with a variety of geomorphological changes (e.g. valley erosion, incision of slope drainage networks) over time that affect earth surfaces and, therefore, often remain unexplored. We analysed 118 interferograms generated from 20 SAR images that covered about 900 km². To understand the spatial pattern of the slope movements and to identify triggering parameters, we correlated surface dynamics with the tectono-geomorphic processes and lithologic conditions of the active front of the Alai Range. We observed spatially continuous, constant hillslope movements with a downslope speed of approximately 71 mm year⁻¹ velocity. Our findings suggest that the lithological and structural framework defined by protracted deformation was the main controlling factor for sustained relief and, consequently, downslope mass movements. The analysed structures revealed integration of a geological/structural setting with the superposition of Cretaceous–Paleogene alternating carbonatic and clastic sedimentary structures as the substratum for younger, less consolidated sediments. This type of structural setting causes the development of large-scale, gravity-driven DSGSD and slow mass movement. Surface deformations with clear scarps and multiple crest lines triggered planes for large-scale deep mass creeps, and these were related directly to active faults and folds in the geologic structures. Our study offers a new combination of InSAR techniques and structural field observations, along with morphometric and seismologic correlations, to identify and quantify slope instability phenomena along a tectonically active mountain front. These results contribute to an improved natural risk assessment in these structures. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd     

Bed stability variations after check dam construction in torrential channels (South‐East Spain)

The effects of check dams on the bed stability of torrential channels have been analysed in several tributary basins of the Segura and Guadalentín rivers (South‐East Spain). In order to illustrate the large variability in channel bed‐forms and bed sediment sizes along the stream, 52 reaches of 150 m in length were surveyed. This variability is due to the behaviour of check dams, which depends on bedrock control, bed slope, channel roughness, lateral sediment input and a highly variable sediment transport capacity. Though the purpose of check dams is to diminish the boundary shear stress, reducing the longitudinal slope, and to stabilize the channel bed, downstream they reduce the volume of channel‐stored material, favouring local scour processes, and upstream they can destabilize the sidewalls. The results enable us to evaluate the impact of every check dam on the bed morphology, distinguishing the structures installed in limy marl areas (e.g. catchment of the Cárcavo rambla, Cieza) and in schist and slate terrains (e.g. catchment of the Torrecilla rambla, close to Lorca). In the first type, bedrock and moderately thick granular beds predominate downstream from the check dams, so that the length of bedrock reaches and increase of roughness due to scour processes are the best indicators to verify its geomorphological effectiveness. On the other hand, the metamorphic areas drained by ramblas and gullies produce great quantities of gravel that are retained by check dams, creating more uniform and permeable beds, where the balance between sedimentation and scouring, and the ratio τ_c84/τ₀ (RBS), appear to be the parameters most frequently adopted to estimate the bed stability. Analysis of slope adjustments and the application of other indices to estimate the bed substrate stability (LRBS, SRI) and the structural influence of the dams (SIBS) corroborate the differences in bed stability found in the corrected reaches in each catchment. Copyright © 2007 John Wiley & Sons, Ltd.     

Isotopic composition (δ18O and δD) of precipitation and groundwater in a semi‐arid,mountainous area (Guadiana Menor basin,Southeast Spain)

