Evidencias de albitización de carbonatos mesozoicos: estudio petrológico de albitas autigénicas al noroeste del Macizo Bortziriak-Cinco Villas, este de la Cuenca Vasco-Cantábrica

The presence of authigenic Na-feldspars in sedimentary carbonate rocks is unusual and its origin is controversial in terms of genesis and timing. The use of optical microscopy, cathodoluminescence and in situ semi-quantitative EDX analysis techniques, has allowed the identification and characterization of authigenic albite crystals in the Mesozoic pre- and syn-rift carbonates of the northwestern margin of the Bortziriak-Cinco Villas Massif, in the northeastern Basque- Cantabrian Basin (western Pyrenees). The euhedral habit, crystal size, spatial distribution and crosscutting relationships, together with the pure albitic composition, suggest a relatively early replacement origin. Compaction of sediments during burial, besides possible fluid migration linked to the intense syn-rift halokinetic activity, may have been decisive for the mobilisation of cations, and hence, for the albitization of the carbonate rocksLa presencia de feldespatos sódicos autigénicos en rocas sedimentarias carbonáticas es inusual y su origen es controvertido en términos de génesis y cronología. El empleo de la microscopía óptica, catodoluminiscencia y los análisis semi-cuantitativos in situ por EDX, han permitido la identificación y caracterización de albitas autigénicas en los carbonatos pre- y sinrift del Mesozoico, en el margen noroeste del Macizo de Bortziriak-Cinco Villas, al noreste de la Cuenca Vasco-Cantábrica (Pirineos occidentales). El hábito euhédrico, el tamaño de cristal, la distribución espacial y las relaciones de corte, junto a la composición albítica, sugieren un origen relativamente temprano por remplazamiento. La compactación por enterramiento de los sedimentos además de la posible migración de fluidos relacionada con la intensa actividad halokinética syn-rift, pudo ser decisiva para la movilización de cationes, y, por lo tanto, para la albitización de las rocas carbonatada

Rift-margin extensional forced folds and salt tectonics in the eastern Basque-Cantabrian rift basin (western Pyrenees)

In this paper we present and discuss Cretaceous extensional folds of the eastern Basque-Cantabrian Basin (Northern Spain). Geometry and kinematics of folds is constrained by means of structural and sedimentological fieldwork integrated with geological mapping, revealing an intimate link between coeval folding, extensional faulting, and salt mobilization. In detail, the Mesozoic succession of the northwestern and southern borders of the Palaeozoic Bortziriak-Cinco Villas massif (eastern margin of the BCB) host late Albian–early Cenomanian syn-rift forced folds. The studied forced fold axes trend parallel and are located above main and inferred Cretaceous syn-sedimentary basement faults. Structural data indicate that these folds formed during the late Albian − early Cenomanian interval. The presence of Upper Triassic clay and evaporite outcrops along and/or close to the axes of folds and their stratigraphic relationship with Upper Cretaceous strata indicate their halokinetic origin and extrusion during folding. The trigger of salt tectonics is attributed to a basement extensional pulse during the Bay of Biscay – Pyrenean rifting. Related high subsidence-rates allowed salt to flow towards faults, forming salt walls and causing the inflation and folding of the overburden.This research was funded by grant BFI05.398 from the Basque Government to A. Bodego and grant AP98-44159606 from the Spanish Science Ministry to E. Iriarte. Funds were also supplied by Ministerio de Educación y Ciencia (MEC) – Ministerio de Ciencia e Innovación (MICINN) (projects CGL2006-05491/BTE and CGL2009-08545) and Euskal Herriko Unibertsitatea (UPV/EHU) (projects EHU06/62, UNESCO06/03 and EHUA15/18)

