Person:
Gómez Fernández, Juan José

First Name

Juan José

Last Name

Gómez Fernández

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Area

Estratigrafía

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Now showing 1 - 10 of 58

The Global Boundary Stratotype Section and Point (GSSP) of the Toarcian-Aalenian Boundary (Lower-Middle Jurassic)
(International Union of Geological Sciences, 2001) Cresta, S.; Goy, Antonio; Ureta Gil, María Soledad; Arias Fernández, María del Carmen; Barrón López, Eduardo; Bernard García, Julio; Canales Fernández, María Luisa; García Joral, Fernando; García Romero, Emilia; Gialanella, P.R.; Gómez Fernández, Juan José; González, J.A.; Herrero Matesanz, Concepción; Martínez Gutiérrez, Gemma; Osete López, María Luisa; Perilli, Nicola; Villalaín, J.J.
The Global Boundary Stratotype Section and Point (GSSP) for the Aalenian Stage, formally defined at the base of bed FZ107 in the Fuentelsaz section, Castilian Branch of the Iberian Range (Spain), has been ratified by the IUGS. Multidisciplinary biostratigraphical data, based on ammonites, brachiopods, ostracods, bivalves, foraminifera, calcareous nannofossils assemblages and palynomorphs, assure worldwide correlations; magnetostratigraphic data increase this correlation power. The position of the boundary coincides with the first occurrence of the ammonite assemblage characterized by Leioceras opalinum and Leioceras lineatum and corresponds with a normal polarity interval correlated with the up-to-date Jurassic magnetic polarity time scale (Gradstein and others, 1994; Ogg, 1995).
Las unidades carbonatadas y evaporíticas del tránsito Triásico-Jurásico en la región de Lécera (Zaragoza, España)
(Universidad Complutense de Madrid. Departamento de Estratigrafía, 1999) Gómez Fernández, Juan José; Goy, Antonio
Uno de los principales retos para la estratigrafía de los materiales del MesozoIco de la Cuenca Ibérica es el reconocimiento del límite entre el Triásico y el Jurásico. Los datos del subsuelo proporcionados por los sondeos de hidrocarburos perforados en las panes no aflorantes de la cuenca muestran la presencia de una unidad evaporítica situada entre la Fm. Imón y la Fm. Cuevas Labradas. Estas evaporitas se encuentran normalmente disueltas en superficie, en donde está representada únicamente por materiales carbonatados no disueltos que constituyen la Fm. Camiolas de Cortes de Tajuña. Sin embargo, esta sucesión evaporítica aflora en la región de Lécera, lo cual ha permitido estudiar en superficie los materiales evaporíticos de la Fm. Yesos, anhidritas y carbonatos de Lécera (Gómez y Goy, 1998). Los datos palinológicos confirman una edad Camiense para la facies Keuper y una edad Hettangiense para las Carniolas, situadas en este afloramiento por encima de la Fm. Lécera, mientras que los datos regionales indican una edad Retiense para los carbonatos de la Fm. Imón. Todos estos datos sugieren que el límite entre el Triásico y el Jurásico se encuentra dentro de la Fm. Lécera.
El Sinemuriense y el Pliensbachiense en la sección de Alfara, cordillera costero-catalana (Tarragona)
(Universidad Complutense de Madrid. Departamento de Estratigrafía, 1998) Comas-Rengifo, María José; Gómez Fernández, Juan José; Goy, Antonio; Rodrigo, A.
Los materiales del Jurásico Inferior de la región de Alfara, en la Cordillera Costero-Catalana, han sido motivo de numerosos estudios bioestratigráficos desde los primeros años del siglo xx, aunque son pocos los afloramientos donde pueden observarse en continuidad. La reciente construcción de la carretera que une Alfara de Carlés con Tortosa permite reconocer, sobre la Formación Imón del Triásico Superior, la totalidad de las unidades del Jurásico Inferior. En este trabajo se estudian la Formación Cuevas Labradas, «Unidad de Almonacid de la Cuba» y Formación Barahona, todas ellas con características similares a las reconocidas en la Cordillera Ibérica (Goy et al., 1976; Comas-Rengifo, 1982). Los materiales que las constituyen se organizan en secuencias de somerízación que pueden terminar con costras ferruginosas y a veces con hardgrounds. Los fósiles de invertebrados son escasos hasta los niveles superiores de la Fm. Cuevas Labradas, por lo que el límite Sinemuriense/Pliensbachiense no puede ser marcado con precisión. No obstante, existen asociaciones de braquiópodos y algunos ammonites que son típicos del Fliensbachiense inferior. Por otra parte, la Formación Calizas y calizas margosas de Sant Blai es notablemente más fosilífera e incluye en su parte inferior asociaciones de braquiópodos y ammonites característicos del Toarciense inferior.
