Agradación fluvial en la llanura deltaica de Haslital (Alpes Suizos). Análisis de facies sedimentarias y modelización cronoestratigráfica

El delta de Haslital (12 km de largo, 1 km de ancho), en los Alpes Berneses, ha progradado en el lago Brienz tras la retirada progresiva del glaciar Aare después del Último Máximo Glacial. Los deltas formados en cubetas de sobreexcavación glaciar pleistocenas constituyen cuencas sedimentarias de gran efectividad. El estudio de los registros sedimentarios en estas formaciones, así como la reconstrucción del proceso de agradación aluvial, proporcionan información sobre la dinámica fluvial, y los cambios ambientales y antropoinducidos ocurridos en las cuencas hidrográficas alpinas. Se reconstruye la litoestratigrafía de la llanura deltaica mediante cuatro secciones transversales a la dirección general del delta, formadas cada una de ellas por más de 25 sondeos someros (2 m de profundidad) y dos sondeos profundos (profundidad variable, hasta 9 m). El modelo cronológico de las secciones se calcula por medio de dataciones AMS 14C, en combinación con datos históricos de paleoinundaciones y migración de los canales (Schulte et al., 2015), lo que permite establecer una interpretación cronoestratigráfica precisa de la dinámica aluvial más moderna. La identificación de diferentes facies sedimentarias propias de la arquitectura fluvial aporta información sobre los cambios en los procesos de acreción vertical y lateral (Houben, 2007). La localización y geometría de facies sepultadas de canal-levée (unidades de gravas y arenas gruesas) muestran la posición del lecho del Aare en la llanura de inundación. Los resultados indican una notable movilidad del lecho (siguiendo un patrón oscilatorio) durante el Holoceno Tardío. Asimismo, facies de depósitos finos, con alto contenido de materia orgánica, y niveles turbosos denotan la existencia de áreas estables, en las que las inundaciones presentan una baja incidencia. Se analiza la textura (por difracción láser), la geoquímica (por fluorescencia de rayos X), y el contenido de carbono orgánico (método LOI) de las facies sedimentarias, que corresponden a los diferentes ambientes deposicionales internos de la llanura aluvial: depósitos de canal, de levée y crevasse splay, de overbank (e.g. Hoffmann, 2006; Houben, 2007; Erkens, 2009), y de depresión interdistributaria (Schulte et al., 2009), con el fin de establecer las propiedades físico-químicas distintivas de cada uno de ellos. Los resultados sugieren una vinculación entre el carácter textural y geoquímico de las distintas unidades, cuya estructura está definida por la clasificación granulométrica, la litología de las áreas fuente y los procesos postsedimentarios (Schulte et al., 2015). Una vez caracterizados los ambientes deposicionales, se estudian las tasas de agradación y el nivel de representatividad (cuantificación volumétrica) de cada uno de ellos en el conjunto de la llanura de inundación, con el fin de determinar la variabilidad espacial del proceso de agradación. La reconstrucción de alta resolución de la disposición de las facies permite expresar los resultados en términos de masa de material almacenado, por medio de la aplicación de coeficientes de densidad aparente (Brown et al., 2009). La tasa de agradación desciende longitudinalmente desde al ápice hacia el sector distal de la llanura deltaica; e indica también un descenso proporcional a la distancia del canal, que revela la mayor o menor interconexión de los ambientes deposicionales con los eventos de inundación. Ambos resultados apuntan a un crecimiento asimétrico de la llanura de inundación. Finalmente, se ha realizado un modelo 3D en SIG para calcular el volumen de material fluvial almacenado según ventanas temporales de 300 años, y detectar así las posibles tendencias temporales en la agradación de la llanura aluvial. Los resultados del modelo se analizan en relación a los factores externos que controlan el proceso de sedimentación en el delta de Hasli. Las pulsaciones de agradación muestran su vinculación a forzamientos climáticos (variabilidad de baja frecuencia) y/o antrópicos (cambios en los usos del suelo, acciones de gestión hidráulica), y la reorganización interna local del sistema. Desde el punto de vista metodológico, se considera que el enfoque, basado en la modelización cronoestratigráfica de facies