Barranco De Research Articles

Li enrichment in peridotites and chromitites tracks mantle-crust interaction

The ultramafic massifs of the Serranía de Ronda in southern Spain are the Earth's largest exposures of subcontinental lithospheric mantle (SCLM) peridotites (∼450 km2). These ultramafic massifs experienced asthenosphere melt percolation during their crustal emplacement. Mixing of these mafic melts with anatectic melts and fluids led to the formation of a world's unique Ni-arsenide-rich chromitite ores (hereafter CrNi ores) associated with orthopyroxenite and/or cordieritite (i.e., > 90 % volume of cordierite) hosted within the peridotites. This study uses laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to investigate the Li in rock-forming minerals of peridotite and CrNi ores to evaluate the role of Li as crustal tracer. Clinopyroxene crystallized from asthenospheric melts exhibits high Li contents (up to 8.5 ppm), exceeding the average values of the upper mantle (∼ 0.7 ppm), whereas orthopyroxene, olivine, and Cr-spinel from peridotite are mostly Li-depleted. In contrast, all rock-forming minerals of CrNi ores have abnormally high Li contents, displaying an overall Li enrichment trend toward the external parts of ultramafic massifs, on the way to the crustal rocks. This trend is evident in Cr-spinel from the CrNi ores, which display 6.9–7.9 ppm Li in the deepest portions of the massif (Arroyo de la Cala CrNi ore) up to 1.4–8.5 ppm in the shallowest part (La Gallega CrNi ore), as well as in orthopyroxenes that have 31.3–44.7 ppm Li in Arroyo de la Cala, and 45.1–51.4 ppm Li in La Gallega. Cordierite is present only in the CrNi ores situated in the external part of the ultramafic massifs, exhibiting 113.15–160.82 ppm Li in the Barranco de las Acedías CrNi ore and 36.5–60.5 ppm Li in La Gallega CrNi ore. Similarly to Li, LREE, fluid-mobile elements (K, Rb, Ba), and Sr in orthopyroxenes from the CrNi ores display enrichment from the inner to the outer parts of the ultramafic massif. These geochemical variations suggest that Li enrichment in CrNi ores and host peridotites was a twofold process: (1) asthenospheric melt percolation slightly increased Li abundances in the SCLM peridotites by modal and cryptic metasomatism involving clinopyroxene; (2) additional infiltration of Li-bearing crustally-derived fluids during the intracrustal emplacement of the mantle section boosted the Li contents of minerals in the CrNi ores. Our results highlight that Li may effectively track the interaction of the SCLM with crustal components.

The need to calibrate the surface hydrological model of Tenerife in the face of adverse meteorological phenomena such as the one that occurred on February 1, 2010, which produced heavy runoffs in Bco. de Santos.

The watershed of the Barranco de Santos is one of the largest on the island of Tenerife. The riverbed has its source at an altitude of 945 metres above sea level, on the Las Mercedes mountain, and flows through the Vega de La Laguna, descending towards the sea, bordering the Anaga mountains to the southwest and finally flowing into the Los Llanos dock in the port of Santa Cruz de Tenerife. Its route of more than 16 km has stretches where it becomes a real canyon, with cliff walls on its banks up to a hundred metres high. The average rainfall on the island of Tenerife is generally not very high, which means that the riverbed does not normally flow except in torrential episodes, which can cause unforeseen flooding, causing great material damage and even personal injury.\nDespite the large size of this basin, there are no flow gauges with which to estimate discharge volumes. This is mainly due to the fact that the episodes that produce runoff in the channel are usually sporadic and torrential. This document analyses the adverse phenomenon that occurred on 1 February 2010 and which gave rise to heavy runoff in the Barranco de Santos basin.

Obsidian hydration dating helps understand pre-hispanic land use on the volcanic island of Tenerife, Canary Islands, Spain