Utilidad sedimentológica y estratigráfica de los fósiles reelaborados.
(Dpto. de Paleontología de la Fac. de Ciencias Geológicas, Instituto de Geología Económica, Museo Nacional de Ciencias Naturales, 1990) Fernández López, Sixto Rafael; Gómez Fernández, Juan José; Fernández López, Sixto Rafael
In many cases the reelaborated fossils are the best preserved of the assemblages. Even they can not be used to establish and identify biostratigraphical or chronostratigraphical units, the reelaborated fossils are useful for sequential and discontinuities analysis, for location of source areas of sediments, as indicators of paleocurrents, and for identification of sedimentary environments and paleogeography. Some reelaborated fossils are the only existing record of eroded sediments. They permit the obtention of data on episodes of the Geological History of which the stratigraphic record is not available anymore.
The epiclastic barrier-island system of the Early‒Middle Jurassic in eastern Spain
(Springer, 2018-06) Cortés Nemesio, José Emilio; Gómez Fernández, Juan José
Background During the Early-Middle Jurassic, several mainly volcaniclastic submarine eruptions, which followed well marked lineaments, took place in the Iberian Ranges of eastern Spain. Some of these volcanoes were occasionally emerged during sea-level lowstand periods. Purposes In this work we aim to present the signs indicating that a huge volcanic pile, located in the Sierra de Javalambre (Teruel, Spain), could have been subjected to emersion, reworking and colonization by flora. We also intend to date the volcanism and to delimit the most likely period of time when emersion, reworking and colonization were produced. Methods The research work was supported by geological mapping, as well as by preparing stratigraphic sections and their palaeontological sampling. Biostratigraphical dating was achieved though taxonimical determination of ammonites, brachiopods, and data from pre-existing palynological studies. Results As a result of the shallow marine and subaerial partial erosion of the volcanic edifice, epiclastic bodies, some of which show large scale cross-bedding and bar geometry, were generated. These bedforms are interpreted as sandwaves constituting a barrier-island system protecting a lagoon on which low-energy sediments, rich in plant remains, together with washover fan facies were deposited. Conclusions An Early Toarcian, Serpentinum Chronozone age for the volcanism is indicated by the brachiopod and ammonite content of infra- and inter-volcanic sediments. However, burial of the volcanic mound by the carbonates of the surrounding platforms ended in the Late Aalenian Bradfordensis Chronozone, about 10 million years after the eruption. This delay was partly due to a significant regional sedimentary gap marked by the hiatus of the Late Toarcian (from the Late Variabilis Chronozone) to the Late Aalenian (Bradfordensis-Concavum chronozones). The emersion of the volcanic pile, the colonization of the emerged islands by continental vegetation and the instauration of the epiclastic barrier-island system occurred between part of the Aalenian Murchisonae and part of the Bradfordensis chronozones. The concurrence of the porous epiclastic lithofacies together with the organic-rich lagoonal sediments could represent an analogue model of an untypical hydrocarbon system located in neritic position, which could probably be applied in other areas of extensive emerged submarine volcanoes present in the geological record.
Le Dogger de Caudiel (Castellón): sedimentologie des Carbnates developpes sur un "monticule" de materiaux volcaniques.
(Université Paul-Sabatier. Laboratoire de Géologie Sédimentaire et Paléontologie, 1985) Fernández López, Sixto Rafael; Gómez Fernández, Juan José; Goy, Antonio