sedimentarias, proporciona una explicación tanto de la componente espacial como de la componente temporal del proceso de acumulación fluvial en la llanura deltaica; y genera información válida para la gestión local de riesgos de inundación, en relación al problema de la agradación en llanuras de inundación y cursos fluviales.The Hasli delta (12 km long, 1 km wide), located in the Bernese Alps, has prograded on Lake Brienz during the last 16000 years, after the retreat of the Aare glacier at the end of the last glaciation. The deltas formed in Pleistocene glacial overdeepened valleys constitute highly effective sediment sinks, thus the study of sedimentary records in these formations, as well as the reconstruction of alluvial aggradation processes, provide information on river dynamics and environmental or human induced changes in alpine watersheds. This work performs a lithostratigraphycal reconstruction of the Hasli delta plain by analyzing four cross sections, wherein each is formed by more than 25 shallow boreholes (2 m deep) and two deep boreholes (variable depth up to 9 m). The chronological model of the cross sections is obtained by AMS 14C datings, together with information of paleofloods and channel migration compiled from historical sources (Schulte et al., 2015), which provides a precise chronostratigraphic interpretation of the most recent alluvial dynamics. The identification of different sedimentary facies associated with the fluvial architecture structures provides information on changes of vertical and lateral accretion processes (Houben, 2007). The location and geometry of buried channel-levee facies (gravel and coarse sand layers) indicate the past position of the Aare bed in the floodplain. Results show a significant mobility of the riverbed (following an oscillatory pattern) during the Late Holocene. Furthermore, fine sedimentary deposits and peat layers represent the existence of stable areas where floods have a low incidence. The analysis of texture (laser diffraction), geochemistry (XRF core scanner) and organic carbon content (LOI) is performed in different sedimentary facies that correspond to the distintc depositional environments of the floodplain, such as: channel, levee and crevasse splay, overbank (e.g. Hoffmann, 2006; Houben, 2007; Erkens, 2009), and interdistributary depressions (Schulte et al., 2009). This analysis allows the characterization of the physical and chemical properties of each facies. The results suggest a link between textural and geochemical properties of the different units, whose structure is defined by grain size sorting, lithology of source areas, and post sedimentary processes (Schulte et al., 2015). Once the depositional environments properties are established, their aggradation rates are analyzed, and a volumetric quantification is performed, in order to determine the spatial variability of the aggradation process derived from the different units. The high resolution reconstruction of the facies architecture also allows to estimate the stored material mass, by considering the bulk density coefficients of each unit (Brown et al., 2009). The analysis of aggradation rates shows a longitudinal decrease from the apex towards the distal section of the delta plain; and also indicates a proportional reduction with distance to the channel, which is related to the interconnection degree of depositional environments with flood events. Both results point to an asymmetrical growth of the floodplain. Finally, a GIS 3D model is executed in order to calculate the fluvial sediment storage, which is subdivided in 300-year time slices, thus contributing to identify temporal trends in floodplain aggradation. The results are analyzed in relation to external factors controlling sedimentation processes in the Haslital delta, and show the influence of climate and/or anthropogenic changes (land-use changes, hydraulic management), as well as the local internal system settings. From a methodological point of view, it is considered that the facies-based approach implemented in this work, based on the chronostratigraphical modeling of sedimentary units, provides an explanation of both the spatial and temporal components of delta plain sedimentary accumulation; and provides valid information for local flood risk management, concerning the problem of floodplain (and fluvial systems) aggradatio

