Biostratigraphic study with planktic foraminifera of the Santonian-Campanian in the Deba-Zumaia section (Gipuzkoa): New biozonation with heterohelicids

A biostratigraphic study with Santonian and Campanian planktic foraminifera was carried out in the turbiditic facies of the coastline between Deba and Zumaia (Gipuzkoa), which comprises the Itziar and Aguinaga formations. Due to the low abundance of planktic foraminifera, particularly in globotruncanids, the biostratigraphic study was based on species belonging to the group of heterohelicids. We have identified 7 biozones, one of which (Sigalia rugocostata Zone) has been defined in this work. The position of the Santonian/Campanian boundary has been recognized for the first time in the Basque Coast Geopark through the use of this new biozonation with heterohelicidsSe ha realizado un estudio bioestratigráfico con foraminíferos planctónicos del Santoniense y Campaniense en las facies turbidíticas del tramo litoral entre Deba y Zumaia (Guipúzcoa), el cual comprende las formaciones Itziar y Aguinaga. Debido a la escasez de foraminíferos planctónicos del grupo de globotruncánidos, el estudio bioestratigráfico se ha basado en especies pertenecientes al grupo de los heterohelícidos. Se han identificado 7 biozonas, una de las cuales (Zona de Sigalia rugocostata) ha sido definida en este trabajo. Esta nueva biozonación ha permitido reconocer por primera vez la posición del límite Santoniense/Campaniense en el Geoparque de la Costa Vasc

Posets pluton: a geochronological piece in the puzzle of the Axial Zone of the Pyrenees

[EN]A detailed geochronological study was conducted on zircons from a diorite sample of the Posets pluton (Axial Zone, Pyrenees). The extracted igneous zircons constrain the emplacement of the pluton to 302 +/- 2 Ma and 301 +/- 3 Ma, by means of U-Pb sensitive high-resolution ion microprobe (SHRIMP) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses, respectively. Considering the syn- to late-tectonic emplacement of the Posets pluton during the main Variscan deformation event (D-2), the obtained ages constrain the long-lasting D-2, associated with the dextral transpression registered through the Axial Zone of the Pyrenees.This work was supported by grants EHUA13/03 and GIU20/017 from the University of the Basque Country (UPV/EHU) and CGL2017-82976 from the Ministerio de Economia, Industria y Competitividad / Agencia Estatal de Investigacion / Fondo Europeo de Desarrollo Regional, European Union. E. Druguet, Y. Denele, an anonymous reviewer and the editor Olivier Lacombe are thanked for reviews and discussions that improved the final manuscript

Actividades de divulgación del patrimonio geológico en geoparques

p. 61-68En los últimos años se ha producido un incremento en la consideración del patrimonio geológico como recurso que enfatiza el valor científico, educativo y recreativo de la geología. Una de las consecuencias de este crecimiento es la delimitación de áreas con estrategias de desarrollo socioeconómico y cultural centradas en la gea. Este es el caso de los territorios con categoría de parques geológicos y geoparques, en los cuales es habitual el desarrollo de diferentes estrategias de divulgación geológica que pueden ser útiles en la enseñanza formal de la geología. En este artículo se describen cuatro experiencias de divulgación geológica desarrolladas en territorios con alguna de estas categorías: el Geoparque de la Costa Vasca, la Fundación Dinópolis de Teruel, el Geoparque de la Comarca de Molina de Aragón y del Alto Tajo, y el Parque geológico de Chera.S

Environmental evolution of the Deba estuary (Basque Coast Geopark) during the Holocene and Anthropocene

