Duero Basin Research Articles

Interdisciplinary Research for the Delimitation of Catchment Areas of Large Deep Karstic Aquifers: Origin of the Thermal Springs of Alhama de Aragon and Jaraba (Spain)

The integration of different sources of geological and hydrogeological information and the application of interdisciplinary methods have informed the origin of the thermal springs of Alhama de Aragón and Jaraba, as well as other associated semi thermal springs (1200 L/s of combined flow, 711 L/s at over 30 °C), which is the main objective of this article. These springs come mainly from the autogenous recharge that occurs in the Cretaceous calcareous outcrops that border the Almazán Basin to the north, both in the Ebro Basin (Jalón Valley) and in the Duero Basin. The aquifer, shaped by upper Cretaceous limestones under the Palaeogene and Neogene rocks of the Almazán Basin, has extensive depths of more than 4000 m in the NE sector. This hydrostratigraphic unit has been affected by a generalized pre-Paleogene karstification that provides the main porosity to the aquifer. The underground flow moves in a NW–SE direction, crossing the Duero–Ebro divide, favoured by the topographic difference in elevation between the two basins. The regional flow is coherent with the progressive increase in temperature, infiltrating recharge water age (about 20–25 years in the semi-thermal springs, and more than 60 years in the Alhama and Jaraba springs), mineralization, and flow of the springs through which the system discharges. This issue is key to being able to design any sustainable conservation strategy in terms of quantity and quality of resources within the recharge area of the most important thermal springs in Spain. The Jaraba and Alhama de Aragón hot springs share the same or similar temperature, chemical composition, and geological contact of the spring. Their tritium isotopic composition and its evolution over time are practically the same. Their isotopic composition in D and 18O is also very similar. Both springs share the same recharge zone of similar altitude and constitute the end of flow tubes of similar length and flow rate.

Extended-range luminescence and ESR dating of Iberian fluvial terraces (Duero and Guadiana basins) associated with the Lower Palaeolithic sites of La Maya I, II, III, Burganes and Albalá (west-central Spain)

The major river basins of the Iberian Peninsula that drain towards the Atlantic coast contain extensive Lower Palaeolithic (Acheulean) records associated with well-preserved fluvial terrace sequences. These open-air archaeological records are often difficult to constrain chronologically due to a lack of suitable material for dating (e.g., faunal remains) or because their Middle Pleistocene antiquity precludes the use of otherwise routinely applicable geochronometric techniques such as conventional optically stimulated luminescence (OSL) dating. As a result, many important Iberian Acheulean sites lack precise and accurate chronologies, and their existing temporal frameworks are based solely on morphostratigraphic correlations with regional fluvial terrace systems. Here we present the first application of extended-range luminescence dating – namely multi-grain post-infrared infrared stimulated luminescence (pIR-IRSL) dating of K-feldspars and single-grain thermally transferred-OSL (TT-OSL) dating of quartz – to a series of terrace sequences in the Duero basin (central sector) and Guadiana basin, as well as associated Lower Palaeolithic sites of La Maya I, II and III along the Tormes River, Burganes (and related sites) along the Tera River, and Albalá along the Guadiana River. Additionally, we present results of a parallel electron spin resonance (ESR) quartz dating study of the Tormes River terrace (Duero basin), which has been undertaken independently on the same samples to enable stratigraphically paired dating comparisons. Our study indicates that sedimentary quartz from this sector of the Duero basin produces very weak TT-OSL signals, variable Al signal repeatability and below-average Ti signal fitting uncertainties, though it is still possible to determine consistent comparative ages using the measurements protocols employed here. For samples where both pIR-IRSL and TT-OSL signals were measured, the paired luminescence dating ages are in agreement at 1σ. Agreement between the quartz ESR and TT-OSL ages is also observed for one sample from the Tormes River. However, the ESR signals (both Al and Ti) of a second sample showed insufficient bleaching and age overestimation in comparison to the paired TT-OSL dataset. Comparison of our latest dating results with published chronological datasets point to some fluvial terraces of the Duero basin potentially having diachronous formation histories. Despite this, our combined chronological results show that the terrace systems are chronologically ordered and suggest that, regionally, the +8 to +34 m terraces likely post-date marine isotope stage (MIS) 10, whilst the +50 m terraces formed prior to, or during, MIS 10. The related Acheulean sites that contain lithic material in stratigraphic position are dated to MIS 9–7 (193–314 ka at 2σ age range), and temporally overlap with the early Middle Palaeolithic records in the Duero basin, also dated here to MIS 8–7 (or 159–259 ka at 2σ). Our results are consistent with previous observations regarding the chronological overlap of these two technologies in the region, and support the possibility of a non-linear pattern of replacement for the Acheulean in the Iberian Peninsula during the Lower to Middle Palaeolithic transition.