Critical to the survival of island-based human societies is their resilience and adaptation to volcanic hazards. We here evaluate pre-Hispanic (before 15th century AD) land use patterns on the volcanic island of Tenerife, Canary Islands, Spain using obsidian hydration dating (OHD). The samples studied include archaeological artifacts and natural rock chips from multiple sites of different elevation and micro-climate settings. We systematically collected samples from the southern dry area around Barranco de las Monjas in the Bandas del Sur. These include a total of 28 isolated artifact scatters (here, a scatter is defined as a minimum spatial unit of artifacts distributed spatially limited range on the surveyed surface), one dwelling, and several pyroclastic deposits containing obsidian clasts. We also collected several artifacts adjacent to a large obsidian flow of Tabonal Negro in the Las Cañadas Caldera. Unsystematic surveys in north of Mt. Teide identified large obsidian outcrops located at Tabonal de los Guanches and Charco del Viento. Size differences among surface-derived obsidian artifacts (i.e., Bandas del Sur, Las Cañadas Caldera, Icod Valley) suggest that pre-Hispanic groups utilized obsidian from multiple outcrops over wide areas. Hydration analysis on 136 obsidian flakes collected from both surface and buried contexts showed only minor obsidian hydration rims (5% of total samples) and varied mean rim thicknesses (0.6–3.5μ). The low percentage of hydration rim formation may be caused by environmental factors such as wind erosion, thermal effects from volcanic or natural ground fires, or due to obsidian geochemistry (low SiO2 and water content of phonolitic obsidian). Surface-collected obsidian flakes from the southern dry area do contain hydration rims along internal fissure. The estimated hydration rates from these samples can provide an approximate age when compared to buried obsidian artifacts with associated radiocarbon dates.

Can material of a putatively extinct new species of Ruta (Rutaceae), preserved with mummies, provide new knowledge about evolution in the Canary Islands flora?

Based on analyses carried out with plant material found in mummy shrouds preserved in the archaeological museum El Museo Canario, a putatively extinct new species of Ruta (Rutaceae) was identified and is described here as R. museocanariensis. The mummies were found in the funerary sites of Acusa and the Barranco de Guayadeque on Gran Canaria, Canary Islands, Spain. This article discusses taxonomic relationships with other species of the genus, aspects of colonization and evolutionary processes on islands. The archaeological plant material consists of vegetative and reproductive branches with leaves, remains of flowers and capsules. Several morphological traits, especially the type of fruits, establish a clear difference between Ruta species from Gran Canaria and the mainland (dehiscent) and species from the W Canary Islands (indehiscent). The discovery of R. museocanariensis, with dehiscent fruits, suggests that indehiscence is a post-colonization evolutionary process in the Canary Islands. It also supports a stepping-stone model of inter-island colonization with Gran Canaria as its starting point, in agreement with the age of the islands and to some extent with their distance from the mainland. Citation: Marrero-Rodríguez Á., Vidal-Matutano P., Delgado-Darias T., Jaén-Molina R., Morales-Mateos J., Alberto-Barroso V. & Velasco-Vázquez J. 2023: Can material of a putatively extinct new species of Ruta (Rutaceae) preserved with mummies provide new knowledge about evolution in the Canary Islands flora? – Willdenowia 53: 5–23. Version of record first published online on 7 February 2023 ahead of inclusion in April 2023 issue.

The Others of the Ravine

Abstract In the society and culture of the Canary Islands, ravines (barrancos in Spanish) are spaces that contain a wealth of meanings and perceptions attached to a collective imagination. These natural scars that mark and characterize the island's geography represent scenes of dissidence, as will be shown through the spatial and geographic stories of various transsexuals and transvestites who lived in Tenerife between 1970 and 1990; the specific character of their testimonials is situated in a specific context: El Cabo, a barrio in Tenerife, as well as the Santos Ravine (Barranco de Santos in Spanish). The state repression, marginalization, and violence against sexually dissident people during this age will be the main context of analysis. In a brief journey through history, these aspects will be placed in relation to key events from the Francoist dictatorship on the islands, a travel journal of the nineteenth century, and passages from the conquest of the Canary Islands in which the ravines, among them the Santos Ravine itself, take on a relevant importance. Finally, this study will mention the existence of a chapel consecrated to the Virgin of Candelaria in this environment as possibly the most significant crystallization of the otherness of the ravine. This study thereby contemplates reviewing these spaces on the basis of their formation as media in which specific Canary Island subjectivities can be located.