RESUMEN: Se han estudiado las asociaciones de foraminíferos de dos sondeos largos y uno corto en el estuario del Deba con el fin de realizar la interpretación ambiental de su registro sedimentario. Adicionalmente, se han llevado a cabo análisis geoquímicos en el sondeo corto, y análisis microfaunísticos y geoquímicos en ocho muestras superficiales tomadas a lo largo del estuario. Los resultados han permitido la reconstrucción de sus ambientes sedimentarios durante el Holoceno y el Antropoceno. El registro holoceno está principalmente controlado por el ascenso relativo del nivel marino, mientras que las muestras superficiales y el sondeo corto muestran la influencia antropogénica en los sedimentos más recientes.ABSTRACT: Benthic foraminiferal assemblages of two long boreholes and one short core drilled in the Deba estuary were studied for environmental interpretation of its sedimentary record. Additional geochemical analyses in the short core, together with the microfaunal and geochemical analysis of eight surface samples along the estuary were also performed. The results allow for the reconstruction of the Deba estuary environment during the Holocene and Anthropocene. The Holocene record is mainly controlled by the relative sea-level rise, whereas the surface samples and the short core exhibit human influence in the most recent sediments.Trabajo financiado por los proyectos Antropicosta (CGL2013-41083-P), Harea-Grupo de Investigación en Geología Litoral (IT976-16) y Estuarios del Geoparque de la Costa Vasca (US13/02). Francisco Fatela (Universidade de Lisboa) y un/a revisor/a anónimo/a mejoraron la versión original de este trabajo con sus indicaciones. Contribución nº 49 de la Unidad de Investigación Geo-Q Zentroa (Laboratorio Joaquín Gómez de Llarena). N. El Bani Altuna ha estado financiada por la beca no. 223259 para Centros de Excelencia del Consejo de Investigación Noruego

Anisotropy of magnetic susceptibility of the Pyrenean granites

In this paper, we report on a compilation of more than 2200 sites (more than 10,000 individual measurements) where anisotropy of magnetic susceptibility (AMS) was studied in granites from the Variscan Pyrenees. The standardization and homogenization of this information has allowed us to produce three Main Maps that synthesize all the information related with the AMS of the Pyrenean granites. We also describe the problems found during the construction of the database (variable geo-positioning, different published information, etc.). The information derived from 21 granite bodies, the database, and the synthesis maps (magnetic susceptibility, Km, and the orientation of the magnetic foliation, plane perpendicular to k3, and of the magnetic lineation, k1) allow us to see for the first time a complete image of this important kinematic and petrographic indicator

The Global Stratotype Sections and Points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages at Zumaia, Spain

The global stratotype sections and points for the bases of the Selandian (Middle Paleocene) and Thanetian (Upper Paleocene) stages have been defined in the coastal cliff along the Itzurun Beach at the town of Zumaia in the Basque Country, northern Spain. In the hemipelagic section exposed at Zumaia the base of the Selandian Stage has been placed at the base of the Itzurun Formation, ca. 49 m above the Cretaceous/ Paleogene boundary. At the base of the Selandian, marls replace the succession of Danian red limestone and limestone-marl couplets. The best marine, global correlation criterion for the basal Selandian is the second radiation of the important calcareous nannofossil group, the fasciculiths. Species such as Fasciculithus ulii, F. billii, F. janii, F. involutus, F.pileatus and F. tympaniformis have their first appearance in the interval from a few decimetres below up to 1.1 m above the base of the Selandian. The marker species for nannofossil Zone NP5, F. tympaniformis, first occurs 1.1 m above the base. Excellent cyclostratigraphy and magnetostratigraphy in the section creates further correlation potential, with the base of the Selandian occuring 30 precession cycles (630 kyr) above the top of magnetochron C27n. Profound changes in sedimentology related to a major sea-level fall characterize the Danian-Selandian transition in sections along the margins of the North Atlantic. The base of the Thanetian Stage is placed in the same section ca. 78 m above the Cretaceous/Paleogene boundary. It is defined at a level 2.8 m or eight precession cycles above the base of the core of the distinct clay-rich interval associated with the Mid-Paleocene Biotic Event, and it corresponds to the base of magnetochron C26n in the section. The base of the Thanetian is not associated with any significant change in marine micro-fauna or flora. The calcareous nannofossil Zone NP6, marked by the first occurrence of Heliolithus kleinpelli starts ca. 6.5 m below the base of the Thanetian. The definitions of the global stratotype points for the bases of the Selandian and Thanetian stages are in good agreements with the definitions in the historical stratotype sections in Denmark and England, respectively