Ebro Basin Research Articles

Disentangling arthropod and plant resources consumed by Orius spp. in peach and alfalfa crops by metagenomic analysis

Agricultural intensification is affecting the biological control of insect pests, an important component for sustainable crop production. To understand the changing patterns of insect abundance within an agroecosystem, it is necessary to disentangle the trophic interactions between species, and metabarcoding is an excellent alternative to show them. In the Ebro Basin (NE Iberian Peninsula), agricultural landscapes are composed of a mosaic of crops scattered with natural and semi-natural habitats, where the presence of Orius spp., used as biocontrol agents, is well known. To shed light on their predatory role in this area, a previously developed metabarcoding multi-primer method has been used to study the arthropod and plant most frequently resources consumed by some field-collected Orius, sampled at different dates in a peach and an alfalfa adjacent crop. Their high-throughput sequencing (HTS) analysis showed the consumption of 15 arthropod and 12 plant taxa. Eight of them were consumed by O. laevigatus, six by O. majusculus and 23 by O. niger. The obtained results showed that HTS is a powerful tool in studies of trophic interactions in agroecosystems. Among the detected arthropods, other natural enemies were present, showing a certain degree of intraguild predation, which has been demonstrated by developing a new added strategy in the bioinformatic analysis. Detected plant consumption indicates that Orius forages on several plant species, showing their movement from them to the sampled crops. These plants could have a potential role in attracting or maintaining these predators in both crops in biological control strategies.

Late Quaternary palaeoenvironmental controls on concentric talus evolution in the Central Ebro Basin (NE Spain)

The polyphasic evolution of the testimonial buttes in the central area of the Ebro basin (Los Monegros) is analysed. This is a semiarid area that favours high erosion rates. An evolutionary model of the Jubierre hills is presented that shows the environmental cycles represented by aggradational and degradative processes on the slopes that resulted in the present arrangement of talus flatiron rings. In the four studied cases, talus relicts are composed of detritic material from a disappeared caprock pediment. Four slope stages (S4 to S1) that formed under stable climate conditions are identified. Older stages (S4 and S3) are estimated by comparison with other talus flatirons in the region. The S2 stage contains Bronze Age archaeological remains and the radiocarbon age obtained was 1608–1446 years cal BC (2σ), while S1 is younger. A palaeoenvironmental interpretation was made for these aggradational stages (S4 to S1). The active erosion of these hills led to a relief inversion, and talus flatirons remain as the only features revealing the presence of the relict hills and past human occupations.

Past and present Geomorphological hazard and cultural heritage loss in El Castellar castle scarp (central Ebro Basin, Spain)

The ruins of the Medieval castle and village of El Castellar are located on an abrupt 1.2-km-long scarp of Miocene gypsums, in the central sector of the Ebro depression. The Medieval remains of the main El Castellar castle are perched on a 100 m cliff on the Ebro River. Considering the historical and geoarchaeological relevance of El Castellar settlement, this investigation aimed to study the geomorphological and paleoenvironmental context of the site during and after the settlement and its later evolution, including its current state. Geomorphological data suggest that in Medieval times its constructions were favored by the MCA environmental conditions. During that times, the Ebro River was located in a centered position on its floodplain, and lateral alluvial fans protected the scarp from basal erosion. Later, during the LIA, great climatic flows and recurrent floods changed the river dynamics and promoted the river channel movement against the scarp, destabilizing its foot and generating large landslides and rockfalls, thus promoting its retreat. The village buildings and castle at the top of the scarp were seriously damaged. For several reasons, the area is not easily accessible, but it still contains a relevant archaeological heritage that deserves to be studied and preserved.

Ceratium furcoides (Levander) Langhans in reservoirs at the Ebro watershed, Spain and Sao Paulo state, Brazil

This study compares the morphological characteristics of the dinoflagellate Ceratium furcoides from three Ebro basin reser¬voirs (Spain) and from six reservoirs at São Paulo state (Brazil) with the aim to identify the distinct morphotypes of Ceratium furcoides in Spain and Brazil. We studied the physical and chemical variables to determine the trophic state of each reservoir. Unlike Ceratium hirundinella, Ceratium furcoides is not a frequent species within the plankton community at Ebro Basin reservoirs, however, this species has been responsible of one monospecific bloom at El Val reservoir. Nevertheless, both Ce-ratium species are considered invasive in South America. Ceratium furcoides has displaced C. hirundinella at São Paulo state reservoirs, reaching high densities, to the extent of forming monospecific blooms. Morphometric analysis was performed by optic and electronic microscopy (DIC and SEM respectively). The analysis shows significant differences in: i) total cell length, ii) horns length and iii) presence or absence of a fourth horn. While the microscopic study allows differentiating morphotypes according to the reservoir typology, a deeper study using molecular genetic techniques on the different populations of C. fur¬coides would allow to know better the relationship between the dinoflagellate dynamics and the reservoirs trophic states.