Hiperestentsioa: kontinenteen apurketa ulertzeko eredu berri bat

Kontinenteen apurketa luzaroan ikertu den prozesu geologikoa da. Rifting deritzon prozesu horrek milioika urte irauten ditu, eta kontinente-ertzetan, mendikateetan eta bestelako ingurune geologikoetan topatzen dira fenomeno tektoniko horren aztarnak. Plaka tektonikoen banaketaren interpretazioa, ordea, eboluzionatuz doa ikertzaileen ulermenaren eta aurrerapen teknologikoen arabera. Hiperestentsioaren ideia da interpretazio horren azken berrikuntza. Ideia hori litosfera kontinentalaren deformazio polifasikoan barneratzen da, litosferaren muturreko luzapenean oinarrituz, hain zuzen. Ertz egonkorretan eta gerriko orogenikoetan identifikaturiko egitura geologiko eta eremu estruktural bereizgarriek ahalbidetzen dute fenomeno horren bilakaeraren nolakotasuna definitzea. Magman txiroak bezala ezagutzen diren ertz egonkorretako eremu horiek dira hurbileko domeinua, necking domeinua, urruneko domeinua edo hiperluzatua eta kanpoko domeinua. Domeinu horietako bakoitza riftingaren deformazio faseekin lotzen da; fase horiek litosfera kontinentalaren luzapena, mehetzea, mantuaren azaleratzea eta lurrazal ozeanikoaren zabaltzea dira. Esan bezala, iraganean hiperluzatutako arroetan ari da garatzen ikerketa, eta hipotesi horren bitartez ulertzen hasia da, honezkero, Euskokantauriar arroa (EKA) barneratzen duen Iberia eta Eurasia arteko Mesozoikoko rift-sistemaren garapena. Urteetan arroan bildutako datuek, behintzat, horretara bultzatzen dute. Pirinioen mendebaldean deskribaturiko mantuaren azaleratzeak eta arroan deskribaturiko hamaika prozesuk indartu dute Kretazeoko riftingean hiperestentsioak izan zezakeen garrantzia; azken horrek, gainera, garai hartako EKAren eboluzio geologikoaren paradigma argitu dezake.; Continental breakup is a geological process which has been deeply learnt. The keys of that tectonic phenomena, the so-called rifting process that lasts millions of years, can be found worldwide within rifted margins, mountain chains and other geological settings. However, the interpretation of tectonic plate rupture evolves while researcher´s comprehension and technology advance. Hyperextension is the last update within that interpretation. This revolutionary idea involves the extreme polyphasic extensional deformation of the continental lithosphere. Characteristic geological structures and structural domains identified within passive margins and orogenic belts, allow to define the evolution of this phenomena. Domains such as the proximal domain, necking domain, distal or hyperextended domain and outer domain are distinguishing features within magma poor rifted margins. These domains are linked to specific deformation phases during rifting, being stretching and thinning of continental lithosphere, mantle exhumation and oceanic crust spreading part of these process. As said, research is being carried out in hyperextended basins, and the evolution of the Iberia-Eurasia Mesozoic rift system, which involves the Basque-Cantabrian Basin (BCB), is already being understood within that hypothesis. Data collected over years in the BCB, at least, suggest that. Mantle exhumation described in the western Pyrenees and several processes linked to that within the BCB, reinforces the significance that hyperextension could have occurred during the Cretaceous rifting, shedding light to the paradigm concerning the evolution of the BCB

The stones of Begoña Cemetery (Bilbao, Bizkaia)

El Cementerio de Begoña (Bilbao, Bizkaia) fue desmantelado durante el 2022 y se transformará en un parque con “memoria”. Conservará determinados elementos construidos con el objetivo de trasmitir la historia de este lugar a los visitantes. La investigación petrológica sobre las rocas de construcción y ornamentales emplazadas en las sepulturas y panteones ha permitido conocer su uso a lo largo de la historia y su origen y seleccionar los elementos más representativos para su conservación en el futuro parque. Una de las conclusiones del estudio es que el uso de la piedra ha ido variando a lo largo del tiempo. Durante la primera etapa del cementerio (siglo XIX), se utilizaron calizas y areniscas de procedencia local. Durante las últimas etapas (mitad del siglo XX y XXI) se constata la entrada de materiales nacionales e internacionales: calizas, mármoles y rocas plutónicasThe cemetery of Begoña (Bilbao, Bizkaia) was dismantled in 2022 and will be transformed into a park with “memory”. Certain construction elements will be preserved in order to transmit the history of the site to the visitors. The petrological study of the building and ornamental stones emplaced in the graveyards and mausoleums has permitted deciphering their use throughout the history and their origin, as well as selecting the most representative elements for their conservation in the future park. One of the main conclusions is that the use of the stone has changed through the time. During the first phase of the cemetery (19th century), limestones and sandstones of local origin were used. On the contrary, (late half of 20th century and 21st century) limestones, marbles and plutonic rocks of national and/ or international origin were use

