Evolution of the Júcar-Cabriel fluvial system on the Mediterranean watershed of the Iberian Peninsula (Valencia, eastern Spain)

This study presents the characterization and chronology of the Quaternary terrace sequence developed in the confluence zone of the Júcar and Cabriel river valleys. The study area covers a radius of 10 km from the confluence of the two valleys near the locality of Cofrentes (Valencia). It is located in the northern zone of the Ayora-Cofrentes Graben in the northeastern sector of the External Prebetic Zone adjacent to southern Iberian Chain. This N-S graben is an inherited tectonic feature with an axial salt wall subject to different periods of fluvial dissection and refilling since at least the end of the Messinian Salinity Crisis (MSC). Regional isostatic uplift and local uplift and subsidence processes related to salt flow and dissolution during the Quaternary period, favored by fluvial entrenchment and terrace development. The terrace system and the previous pre-incision erosional and depositional surfaces are analyzed from a geomorphological point of view. The terrace system only develops within the soft Mio-Pliocene sedimentary fill of the graben, whilst upstream and downstream this zone the studied valleys develop important gorges (canyons) carved in the Cretaceous tablelands (Caroch Massif) and Mio-Pliocene deposits (Llanura Manchega). The geochronological control is established from 20 numerical ages obtained by different dating methods, such us Electron Spin Resonance (ESR), Optically Stimulated Luminescence (OSL) in detrital sequences and Th/U series in calcareous tufa deposits. Additionally, four K/Ar dates available for volcanic materials disrupting the upper and oldest terrace have been considered. A total of 14 terrace levels were identified between +130–135 m (T1) and +3–4 m (T14) of relative height above the river thalwegs. The T1 has an approximate age of c. 1.6–2.0 M.a. as indicate the age of the volcanic materials from the Agras Volcano intruded in the terrace, marking the onset of Quaternary fluvial dissection in the zone. The obtained geochronological data indicate that the Lower-Middle Pleistocene boundary is slightly above T6 (+60–65 m), which has an ESR age of 577 ± 43 ka. This terrace also documents the onset of the most important period of rise of the salt within the graben interfering drainage development. The geochronological data indicate the occurrence of a second eruptive event during the second half of the Middle Pleistocene related to the terraces T7 (+50 m) and T8 (+35–40 m), updating the volcanic activity in the zone. The beginning of the Upper Pleistocene is recorded by the top sequences of the T9 terrace (+25–30 m) where numerous OSL and Th/U data have been obtained with ages between ca. 105 and 81 ka (MIS 5). However, these young terraces (T8 to T13) are thickened (8–10 m) recording Middle Pleistocene sediments in their basal sequences with ages between ca. 193 and 137 ka (MIS 6). The study provides important data on valley evolution under the interference of volcanic activity, salt –related deformation (diapirism, solution subsidence) and fluvial incision fostered by the rise of the axial diapir (salt wall) protruding the graben since at least the Brunhes-Matuyama boundary. The analyzed fluvial evolution documents interesting cases of river capture, drainage antecedence and tectonic adaptation of the drainage throughout the Quaternary Period. The paper also poses interesting geochronological data on the long-term Quaternary evolution of Mediterranean valleys in the Iberian Peninsula, poorly explored to the dat

Fish mortality associated to volcanic eruptions in the Canary Islands

The Canary Islands are an active volcanic archipelago. In the last decade, volcanic activity has occurred twice on the youngest and western most islands: El Hierro (submarine eruption) in 2011-12, and La Palma (subaerial eruption) in 2021. 70 fish specimens of different species from El Hierro volcano and 14 from La Palma were necropsied. A notable high and early mortality of fishes was registered during the submarine eruption of El Hierro. In most of them, generalized congestion in the gills, liver, spleen, kidney, heart and rete mirabile of the swim bladder was observed. Some specimens also presented exophthalmia, gastric eversion, ocular haemorrhages, over-inflation of swim bladder and gas bubbles mainly on the skin and cornea. The eruption of La Palma volcano was characterized by the emission of large amounts of lava flows and pyroclastic deposits (mainly ash in size) both, on land and sea. Lava flowed on land and eventually reached the sea, forming lava deltas in the coastline of La Palma. This event was also associated with an increase in fish mortality in locations near to the lava deltas. Fishes presented ash particles in opercula/oral cavities and gills. In addition, several fishes presented an intense intestinal impaction composed of volcanic material including ashes and hyaloclastites fragments. To our best knowledge this study describes, for the first time, pathological findings in dead fishes associated with two different styles of recent volcanic eruptions in the Canary Islands