Upper Hauterivian nautiloids and associated invertebrate assemblage from the Barranco de la Muela section (southeastern Spain): Systematic, biostratigraphic and palaeoenvironmental implications

The lower part of the Lower Cretaceous Bolos Sandstone Formation as exposed in the Barranco de la Muela section (Sierra de la Muela Range, southeastern Spain) yields two species of ornamented nautiloids, Cymatoceras neocomiense and Eucymatoceras plicatum. These have been collected together with other cephalopods (ammonoids, belemnites) and different invertebrates (corals, brachiopods, bivalves, gastropods, echinoids). This fossil assemblage includes numerous large macroconchs of the ammonite Pseudothurmannia mortilleti, here considered as a senior synonym of P. catulloi, index species of the homonymous subzone of the upper Hauterivian “Pseudothurmannia ohmi” Zone. On this basis, the here reported findings constitute the first biostratigraphically well-constrained records of C. neocomiense and E. plicatum, namely in the Pseudothurmannia catulloi Subzone. The presence of these two ornamented and relatively depressed nautiloids in fine sandstone levels interbedded with sandy marls of the Bolos Formation, together with the palaeoecological characteristics of the associated fauna suggest a nearshore to inner-middle shelf, shallow to moderately deep palaeoenvironment with mixed siliciclastic-carbonate sedimentation, and high to moderate energy.

Mercury levels in a sample of the population in Southern Bolívar - Colombia at risk of environmental exposure

BACKGROUND AND AIM: Mercury contamination is a relevant problem today, due to the toxic effects it can have, ranging from cancer to nervous system disorders. Artisanal gold mining is an important source of mercury, due to the vapors from the process and the discharge into soils and bodies of water, reaching other trophic chains, biomagnifying and affecting humans METHODS: This research aimed to determine the serum levels of total mercury and methylmercury in a population under 18 years of age in the south of Bolivar in municipalities such as Barranco de Loba, Pueblo Mejia and Mina Azul in the Department of Bolivar - Colombia As a sampling technique, the protocol for collecting DBS (Dried Blood Spots in 19 inhabitants was implemented and static analysis was performed. RESULTS:The results showed methylmercury levels of 0.490–11.616 mcg/L, inorganic mercury of 0.302–7.120 mcg/L and total mercury of 1.844–13.772 mcg/L, values above the reference data (United States Environmental Protection Agency). In addition, a strong association was found between age, proximity to the river and total mercury concentrations. CONCLUSIONS:Note that these are preliminary studies, however, they alert future consequences that may be presented by the population vulnerable to this type of contamination. KEYWORDS: Heavy metals, Water quality, Exposures, Cancer and cancer precursors

Rainfall and water yield in Macizo del Caroig, Eastern Iberian Peninsula. Event runoff at plot scale during a rare flash flood at the Barranco de Benacancil

Floods are a consequence of extreme rainfall events. Although surface runoff generation is the origin of discharge, flood research usually focuses on lowlands where the impact is higher. Runoff and sediment delivery at slope and pedon scale receiving much less attention in the effort to understand flood behaviour in time and space. This is especially relevant in areas where, due to climatic and hydrogeological conditions, streams are ephemeral, so-called dry rivers (“wadis”, "ramblas" or “barrancos”) that are widespread throughout the Mediterranean. This paper researches the relationship between water delivery at pedon and slope scale with dry river floods in Macizo del Caroig, Eastern Iberian Peninsula. Plots of 1x1, 1x2, 1x4, and 2x8 m located in the “El Teularet” Soil Erosion and Degradation Research Station were monitored from 2004 to 2014 to measure soil and water delivery. Rainfall and flow at the dry river Barranco de Benacancil were also monitored. Results show that runoff and sediment discharge were concentrated in few events during the 11 years of research. A single flood event was registered in the channel on September 28, 2009, however, the runoff was registered 160 times at the plots. Runoff discharge was dependent on the size of the plots, with larger plots yielding lower runoff discharge per unit area, suggesting short runoff-travel distance and duration. Three rainfall events contributed with 26% of the whole runoff discharge, and five achieved 56% of the runoff. We conclude that the runoff generated at the plot scale is disconnected from the main channel. From a spatial point of view, there is a decrease in runoff coefficient along the slope. From a temporal point of view, the runoff is concentrated in a few rainfall events. These results show that the runoff generated at plot and slope scale does not contribute to the floods except for rainfall events with more than 100 mm day-1. The disconnection of the runoff and sediment delivery is confirmed by the reduction in the runoff delivery at plot scale due to the control of the length of the plot (slope) on the runoff and sediment delivery.