Análisis de la enseñanza de los procesos geológicos externos en la educación secundaria obligatoria del País Vasco

Los expertos han constatado una pérdida de interés hacia la geología de la población en general que podría estar relacionada con su exclusión progresiva en el currículo básico en la educación obligatoria. Sin embargo, es necesario que el alumnado que finaliza la Educación Secundaria Obligatoria (ESO) adquiera una correcta alfabetización en Ciencias de la Tierra, en la que entender los procesos geológicos externos y su acción en el relieve es un contenido clave. Este estudio ha evaluado qué procesos geológicos externos se enseñan en la ESO de la Comunidad Autónoma del País Vasco, mediante el análisis de los libros de texto más utilizados y la realización de cuestionarios al profesorado. Ambas fuentes revelan que el estado actual de su enseñanza muestra deficiencias y necesita mejoras, tales como dedicarle el tiempo y espacio que le corresponde o mejorar la calidad de los textos empleados.Analysis of teaching external geological processes in the compulsory secondary school of the Autonomous Community of the Basque Country Abstract: Experts have noted that the interest of the general population in geology has decreased. This seems to be related to an exclusion of geology from compulsory education curriculum. However, it is mandatory that the students who complete compulsory secondary school acquire a correct literacy in Earth Sciences, in which understanding external geological processes and their action on the relief is a key content. Our study has evaluated which external geological processes are taught in the compulsory secondary school of the Autonomous Community of the Basque Country. To this end, the most commonly used textbooks were analyzed and teachers were asked to fill out questionnaires. Both sources reveal that the current teaching of this unit shows deficiencies and, consequently, needs improvement in both the quality of the texts used and in the time and space devoted to this unit

Geology and Cultural Heritage workshops in Unesco Las Loras Geopark (Burgos/Palencia)

Relacionar el patrimonio cultural y la geología de un territorio permite acercar a la población esta ciencia, que, en la mayoría de los casos, es menos conocida. En los Geoparques Unesco la interacción con la población y las entidades locales es fundamental para establecer proyectos de desarrollo y conservación, sobre todo en zonas despobladas. Por este motivo las actividades de divulgación son esenciales. Este trabajo presenta dos talleres realizados en dos iglesias, situadas en el Valle de Valdelucio del Geoparque Unesco Las Loras, como ejemplo de divulgación geológica en torno al patrimonio cultural en una zona con alta tasa de despoblación. Este tipo de actividades ofrece a los lugareños y visitantes una perspectiva del entorno novedosa, geológica, que compagina con el patrimonio cultural y realza el valor de la zona.Relating the cultural heritage and the geology of a territory allows the population to get closer to this science, which, in most cases, it is not well known. In Unesco Geoparks, interaction with the population and local entities is essential to establish development and conservation projects, especially in unpopulated areas. For this reason, outreach activities are essential. This work presents two workshops carried out in two churches, located in the Valdelucio Valley of the Unesco Las Loras Geopark, as an example of geological dissemination around cultural heritage in an area with a high rate of depopulation. This type of activity offers locals and visitors a new geological perspective of the environment that combines with the cultural heritage and enhances the value of the are

Cantera Gorria and Red Ereño: Natural and Cultural Geoheritage (Basque Country, Spain)

[EN] Construction and ornamental stones are important elements of cultural heritage and geoheritage. The quarries, where these materials are extracted, are a type of site that combines these two types of heritage. Both the ornamental character of the rock and its place of origin can be deeply rooted in the local society. Red Ereno is a red micritic limestone (Lower Cretaceous) with abundant white rudist fossil shells. This stone has been exploited since Roman times in the north of the Iberian Peninsula (Basque Country, Spain) and exported internationally. The main quarry related to the extraction of Red Ereno, Cantera Gorria, is currently a cultural and geoheritage site. This emblematic site brings together numerous geologic (palaeontological, petrological, geomorphological and tectonic) and mining features that make it a reference point for both research and teaching activities. The link between geoheritage and cultural heritage that exists in Cantera Gorria is evident and makes this place an essential point for dissemination of geology as well as for tourism. The quarry is currently abandoned, and because of this, there is an urgent need for its protection and development, and in order to increase awareness of its importance and potential use.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. UPV/EHU Research Group IT-029/16 (Government of the Basque Country)