Mega-tsunami conglomerates and flank collapses of ocean island volcanoes

Co-auteur étrangerInternational audienceMarine conglomerates at high elevation on the flanks of ocean islands are usually interpreted as evidence of mega-tsunamis generated by volcano flank collapses, although their origin is sometimes debated (elevated littorals vs. tsunami). In this review, we introduce case studies of well-documented examples of tsunami conglomerates in Hawaii (Pacific Ocean), the Canary and Cape Verde Islands (Atlantic Ocean), and Mauritius Island (Indian Ocean). Other less-documented marine conglomerates are also presented as tsunami candidates. Then, we build a comprehensive picture of the general characteristics of these conglomerates and the different methods that can be applied to date them. Different perspectives of research are proposed, especially on the use of tsunami conglomerates as proxies for better constraining numerical models of ocean island flank collapses and associated tsunamis. We also discuss the possible links between volcano growth, flank instability, and climate

The influence of natural fire and cultural practices on island ecosystems: insights from a 4800 year record from Gran Canaria, Canary Islands

Aim: Long-term ecological data provide a stepped frame of island ecosystem transformation after successive waves of human colonization, essential to determine conservation and management baselines. However, the timing and ecological impact of initial human settlement on many islands is still poorly known. Here we report analyses from a 4800-year sedimentary sequence from Gran Canaria (Canary Islands), with the goal of disentangling forest responses to natural fire from early human pressure on the island.Location: La Calderilla, a volcanic maar caldera at 1770 m a.s.l. on Gran Canaria.Taxon: plants and fungi.Methods: A core from the caldera infill was analysed for sediment properties, pollen, micro- and macrocharcoal, with radiocarbon and biochronology dating. Fossil data were statistically zoned and interpreted with the help of cross-correlation and ordination analyses. Surface samples and a pollen–vegetation training set were used as modern analogues for vegetation reconstruction.Results: Before human settlement (4800–2000 cal. yr BP), pine (Pinus canariensis) pollen dominated. Extensive dry pine forests characterised the highlands, although with temporary declining phases, followed by prompt (sub-centennial scale) recovery. Towards 2280 cal. yr BP there was a shift to open vegetation, marked by an increase in coprophilous spores. Coincidental with independent evidence of human settlement in the pine belt (2000–470 cal. yr BP) there was a decline of pine and a peak in charcoal. Following historic settlement (470–0 cal. yr BP), pollen producers from anthropogenic habitats, secondary vegetation and coprophilous fungi increased in abundance, reflecting higher pressure of animal husbandry and farming. Modern moss polsters reflect extensive reforestation since 1950 CE (Common Era).Main conclusions: From 4800 cal. yr BP, the pristine vegetation covering the Gran Canaria highlands was a mosaic of dry pine forests and open vegetation. The pine forests sustained intense fires, which may well have promoted habitat diversity. Human interference was initiated around 2280 cal. yr BP probably by recurrent cultural firing and animal husbandry, triggering a steady trend of forest withdrawal and expansion of grasses and scrubs, until the final disappearance of the pine forest locally in the 20th century. Grasslands were found to be of ancient cultural origin in the summit areas of Gran Canaria, although they underwent an expansion after the Castilian Conquest

El registro geológico como herramienta para la evaluación de la peligrosidad volcánica: Estudio del caso de la erupción de hace 4200 años en Cerro Blanco (Catamarca, Puna Sur)