Postcranial anomalies of Eocene freshwater pleurodiran and cryptodiran turtles from the Spanish Duero Basin.

Testudines are one of the best-represented taxonomic groups among the Paleogene taxa of the Duero Basin (Castile and Leon Autonomous Community, central Spain). Among them, Neochelys (Podocnemidide) and Allaeochelys (Carettochelyidae) are most abundant, allowing the population to be assessed for osteological anomalies. The abundance of postcranial remains of both taxa allows us to identify several individuals with potential anomalies, mostly in their shells. Some of them have already been described in previous studies, but most of them are still unpublished. The objective of this study is to analyze in detail the anomalous Neochelys and Allaeochelys remains. As a result, different categories of causal agents (such as bacteria, fungi, parasites, or trauma) have been identified as potential producers of the anomalies in these freshwater turtles. Information regarding the pathogenesis and healing stages of some of these anomalies is provided.

Petrology and Geochemistry of Highly Differentiated Tholeiitic Magmas: Granophyres in the Messejana–Plasencia Great Dyke (Central Iberia)

The Messejana–Plasencia great dyke (MPGD) is a Late Triassic tholeiitic gabbro intrusion related to the Central Atlantic Magmatic Province. Its large outcrop extent (~530 km), combined with its prolongation below the Duero basin (additional 100 km), makes it one of the world’s largest dykes known. We have studied felsic granophyric bodies appearing in its northernmost segment at different scales, from mm-sized (interstitial micrographic pockets) to felsic dykes of up to 10 m thick and 1.5 km long, intruding within the gabbros. Significant differences exist in the mineral and whole-rock composition of gabbros and granophyres, including the Sr–Nd isotopic ratios. The chemical variation in the gabbros is coherent with fractionation of olivine, clinopyroxene and plagioclase at depth. However, the presence of a compositional gap between gabbros and granophyres (absence of intermediate compositions) and the formation of these late-stage intergranular felsic melts within the gabbro mesostasis suggest that they could be derived by liquid immiscibility. The Sr–Nd isotopic heterogeneity in the MPGD gabbros and the presence of zircons with Variscan ages (~286 Ma), inherited from granulitic rocks, indicate that the mafic magmas experienced some degree of lower crust assimilation during fractionation close to the Moho depth. On the contrary, the scarce xenocrystic Variscan zircon crystals found in a granophyric dyke within the MPGD gabbro display similar textures and ages (~299 Ma) to those of the country rock granites and point to contamination at a different crustal level.

A new Crocodyloidea from the middle Eocene of Zamora (Duero Basin, Spain).

The eusuchian crocodyliforms recorded in the Eocene levels of the Spanish Duero Basin belong to three lineages: Planocraniidae, with the species Duerosuchus piscator; Alligatoroidea, represented by several specimens of the genus Diplocynodon; and Crocodyloidea, which includes several specimens traditionally attributed to Asiatosuchus. The genus Asiatosuchus, established in 1940 based on a middle Eocene species from Mongolia, has subsequently served as a wastebasket taxon for Paleogene remains belonging to several species, not only from Asia but also belonging to the European and North American records. Many of these species are known by highly fragmentary remains, sharing the presence of characters such as a flat and triangular skull, and long symphyses in the lower jaw, recognized as characteristic for the crocodyloids. In addition to isolated cranial remains, among the material traditionally attributed to Asiatosuchus at the Duero Basin stands out a nearly complete skull and a left mandible, from the middle Eocene area of Casaseca de Campeán (Zamora Province). The present study analyses in detail these specimens, previously reported during the 1980s, but analyzed in a very preliminary way. They are included for the first time in a phylogenetic analysis to establish the systematic position of this Spanish form. The results confirm that it corresponds to a new species of basal crocodyloid, defined here as Asiatosuchus oenotriensis sp. nov.