Hydroclimatic and geochemical palaeoenvironmental records within tufa: A cool-water fluvio-lacustrine tufa system in the Wadi Dabsa volcanic setting, western Saudi Arabia

A series of uncharacterised tufa deposits within the lowland volcanic provinces of western Saudi Arabia are investigated here in order to account for their presence and to examine their utility as a palaeoenvironmental archive. The Wadi Dabsa basin, in the Harrat Al Birk, is part of the Saharo-Arabian region, where there is increasing evidence for multiple hominin dispersals during windows of reduced aridity during the last ~400 ka of the Late Quaternary. This first and detailed petrological and geochemical characterisation of these tufa carbonates is particularly important for palaeoenvironmental and climatological reconstruction at a site that contains a major concentration of Early and Middle Stone Age artefacts. We aim to determine the nature of deposition, to answer whether these are cool, freshwater tufa or hydrothermal travertine, and to establish what the tufa settings, stratigraphies and facies reveal about the hydroclimatic regime in this semi-arid environment.A widespread lacustrine-paludal and fluvial tufa system is preserved, as well as topographically-controlled tufa barrages and cascades. Observable sections, exposed by incision, reveal a thickness of tufa deposits of 3 to 6 m in places, which contain two packages of tufa-cemented conglomerate facies. This allows us to provide a conceptual model for the deposition of semi-arid tufa, based on existing type sites in the Naukluft Mountains of Namibia and the Ebro Basin of Spain. The varied topography within this volcanic harrat provides a setting at Wadi Dabsa that combines the low-lying lacustrine-paludal model from Spain with the steeper and higher-energy model from Namibia. The two tufa-cemented bedload units and the evidence for post-depositional erosion of other tufa facies indicates a shifting hydroclimatic regime, with episodes during which the basin contained water and there was steady flow in the fluvial channels, alternating with episodes of high-energy flashy flows.Geochemical analysis using 87Sr/86Sr isotopic ratios (0.7049 to 0.7056 with one sample at 0.7062) and stable carbon isotopes (−12.9 to −6.3‰) reveal that these are cool-water tufas were deposited from meteoric water that has interacted with both metamorphosed limestone in the Asir Escarpment and the mafic metavolcanic bedrock of the Wadi Dabsa Basin, without a geothermal influence. These tufa are low-concentration‑magnesium calcite, with traces of quartz (to a maximum of 3%) and other silicates. Some samples have ≤7.5% palygorskite, which along with petrological evidence for microbial filaments suggests the importance of biomineralisation by cyanobacteria within some of these tufa. Petrological analysis shows the fabrics are dominated by micrite cements with some microspar, and very little post-depositional alteration. Where samples are banded, this reflects variation in calcite crystal size as opposed to any striking variations in mineralogical composition. Oxygen stable isotopic composition (−14.6 to −1.9‰) indicates deposition from an isotopically more depleted rainfall source than the modern day, noting additional corrections for unknown past temperature and any other fractionation effects are needed. Depleted rainfall sources in this region may relate to either a far-travelled Atlantic moisture source or a higher-intensity Indian Ocean monsoon source, or some combination.

New perspectives on the Sertorian War in northeastern Hispania: archaeological surveys of the Roman camps of the lower River Ebro

AbstractIn recent decades, conflict archaeology has renewed study of the Roman Republican military, with Hispania as one of the most prolific areas of research. Following this trend, since 2006 the University of Barcelona has conducted archaeological investigations at several sites in the lower Ebro basin. When no structures or archaeological layers remained in situ, surface survey became a key methodology. Based on the artifacts retrieved during surface survey, this article identifies four new military establishments dated to the first half of the 1st c. BCE and reinterprets the campaigns of the Sertorian War in northeastern Spain.

