Coupling textural and stable-isotope variations in fluvial stromatolites: Comparison of Pleistocene and recent records in NE Spain

Textural and stable isotopic features of two middle Pleistocene fluvial stromatolite profiles are compared to a recent stromatolite, both formed in the River Piedra system (NE Spain), to test the reliability of climatic, hydrologic and depositional information derived from ancient records. The Pleistocene stromatolites formed in a multi-domed, highly-inclined cascade-barrage. The recent stromatolite also formed in a highly-inclined cascade of the River Piedra, the sedimentary conditions of which were periodically examined between the years 2000 and 2012. The Pleistocene stromatolites are formed of an alternation of 1) thin large-crystal laminae (type A), with elongated crystals up to 1 mm long, and 2) thick small-crystal laminae (type B), consisting of cyanobacterial fan- and bush-shaped bodies. The textural and isotopic comparison with the recent stromatolite shows that each A–B couplet corresponds to one year. The type-A laminae are comparable to the macrocrystalline laminae that occur in the cool-period deposits of the recent stromatolite, and the type-B laminae are comparable to the warm-period deposits of the recent stromatolite. Water temperatures (Tw), calculated from d 18 O calcite and present measures of d 18 O water , were similar in the Pleistocene and recent specimens, and close to the measured river Tw. Thus, the Pleistocene stromatolites formed not far from isotopic equilibrium, as did the recent stromatolite. The Pleistocene d 18 O calcite biannual oscillation is wider in amplitude than in the recent stromatolite, which suggests larger differences in Tw through the year in the Pleistocene than at present. The Pleistocene d 13 C calcite does not show any pattern; and the values are slightly higher than the recent ones. The co-evolution of d 18 O and d 13 C is parallel in the Pleistocene stromatolites, matching the recent stromatolite behavior. These results and their comparison with other ancient examples prove that textural and isotopic features in ancient stromatolites are useful tools to infer past depositional, climatic and hydrological conditions. Moreover, interpretations from recent fluvial stromatolites can be extrapolated to past environments to help decipher patterns of past processes, in cases where both recent and ancient stromatolites can be compared within one environmental setting. Such comparisons may be used to help interpretations of ancient stromatolites where the modern ones are not available to study

Tufa sedimentation in changing hydrological conditions: the River Mesa (Spain)

The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3/s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow –mainly from groundwater inputs– and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid conditions

Intrinsic and extrinsic controls of spatial and temporal variations in modern fluvial tufa sedimentation: A thirteen-year record from a semi-arid environment

Sedimentological and hydrochemical parameters of the River Piedra (north-east Spain) were monitored every six months (from 1999 to 2012) at 24 sites, at which tablets were installed all along the river. The river water is of HCO3–SO4–Ca type and is notably influenced by inputs from upstream karstic springs. Tufa deposition was first detected 8 km downstream of these springs and greatly increased from there, primarily along the steeper stretch (i.e. within the Monasterio de Piedra Natural Park); then, deposition decreased through the most downstream stretch, with smaller ground water inputs. The spatial evolution of the tufa thickness, with parallel variations of PWP (Plummer, Wigley, Parkhurst) rates, was thus determined by the river water pCO2 which was controlled by ground water inputs and by the river bed slope. Five fluvial subenvironments and seven sedimentary facies were characterized. The water flow conditions are the primary factor responsible for the distinct deposition rates of facies, mainly through CO2-outgassing. Stromatolites and moss-tufa and alga-tufa had the highest rates, whereas loose tufa formed in slow-flowing water and tufa of spray areas had thinner deposition. A six-month pattern in the deposition rate was detected through thickness measurements. That pattern was parallel to the seasonal PWP rates. The increased deposition during warm periods (spring and summer; mean: 5·08 mm) compared with cool periods (autumn and winter; mean: 2·77 mm) is linked chiefly to temperature, which controlled the seasonal changes in the physico-chemical and biological processes; this finding is supported by a principal components analysis. Seasonal variations of insolation and day duration also contributed to such a deposition pattern. Large discharge events, which provoked erosion of tufa deposits and dilution of water, caused the reversal of the seasonal deposition rate pattern. Stromatolites are likely to preserve the most complete sedimentary record. Although tufas are a potentially sensitive record of climate-related parameters, erosion is an intrinsic process that may overwhelm the effects of such parameters. This issue should be considered in palaeoclimatic studies based on the tufa record, particularly in semi-arid conditions

Tufa sedimentation in changing hydrological conditions: the River Mesa (Spain)