XXI Congreso Geológico Argentino, del 14 al 18 de marzo, 2022, Puerto Madryn (Chubut)En zonas volcánicas activas, entendiendo como tales aquellas que han tenido alguna erupción durante el Holoceno (aproximadamente en los últimos 11.700 años), el registro geológico nos permite identi ficar estas erupciones y acotar una gran cantidad de parámetros eruptivos. Esta información sirve no sólo para reconstruir las erupciones pasadas, sino que permite predecir, entre otros, el tipo de magma, el estilo eruptivo o el rango de magnitud del evento. En suma, el pasado es la clave del futuro. De esta manera, el registro geológico (particularmente el holoceno) se convierte en una herramienta de gran utilidad para evaluar la peligrosidad del volcanismo activo. En este contexto, un caso de estudio excepcional es la gran erupción del Complejo Volcánico de Cerro Blanco (CVCB), en la Zona Volcánica Central de los Andes, noroeste de Argentina, datada en 4410-4150 a cal AP. Este evento eruptivo es uno de los principales que han ocurrido durante el Holoceno en el mundo (Fernández-Turiel et al. 2019, Osterrieth et al. 2019). El registro geológico investigado en las provincias de Catamarca, Tucumán y Santiago del Estero evidencia una erupción explosiva riolítica que formó depósitos piroclásticos de caída en un área de aproximadamente 500,000 km2, acumulando >100 km3 de tefra (volu- men total bruto, equivalente a unos 70 km 3 de volumen DRE). Este último valor excede el umbral inferior del Índice de Explosión Volcánica (VEI) de 7. Los depósitos de caída cineríticos cubrieron extensas áreas localizadas a más de 400 km de la fuente y los depósitos deflujos piroclásticos inundaron los valles vecinos alcanzando distancias de varias decenas de kilómetros (Báez et al. 2020, Fernández-Turiel et al. 2019). El descubrimiento de la gran erupción holocena del Complejo Volcánico de Cerro Blanco ha puesto de manifiesto que el sur de la Puna es una zona volcánica muy activa y que, como tal, la evaluación de la peligrosidad volcánica debe ser reconsiderada, de la misma manera que las medidas de mitigación de riesgos relacionadas con futuras erupciones explosivas de gran magnitud. Esta investigación fue financiada por los Proyectos ASH y QUECA (MINECO, CGL2008-00099 y CGL2011- 23307). Agradecemos el apoyo analítico del Laboratorio de Geoquímica labGEOTOP (infraestructura cofinan- ciada por ERDF-EU Ref. CSIC08-4E-001) y el Laboratorio de DRX (infraestructura cofinanciada por ERDF-EU Ref. CSIC10-4E-141) de ICTJA-CSIC, y los laboratorios de EPMA y SEM de CCiTUB. Este estudio se realizó en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias) y GEOPAM (Generalitat de Catalunya, 2017SGR 1494).Esta investigación fue financiada por los Proyectos ASH y QUECA (MINECO, CGL2008-00099 y CGL2011- 23307). Agradecemos el apoyo analítico del Laboratorio de Geoquímica labGEOTOP (infraestructura cofinan- ciada por ERDF-EU Ref. CSIC08-4E-001) y el Laboratorio de DRX (infraestructura cofinanciada por ERDF-EU Ref. CSIC10-4E-141) de ICTJA-CSIC, y los laboratorios de EPMA y SEM de CCiTUB. Este estudio se realizó en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias) y GEOPAM (Generalitat de Catalunya, 2017SGR 1494)

El registro geológico como herramienta para la evaluación de la peligrosidad vocánica: Estudio del caso de la isla de El Hierro (Islas Canarias, España)