Sustainability of Duero Water Systems for Crop Production in Spain

In recent decades, increased water demand combined with the effects of climate change has endangered water availability in many regions. In this context, sustainable water management has become a priority, seeking to balance human needs with the conservation of aquatic ecosystems. In the Duero basin (Spain), the availability of water is especially relevant for agricultural purposes, representing 93% of the total water needs. This study focuses on identifying and assessing the short-term sustainability of irrigated crop production in the Duero River basin. The maximum potential availability of surface water for irrigation was estimated and compared with the short-term agricultural surface water demand. The analysis was based on the use of a high-spatial-resolution (500 × 500 m) GIS-based model named WAAPA, and three indexes were used to evaluate and analyze the results. The results show that by analyzing the river basin in an aggregate form, the demands for irrigation were met, in which the reservoirs played an important role. When the analysis was downscaled to tributaries or even small streams, non-sustainable situations were identified. This shows the importance of using high-spatial-resolution models to improve, maintain, and achieve sustainability in the production of irrigated crops.

The Kaolin and Bentonite Deposit of Tamame De Sayago (Zamora, Spain): Mineralogy, Geochemistry, and Genesis

A geological, mineralogical, and geochemical characterization of the Tamame de Sayago (Zamora, Spain) deposit was carried out with the aim of knowing the conditions that facilitated the genesis in the same deposit of kaolinite and smectites. The alteration processes affecting a Variscan granite were deduced throughout the study of a very wide group of representative samples by X-ray diffraction (XRD), scanning electron microscopy (SEM), chemical analyses of major, minor, and trace elements, as well as δ18O, δ34S stable isotope and K/Ar dating analyses. In addition, 2D and 2.5D graphs of the kaolinite and smectite isoconcentrations were obtained from core data. According to the color and texture, two different clayey rock types were identified and named as homogeneous alteration zones (ZAHO) and heterogeneous alteration zones (ZAHE). The ZAHO are regoliths in which the granite texture is preserved, and the feldspars are almost completely kaolinized. In the ZAHE, the original texture of the granitic rock is lost, and the main clay mineral is smectite. The mineralogical composition is similar, with kaolinite, smectite, mica, quartz, scarce feldspar, and occasionally natroalunite and APS (aluminum-phosphate-sulphate); however, the mineral concentration varies considerably because ZAHO are rich in kaolin areas whereas ZAHE are bentonitic areas. Both rock types contain numerous veins and nodules. The weathering of the Paleozoic granite alongside the absence of sedimentation during the Mesozoic led to the formation of kaolinite that is preserved in ZAHO materials. Nonetheless, during the Cretaceous–Tertiary transit, the conditions of tectonic stability varied. Late Variscan faults reactivated which allowed the percolation of Mg- and Ca-rich hydrothermal fluids through the already kaolinized granite, increasing the alteration of the primary silicates and leading to the formation of smectites in ZAHE materials. The amount of smectites is greater closer to the faults. The stable isotopes indicate the meteoric nature of the low-temperature hydrothermal fluids. The K/Ar data obtained from the natroalunite of veins indicate that those hydrothermal fluids circulated in different pulses from 66.4 ± 1.7 to 58.8 ± 1.5 Ma, as a minimum. Those ages are coincident with the first formation stages of the Duero Basin.

How Mitochondrial DNA Can Write Pre-History: Kinship and Culture in Duero Basin (Spain) during Chalcolithic and Bronze Age

The chronological period from the beginning of the Chalcolithic Age to the end of the Bronze Age on the Iberian northern sub-plateau of the Iberic Peninsula involves interesting social and cultural phenomena, such as the appearance of the Bell Beaker and, later, the Cogotas I cultures. This work constructs a genetic characterisation of the maternal lineages of the human population that lived on the northern sub-plateau between 5000 and 3000 years ago through an analysis of mitochondrial DNA (mtDNA), a kind of genetic marker that is inherited through maternal lineages, unaltered from generation to generation. Population and cultural questions are investigated through mtDNA analyses. This study intends to shed light on the following questions. Were individuals who were buried together in multiple or collective burials biologically related through their maternal lineages? Were there distinct maternal human lineages in the same or different geographical areas if different material cultures (Bell Beaker and Cogotas I) were associated with the arrival of new human populations who established close biological relationships with the endogenous populations? Or could this be the result of the transmission of knowledge without human populations mixing? Another important question is whether the material cultures were related to the female populations. We analysed 91 individuals from 28 different archaeological sites of the Iberian northern sub-plateau from four different chrono-cultural periods (Pre-Bell Beaker, Bell Beaker, Proto-Cogotas I, and Cogotas I), from the end of the Chalcolithic Age up to the Bronze Age. There were two historical moments of new populations arriving: the first during the Pre-Bell Beaker period, associated with the K mtDNA haplogroup, and the second during the Proto-Cogotas I culture, with new lineages of the H, HVO, and T haplogroups. Neither of these new population flows were directly associated with the maximum development of the two main material cultures Bell Beaker and Cogotas I, so they must have occurred immediately beforehand, during the Pre-Bell Beaker and Proto-Cogotas I periods, respectively. However, we cannot discard an association between the populations and material cultures. Curiously, it has also been observed that there was also a tendency towards multiple burials, in which the individuals who were buried together belonged to the same maternal lineage, during these two periods of population change. This study has shed some light on the populational changes that occurred through these different periods in this specific geographical area of the northern sub-plateau of the Iberian Peninsula.

