Suchergebnisse

We present a new crustal-scale transect of the eastern Basque-Cantabrian Zone, through the Cinco Villas Massif, the Leiza-Aralar Thrust System and the South-Pyrenean Zone. The restoration of this transect to its pre-shortening stage allows us to assess the architecture of the hyperextended domain and the style of the Alpine contractional deformation. During the Cretaceous, extension led to a hyperthinned crust with local mantle unroofing to the base of the eastern Basque-Cantabrian Basin. The mantle unroofing process was driven by a complex system of detachments putting into contact Mesozoic sediments in the hanging wall with mantle rocks in the footwall. At this stage, extensive fluid circulation caused serpentinization of the uppermost mantle body. Furthermore, the thermal anomaly created during the unroofing caused high temperature metamorphism of the overlying sediments of the Leiza detachment system and hydrothermalism in further basins. The Alpine convergence gave rise to the tectonic inversion of the Mesozoic basins. Tectonic structures inherited from the Cretaceous hyperextension played a major role in mountain building. The southward indentation of the European crust forced the northwards subduction of the Iberian crust and the basement-cover decoupling along the Triassic evaporites. Restoration of this section to the end of the extensional period enabled us to estimate a shortening of~90 km. ; En este trabajo se presenta un nuevo modelo de estructura cortical en el borde oriental de la Zona Vasco-Cantábrica, atravesando el Macizo de Cinco Villas, el sistema de cabalgamientos de Leiza-Aralar y la Zona Surpirenaica. La restauración de esta sección al estadio previo a la convergencia alpina permite establecer la arquitectura del dominio cortical hiperextendido Mesozoico y el estilo de la deformación compresiva posterior. Durante el Mesozoico, la deformación extensional asociada a la apertura del Golfo de Vizcaya dio lugar a la formación de dominios de corteza hiperextendida y a la exhumación parcial del manto bajo la Cuenca Vasco-Cantábrica oriental. El proceso de exhumación del manto se produjo por la acción de un complejo sistema de detachments extensionales que pusieron en contacto la cuenca cretácica en el bloque superior con el manto en su bloque inferior. En este estadio, la intensa circulación de fluidos a lo largo de estos detachments causó la serpentinización de la parte superior del cuerpo mantélico. Además, la anomalía térmica creada en este proceso, generó un metamorfismo de alta temperatura que afectó a los materiales mesozoicos localizados inmediatamente sobre el manto exhumado, así como hidrotermalismo en cuencas más alejadas de la aureola metamórfica. La orogenia Alpina dio lugar a la inversión de las cuencas mesozoicas, y las estructuras tectónicas heredadas de la etapa de hiperextensión cortical jugaron un papel determinante en la configuración de la estructura orogénica. La indentación hacia el sur de la corteza Europea en la corteza Ibérica forzó la subducción de esta última hacia el norte y el desacoplamiento del basamento con respecto a la cobertera sedimentaria mesozoico-terciaria a lo largo del nivel de despegue de las evaporitas del Triásico superior. La restauración de esta sección cortical al final del periodo extensional indica un acortamiento cenozoico de aproximadamente 90 km. ; We thank the PhD financial support for IDF given by the University of Oviedo-Banco Santander, Government of the Principality of Asturias and the FPU grant of the Spanish Ministry of Education. This is a contribution of the ESF TopoEurope Project PYRTEC (SV-PA-10-03-IP2- PYRTEC), the Consolider-Ingenio 2010 Project TOPOIBERIA (CSD2006-00041) and the Ministry of Economy and Competitiveness Project MISTERIOS (CGL2013-48601-C2-2-R). ; Peer reviewed