Dried blood spots to characterize mercury speciation and exposure in a Colombian artisanal and small-scale gold mining community

The artisanal and small-scale gold mining (ASGM) sector uses the most mercury (Hg) worldwide. Despite health concerns associated with high Hg exposures in these communities, ASGM sites are often situated in resource limited and remote regions which challenge traditional human biomonitoring approaches. To help overcome such challenges, here we report on the development of a high-quality method to characterize chemical speciation of Hg in dried blood spots (DBS), and then apply this method to assess Hg exposures in people sampled from an ASGM community (Pueblito Mejia) and a nearby town (Barranco de Loba) in Colombia. We collected DBS and urine samples from 35 individuals in 2018, and used these to assess occupational (DBS inorganic Hg (InHg) and urine total Hg (THg) measures) and environmental (DBS methylmercury (MeHg) measures) exposure of participants to different forms of Hg. The accuracy and precision of the DBS-based measures generally met assay performance guideline. In study participants, the mean concentrations of DBS MeHg, InHg, and THg, and urine THg were 1.9, 4.1, 6.0, and 3.1 μg/L, respectively. For 37% of the participants, DBS THg values exceeded the 5 μg/L ‘alert level’ proposed by the German HBM Commission. About 60% of the blood Hg was in the InHg form thus exemplifying a need to speciate Hg in blood sampled from ASGM sites to better understand the contributions of environmental and occupational exposure sources. This study demonstrates the feasibility of using DBS for Hg speciation exposure assessments in remote and resource-limited areas such as ASGM communities.

Syndepositional tectonics and mass-transport deposits control channelized, bathymetrically complex deep-water systems (Aínsa depocenter, Spain)

ABSTRACTThe inception and evolution of channels in deep-water systems is controlled by the axial gradient and lateral confinement experienced by their formative flows. These parameters are often shaped by the action of tectonic structures and/or the emplacement of mass-transport deposits (MTDs). The Arro turbidite system (Aínsa depocenter, Spanish Pyrenees) is an ancient example of a deep-water channelized system from a bathymetrically complex basin, deposited in an active tectonic setting. Sedimentologic fieldwork and geologic mapping of the Arro system has been undertaken to provide context for a detailed study of three of the best-exposed outcrops: Sierra de Soto Gully, Barranco de la Caxigosa, and Muro de Bellos. These locations exemplify the role of confinement in controlling the facies and architecture in the system. Sedimentologic characterization of the deposits has allowed the identification of fifteen facies and eight facies associations; these form a continuum and are non-unique to any depositional environment. However, architectural characterization allowed the grouping of facies associations into four depositional elements: i) weakly confined, increasing-to-decreasing energy deposits; ii) progradational, weakly confined to overbank deposits; iii) alternations of MTDs and turbidites; iv) channel fills. Different styles of channel architecture are observed. In Barranco de la Caxigosa, a master surface which was cut and subsequently filled hosts three channel stories with erosional bases; channelization was enhanced by quasi-instantaneous imposition of lateral confinement by the emplacement of MTDs. In Muro de Bellos, the inception of partially levee-confined channel stories was enhanced by progressive narrowing of the depositional fairway by tectonic structures, which also controlled their migration. Results of this study suggest that deep-water channelization in active tectonic settings may be enhanced or hindered due to: 1) flow interaction with MTD-margin topography or; 2) MTD-top topography; 3) differential compaction of MTDs and/or sediment being loaded into MTDs; 4) formation of megascours by erosive MTDs; 5) basin-floor topography being reset by MTDs. Therefore, the Arro system can be used as an analog for ancient subsurface or outcrop of channelized deposits in bathymetrically complex basins, or as an ancient record of deposits left by flow types observed in modern confined systems.

Ecology and distribution patterns of Chara connivens (Charophyta, Characeae) on the Canary Islands – the first record from Fuerteventura

Abstract The paper presents the first record of a Chara connivens (Characeae) stand from Fuerteventura (Canary Islands, Spain). The species was previously recorded only on Tenerife and Lanzarote, mostly in marine and artificial habitats. Physicochemical parameters of water and morphological features of the thalli and plant community were analyzed. General habitat requirements of C. connivens populations located in Europe, North Africa, and South-West Asia were reviewed. The newly described stand was located in a natural rock crevice that was part of a riverbed in El Barranco de las Peñitas (Penitas Canyon). This habitat was unshaded and filled with brackish water. C. connivens co-occurred with Cladophora glomerata and Ruppia maritima. Our report on the presence of C. connivens in the Spanish territory of the Atlantic Ocean is the first in almost 40 years. The distribution of C. connivens and its plant associations on the Canary Archipelago are poorly explored, which is why this topic requires further research.