New insights into shepherds’ activities: Multi-proxy approach applied to fumier deposits from the north of Iberian Peninsula

The use of caves and/or rock shelters as a refugee for herds was a common practice in the Mediterranean area since the early Neolithic. Shepherds move the herds to pastures in higher altitudes, away from the settlements where the animals graze nearby the shelters where livestock is regrouped. Dung and residues produced during the occupation of these shelters were generally heaped and burnt to clean the site and prepare it for new usage, forming a characteristic deposit known as fumier. Fumier deposits are a great source of information to understand past herding practices including the animal's stabled, the management of the residues, the landscape, and the use of plants. In addition, they can provide a better understanding of site formation and postdepositional processes of archaeological sediments in caves and shelters including the impact of fire. Specific microarchaeological analyses are usually utilized to study fumier deposits. Here we present a multi-proxy approach that includes phytoliths, spherulites, ash pseudomorphs, and FTIR analyses, applied to the Neolithic levels of San Cristóbal, Los Husos II (Álava, Spain) and El Mirador (Burgos, Spain), located in the upper Ebro and Duero basins. This area in the north of the Iberian Peninsula constitutes a strategic location for the spread of the productive economy to the north, west, and interior of the Iberian Peninsula. Except for the lower Level XIII of San Cristóbal, where domestic activities were documented, our results showed similar behavior for the three studied sites, with no significant differences neither in terms of plant presence nor in the formation processes of the deposits. Up to seven and two possible complete stabling episodes were identified: three and two possible ones in San Cristóbal, and four in Los Husos II. Among the plants identified grasses of the C3 Pooideae subfamily were dominant, probably representing local grasses. The combining presence of thermally altered phytoliths, spherulites, and ash pseudomorphs points that the stabling episodes burned for several hours with temperatures ranging between 500 °C and 700 °C.

Connecting the Iberian Range with the Basque-Cantabrian Basin: The structure of the Sierra de Atapuerca (Spain)

We present a structural model of the Sierra de Atapuerca which constitutes the transition zone between the Iberian Range and the southwestern Basque Cantabrian Basin, NW Spain, where the Sierra de Atapuerca is located. The interpretation integrates both subsurface well and seismic hydrocarbon exploration data with surface geology. According to our interpretation, the Sierra de Atapuerca consists of a pop-up basement involved structure and is part of a NW-SE transpressive strike-slip band formed by high-angle faults segmented by transfer faults with a NE-SW direction. All this strike-slip alignment is located in the northern area of the Duero Basin and forms the footwall of the Duero North Thrust, which has transported the Folded Band and the Burgalesa Platform over this area thanks to a Triassic detachment, in a thin-skinned tectonics context. The Rojas and NW Demanda tectonic arcs represent the structural terminations of the Basque-Cantabrian Basin and Iberian Range domains, respectively, with the Sierra de Atapuerca located between both. The current structure of this zone is the result of an Alpine tectonic inversion of a previous Mesozoic extensional configuration, inherited from late Hercynian faults.