We characterize the precipitation and groundwater in a mountainous (peaks slightly above 3000 m a.s.l.), semi‐arid river basin in SE Spain in terms of the isotopes ¹⁸O and ²H. This basin, with an extension of about 7000 km², is an ideal site for such a study because fronts from the Atlantic and the Mediterranean converge here. Much of the land is farmed and irrigated both by groundwater and runoff water collected in reservoirs. A total of approximately 100 water samples from precipitation and 300 from groundwater have been analysed. To sample precipitation we set up a network of 39 stations at different altitudes (800–1700 m a.s.l.), with which we were able to collect the rain and snowfall from 29 separate events between July 2005 and April 2007 and take monthly samples during the periods of maximum recharge of the aquifers. To characterize the groundwater we set up a control network of 43 points (23 springs and 20 wells) to sample every 3 months the main aquifers and both the thermal and non‐thermal groundwater. We also sampled two shallow‐water sites (a reservoir and a river). The isotope composition of the precipitation forms a local meteoric water line (LMWL) characterized by the equation δD = 7·72δ¹⁸O + 9·90, with mean values for δ¹⁸O and δD of − 10·28‰ and − 69·33‰, respectively, and 12·9‰ for the d‐excess value. To correlate the isotope composition of the rainfall water with groundwater we calculated the weighted local meteoric water line (WLMWL), characterized by the equation δD = 7·40δ¹⁸O + 7·24, which takes into account the quantity of water precipitated during each event. These values of (dδD/dδ¹⁸O)< 8 and d‐excess (δD–8δ¹⁸O)< 10 in each curve bear witness to the ‘amount effect’, an effect which is more manifest between May and September, when the ground temperature is higher. Other effects noted in the basin were those of altitude and the continental influence. The isotopic compositions of the groundwater are represented by the equation δD = 4·79δ¹⁸O − 18·64. The groundwater is richer in heavy isotopes than the rainfall, with mean values of − 8·48‰ for δ¹⁸O and − 59·27‰ for δD. The isotope enrichment processes detected include a higher rate of evaporation from detrital aquifers than from carbonate ones, the effects of recharging aquifers from irrigation return flow and/or from reservoirs' leakage and enrichment in δ¹⁸O from thermal water. Copyright © 2010 John Wiley & Sons, Ltd.     

Recharge sources and hydrogeological effects of irrigation and an influent river identified by stable isotopes in the Motril‐Salobreña aquifer (Southern Spain)

Measurement of the stable isotopes oxygen‐18 and deuterium in water is an important tool to characterize aquifer recharge sources. In the driest areas of the Mediterranean, this application is of special interest due to the scarcity of water and the resulting common incidence of human influence on natural hydrological systems. The Motril‐Salobreña detrital aquifer (southern Spain) is a clear example of such an impact as inhabitants have designed irrigation systems and a dam was recently built across the course of the Guadalfeo River, which feeds the aquifer. The sampling of (river or ground) water has allowed the determination of stable isotope contents (oxygen‐18 and deuterium), both temporally and spatially, and the relative importance of the main recharge sources in certain sectors. In addition, we were able to infer seasonal trends and to improve existing knowledge of the main flow paths and the position of a seasonal groundwater divide. Data analysis shows evaporation plays a minor role (despite the high temperatures in the zone), scarce rainwater influence, and the overwhelming contribution of recharge from the Guadalfeo River and from the carbonate aquifer (Escalate aquifer) in contact with the Motril‐Salobreña aquifer. Irrigation return flow during the summer months comprises the main recharge due to the significant volumes of water that infiltrate. The construction of the dam will almost certainly entail great changes in the current dynamics of the hydrogeology of the Motril‐Salobreña aquifer; therefore, knowledge of its behaviour is crucial in order to carry out sustainable use of its groundwater resources. Copyright © 2011 John Wiley & Sons, Ltd.     

Fluvial response to climatic and anthropogenic forcing in the Moselle drainage basin (NE France) during historical periods: evidence from OSL dating

The aim of this paper is to study a low energy fluvial system response to natural and anthropogenic forcing during the last two millennia. In contrast with longer timescales (Holocene to Quaternary), historical sedimentary archives are sparse in such systems which are typically characterized by the predominance of erosion compared with aggradation. We studied three main sections in the Moselle valley (northeastern France) by a multi‐proxy approach combining morphology, sedimentology, archaeological evidence, historical archives, and dating. The geochronological framework was based on Optically Stimulated Luminescence (OSL) and validated by independent age control. The exposed sediments were allocated to different historical periods from Roman period to present. The first results show that, in contrast with many other fluvial systems, the Moselle and its tributaries did not experience major changes during historical periods. Climatic changes such as the Little Ice Age had a minor influence on floodplain aggradation (e.g. in grain size or sedimentation rates) in the Moselle valley and were only able to affect the fluvial style. This provides evidence that the reworking of sediments is the main fluvial process at short timescales in the valley floors of the Moselle catchment. In contrast, anthropogenic forcing seems important not only during recent centuries but also since Roman times. This is suggested by the case‐study of the Metz‐Mazelle section where significant headward erosion and sedimentation were recognized, and may be related to human occupation. The results therefore point to a need for increasing geoarchaeological and geochronological research in the Moselle catchment and similar low energy fluvial systems. Such research is actually essential to improve the knowledge of the fluvial response to environmental changes during the historical periods and to recognize the respective influence of natural variability and human forcing. Copyright © 2012 John Wiley & Sons, Ltd.     