The Macrocoma Chapuis from the Canary Islands, with description of a new species (Coleoptera Chrysomelidae Eumolpinae)

The known species of Macrocoma from the Canary Islands are reviewed and the aedeagi illustrated. Macrocoma pelikani n. sp. is described from Gran Canaria, Barranco de Guayadeque. M. franzi Palm, 1976 is downgraded to subspecies of M. splendidula (Wollaston, 1862) and the following nomenclatural changes are proposed: M. splendidula ssp. franzi Palm, 1976 n. stat., M. splendidula ssp. palmaensis Palm, 1977 n. stat. a key to species identification and a catalogue with new locality data are also provided.

Orcemys, a new genus of arvicolid rodent from the early Pleistocene of the Guadix–Baza Basin, southern Spain

A new arhizodont arvicoline rodent is described from early Pleistocene deposits of Barranco de los Conejos and Barranco del Paso in the Guadix–Baza Basin of southern Spain. The molars of Orcemys appear to represent a paedomorphic origination from a large rhizodont Mimomys. A few dental characters of Orcemys are superficially similar to those of the lagurines, but the presence of sparse cementum in reentrant folds and a Mimomys-kante formed opposite T5 on the first lower molar clearly identify Orcemys as an arvicoline. The character mosaic of Orcemys is unique among large early Pleistocene voles and the dentition of a potential ancestor probably resembled that of Mimomys medasensis with a tendency towards simplification. With Tibericola vandermeuleni and Mimomys oswaldoreigi, Orcemys represents one of the earliest experiments with arhizodonty among European voles. Including Mimomys medasensis at Barranco del Paso, this set of arvicolids redefines a previously recognized early Pleistocene MmQ1 biozone in Spain.

Alicante Beach- City Sustainable Development

Our research is focused on the city of Alicante (Spain). In concrete, the sunken area studied is placed at the south of Alicante Port, being the point of entry from the airport to the city. There are two important reasons that have generated that depressed area. Firstly, the development of the city has led to a change in the use of the soil, and secondly, the extension of Alicante Port. This area used to be a metallurgical industrial zone, but during the last 40 years, it has overcome an urban growth. The European Office for Harmonization in the Internal Market (OHIM), the most modern Film Studio in Europe ‘Ciudad de la luz’, a desalination plant and residential complexes and offices have settled down there. Unfortu nately, all this development has occurred without taking into account the coastal needs. Regarding to that, several elements that contribute to the deterioration of the area can be found along the coast, that is the mouth of a rift called ‘Barranco de las Ovejas’ at north, the ‘Agua Amarga’ rift at south and the desalination sewage pipe. Besides, there is a merchandise train line adjoining the Maritime-Terrestrial Public Domain that provides service to the port, but hinders the way for pedestrians going to the beach.

Paleoecological quantitative analysis based on benthic foraminifera of the Aalenian–Bajocian boundary (upper Bradfordensis–lower Discites) in the Barranco de Agua Larga section (Betic Cordillera, Southern Spain)

To report, for the first time, the benthic foraminiferal assemblages recorded across the upper Bradfordensis–lower Discites ammonite zones (Aalenian–Bajocian boundary, Middle Jurassic) in the Barranco de Agua Larga section (Betic Cordillera, Southern Spain),in order to infer the paleecological conditions that affected their development. A total of 17 samples were collected in this reference section, and the composition of the foraminiferal assemblages recorded throughout the studied stratigraphical was analyzed using quantitative data obtained through the estimation of relative abundances and the calculation of several diversity indexes. The assemblages are abundant (a total of 3, 139 well-preserved specimens) and diverse(82 species). Their composition displays close similarities to those already described for the Jurassic carbonate platforms of the Boreal Realm (Type-A), Boreal Atlantic subdivision. The studied assemblages were developed in distal marine environmental conditions, at a depth situated above the level of the calcite compensation, well oxygenated and with normal salinity, although for certain times (Aalenian–Bajocian boundary) unfavorable environmental conditions could have developed. The sharp decrease in the abundance and diversity that was recorded during the Aalenian–Bajocian transition has also been recognized in other coeval basins of the Iberian Plate paleomargin, thus representing a bioevent of regional rank.