Shell characterization of the youngest valid species of the European Eocene genus Neochelys (Pleurodira, Podocnemididae): The Spanish Bartonian Neochelys salmanticensis

The freshwater pleurodiran turtle Neochelys is the best-represented member of Podocnemididae in the European record, being known by eight Eocene species. The youngest of them is the Bartonian (middle Eocene) Neochelys salmanticensis, from the Duero Basin (Salamanca Province, Central Spain). It corresponds to the largest representative known for this genus, its shell reaching 50 cm in length. Despite this form was defined several decades ago, the information currently available on it is very limited, being restricted to shell remains of less than 10 individuals. In fact, this species lacks a valid diagnosis, considering the current knowledge about the genus. Numerous remains (i.e., more than 1,200) of the shell of this Spanish species are identified. Its detailed study is presented here, so that the anatomy of its shell is characterized in detail. In addition, several aspects related to its intraspecific variability are analyzed, relative to the individual, ontogenetic, and sexual variability. In this way, the shell of N. salmanticensis can be characterized with greater precision than that of any other species of the genus.

Analysis of the Anomalies in a Middle Eocene Shell of Neochelys (Pleurodira, Podocnemididae) from the Duero Basin (Zamora, Spain)

Turtle shells frequently exhibit anomalous osseous modifications on their surface which can sometimes compromise the survival of the organism. Nowadays, despite the large number of anomalies identified in both extant and extinct turtle shells, the etiology, as well as the pathogenesis, of the various osseous modifications remains unknown in most documented extinct representatives. In fact, the interpretation of these anomalies in most fossil turtles is often speculative, the great majority of anomalous osseous modifications being attributed to vertebrate feeding traces, without considering other potential causative agents. In this context, we herein re-analyzed the shell anomalies recognized in an individual determined as Neochelys sp. (Pleurodira, Podocnemididae) from the middle Eocene (Lutetian) of the El Tejar fossil site (Corrales del Vino, Zamora, Spain), previously proposed as traumatic injuries resulting from a crocodile attack. The re-evaluation of these osseous alterations through detailed physical examination, comparison through direct observation and from the literature on extant turtles, and the use of the files obtained from a computerized axial tomography scan, allows the proposal of diverse causal agents, none of them supporting the previous interpretation. In addition, information regarding the pathogenesis and stages of the healing of the shell anomalies studied herein is provided.

Effectiveness of Adaptive Operating Rules for Reservoirs

In this paper, a methodological proposal is made to develop an adaptive decision support system for reservoir management. The system is based on an optimization model that determines operating rules that meet certain optimality conditions based on the state of the reservoir at a certain time and on a streamflow forecast, if available. The model is based on Spiliotis et al. in Water Resour Manage 30:5759-5778, where a general methodology was developed to specify static operating rules for reservoir systems. The proposed methodology consists of modifying the optimization procedure developed in the previous work to dynamically update operating rules to adapt management to the changing situation. To evaluate its effectiveness, the methodology was applied to the Pisuerga-Carrión reservoir system, in the Spanish part of the Duero basin. The results obtained with adaptive rules were compared with those obtained applying the same static operating rule for the entire analysis period. Adaptive rules were found to lead to better operating results, particularly if a successful streamflow forecast method is available.

River Diatoms Reflect Better Past than Current Environmental Conditions

The time required for diatom assemblages to integrate the abiotic variables of the aquatic environment has been subject of discussion for many years, with contrasting opinions as shown by field observations and experiments. Numerous diatom-based water quality indices are being used in the bioassessment of freshwaters; one of the most widely used (Specific Polluosensitivity Index or SPI) is compared in this study with water quality status as measured by the Water Quality Index (WQI) obtained from limnological parameters measured at 37 fluvial stations belonging to the Duero Basin (NW Spain). The correlation existing between both metrics was determined using different time lags between water and diatom sample collection. Results show that the correlation coefficient increases as the time gap decreases, but is maximal when comparing WQI scores measured one month before diatom sampling. We thus confirm the initial hypothesis that diatom indices actually indicate past (1 month ago) and not current water conditions in rivers. The practical consequences of this finding are briefly discussed.