Applying multifractality and the self‐organized criticality theory to describe the temporal rainfall regimes in Andalusia (southern Spain)

A multifractal analysis of hourly and daily rainfall data recorded at four locations of Andalusia (southern Spain) was carried out in order to study the temporal structure of rainfall and to find differences between both time resolutions. The results show that an algebraic tail is required to fit the probability distribution of the extreme rain events for all the cases. The presence of a multifractal phase transition associated with a critical moment in the empirical moments scaling exponent function was also detected. Both facts indicate that the rainfall process is a case of self‐organized criticality (SOC) dynamics, although the results differ for each place according to the time resolution and the nature of the rainfall, either convective or frontal. This SOC behaviour is related to a statistically steady state that implies the presence of clusterization in the time‐occurrence sequence of rain events. Such fluctuations have been shown by performing the analysis of the Fano and Allan factors and the count‐based periodogram. The values for the “synoptic maximum”, the typical lifetime of planetary scale atmospheric structures, have been obtained for each place and some important periodicities have been detected when dealing with extremes. Copyright © 2007 John Wiley & Sons, Ltd.     

Origin and type of rainfall for recharge of a karstic aquifer in the western Mediterranean: a case study from the Sierra de Gador–Campo de Dalias (southeast Spain)

Isotope signatures in precipitation from the Global Network for Isotopes in Precipitation around the Mediterranean basin and literature data are compared with isotopic data from a large karstic aquifer in southeast Spain to explain the origin and type of the precipitation events dominating recharge. Analysis of the deuterium excess d at the scale of the Mediterranean basin and at the regional scale allows us to understand the isotopic context of the study area: Campo de Dalias and the Sierra de Gador (Almería province). The origin of precipitation can be determined from its d value. The d value changes as a function of the initial evaporation condition. It depends on the relative humidity and temperature during the evaporation producing the water vapour of the clouds. The water vapour, which dominates the study area, is generated in two areas: the Atlantic Ocean (d = 10‰) and the western Mediterranean basin (d = 15‰). With increasing precipitation volume, the western Mediterranean character dominates. These heavier storms contribute mainly to recharge, as illustrated by the d value of 13·6‰ in deep groundwater of the Campo de Dalias. Weighted d values increase with the volume of precipitation, giving a significant relationship for the southern and eastern coasts of the Iberian Peninsula. This selectivity of d to monthly precipitation was used to estimate the return period of precipitation leading to aquifer recharge at 0·9–4·9 years. Moderate rainfall, which occurs more frequently, still represents ～60–90% of the total precipitation. One of the challenges to meet ever‐growing water demands is to increase recharge from moderate events yielding intermediate quantities per event, but forming the bulk of the annual precipitation. Copyright © 2006 John Wiley & Sons, Ltd.     

Paleomagnetism of Jurassic to Miocene sediments from the Apenninic carbonate platform (southern Apennines, Italy): evidence for a 60° counterclockwise Miocene rotation