Pes shape variation in an ornithopod dinosaur trackway (Lower Cretaceous, NW Spain): New evidence of an antalgic gait in the fossil track record

Trackways can provide unique insight to animals locomotion through quantitative analysis of variation in track morphology. Long trackways additionally permit the study of trackmaker foot anatomy, providing more insight on limb kinematics. In this paper we have restudied the extensive tracksite at Barranco de La Canal-1 (Lower Cretaceous, La Rioja, NW Spain) focussing on a 25-m-long dinosaur (ornithopod) trackway that was noted by an earlier study (Casanovas et al., 1995; Pérez-Lorente, 2003) to display an irregular pace pattern. This asymmetric gait has been quantified and photogrammetric models undertaken for each track, thus revealing distinct differences between the right and the left tracks, particularly in the relative position of the lateral digits II–IV with respect to the central digit III. Given that the substrate at this site is homogenous, the consistent repetition of the collected morphological data suggests that differences recorded between the right and the left tracks can be linked to the foot anatomy, but more interestingly, to an injury or pathology on left digit II. We suggest that the abnormal condition registered in digit II impression of the left pes can be linked to the statistically significant limping behaviour of the trackmaker. Furthermore, the abnormal condition registered did not affect the dinosaur's speed.

Analysis of Behaviour of Phase S Capacitive Tap Insulator of Interconnection 1,220 kV, in Jinamar Power Plant (Island of Gran Canaria, Canary Islands, Spain)

In the island of Gran Canaria, Canary Islands, there are two Power Plants called Jinamar Power Plant and Barranco de Tirajana Power Plant, both property of Unelco Generacion, a subsidiary of Endesa Generacion. The first one is placed in the northeast of the island, near its capital, Las Palmas de Gran Canaria, and the other is in the southeast, near the most significant touristic area of the island. Both plants are interconnected by means of four transmission lines, two with a voltage of 220 kV and the other two with 66 kV. Since its commissioning in 1995, several phase to ground shortcircuits have occurred in one of the capacitive tap insulators in the 220 kV lines, in Jinamar side, without a clear cause for them, causing problems of different kind in the electrical system of Gran Canaria. From construction of tap insulators to environmental conditions, every possible factor was carefully studied and laboratory tests were made. In this paper it is described the analysis that was carried out and how a deep study of every possible cause drove to a definitive solution of the problem.

Contribution à la paléolimnologie du Plio-Pléistocène du bassin de Baza (SE Espagne) à partir de l’étude des diatomées

Several outcrops with diatoms have been identified in the Neogene-Quaternary Baza basin. The most relevant two are located in the NE margin, in different lithostratigraphic units. Their diatom flora is dominated by Epithemia adnata and Epithemia turgida, a littoral epiphytic aquatic plants. These diatom assemblages are typical of fresh to slightly brackish waters in shallow and alkaline lakes. Those two diatomitic deposits are interstratified between alluvial sediments and represent permanent shallow lakes developed during two wet periods of time. Barranco de las Lumbres is the oldest of these lake events and is dated by fauna and paleomagnetism as late Miocene (Turolian). The upper beds of the younger lake episode (Rincon de la Losa) is dated by paleomagnetism and mammals at 1.9 Ma. In addition to these marginal diatomitic deposits, other outcrops with diatoms have been identified in more central areas of the Basin in Galera village, the lower part of Barranco del Agua section is composed of gypsum, carbonates and dark-brown clays and marls. Here epiphytic shallow-water diatoms Epithemia adnata, Epithemia turgida and some planktonic littoral forms (Fragilaria sp.) suggest a shallow fresh to oligosaline water environment. Additional diatomaceous deposits were located in a more evaporitic zone of the basin near the town of Castillejar. This outcrop presents species (Navicula digitoradiata and Surirella ovalis), which indicate distinctive more saline waters and environment. The distribution of the diatom flora in the Baza basin is consistent with stratigraphic data, which indicates an increase of evaporitic facies towards the center of the basin and the occurrence of different kinds of waters within the lake system. The isotopic composition (δ34S, δ18O) of the gypsum samples of Baza basin (Gibert et al.,2007a) is consistent with a Triassic origin of the sulphate as a result of chemical recycling. These data also suggest that a similar recycling mechanism operated in the saline lake system, where the gypsum sediments from the margins were coevally recycled towards the inner part.