Automatic Zonation and Correlation of Well Logs for a Tectono-Sedimentary Interpretation in the Continental Siliciclastic Basin of Duero River (Iberian Peninsula)

Abstract A procedure to automatically correlate well logs measured in boreholes that are located in continental siliciclastic basins by using two different methods is shown. The first method is applied to the parametric layers that were determined in each borehole starting from the values of their geophysical parameters and consists of correlating, by cross-association, the columns formed by these layers. The second method consists of cross-correlating the geophysical stretches or units, which are established as sets of layers with similar characteristics that are sufficiently different from the average values in the adjacent stretches. The evaluation of the correlation results requires showing the criteria that are used for determining the parametric layers that are obtained from the well logs, the result of which is called segmentation in this study. This evaluation also requires to show the techniques that are used to determine the geophysical stretches by a process that is called stretching in this study. The reason for using different correlation methods is that cross-association of layers provides high resolution but relatively smaller spatial extent, whereas cross-correlations of geophysical stretches provide higher spatial extent but lower resolution. Thus, the cross-association results have been used both to assess the correlations in boreholes that are relatively close (distances<10 km) and to support the establishment of the stretch correlation criteria. The developed methodology is applied to a set of boreholes located in the Duero Basin (Spain). From the results obtained, an evaluation of the correlations with respect to the distances between boreholes was carried out. Furthermore, it is shown that the correlations between geophysical stretches enable identifying the correspondences between these and the tectono-sedimentary sequences (activation-relaxation of a tectonic phase) that are established in the literature.

From Spatial Characterisation to Prediction Maps of the Naturally Occurring Radioactivity in Groundwaters Intended for Human Consumption of Duero Basin, Castilla y León (Spain)

According to the European Council Directive 51/2013 EURATOM, the radionuclide content in human consumption waters must comply with the stated recommendations to ensure the protection of public health. The radiological characterisation assessed in Laboratorio de Radiaciones Ionizantes y Datación of Universidad de Salamanca, in more than 400 groundwater samples gathered from intakes intended for human consumption from the Castilla y León region (Spain), has provided worthwhile data for evaluating the spatial distribution of the radioactivity content in the Duero basin. For this purpose, geostatistical exploration and interpolation analysis, using the inverse distance weighting (IDW) method, was performed. The IDW prediction maps showed higher radioactivity occurrence in western and southern areas of the study region, mainly related to the mineralogical influence of the igneous and metamorphosed outcroppings in the Cenozoic sediments that formed the porous detritic aquifers of the Duero basin edges. The hydraulic characteristics promote the distribution of these radioactivity levels towards the centre of the basin as a consequence of the unconfined nature of the aquifers. Prediction maps provide a worthwhile tool that can be used for better planning and managing of groundwater monitoring programmes.

Seismites in Miocene gypsum microbialites: Multiproxy tools for paleoenvironmental reconstruction of saline lakes

This work provides the first evidence of seismites within Miocene gypsum microbialites deposited in inland lakes. Seismites are observed on good quality outcrops in two separated successions of the Madrid and Duero basins (central Spain) that are sited nearby strike-slip faults. The successions consist of sandy gypsum facies interbedded with gypsiferous mudstone and marlstone. The association of microbial induced sedimentary structures (MISS) with mineralogical biosignatures such as intrasediment-grown lenticular gypsum, dolomite with inner biomolds and other biological induced minerals, supports that gypsum beds represent microbialites. Gypsum microbialites are characterized by parallel-lamination, cross-bedding and laminated leveling structures. The rapid mineralization of the microbial mats and biostabilization processes may play a role in the preservation of the depositional structures in sulfates. In addition to MISS, several categories of large-scale soft-sediment deformation structures (SSDSs) reflecting ductile and brittle behavior repeat vertically through the successions. These are classified as load casts, pillows, dish structures, convolute bedding and lamination, plastic intrusions, fluid escape tubes, mud/sand volcanoes, Neptunian dikes and fractures. The deformation structures in crystalline sediments are interpreted to be caused by seismic shocks of magnitude over 5 related with syndepositional fault movements. Micromorphological analysis of gypsum beds reveals distinctive features such as cracked crystals, oriented crystals filling dikes and horizontal microstylolites that also indicate seismic shocks. Comparison between the two basins shows some differences in the type and vertical distribution of structures, and this suggests that earthquakes were less frequent and of higher magnitude in the Madrid Basin. The results confirm that microbial gypsum deposits have both high susceptibility to earthquakes and high potential to preserve a wide range of information of the sedimentary environment, including paleoecology, paleogeochemistry, paleohydrodynamics, and seismogenic behavior of microbial sediments and faults.