A 2600-year history of floods in the Bernese Alps, Switzerland: frequencies, mechanisms and climate forcing

A 2600-yr long composite palaeoflood record is reconstructed from high-resolution delta plain sediments of the Hasli-Aare floodplain on the northern slope of the Swiss Alps. Natural proxies compiled from sedimentary, geochemical and geomorphological data were calibrated by textual and factual sources and instrumental data. No fewer than 12 of the 14 historically recorded extreme events between 1480 and the termination of the Hasli-Aare river channel correction in 1875 were also identified by coarse-grained flood layers, log(Zr/Ti) peaks and Factor 1 anomalies. Geomorphological, historical and instrumental data provide evidence for flood damage intensities and discharge estimations of severe and catastrophic historical floods. Spectral analysis of the geochemical and documentary flood series and several climate proxies (TSI, δ18O, tree-rings, NAO, SNAO) identify similar periodicities of around 60, 80, 100, 120 and 200 years during the last millennia, indicating the influence of the North Atlantic circulation and solar forcing on alpine flood dynamics. The composite floodplain record illustrates that periods of organic soil formation and deposition of phyllosilicates (from the medium high catchment area) match those of Total Solar Irradiance maxima, suggesting reduced flood activity during warmer climate pulses. Aggradation with multiple sets of flood layers with increased contribution of siliciclasts from the highest catchment area (plutonic bedrock) (e.g., 1300-1350, 1420-1480, 1550-1620, 1650-1720 and 1811-1851 cal yr AD) occurred predominantly during periods with reduced solar irradiance, lower δ18O anomalies, cooler summer temperatures and phases of drier spring climate in the Alps. Increased water storage by glaciers, snow cover and snow patches susceptible to melting processes associated with rainfall episodes and abrupt rises in temperature substantially increased surface run-off on slopes and discharges of alpine rivers. This interpretation is in agreement with the findings that the severe and catastrophic historical floods in the Aare since 1670 occurred mostly during positive SNAO pulses after years or even decades dominated by negative SNAO and cooler annual temperatures

Role of the IL33 and IL1RL1 pathway in the pathogenesis of Immunoglobulin A vasculitis

Cytokines signalling pathway genes are crucial factors of the genetic network underlying the pathogenesis of Immunoglobulin-A vasculitis (IgAV), an inflammatory vascular condition. An influence of the interleukin (IL)33- IL1 receptor like (IL1RL)1 signalling pathway on the increased risk of several immune-mediated diseases has been described. Accordingly, we assessed whether the IL33-IL1RL1 pathway represents a novel genetic risk factor for IgAV. Three tag polymorphisms within IL33 (rs3939286, rs7025417 and rs7044343) and three within IL1RL1 (rs2310173, rs13015714 and rs2058660), that also were previously associated with several inflammatory diseases, were genotyped in 380 Caucasian IgAV patients and 845 matched healthy controls. No genotypes or alleles differences were observed between IgAV patients and controls when IL33 and IL1RL1 variants were analysed independently. Likewise, no statistically significant differences were found in IL33 or IL1RL1 genotype and allele frequencies when IgAV patients were stratified according to the age at disease onset or to the presence/absence of gastrointestinal (GI) or renal manifestations. Similar results were disclosed when IL33 and IL1RL1 haplotypes were compared between IgAV patients and controls and between IgAV patients stratified according to the clinical characteristics mentioned above. Our results suggest that the IL33-IL1RL1 signalling pathway does not contribute to the genetic network underlying IgAV.Acknowledgements: We are indebted to the patients and healthy controls for their essential collaboration to this study. We also thank the National DNA Bank Repository (Salamanca) for supplying part of the control samples. This study was supported by European Union FEDER funds and `Fondo de Investigaciones Sanitarias´ (Grant PI18/00042) from ‘Instituto de Salud Carlos III’ (ISCIII, Health Ministry, Spain). DP-P is a recipient of a Río Hortega programme fellowship from the ISCIII, co-funded by the European Social Fund (ESF, `Investing in your future´) (Grant Number CM20/00006). SR-M is supported by funds of the RETICS Program (RD16/0012/0009) (ISCIII, cofunded by the European Regional Development Fund (ERDF)). VP-C is supported by a pre-doctoral grant from IDIVAL (PREVAL 18/01). BA-M is a recipient of a `López Albo´ Post-Residency Programme funded by Servicio Cántabro de Salud. LL-G is supported by funds from IDIVAL (INNVAL20/06). OG is staff personnel of Xunta de Galicia (Servizo Galego de Saude (SERGAS)) through a research-staff stabilization contract (ISCIII/SERGAS) and his work is funded by ISCIII and the European Union FEDER fund (Grant Numbers RD16/0012/0014 (RIER) and PI17/00409). He is beneficiary of project funds from the Research Executive Agency (REA) of the European Union in the framework of MSCA-RISE Action of the H2020 Programme, project 734899—Olive-Net. RL-M is a recipient of a Miguel Servet type I programme fellowship from the ISCIII, co-funded by ESF (`Investing in your future´) (Grant Number CP16/00033)