The Cantabrian Mountains have been interpreted as a Paleozoic basement block uplifted during an Alpine deformation event that led to the partial closure of the Bay of Biscay and the building of the Pyrenean range in the Cenozoic. A detailed interpretation of deep seismic reflection profile ESCIN-2 and the two-dimensional seismic modelling of the data allowed us to construct a N-S geological cross section along the southern border of the Cantabrian Mountains and the transition to the Duero Cenozoic foreland basin, highlighting the Alpine structure. The proposed geological cross section has been constrained by all geophysical data available, including a 2-D gravity model constructed for this study as well as refraction and magnetotelluric models from previous studies. A set of south-vergent thrusts dipping 30 to 36° to the north, cut the upper crust with a ramp geometry and sole in the boundary with the middle crust. These thrusts are responsible for the uplift and the main Alpine deformation in the Cantabrian Mountains. A conspicuous reflective Moho shows that the crust thickens northwards from the Duero basin, where subhorizontal Moho is 32 km deep, to 47 km in the northernmost end of ESCIN-2, where Moho dips to the north beneath the Cantabrian Mountains. Further north, out of the profile, Moho reaches a maximum depth of 55 km, according to wide-angle/refraction data. ESCIN-2 indicates the presence of a tectonic wedge of the crust of the Cantabrian margin beneath the Cantabrian Mountains, which is indented from north to south into the delaminated Iberian crust, forcing its northward subduction. © 2016 Author(s). ; This study was part of the PhD thesis of J. Gallastegui and was supported by a FPU grant and research projects GEO 90-0660-1086 and PB92-1013 funded by CICYT (Committee of Science and Technology of the Spanish Ministry of Education and Science) and FICYT (Foundation for the Science and Technologic Research, Government of Asturias, Spain). Part of the study has also been financed by the Spanish Ministry of Science through the "TOPOIBERIA" Consolider Project (ref:MEC-06-CSD2006-0041) and the MISTERIOS Project (ref:MINECO-13-CGL2013-48601-C2). ; Peer reviewed

The presence of ophicalcites in serpentinized peridotites together with fragments of these rocks in Cretaceous breccias along several North‐Pyrenean basins led to the interpretation of complete mantle exhumation to the seafloor. The westernmost outcrop of peridotites in the Pyrenean‐Cantabrian belt is located in Ziga (eastern Basque‐Cantabrian Basin), associated to a band of HT metamorphism related to the Leiza fault (Marble Unit). We present a petrological and geochemical study of the marbles and Ziga peridotite‐hosted calcite, including standard stable isotope composition and clumped isotope geothermometry. These isotopic techniques allow the determination of different types of formational fluids and crystallization temperatures, and are a useful tool for studying carbonation processes in hyperextended basins. Fieldwork and analytical studies lead us to conclude that during the opening of the Bay of Biscay, mantle rocks were unroofed at the base of the sedimentary pile of the eastern Basque‐Cantabrian Basin. However, the ophicalcite veins were recrystallized from meteoric fluids at low temperatures (≤49°C). The primary carbonate phase may have been formed either during the mid‐Cretaceous unroofing of the mantle or in a post‐exhumation stage. The process of mantle exhumation was accompanied with HT‐LP metamorphism and fluid circulation along major faults that reset the marine isotopic signature in the nearest marbles. For comparison, ophicalcites from Urdach and Lherz (North‐Pyrenean Zone) were included in the clumped isotope study. Results show that they were recrystallized from hot (∼200–230°C), saline fluids, and from meteoric fluids at near ambient temperatures (∼32–42°C), respectively. ; We thank the PhD financial support for IDF, given by the University of Oviedo‐Banco Santander, Government of the Principality of Asturias and the FPU grant of the Spanish Ministry of Education, Culture and Sport. This is a contribution of the Ministry of Economy and Competitiveness Project MISTERIOS (CGL2013‐48601‐C2‐2‐R), the Consolider‐Ingenio 2010 Project TOPO‐IBERIA (CSD2006‐00041), and the ESF TopoEurope Project PYRTEC (SV‐PA‐10‐03‐IP2‐PYRTEC). ; Peer reviewed

Marine plastic pollution is worse than expected, and we are starting to realize its full extent and severity. Solving the plastic pollution problem is not easy, as it requires the action and commitment of all sectors of our society. With a coastline extending over 4,000 km (from 18 degrees S to 56 degrees S), Chile is a maritime country, and since plastics are potentially harmful for marine and coastal ecosystems, food security, and public health, plastic pollution is a real threat. Chile is the sixth-largest exporter of seafood (fish, invertebrates, and algae) in the world, but the extent of plastic contamination of marine organisms, its potential effects on commercial species and aquaculture, and its subsequent effects on human health are mostly unknown. Chile has recently introduced some legislation to prevent plastics from reaching the environment and the coastal ocean. Governmental and non-governmental organizations have joined an informal alliance to take action against plastic pollution, both at a national and regional level, but stronger involvement of producers and commerce is required for effective measures. Chilean scientists working on plastic pollution have created the Scientific Plastic Pollution Alliance of Chile network, aiming to promote collaborative and coordinated research focused on this pollutant. The wide geographical extent of Chile, with researchers working in diverse ecosystems, provides a unique opportunity to better understand the consequences of one of the most recent and severe threats to biodiversity. Rather than solely presenting the plastic pollution problem from the scientific perspective, this paper includes views from different sectors of society. Mitigating plastic pollution is exceptionally complex, with this study highlighting the importance of local engagement, media, solving social inequities, new legislation, and law enforcement in order to advance on decreasing plastic pollution from a country-wide perspective.