San Quirce (Palencia, Spain): new chronologies for the Lower to Middle Palaeolithic transition of south‐west Europe

AbstractSan Quirce is an open‐air archaeological site situated on a fluvial terrace in the Duero basin (Palencia, northern Iberia). This paper presents new and consistent chronologies obtained for the sedimentary sequence using post‐infrared infrared stimulated luminescence (pIR‐IR) dating of K‐feldspars and single‐grain thermally transferred optically stimulated luminescence (TT‐OSL) dating of quartz. The new dating results indicate that the sequence is older than ~200 000 years and place San Quirce Level III within marine isotope stages (MIS) 8 and 7, between 274 ± 13 ka and 238 ± 13 ka. The main lithic assemblage at San Quirce comes from Level III. The predominant tool types found in this level are hammerstones, manuports and flakes, with a small proportion of cores and a significant presence of denticulates. Adaptation to local environmental conditions resulted in distinctive cultural habits, which were embedded in the cultural tradition of hominins occupying the site during the final third of the Middle Pleistocene. San Quirce preserves a simple cultural tradition that was employed by local hominins to engage in a diverse array of activities, and highlights the cultural diversity that appears to have been a characteristic feature of the Lower to Middle Palaeolithic transition 300–200 ka.

Water, Energy, Food and Environment Nexus in Six Irrigation Districts from the Spanish Duero Basin

Background and Objective: Irrigated agriculture is a key factor to foster crop production and the agribusiness sector. It also contributes to develop rural areas and maintain the population in Spanish rural villages. However, water resources are not always available to fulfill crop water requirements when needed. In addition, the Spanish Plan for modernization of hydraulic irrigation infrastructures (2000) has increased energy consumption and drastically has raised the energy cost in the last five years. Natural environment in irrigated areas has modified and the application of agrochemicals and pesticides, together with aquifer’s over exploitation, have degraded groundwater quality and have extinct river fishes. In the one hand, the European, National and Regional Normative on ecosystems requirements and services, must be met. On the other hand, farmers want to stay in the rural areas as long as their gross income be higher than the farming’ expenses. Likewise, climate change predictions in semi and arid areas foresee an increase in temperature, which will increase crop water needs, and droughts’ increase. Duero is the second largest Spanish river which supplies water to a larger and depopulated area where agriculture is the major economic sector. The irrigated area has doubled in the last fifteen years and irrigation consumes 85% of total water resources at present. Perspectives for the near future highlight the need to foster rural development and settle population. The challenge ahead is to maintain irrigation but tackling the issues on water scarcity, energy prices and fertilizer cost. This work is aimed at providing some clues on the water-energy-food-ecosystem nexus in rural areas of the Duero basin.
 Methodology: Six Duero irrigation districts (ID) (Adaja, Tordesillas, Aranda-Tordesillas, Tordesillas-Zamora, Villalar de los Comuneros and Carracillo) have been selected and the study focuses on the evolution of water and energy consumption, as well as the main crops production, the ecosystems’ status and the major municipalities population trends across the IDs, from 2010 to 2020.
 Results and Conclusion: The annual average water supply was different among IDs; the highest value corresponded to “Tordesillas” (6895 m3/ha) and “Adaja” (6287 m3/ha). The energy consumption was very high in all IDs. Likewise, the highest water productivity and total gross income indices corresponded to potato and sugar beet and the lowest to barley and sunflower. The total production costs in the last two crops were higher than the gross income and consequently, it would result in economic losses in the case of subsidies lack. The population in the main municipalities of the six IDs has decreased in the study period and does not meet the goal of the Spanish Plan for modernizing irrigation systems of maintaining/increasing population in rural areas. The results would be a valuable tool to develop sustainable solutions (at regional scale) for fair and sustainable sharing food production resources that will affect the water, energy, food and ecosystem (WEFE) nexus.

Using SP logs to estimate the water quality of borehole layers in the Duero basin (Iberian Peninsula)

ABSTRACT This work presents a proposal for the use of spontaneous potential logs to estimate the water quality in permeable layers of a formation that are located below the water table in uncased boreholes. These estimates aim to obtain the values for conductivity and total dissolved solids, which would enable us to learn their distributions with depth and determine the optimal extraction levels prior to completing these boreholes. This proposal consists of a methodology to process and interpret spontaneous potential logs. Laboratory measurements have been necessary to obtain the water resistivities versus their equivalent resistivities and versus the total dissolved solids. In addition, continuous analytical relationships have been developed for the range of applications found, and specific algorithms have been developed to determine the baseline of the spontaneous potential log. This methodology has been applied to a group of 27 boreholes located in the southern Duero continental detrital basin.