The impacts of exceptional rainfall on phosphorus mobilisation in a mountain agroforestry catchment (NE, Spain)

Erosion causes significant soil and nutrient losses that can reach streams and degrade habitats. Phosphorus (P) is among the nutrients of greatest concern for water pollution. Due to the increase in the number of storm events over the last decade, which could rise further under climate change scenarios, a more in-depth analysis of the effect of rainfall on the behaviour of P in fragile environments is needed. Little is known about the mobilisation and export of P in mountainous Mediterranean agroecosystems. To contribute to this knowledge, this research analysed the variability of P in the sediments of streambeds of different orders in an agroforestry area of the Northern Ebro Basin (Aragón, Spain) following an exceptional rainfall event; the implications of different land uses were also explored. Sediment composition was assessed before and after the rainfall event in three nested subcatchments and then related to soil properties. Phosphorus was mostly linked to the mineral fraction (mainly to silicates), while the links between P with clay and organic matter (P-clay, P-OM) were very weak. The P-OM links occurred only in the soils of forested areas. Agricultural lands, which are prone to erosion and had the highest P concentrations, contribute to P release. However, the streambeds and the lateral erosion of channel banks by floods triggered by the rainfall event should be considered as the main contributors to the export of P. The high intensity rainfall event led to 35% and 60% reductions in clay and OM, respectively, and to an enrichment of P in the sediments, the concentrations of which were lower in the headwaters than downstream. This means that the P in streambeds remains exposed in relatively high concentrations following extreme rainfall events with implications for the P cycle and water pollution.

Integrating ecosystem benefits for sustainable water allocation in hydroeconomic modeling.

The increasing concern about the degradation of water-dependent ecosystems calls for considering ecosystems benefits in water management decision-making. Sustainable water management requires adequate economic and biophysical information on water systems supporting both human activities and natural ecosystems. This information is essential for assessing the impact on social welfare of water allocation options. This paper evaluates various alternative water management policies by including the spatial and sectoral interrelationships between the economic and environmental uses of water. A hydroeconomic model is developed to analyze water management policies for adaptation to reduced water availability in the Ebro Basin of Spain. The originality in our contribution is the integration of environmental benefits across the basin, by using endemic biophysical information that relates stream flows and ecosystem status in the Ebro Basin. The results show the enhancement of social welfare that can be achieved by protecting environmental flows, and the tradeoffs between economic and environmental benefits under alternative adaptation strategies. The introduction of water markets is a policy that maximizes the private benefits of economic activities, but disregards environmental benefits. The results show that the current institutional policy where stakeholders cooperate inside the water authority, provides lower private benefits but higher environmental benefits compared to those obtained under water markets, especially under severe droughts. However, the water authority is not allocating enough environmental flows to optimize social welfare. This study informs strategies for protection of environmental flows in the Ebro Basin, which is a compelling decision under the imminent climate change impacts on water availability in coming decades.

The Mesolithic of Atlantic Coastal Spain – a comparison with the Middle Ebro Basin

This paper compares current evidence for Mesolithic adaptations along the north Spanish coast from Galicia in the west to the Basque Country in the east. Significant questions and issues pertinent to Mesolithic research are reviewed, followed by a brief discussion of advances in method and theory over the past 25 years. Cantabria, País Vasco, and Galicia are compared with each other and en bloc with evidence from the middle Ebro over the 12-6 ka BP interval considered to bracket the transition between foraging and domestication economies. Marked differences in the time-space grid, geology, and the resolution of the data hinder these comparisons. A radiocarbon database totaling 610 dates is compiled, cleaned, filtered and analyzed for each region individually using summed calibrated date probability distribution (SPD) curves as a proxy for population density fluctuations over time. Regional curves are then compared with each other and with a global model.

Flint blades and daggers from collective burials dated to the Final Neolithic and Chalcolithic in Southern France