The processes controlling tufa deposition along the River Mesa (NE Spain) were studied from April 2003 to September 2009, based on six-monthly monitoring of physical and chemical parameters of the river water and sedimentological characteristics, including deposition rates on tablets. With a mean annual discharge around 1.5m3 /s, the sedimentation rate (mean 2mm/yr) recorded important spatial, seasonal and interannual variations. The river waters are of the calcium bicarbonate type. In this study, three distinct river stretches were distinguished based on the steady groundwater inputs, some of low-thermal nature. Groundwater discharges controlled the water chemical composition, and some sedimentation features too. At each stretch, an increase in pCO2 and conductivity was measured around the spring sites. Decreasing trends in conductivity or alkalinity with high enough saturation values with respect to calcite were only clearly observed in the intermediate stretch, which had higher tufa deposition rates than the other two. Tufa deposition rates were higher in cool (autumn+winter) than in warm (spring+summer) periods. In some low-rainfall warm periods, tufa deposition was inhibited or limited due to the low flow –mainly from groundwater inputs– and to the dryness of some river sites, which indeed favoured erosion during flooding. A decrease in yearly deposition rates from April 2006 onwards paralleled an important reduction in the river discharge. Groundwater inputs, drought periods and flood events should therefore be considered to understand fluvial tufa sedimentation in semi-arid conditions

Stable-isotope changes in tufa stromatolites of the Quaternary Añamaza fluvial system (Iberian Ranges, Spain)

The stable isotope composition (d13C and d18O) of the laminae in three Quaternary, calcitic, tufa stromatolites of different ages (MIS6, MIS5 and MIS1) in the Añamaza valley are studied and compared with the modern tufa in the Añamaza river. The cyclic textural variations represent thick cyanobacterial growth in the light laminae and thin or absent cyanobacterial growth in the dark laminae. The textural cyclicity is parallel to d18O changes: Each light-dark couplet corresponds to one year in which the light lamina (lower d18O values) represents warmer water temperatures (Tw) than the dark lamina (higher d18O values). This is consistent with the fact that the large crystals composing the dark laminae correspond to precipitation in the absence of microbial films and likely represent the coldest conditions. The d18Ocalcite-derived Tw from MIS5 stromatolite is higher than the MIS6 and MIS1 samples, which agrees with the commonly admitted climatic conditions during MIS5 in NE Iberia. Moreover, d18Oderived Tw from MIS6 suggests a wider yearly Tw range than the two other samples. The higher and more disperse d13C values of the MIS1 stromatolite are consistent with the peculiarities of the vegetal cover and the decreased water availability in the Holocene. Se estudia la composición isotópica ( d13C y d18O) de las láminas de tres estromatolitos calcíticos de diferente edad (MIS6, MIS5 y MIS1), en el valle del río Añamaza, y se compara con tobas actuales de este río. La variación textural cíclica representa un crecimiento cianobacteriano potente en las láminas claras y uno débil o ausente en las oscuras. Esta ciclicidad es paralela a los cambios del d18O: Cada pareja clara-oscura corresponde a un año, donde la lámina clara (menor d18O) representa temperatura de agua (Tw) más cálida que la lámina oscura (mayor d18O). Los cristales grandes que forman las láminas oscuras precipitarían en ausencia de biofilms y posiblemente representan condiciones más frías. La Tw derivada de d18O calcita en la muestra MIS5 es mayor que la Tw en las muestras MIS6 y MIS1, en consonancia con las condiciones climáticas durante el MIS5 en Iberia. Ade- más, la Tw derivada de d18O calcita en la muestra MIS6 sugiere un rango de Tw anual más amplio que en las otras dos muestras. La mayor dispersión y mayores valores de d13C en el estromatolito MIS1 son compatibles con las peculiaridades de la cobertera vegetal y la menor disponibilidad hídrica en el Holoceno

Tracking the oxygen isotopic signature from the rainfall to the speleothems in Ortigosa de Cameros caves (La Rioja, Spain)

A one-year monitoring survey has been carried out in La Paz and La Vin~a Caves in the Ortigosa de Cameros Cave System (NE Iberian Peninsula), in order to track the oxygen isotope signal from rainfall to speleothem calcite, assessing the ability of this signal to retain environmental information. Oxygen isotope signals of rainfall events, drip water —sampled every three months—, and speleothem calcite, precipitated over three-months, are com- pared. Water dripping follows precipitation events in winter, spring and summer, more closely in the near-surface drip points than in the deeper ones. In autumn, dripping is delayed with respect to rainfall, suggesting that water stays in the epikarst before dripping resumes after summer. This delay causes a deviation of the total drip water sig- nal (average d18O=-8.39‰ V-SMOW) from the rainfall signal (average d18O=-7.41‰ V-SMOW). On the contrary, in winter the isotopic signal of drip water keeps the rainfall signal. Calcite isotopic signal (total average d18O=-6.83‰ V-PDB) shows a small offset (0.62–0.75%) with respect to the signal predicted by drip water oxygen composition; this points to a limited kinetic effect in calcite precipitation, therefore calcite retains the signal of rainfall, especially in winter