The tectonic evolution of the Apennine belt/southern Tyrrhenian Sea system is addressed through a paleomagnetic study of Lias to Langhian sediments from the Apenninic carbonate platform (southern Apennines, Italy). Reliable paleomagnetic data gathered from 21 sites document a regional-scale post-Langhian 80° counterclockwise (CCW) rotation. Since previous studies of the Plio-Pleistocene clays spread over the orogen had shown a ∼20°CCW rotation, we conclude that the southern Apennines rotated by 60° during Middle-Late Miocene. Our data provide evidence that the southeastward drift of Calabrian block (and synchronous spreading of the southern Tyrrhenian Sea) induced ‘saloon door’ like deformation of the southern Apennines and Sicily, which underwent similar magnitude (although opposite in sign) orogenic rotations. A paleomagnetically derived paleogeographic reconstruction shows that at 15 Ma (Late Langhian) the Alpine-Apennine belt collided with a NNE-oriented carbonate platform corridor surrounded by oceanic basins. We speculate that both the end of the Corsica-Sardinia rotation and the eastward jump of the locus of back-arc extension (from the Liguro-Provençal to the Tyrrhenian Sea) may have been consequences of this event.     

Validating the KAGIS black‐box GIS‐based model in a Mediterranean karst aquifer: Case of study of Mela aquifer (SE Spain)

Karst Aquifer GIS‐based model (KAGIS model) is developed and applied to Mela aquifer, a small karst aquifer located in a Mediterranean region (SE Spain). This model considers different variables, such as precipitation, land use, surface slope and lithology, and their geographical heterogeneity to calculate both, the run‐off coefficients and the fraction of precipitation which contributes to fill the soil water reservoir existing above the aquifer. Evapotranspiration uptakes deplete water, exclusively, from this soil water reservoir and aquifer recharge occurs when water in the soil reservoir exceeds the soil field capacity. The proposed model also obtains variations of the effective porosity in a vertical profile, an intrinsic consequence of the karstification processes. A new proposal from the Nash–Sutcliffe efficiency index, adapted to arid environments, is presented and employed to evaluate the model's ability to predict the water table oscillations. The uncertainty in the model parameters is determined by the Generalized Likelihood Uncertainty Estimation method. Afterwards, when KAGIS is calibrated, wavelet analysis is applied to the resulting data in order to evaluate the variability in the aquifer behaviour. Wavelet analysis reveals that the rapid hydrogeological response, typical of a wide variety of karst systems, is the prevailing feature of Mela aquifer. This study proves that KAGIS is a useful tool to quantify recharge and discharge rates of karst aquifers and can be effectively applied to develop a proper management of water resources in Mediterranean areas.     

Evaluating a process‐based model for use in streambank stabilization: insights on the Bank Stability and Toe Erosion Model (BSTEM)

Streambank retreat is a complex cyclical process involving subaerial processes, fluvial erosion, seepage erosion, and geotechnical failures and is driven by several soil properties that themselves are temporally and spatially variable. Therefore, it can be extremely challenging to predict and model the erosion and consequent retreat of streambanks. However, modeling streambank retreat has many important applications, including the design and assessment of mitigation strategies for stream revitalization and stabilization. In order to highlight the current complexities of modeling streambank retreat and to suggest future research areas, this paper reviewed one of the most comprehensive streambank retreat models available, the Bank Stability and Toe Erosion Model (BSTEM), which has recently been integrated with several popular hydrodynamic and sediment transport models including the Hydrologic Engineering Center's River Analysis System (HEC‐RAS). The objectives of this paper were to: (i) comprehensively review studies that have utilized BSTEM and report their findings, (ii) address the limitations of the model so that it can be applied appropriately in its current form, and (iii) suggest directions of research that will help make the model a more useful tool in future applications. The paper includes an extensive overview of peer reviewed studies to guide future users of BSTEM. The review demonstrated that the model needs further testing and evaluation outside of the central United States. Also, further development is needed in terms of accounting for spatial and temporal variability in geotechnical and fluvial erodibility parameters, incorporating subaerial processes, and accounting for the influence of riparian vegetation on streambank pore‐water pressure dynamics, applied shear stress, and erodibility parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

Deforestation of water‐repellent soils in Galicia (NW Spain): effects on surface runoff and erosion under simulated rainfall

At three adjacent sites in steeply sloping woodland in Galicia (NW Spain), surface runoff and associated erosion under simulated rainfall (64 mm h^?1) were measured on five occasions between June 1998 and July 1999. Two of the three sites had recently been deforested and topsoil added, and one of these two had been sown with grass, which was germinating at the onset of the study. Deforestation greatly increased runoff and erosion rates, and the recovery of plant cover reduced erosion. All three soils were very hydrophobic due to high levels of poorly humified organic matter, which led to higher runoff rates than expected, especially during dry periods. However, great structural stability prevented there being a significant correlation between runoff rate and soil erosion. Copyright © 2003 John Wiley & Sons, Ltd.     