In Southern France, Late Neolithic collective burials have yielded a large number of retouched or unretouched flint blades which even occur in the form of dagger blades. Their intrinsic (petrographic, technological and typological) data have recently been clarified. In many cases, it is now possible to specify the origin of most of these pieces and to identify their primary (related to the process of manufacturing workshops) and secondary (use wear) characteristics. Out of the eight main raw material categories identified in Southern France only two are regional: Ludian flint from Collorgues in the Gard department and Stampian flint from Mur-de-Barrez in the Aveyron department. The other flint materials stem from the neighbouring regions, i.e. from the western part of Upper Provençe (Bedoulian flint from Vaucluse and banded Oligocene flint from Forcalquier), the north-eastern part of the Iberian peninsula (lacustrine flint from Monegros and evaporitic flint from the Ebro basin), the Touraine region (Turonian of Le Grand-Pressigny) as well as from various Cretaceous flint sources in the Aquitaine region (Bergeracois, Angoumois, Saintonge). In general, the blades found in collective burials are used objects that were part of the personal equipment and that are identical to those found in neighbouring settlements. In most of the territories, it is possible to establish valid correlations between the series of collective burials which in many cases were used over a long period of time and the excavated settlements which were occupied during a shorter period of time and which are generally dated more reliably and can be assigned to well-defined cultural groups. It is then possible to improve the perception of the extrinsic data of these pieces, in particular those related to their cultural and chronological context, and to advance new lines of comparative studies, such as the one discussed here related to the comparison of the data stemming from collective burials in caves with those originating from megalithic monuments or hypogea. As regards the geographical distribution of these types of graves, it should be noted in the first place that it varies greatly according to the natural areas and that these disparities must be taken into account in the quantitative variations recorded. The distribution of each category of flint blades by type of tomb in the various chrono-cultural areas under study does not reveal a clear difference which could be explained by a distinct socio-economic status of the users of these types of tombs. The variations recorded seem to be mainly related to two phenomena. The first is related to the more or less wide scope of the various blade production centres and to the strength of their distribution network, which results in variations in the density of occurrences dependent on the distance from the sources. The second phenomenon that seems to have the greatest impact is related to the chronology and therefore to the periods of use of the various collective burials. By adopting a subdivision of the Late Neolithic into four phases, it is possible to highlight differences. During the Late Neolithic 1 (3500-3200 BCE), flint blades of Provence origin made from Bedoulian flint and banded Forcalquier flint were predominant. During the Late Neolithic 2 (3200-2900 BCE) blades made from Forcalquier flint had the largest diffusion, while new regional networks ensuring the distribution of thick and curved blades developed in two areas: the Mediterranean area as regards the Collorgues site and the Causses region as regards the Mur-de-Barrez site. The Late Neolithic 2b (2900-2700 BCE) and especially the Late Neolithic 3 (2700-2400 BCE) which corresponds to the emergence and development of Chalcolithic metallurgy in the Languedoc and Causses region are marked by a preferential diffusion in the form of flint daggers. Competition between the diffusion networks of the daggers made from Forcalquier flint in the Provence region and those made from Le Grand-Pressigny flint in the Touraine region finds expression in the spread of very sophisticated pieces characterised by ripple-flaking retouch the areas of distribution of which are largely overlapping. These pieces were found in both caves and megalithic monuments, as is the case for the copper daggers.

LOST IN THE QUEST FOR FLINT: A GRAVETTIAN HUNTING CAMP (USATEGI, BASQUE COUNTRY)

SummaryFive decades ago, Usategi Cave (Basque Country) yielded a small Gravettian series that included an Isturitz‐type bone point. This paper presents the first 14C dates for the assemblage and new data obtained by the study of the lithic raw materials, a high proportion of which came from north of the Pyrenees. The discussion of this new information leads to the hypothesis that the occupants of the cave were a group that travelled from the continental Basque Country across the Pyrenean mountain passes and the Ebro basin to procure flint from the nearest outcrop at Urbasa.

Stratigraphic forward modelling of distributive fluvial systems based on the Huesca System, Ebro Basin, northern Spain

AbstractTo better understand the stratigraphic development of sedimentary systems, it is necessary to link the controls on sedimentary processes to the resulting deposits, which in turn allows predictions of stratigraphic architectures at a range of scales. We use a stratigraphic forward model to link the governing parameters to the distribution of deposits within a distributive fluvial system (DFS). The numerical model has been validated against outcrop observations to establish how the depositional processes needed to form the specific sedimentary system have been reproduced. We chose the previously studied Oligocene to Miocene Huesca DFS in northern Spain to investigate and calibrate the model. Additionally, downstream profiles from modern DFS in northern India, and hydrological measurements from the High Island Creek, Minnesota, USA, were used as input parameters for the model in addition to the outcrop data from the Huesca DFS. The resulting model adequately reproduced the real‐world system. Once validated, the analysis of the modelled DFS led to key findings, which expand our understanding of DFS stratigraphic architecture. Reservoir characteristics in radial DFS are dependent on the angle away from the meridian (straight line from the source through the apex to the distal zone of the DFS). The greater the angle is, the coarser the average grain size in the proximal zone is but the finer the average grain size in the medial and distal zones. Lateral variability of net to gross, sandbody thickness and number, and amalgamation ratio is greatest at the transition between the proximal and medial zone and is still significant in the distal part of the DFS. Stratigraphic forward modelling enhanced our understanding of DFS, which leads to reducing risk associated with exploration, production and storage of fluids in subsurface DFS.