Trazabilidad de la señal isotópica del oxígeno desde la lluvia a los espeleotemas en las cuevas de Ortigosa de Cameros (La Rioja, España)

[EN] A one-year monitoring survey has been carried out in La Paz and La Viña Caves in the Ortigosa de Cameros Cave System (NE Iberian Peninsula), in order to track the oxygen isotope signal from rainfall to speleothem calcite, assessing the ability of this signal to retain environmental information. Oxygen isotope signals of rainfall events, drip water —sampled every three months—, and speleothem calcite, precipitated over three-months, are compared. Water dripping follows precipitation events in winter, spring and summer, more closely in the near-surface drip points than in the deeper ones. In autumn, dripping is delayed with respect to rainfall, suggesting that water stays in the epikarst before dripping resumes after summer. This delay causes a deviation of the total drip water signal (average δ18O=−8.39‰ V-SMOW) from the rainfall signal (average δ18O=−7.41‰ V-SMOW). On the contrary, in winter the isotopic signal of drip water keeps the rainfall signal. Calcite isotopic signal (total average δ18O=−6.83‰ V-PDB) shows a small offset (0.62–0.75%) with respect to the signal predicted by drip water oxygen composition; this points to a limited kinetic effect in calcite precipitation, therefore calcite retains the signal of rainfall, especially in winter.[ES] Durante un año se han monitorizado las cuevas de La Paz y La Viña en el Sistema de Cuevas de Ortigosa de Cameros (NE de la Península Ibérica) para rastrear la señal isotópica del oxígeno desde la lluvia a la calcita espeleotémica, y así valorar la capacidad de esta señal para conservar información medioambiental. Se han comparado las señales isotópicas del oxígeno de los eventos de la lluvia, el agua de goteo (muestreada trimestralmente) y la calcita espeleotémica, precipitada también durante cada trimestre. El goteo en las cuevas responde a la precipitación en invierno, primavera y verano, más estrechamente en los puntos más próximos a la superficie que en los profundos. En otoño hay un retraso entre la lluvia y el goteo, lo que sugiere que el agua permanece por un tiempo en el epikarst, antes de que se reanude el goteo después del verano. Este retraso provoca que la señal isotópica del agua de goteo (media total de δ18O=−8.39‰ V-SMOW) se desvíe de la señal de la lluvia (media de δ18O=−7,41‰ V-SMOW). Por el contrario, en invierno la señal isotópica del agua de goteo es muy semejante a la de la lluvia. La composición isotópica de la calcita espeleotémica (media total de δ18O=−6,83‰ V-PDB) presenta un pequeño desfase (0,62–0,75%) respecto al valor que le correspondería por la composición isotópica del agua de goteo; esto indica que los efectos cinéticos durante la precipitación de la calcita son limitados, por lo que ésta conserva la señal de la lluvia, especialmente en invierno.This study was mainly funded by the CGL2009-10455/BTE research project of the Ministry of Science and Innovation and FEDER and the Análisis de Cuencas Sedimentarias Continentales, Geotransfer, PaleoQ y Gemorfología y Cambio Global research groups of the Aragón Government. We are most grateful to Ma Angeles, Sara y Juan for their invaluable help. We also thank to the Ortigosa de Cameros town hall for the cave access. The Government of La Rioja is acknowledged by the meteorological data from Villoslada de Cameros station. We are indebted to the referees for their valuable comments.Peer reviewe

Solar influence and hydrological variability during the Holocene from a speleothem annual record (Molinos Cave, NE Spain)

© 2015 John Wiley & Sons Ltd. We present a multi-proxy approach to reconstructing Holocene climate conditions in northeastern Spain based on an excellent correlation among the lamina thickness, colour parameters and isotope (δ18O and δ13C) variations recorded in a speleothem. An age model constructed from five U/Th dates and annual lamina counting suggests that the uppermost 14.7 cm of the MO-7 stalagmite grew between 7.2 and 2.5 ka before present but experienced a growth hiatus from 4.9 to 4.3 ka. Three spectral analysis methods were applied to 11 time series. The results reveal common solar periodicities on decennial (Gleissberg cycle) and centennial (De Vries-Suess cycle) scales. The onset of Holocene carbonate precipitation in the MO-7 stalagmite appears to be associated with a cold, wet period, whereas the hiatus and the end of growth are related to warm, dry periods. This environmental trend fits well within the regional Holocene climate.This study is a contribution to the CTM2013-48639-C2-1-R (OPERA), CGL2009–10455 and HIDROPAST (CGL2010-16376) projects (Spanish Government-European Regional Development Fund), the UZ2014-CIE-04 project (University of Zaragoza), the GA-LC-030/2011 project (Aragón Government-La Caixa) and the E–28 and S-97 research groups (Aragón Government).Peer Reviewe