Schmidt‐hammer exposure‐age dating (SHD) of snow‐avalanche impact ramparts in southern Norway: approaches,results and implications for landform age,dynamics and development

Schmidt‐hammer exposure‐age dating (SHD) was applied to the problem of dating the diachronous surfaces of five distal river‐bank boulder ramparts deposited by snow avalanches plunging into the Jostedøla and Sprongdøla rivers in the Jostedalsbreen region of southern Norway. Approaches to local high‐precision linear age calibration, which controlled in different ways for boulder roundness, were developed. The mean age (SHD_mean) and the maximum age (SHD_max) of surface boulders were estimated for whole ramparts, crests and distal fringes. Interpretation was further assisted by reference to R‐value distributions. SHD_mean ages (with 95% confidence intervals) ranged from 520 ± 270 years to 5375 ± 965 years, whereas SHD_max ages (expected to be exceeded by <5% of surface boulders) ranged from 675 to 9065 years. SHD ages from the Jostedøla ramparts tended to be older than those associated with the Sprongdøla, rampart crests were younger than the respective distal fringes, and use of relatively rounded boulders yielded more consistent SHD ages than angular boulders. The SHD_mean ages indicate differences in recent levels of snow‐avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and, in smaller numbers, on the distal fringes. SHD_max ages provide minimum age estimates of rampart age (i.e. the time elapsed since the ramparts began to form) and suggest that at least some of the ramparts have been developing since the early Holocene. Copyright © 2015 John Wiley & Sons, Ltd.     

Sediment production in large gullies of the Mediterranean area (NE Spain) from high‐resolution digital elevation models and geographical information systems analysis

Recent studies in the Mediterranean area have shown gully erosion to have a very significant contribution to total soil loss. In the Penedès vineyard region (NE Spain), between 15 and 27% of the land is affected by large gullies and gully‐wall retreat seems to be an ongoing process. Multi‐date digital elevation model (DEM) analysis has allowed computation of sediment production by gully erosion, showing that the sediment production rates are very high by the, up‐to‐date, usual global standards. Here, we present a study carried out using large‐scale multi‐date (1975 and 1995) aerial photographs (1 : 5000 and 1 : 7000) to monitor sediment yield caused by large gullies in the Penedès region (NE Spain). High‐resolution DEMs (1 m grid) were derived and analysed by means of geographical information systems techniques to determine the gully erosion rates. Rainfall characteristics within the same study period were also analysed in order to correlate with the soil loss produced. Mass movement was the main process contributing to total sediment production. This process could have been favoured by rainfalls recorded during the period: 58% of the events were of an erosive character and showed high kinetic energy and erosivity. A sediment production rate of 846 ± 40 Mg ha^?1 year^?1, a sediment deposition rate of 270 ± 18 Mg ha^?1 year^?1 and a sediment delivery ratio of 68·1% were computed for a gully area of 0·10 km². The average net erosion within the study period (1975–95) was 576 ± 58 Mg ha^?1 year^?1. In comparison with other methods, the proposed method also includes sediment produced by processes other than only overland flow, i.e. downcutting, headcutting, and mass movements and bank erosion. Copyright © 2003 John Wiley & Sons, Ltd.     