Models of Neolithisation of Northeastern Iberian Peninsula: New Evidence of Human Occupations During the Sixth Millennium cal BC

Abstract The goal of this article is to discuss the significance of the archaeological evidence from the sites of La Draga (Banyoles, Spain) and Coves del Fem (Ulldemolins, Spain), in the context of the neolithisation of Northeastern Iberia. The 14C dates have been analysed using Bayesian statistics. The stratigraphy of Coves del Fem covers the transition between the last hunter–gatherers of the region and the first farmers. The chronological sequence covers approximately 1,300 years, from 6065–5990 cal BC to 4700–4550 cal BC. The site of La Draga was occupied by the first farmers circa 5300–5230 cal BC when a wooden platform was constructed and first used. Subsequent repairs of the wooden piles have been dated as well. Another use of the wooden platform is documented around 5200–5085 cal BC, although until now new construction evidence has not been documented. La Draga site was reoccupied later, when several travertine structures dated in two moments between the years 5100–4900 cal BC and 4950–4700 cal BC were constructed and used. The radiocarbon dates of Coves del Fem and La Draga support the existence of two different models of neolithisation in Northeastern Iberia. In the southern part of the territory, Coves del Fem suggests that the Holocene hunter–gatherer populations remained in the area until the arrival of the first farmers, in a model similar to the one observed at the Ebro basin. On the contrary, the site of La Draga supports the hypothesis of the first farmers colonising a previously unoccupied territory.

A 1400-years flood frequency reconstruction for the Basque country (N Spain): Integrating geological, historical and instrumental datasets

We present the first reconstruction of past flood events variability in the Basque Country and Western Ebro Basin (Northern Spain) integrating instrumental hydrological datasets (last 20 years), documentary archives (last 700 years) and Lake Arreo (655 m a.s.l.) sedimentary paleoflood record (last 1400 years). In this lake, allochthonous coarse and fine detrital layers (CDL and FDL respectively) intercalated within endogenic laminites were identified and interpreted as high- and moderate-energy flood events. The interplay between human activities and hydroclimate variability has controlled the deposition of these flood layers. Gauged data for the last 20 years suggest that floods are typically generated by heavy rainfall events on saturated soils after several days of continuous rainfall. These events occur mostly during the cold season (Oct–May). The reconstructed frequency of high-magnitude flood events from the lake record is coherent with the historical cold-season floods from Basque rivers. The lowest flood frequency took place during the 6–7th and 10–15th centuries, while higher flood frequency occurred during the 8–9th centuries and the last 500 years. Fluvial and lacustrine paleoflood records and documentary evidence show abrupt and large increases in extreme flood frequency during the termination of the Little Ice Age (1830–1870 CE) and mid to late 20th century, both periods of Rapid Climate Change (RCC). The significant increase in flood frequency observed during RCC suggests that a similar pattern could be expected in the near future with the ongoing global warming.

A multi‐scale approach to laminated microbial deposits in non‐marine carbonate environments through examples of the Cenozoic, north‐east Iberian Peninsula, Spain