XXI Congreso Geológico Argentino, del 14 al 18 de marzo, 2022, Puerto Madryn (Chubut)En zonas activas de islas volcánicas oceánicas, entendiendo como tales aquellas que han tenido algu- na erupción durante el Holoceno (aproximadamente en los últimos 11.700 años), el registro geológico nos permite identificar estas erupciones y acotar una gran cantidad de parámetros eruptivos. Esta información sirve no sólo para reconstruir las erupciones pasadas, sino que permite predecir, entre otros, el tipo de magma, el estilo eruptivo o el rango de magnitud del evento. Esta información resulta clave a la hora de evaluar la peligrosidad volcánica en estas zonas de volcanismo activo. Aquí presentamos la investigación del Proyecto LAJIAL, que tiene por objetivo discernir la actividad volcánica subaérea que ha experimentado la isla durante el Holoceno. El nombre del proyecto alude a la toponimia local con el que se conocen los campos de lava en la Isla de El Hierro, Islas Canarias. El volcanismo subaéreo del Holoceno de El Hierro genera campos de volcanes monogenéticos vinculados a los tres sistemas de dorsales o rifts presentes en la isla (Carracedo et al. 2001, Guillou et al. 1996). Sus mecanismos erupti- vos son típicamente estrombolianos, aunque también hay eventos freatostrombolianos. Las erupciones más recientes con frecuencia forman campos de lava en las plataformas costeras, que se consideran posteriores al último máximo glacial (aprox. 20 ka AP). Las plataformas costeras más desarrolladas se encuentran al final de las dorsales y en el interior de la depresión de El Golfo. Este criterio geomorfológico muestra que más de treinta erupciones subaéreas han tenido lugar en El Hierro desde hace aprox. 20 ka AP. Además, hay muchos edificios volcánicos aparentemente recientes lejos de la costa. La investigación del volcanismo más reciente de la isla, los últimos 11.700 años del Holoceno, abarca un período su ficientemente largo y cercano a la actualidad. Por lo tanto, este período es el mejor para modelar los procesos eruptivos que nos permitirán evaluar los escenarios futuros de la dinámica eruptiva en El Hierro. Combinamos metodologías de cartografía geológica, geomorfología, SIG, cronoestratigrafía, paleomag- netismo, petrología y geoquímica para caracterizar los eventos eruptivos y resolver la tasa de recurrencia eruptiva durante el Holoceno en El Hierro. Esta información es la base sobre la que desarrollar la evalua- ción de la peligrosidad volcánica de El Hierro. Además, es de utilidad para precisar el modelo volcánico de dorsales en las islas volcánicas oceánicas de intraplaca y mitigar los riesgos asociados. Esta investigación sefinancia con el proyecto LAJIAL (ref. PGC2018-101027-B-I00, MCIU / AEI / FEDER, UE) y se realiza en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias, ULPGC) y GEOPAM (Generalitat de Catalunya, 2017 SGR 1494Esta investigación sefinancia con el proyecto LAJIAL (ref. PGC2018-101027-B-I00, MCIU / AEI / FEDER, UE) y se realiza en el marco de los Grupos Consolidados de Investigación GEOVOL (Gobierno de Canarias, ULPGC) y GEOPAM (Generalitat de Catalunya, 2017 SGR 1494)

The Plio–Quaternary volcanic evolution of Gran Canaria based on new K–Ar ages and magnetostratigraphy

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Caracterización de los materiales volcánicos asociados a las erupciones holocenas de La Caldera de Pinos de Gáldar y edificios volcánicos adyacentes (Gran Canaria)

International audienceThe holocene eruption of La Caldera de Pinos de Ca/dar (2,830 years b.p.) is charaeterized by an strombolian cone, several Java flows of basanite composition and fall pyroclastic deposits. This volcano and other neighbour volcanic cones (Valleseco, Montañón Negro -2.970 years b.p.-, Hondo de Fagagesto - 2.210 years b.p.-, Sao and los Berrazales) are almost contemporaneous and they form a NW-SE structural lineation of 9 km. In addition, the lava flows of these volcanic centres show similar petrographic and chemical data, suggesting the same magmatic reservoir. However, the studied ultrabasic xenoliths, clinopyroxenite cumulates and clinopyroxene megacrysts, associated to the pyroclastic deposits from Caldera de Pinos de Galdar, display different textural, mineralogical and chemical charaeteristics as compared to their host basanitic lava flows, therefore these materials were originated under different upper mantle or conditions different parental magmas

Effectiveness of combined unspiked K–Ar and 40Ar/39Ar dating methods in the 14C age range

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Volcanic and structural evolution of Pico do Fogo, Cape Verde

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