Stable carbon-isotope stratigraphy and ammonite biochronology at Madotz, Navarra, northern Spain: implications for the timing and duration of oxygen depletion during OAE-1a

Detailed stable carbon-isotope and biostratigraphic data based on ammonites allow us to reinterpret the timing of the different units of the Madotz section (62 m thick) in Navarra, northern Spain, relative to OAE-1a. We also infer bulk sedimentary rates and the duration of the intervals that include facies indicative of oxygen depletion. The lowermost part of the sequence includes the predominately clastic unit 1 (3 m) overlain in ascending order by subunits 2a (20 m), 2b (24.4 m) and 2c (basal 15 m studied) of the “Madotz Limestone”. Subunits 2a and 2c consist of Urgonian-type pure carbonate rocks. In contrast, subunit 2b consists of mixed carbonate–clastic facies (24.4 m thick) including beds of claystone and clay/shale with dispersed pyrite and scarce or no benthic foraminifera suggestive of oxygen-depleted conditions, and intermittent orbitolinid-rich intervals. δ13Corg data within subunit 2b, between 26.6 and 49.2 m show two excursions of 4.21 and 3.34‰, separated by a central segment with more uniform values around 22.56%. Compared to the high-resolution δ13C stratigraphy of the Early Aptian of the Alpine Tethys, these two positive excursions correlate with segments C4 and C6 of OAE-1a, whereas the central segment correlates with segment C5. New ammonite findings include Deshayesites cf. forbesi Casey and Pseudohaploceras? sp. in the uppermost part of unit 1, and D. cf. forbesi Casey, Pseudosaynella bicurvata (Michelin) and P. raresulcata (d'Orbigny) in the middle part of subunit 2b. The presence of D. cf. forbesi in unit 1 (0–37.7 m) and subunit 2b (lower 14.7 m), the first appearance datum of Pseudosaynella in subunit 2b, and the high relative abundance of Pseudosaynella specimens, support a stratigraphic position correlative with at least the upper part of the D. forbesi Zone (formerly D. weissi Zone). Such an ammonite faunal assemblage implies a lower stratigraphic position in the Lower Aptian (Bedoulian) than previously assigned to the section. Segments C4 and most of C5 comprise the lower part of subunit 2b and correspond to the upper part of the D. forbesi Zone. Based on chemostratigraphic correlations with published Spanish sections (Barranco de las Calzadas, Cap de Vinyet and Cau) in which calibrations of δ13Ccarb stages with ammonite zones was possible, we infer that the interval of the Madotz section between 37.7 and 53.1 m, or the upper part of subunit 2b and the basal part of subunit 2c, whose δ13Corg signal is indicative of stages C5, C6, and perhaps the beginning of stage C7, also correlates with the D. forbesi Zone. Average bulk sedimentation rate for C-isotope stages C4–C6 of OAE-1a ranges from 1.8 to 2.09 cm/kyr in the Madotz section. Facies indicative of oxygen deficiency are restricted to C-isotope stage C4 and part of C5 of OAE-1a. Hypoxic conditions lasted about 95.23–120 kyr and are coeval with deposition of the most prominent claystone and shale layers (1.8 m thick), which display the lowest TIC values (8.16–18.93 weight% CaCO3) and the highest TOC in the section (0.4–0.97%).

Mesorhizobial strains nodulating Anagyris latifolia and Lotus berthelotii in Tamadaya ravine (Tenerife, Canary Islands) are two symbiovars of the same species, Mesorhizobium tamadayense sp. nov.

Barranco de Tamadaya is a deep ravine located in southern Tenerife, which is included within a protected area where several endemic plants grow. Among them, two legumes are catalogued as critically endangered, Anagyris latifolia and Lotus berthelotii. Rhizobial strains isolated from their root nodules grown in soil samples from this ravine harboured symbiotic genes belonging to two distant symbiovars, but they shared identical 16S rRNA gene sequences (rrs). The phylogeny based on the rrs sequences placed these isolates in a separate subbranch that did not include any of the currently recognised Mesorhizobium species, but the resolution of the ribosomal tree did not permit further taxonomic conclusions. Nevertheless, multilocus sequence analysis (MLSA) of four housekeeping genes (atpD, recA, glnII and dnaK) and the rrs gene generated a highly supported Bayesian phylogeny, identifying these isolates as a new Mesorhizobium lineage. DNA–DNA hybridisation homology percentages were lower than 30% compared to type strains of the closest related species, and supported the phylogenetic data. Phenotypic characterisation also distinguished this lineage from the other closest Mesorhizobium species. The polyphasic approach thus confirmed that the isolates represented a novel species for which we propose the name Mesorhizobium tamadayense sp. nov. The type strain is Ala-3T (CECT 8040T, LMG 26736T).