AbstractThis contribution focusses on stromatolites and oncolites as tools to seek diverse environmental and climate information at different temporal scales. The scales are: (a) Low frequency, dealing with macroscopic and megascopic scales, and (b) high frequency, involving calendar and solar frequency bands. Two depositional environments are used for this purpose: (a) Fluvial and fluvial–lacustrine, which can develop under high to moderate gradients, and in low‐gradient conditions, and (b) lacustrine, subject to low‐gradient, hydrologically closed lake conditions. Several current and ancient examples in the Iberian Peninsula allow high‐frequency and low‐frequency analyses. Within the wedge‐shaped depositional units that fill the high‐ to moderate‐gradient, stepped fluvial systems, stromatolites form half domes and lenticular bodies, commonly at the wedge front. Oncolites are uncommon. These stromatolites developed in moderate to fast‐flowing water in stepped cascades and rapids. Their geometry and extent reflect the topography of the bedrock and later ongoing growth. In low‐gradient fluvial and fluvial‐(open) lacustrine systems the depositional units are tabular, low‐angle wedge‐shaped and lenticular and have great spatial facies variability. The dominant oncoid and coated‐stem limestones form gently lenticular stacked bodies, developed in wide, low to high‐sinuosity channels within wide tufaceous palustrine areas and small lakes. In the Ebro Basin saline carbonate lacustrine systems, stromatolites form thin planar to domed and stratiform bodies and are associated with muddy‐grainy laminated carbonates and very rare oncolites, together forming ramp‐shaped units that represent the inner fringes of high lake‐level deposits. This geometry reflects low‐gradient lake surface and shallow water conditions. Textural and structural features allow different ranks of laminae and types of lamination to be distinguished. Texture, together with the δ13C and δ18O values of consecutive laminae, are useful in distinguishing environmental and climate changes operating over different time spans. Periodicity analysis of lamination can help to discern any temporal significance in the lamination.

Interactions between fluvial dynamics and scarp retreat in the Central Ebro Basin during MCA and LIA periods: Palaeogeographical and geoarchaeological reconstruction

The scarp of Remolinos-Juslibol is an abrupt relief formed by Miocene gypsums located on the left bank of the Ebro River, in the vicinity of the city of Zaragoza. This work provides data for the reconstruction of the channel morphology and dynamics of the Ebro River and its interaction with the gypsum scarp from the Little Ice Age (LIA) to the present day. At the same time, several scenarios are also proposed for this interaction during the MCA (Medieval Climate Anomaly). To do this, different proxies are used, such as historical maps and records, morphosedimentary records of the tributary ephemeral streams, data from paleofloods, and the evolution of Medieval castles built on the scarp. During the MCA, the river was centered on its floodplain. Large alluvial fans developed by lateral ephemeral streams coming from the north since at least the Chalcolitic-Bronze age continued with their dominant dynamics during the Medieval times. Interaction with the scarp was scarce during this period and this allowed the building of castles on this relief. Later, the Ebro River moved its meanders towards the scarp, eroding most part of the lateral alluvial fans; in addition, infilled valleys were left hanging by the rapid retreat of the scarp and the events of rockfalls and landslides were very active. The map of Dew Rodolphe (1746) and the dating of these events confirm that this erosive process developed mainly during the second part of the LIA (18–19th centuries). From the middle of the 19th century, the fluvial sinuosity of the Ebro River increased and progressively separated from the scarp, which evolved to the present relative stability, in which landslides and rockfalls are scarce.

The freshwater and terrestrial turtles from Monte Pila and Fuenmayor (La Rioja, northern Spain): new data on the lower Miocene turtle diversity of the Ebro Basin

Abundant turtle fossils from two lower Miocene localities in which this lineage had not previously been studied are described herein. The localities are Monte Pila and Fuenmayor, which are 10 km apart, both located in the Autonomous Community of La Rioja (northern Spain), in the Ebro Basin. Information about the turtles from the lower Miocene levels in this basin was until now restricted to the finds made in the MN3 biozone of the Bardenas Reales of Navarre. Several turtle taxa had been recognized there. However, the material attributed to each of them was scarce. Monte Pila and Fuenmayor are located in biozone MN2. The remains of turtles are abundant in both sites. A terrestrial lineage, recognized at Monte Pila, is not represented in the Bardenas Reales fauna of Navarre. It represents the first record of TitanochelonPérez-García & Vlachos, 2014 in La Rioja and is one of the oldest member of this genus, being assigned to Titanochelon cf. bolivari (Hernández-Pacheco, 1917). The only lineage of turtles identified in Fuenmayor, and the most abundant in Monte Pila, is Ptychogasterinae. All material of this clade of freshwater turtles identified there is compatible with a single form, for which a high range of intraspecific variability is recognized. It is attributed to Ptychogaster (Temnoclemmys) cf. bardenensis Murelaga, Lapparent de Broin, Pereda Suberbiola & Astibia, 1999, this species having been recognized, until now, as exclusive to the Bardenas Reales of Navarre.