Stalactite drip rate variations controlled by air pressure changes: an example of non‐linear infiltration processes in the ‘Cueva del Agua’ (Spain)

A study of drip water from a stalactite in the Cueva del Agua (Granada, southern Spain) over four hydrological years has enabled a detailed characterization of infiltration through the non‐saturated zone of this cave. The most significant aspects are: (1) The drip water regime is not seasonal, but is linked instead to slow infiltration. Sudden changes in the drip water regime are detected, due to infiltration along the preferential flow paths and the draining of water of supersaturated water reserves from the microfissure and pore system. (2) The accumulation of excess rain in the unsaturated zone dislodges the reserve of supersaturated water from the matrix of microfissures and pores, giving rise to an average increase in drip intensity of 2·2 ± 0·5 mm h^?1 and 37 ± 13 µS cm^?1 in the electrical conductivity of the water. (3) Time‐series analysis of the drip water demonstrates a lack of linearity over time of the drip rate, indicating a chaotic regime. (4) When the dripping is constant, barometric oscillation of the air is the principal factor that causes the lack of linearity in the drip flow. In this way, over an average of 2–3 days, a mean variation of the air pressure inside the cave of 10 ± 3·7 mbar causes a mean oscillation in the drip rate of 0·5 ± 0·2 mm h^?1. This increase in air pressure is translated as an increase in the relative thickness of the gaseous phase of the drip water at the cost of the aqueous phase, so reducing the drip intensity of the stalactite. Copyright © 2006 John Wiley & Sons, Ltd.     

The effect of low‐permeability fault zones on groundwater flow in a compartmentalized system. Experimental evidence from a carbonate aquifer (Southern Italy)

The hydrogeological behaviour of fault zones in carbonate aquifers is often neglected in conceptual and numerical models. Furthermore, no information is available regarding the relationships between piezometric levels when significant compartmentalization occurs due to the occurrence of low‐flow fault zones. The aim of this study was to refine the conceptualization of subsurface flow in faulted carbonate aquifers and to analyse relationships between sub‐basins within a compartmentalized aquifer system in Southern Italy. The interactions between compartments that straddle low‐flow faults were investigated over four hydrologic years using a statistical approach to compare (i) the hydraulic heads within two wells located up‐ and down‐gradient of tectonic discontinuities as well as (ii) the rainfall and piezometric levels. The results of this study suggest that a set of barriers exists between the wells, and, therefore, the total head loss observed between the wells (approximately 80 m) should be distributed across several aquitards, with one aquitard exhibiting a relatively high permeability or low degree of integrity. Due to slight differences in permeability, transient conditions in aquitards can occur over relatively short periods, which is in agreement with the results of the statistical data analysis. Consequently, rather than being caused by pure aquitards, aquifer system compartmentalization likely results from slight differences in the permeability between lower‐permeability fault zones and adjacent higher‐permeability protoliths. Copyright © 2014 John Wiley & Sons, Ltd.     

New evidence of sea‐level lowstands and paleoenvironment during MIS 6 and 4 in the Cantabrian coastal karst: the Cobiheru cave (North Iberia)

The geomorphological evolution of the Cobiheru Cave shows the influence of the non‐carbonate coastal mountain ranges on coastal karst evolution, as well as the temporal distribution of the cold‐adapted fauna sites in the Cantabrian Coast. Geomorphological observation and uranium/thorium (U/Th) dating lead to the construction of an evolution model. The model comprises two episodes of cave deposition occurring at c. 60–70 and 130–150 ka, linked to cold climate conditions, global sea‐level lowstands and the erosion of alluvial fans that covered the karst. Moreover, the comparison between the Cobiheru record and some raised beaches identified in previous studies sets the beginning of the sea‐level lowering in the Cantabrian Sea during the marine isotope stages (MIS) 5–4 transition. Two palaeoenvironments are inferred based on finding Equus ferus and Elona quimperiana. A wet deciduous forest would have developed on the emerged marine terrace of the Cobiheru Cave since at least the Middle Pleistocene, and an open landscape with scarce vegetation would have been present at c. 65 ka. The erosional event identified in the Cobiheru Cave helps to understand the temporal distribution of cold‐adapted mammals located in the Asturias region. The probable sites of cold‐adapted fauna developed in caves and alluvial fans would have disappeared after 65 ka. Therefore, palaeontological and palaeoclimate research based on cold‐adapted mammals suggests the occurrence of an hiatus in the palaeontological record prior to 50 ka. Copyright © 2017 John Wiley & Sons, Ltd.