Why Did Red Ereño Limestone Go Red? Linking Scientific Knowledge and Geoheritage Story-Telling (Basque Country, Spain)

Red Ereño is a red-stained ornamental and construction limestone with characteristic white fossil shells. Although exploited since Roman times, marketed worldwide and that the rock itself and its outcrop areas have been included in geological heritage inventories, the origin of its characteristic reddish colour remained unresolved. The aim of this work is to deepen the scientific knowledge of Red Ereño as a basis for understanding the characteristics of this stone and to make this information available for geoconservation actions. The mineralogical and petrological study, mainly based on optical and electron microscopy, X-ray diffraction, and rock magnetism and paleomagnetic techniques, concluded that the red-staining mineral is pigmentary hematite. Moreover, the analysis stated that hematite precipitated after sedimentation but prior to burial diagenesis and before alpine inversion. Based on palaeomagnetic studies, it can be stated that mineralisation occurred during the Late Cretaceous. This work illustrates how scientific research on this potential heritage stone provides key information for geoconservation.This study has been carried out by the UPV/EHU Research Group IT-1678/22 (Government of the Basque Country) in the framework of the project US21/32 under the cooperation agreement between the University of the Basque Country UPV/EHU, Basque Energy Agency (EVE), and Provincial Council of Biscay (BFA). Authors also thank the support of the project PID2019-108753GB-C21 financed by State Research Agency (Spain) [AEI /https://doi.org/10.13039/501100011033]. Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. UPV/EHU Research Group IT-1678/22 (Government of the Basque Country); UPV/EHU, EVE/EEE, DFB/BFA project US21/32

Palaeolithic rock art in Alkerdi 2 cave (Urdazubi/Urdax, Navarra)

En el marco del proyecto de «Caracterización del macizo y sistema kárstico de Alkerdi,de la cueva de Alkerdi y de su entorno de protección», se procede a la exploración de la cavidad de Alkerdi 2. Las labores coordinadas han permitido identificar un conjunto de arte parietal asociado a evidencias arqueológicas en superficie. El estilo de las grafías animales grabadas apunta hacia una atribución Gravetiense para la presencia humana. La datación por radiocarbono de uno de los motivos parietales y de un carbón procedente del contexto arqueológico, lo corroboran. Se trata así de la segunda cavidad decorada durante el Paleolítico en Navarra y la muestra artística más antigua de la Comunidad Foral.Within the framework of the characterization project of the massif and karst system of Alkerdi, the Alkerdi cave and its protective environment, the Alkerdi 2 cavity was explored. The coordinated work has made it possible to identify a set of parietal art associated with archaeological evidence on the surface. The style of the engraved animal points towards a Gravettian attribution for human presence. Radiocarbon dating of one of the parietal motifs and a charcoal from the archaeological context corroborate this idea. This is the second cavity decorated during the Paleolithic in Navarre and the oldest artistic remain in the Autonomous Community

Interbedded mudstone slope and basin-floor sandy deposits in the Ondarooa turbidite system (Albian, Basque-Cantabrian Basin)

El sistema turbidítico de Ondarroa constituye un sistema siliciclástico confinado con forma de L, depositado en una subcuenca marina profunda de tipo pull-apart. El estudio de nuevos afloramientos correspondientes al sistema externo ha permitido caracterizar dos sistemas de dispersión coetáneos perpendiculares. Un sistema de dispersión axial de dirección ESE correspondiente a las corrientes turbidíticas siliciclásticas, y otro sistema de dispersión transversal de dirección NNE representado por potentes slumps lutíticos de talud. El confinamiento de las corrientes turbidíticas axiales y el desarrollo de depósitos de talud habrían estado causados por la actuación sinsedimentaria de la falla de Elgoibar, paralela a los flujos axiales