Quantifying Downstream, Vertical and Lateral Variation in Fluvial Deposits: Implications From the Huesca Distributive Fluvial System

Quantifying sedimentary deposits is crucial to fully test generic trends cited within facies models. To date, few studies have quantified downstream trends alongside vertical and lateral variations within distributive fluvial systems (DFS), with most studies reporting qualitative trends. This study reports on the generation of a quantitative dataset on the Huesca DFS, Ebro Basin, Spain, in which downstream, vertical and lateral trends in channel characteristics are analyzed using a fusion of field data and virtual outcrop model derived data (VOM). Vertical trend analysis reveals that the exposed portion of the Huesca DFS does not show any systematic changes through time, which suggests autogenic-driven local variability. Proximal-to-distal trends from field data display a downstream decrease in average channel body thicknesses (13.1–0.7 m), channel deposit percentage (70–4%), and average storey thicknesses (5.2–0.7 m) and confirm trends observed on other DFS. The VOM dataset shows a similar downstream trend in all characteristics. The range in values are, however, larger due to the increase in amount of data that can be collected, and trends are thus less clear. This study therefore highlights that standard field techniques do not capture the variability that can be present in outcrops. Channel percentage was found to be most variable (37% variation) in the medial setting, whereas channel body thickness is most variable (∼15 m range) in the proximal setting. Storey thickness varied in both the proximal and medial settings (range of 9 and 11 m for field and VOM data respectively) becoming more consistent downstream. Downstream shifts in architecture are also noted from massive, highly amalgamated channel-body sandstones in proximal regions to isolated or offset-stacked channel-bodies dominating the distal region. Trends are explained by spatial variability in DFS processes and preservation potential. The overlap present indicates that no single value is representative of position within a DFS, which has important implications for interpreting the location that a data point sits within a DFS when using limited (i.e., single log) datasets. These comparative results contribute to improving the accuracy of system-scale downstream predictions for channel characteristic variability within subsurface deposits.

Miocene to present-day tectonic control on the relief of the Duero and Ebro basins confluence (North Iberia)

ABSTRACT This article presents a morpho-structural map at 1:50,000 scale of the confluence area between three regional units: (1) the Burgalesa Platform (Mesozoic; Cantabrian Mountains), (2) the Duero Basin and (3) the Ebro Basin (Cenozoic foreland basins). The map covers an area of 527 km2 in north Iberia. Additionally, structural lineaments such as joints are well preserved and documented in the Upper Cretaceous sediments of the Burgalesa Platform, represented by four main sets regarding their orientation. The foreland basins are incised in Miocene materials by rivers that have developed a complex drainage system controlling the deposition of the most recent alluvial sediments, following the four structural orientations. The map, together with the analysis of orthophotos and a Digital Terrain Model, and outcrop-scale observations, have led us to document the influence of the Miocene to present-day compression and strike-slip tectonic regime on the configuration of the drainage system and the geomorphological features.

Late Pliocene-Pleistocene incision in the Ebro Basin (North Spain)

The Ebro Basin constitutes the central part of the southern foreland of the Pyrenees. It was endorheic during the Cenozoic and accumulated sediments. By the end of the Miocene, erosion and river incision reconnected the basin to the Mediterranean Sea, establishing a post-opening drainage network. Those rivers left terraces that we study in this work. We first synthesize previous works on river terraces that are widely dispersed in the basin. We provide new age constraints, up to 3 Ma, obtained thanks to cosmogenic nuclides using both profile and burial methods. We derive a unified fluvial terrace chronology and a homogenized map of the highest terraces over the entire Ebro Basin. The dated terraces labeled A, B, C, D, and E are dated to 2.8 ± 0.7 Ma, 1.15 ± 0.15 Ma, 850 ± 70 ka, 650 ± 130 ka, and 400 ± 120 ka, respectively. The chronology proposed here is similar to other sequences of river terraces dated in the Iberian Peninsula, around the Pyrenees, and elsewhere in Europe. The oldest terraces (A, B, C) are extensive, indicating they form a mobile fluvial network while from D to present, the network was stable and entrenched in 100 to 200 m-deep valleys. The transition from mobile to fixed fluvial network is likely to have occurred during the Middle Pleistocene Transition (MPT, between 0.7 and 1.3 Ma), when long-period/high-intensity climate fluctuations were established in Europe. We estimate that between 2.8–1.15 Ma and present, the incision rates have tripled.