Las asociaciones de ostrácodos en secuencias aluviales como indicadores de cambios ambientales holocenos (Bardenas Reales de Navarra, Cuenca del Ebro, NE Península Ibérica)

En este trabajo se estudian las asociaciones de ostrácodos identificadas en tres unidades aluviales preservadas en Bardenas Reales de Navarra (Cuenca del Ebro, NE Península Ibérica), para reconstruir la evolución paleoambiental de esta área durante el Holoceno final. Las especies de ostrácodos más comunes en las muestras estudiadas son Ilyocypris bradyi Sars y Paralimnocythere aff. psammophila (Flössner), acompañadas por Pseudocandona albicans (Brady). Las variaciones en su abundancia relativa a lo largo de dichas unidades aluviales permiten caracterizar cambios internos en el ambiente de depósito. Así, la unidad depositada entre 4763±87 y 2848±55 años cal. BP presenta como especie más abundante a I. bradyi, lo que indica la existencia de pequeños arroyos o riachuelos con agua corriente que se desarrollaron probablemente en llanuras de inundación fluviales. Sin embargo, de 2848±55 a 836±65 años cal. BP Paralimnocythere aff. psammophila es la especie dominante, representando el establecimiento de un medio acuático efímero y de aguas estancadas, posiblemente relacionado con condiciones climáticas más áridas (Anomalía Climática Medieval). Finalmente, la asociación de ostrácodos identificada en el Reciente (191±97 a 127±82 años cal. BP) está constituida principalmente por I. bradyi, que indicaría la presencia de nuevo de aguas corrientes. Esta última asociación parece estar vinculada a la influencia de condiciones climáticas húmedas y frías (Pequeña Edad del Hielo) durante el Reciente en esta área. Por lo tanto, la evolución paleoambiental para el Holoceno final de Bardenas Reales de Navarra, identificada a partir de las asociaciones de ostrácodos, muestra una buena correlación con los cambios climáticos rápidos holocenos deducidos en otros registros continentales del NE de la Península Ibérica. In this paper, the ostracod assemblages identified in three alluvial units preserved in Bardenas Reales de Navarra (Ebro Basin, NE Iberian Peninsula) have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area during the late Holocene. The most common ostracod species in the studied samples are Ilyocypris bradyi Sars and Paralimnocythere aff. psammophila (Flössner), accompanied by Pseudocandona albicans (Brady). Variations in their relative abundance along these alluvial units allow us to characterize internal changes in the depositional environment. Thus, the unit deposited between 4763±87 and 2848±55 years cal. BP is dominated by I. bradyi, indicating the presence of small streams with running water developed probably in fluvial flood plains. Nevertheless, from 2848±55 to 836±65 years cal. BP Paralimnocythere aff. psammophila is the dominant species, representing the establishment of an ephemeral and stagnant aquatic environment, mainly related with more arid climatic conditions (Medieval Warm Period). Finally, the ostracod assemblage identified in Recent times (191±97 to 127±82 years cal. BP) is mainly dominated by I. bradyi, which indicates the presence of running waters. This later assemblage probably defines the influence of cold and wet climatic phase (Little Ice Age) during Recent times in this area. The palaeoenvironmental evolution identified from the late Holocene according to ostracod assemblages in Bardenas Reales de Navarra shows good correlation with rapid climatic changes deduced from other continental records of the NE Iberian Peninsula

Hitos turísticos urbanos y su representación en las producciones audiovisuales: el caso de España (2000–2021)

Esta investigación tiene como principal objetivo conocer el grado de coincidencia entre los hitos o lugares de más interés turístico y los espacios urbanos representados en las principales producciones audiovisuales rodadas en el siglo XXI. El trabajo se basa en algunas de las ciudades más relevantes a nivel turístico de la geografía española, así como en territorios insulares de especial importancia turística. La investigación es de naturaleza analítico-descriptiva, con una metodología cuantitativa y la utilización de la técnica de observación científica. Uno de los principales resultados obtenidos es la existencia de un alto grado de coincidencia entre algunas de las localizaciones proyectadas en las películas y series seleccionadas con los lugares de más interés turístico de las ciudades e islas analizadas