Au cours du Callovien, du Bathonien et du Bajocien se produisirent, dans la région de Caudiel, des processus de remaniement qui affectèrent les matériaux carbonatés et les roches volcaniques existantes. Les données taphonomiques et bio-stratigraphiques recueilles confirment la présence, au sein des intercalations volcaniques considérées du Jurassique moyen, de sédiments anté-bajociens, ce qui indique un âge anté-bajocien pour le volcanisme correspondant. Les données biostratigraphiques disponibles ne permettent pas d'affirmer qu'il y eut une émission volcanique quelconque, d'âge bajocien ou post-bajocien, dans ce secteur de la Cordillere Ibérique. Les matériaux pyroclastiques originels formèrent un relief au-dessus du fond marin qui détermina la distribution locale des boues calcaires durant le Bajocien, le Bathonien et le Callovien. L'analyse séquentielle de ces sédiments carbonatés met en évidence les tendances régressives des séquences bajociennes et calloviennes par opposition à la tendance transgressive des dépôts bathoniens. De plus on note l'accroissement relatif d'extension géographique des séquences calloviennes par rapport à leurs homologues du Bajocien et du Bathonien, qui prendrait fin à la limite Callovien-Oxfordien avec l'homogénéisation du fond marin.
Evolution tectono-sedimentaire et genese des associations d'ammonites dans le secteur central du Bassin Iberique (Espagne) pendant l'Aalenien.
(Assoc. des Facultés Catholiques de Lyon, 1990) Fernández López, Sixto Rafael; Gómez Fernández, Juan José
A la limite Lias-Dogger, le Bassin Ibérique correspondrait a une marge passive se disloquant en panneaux montrant des facies différents. Un des meilleurs exemples du comportement différentiel des blocs limités par des failles actives se trouve dans le secteur central du bassin, où la Faille de Noguera-Aguaton individualisait deux secteurs : celui d' Albarracin et celui de Menera. La discontinuité stratigraphique de plus grande amplitude se situe a la limite Toarcien-Aalénien dans le secteur d'Albarracin et a l'intérieur de l' Aalénien dans le secteur de Menera. Le changement paléogéographique le plus important pour la plate-forme se produit a la limite de l'Aalénien inférieur/Aalénien moyen . La sédimentation de ces secteurs correspond a un environnement de plate-forme externe tres peu profonde, soumise a des émersions locales répétées et les associationss uccessives d'ammonites sont surtout le résultat de nécrocinese régionale a partir d'aires épicontinentales plus septentrionales. [ABSTRACT] At the Lias-Dogger boundary the Iberian Basin corresponded to a passive margin where different facies conditioned by the presence of several faulted blocks were developped. One of the best examples showing the synsedimentary differential behaviour of the fault-bounded blocks was found in the central sector of the basin, where the Noguera-Aguaton Fault individualized two blocks : the Albarracin and the Menera ones. The most important stratigraphic discontinuity in the Albarracin Sector is located in the limit between the Toarcian and the Aalenian. However in the Menera Sector the most important stratigraphic discontinuity is located within the aalenian sediments. The biggest paleogeographical change in the platform occurred in the boundary between Early and Middle Aalenian. Sedimentation in this sectors corresponds to a very shallow external platform environment with repeated local emersions. The successive ammonite associations were mostly the result of regional nekrokynesis from septentrional epeiric seas
Primera fase de post-rifting: Jurásico Inferior y Medio.
(Sociedad Geológica de España, 2004) Gómez Fernández, Juan José; Fernández López, Sixto Rafael; Goy, Antonio; Vera, J.A.
Rapid warming and ostracods mass extinction at the Lower Toarcian (Jurassic) of central Spain
(Elsevier Science B.V., Amsterdam., 2010) Gómez Fernández, Juan José; Arias Fernández, María del Carmen
Here we present the results of the study of two Lower Toarcian carbonate sections located in the Iberian Range of central Spain. Analyses of stable isotope on belemnite calcite allowed calculation of seawater palaeotemperature variations, which were compared with the stratigraphical distribution of ostracods. These organisms are particularly sensitive to ratios of temperature and salinity variations and hence are good indicators of climate changes. From a cooling interval, with seawater temperatures of 13.2 °C recorded at the Pliensbachian−Toarcian transition, seawater temperature began to rise in the lowermost Toarcian Tenuicostatum Zone, reaching average temperatures between 14.6 °C and 16.3 °C during the time of deposition of this Zone. Coinciding with this seawater warming, up to 85% of the ostracods species progressively disappeared during a period of approximately 300 kyr, marking the extinction interval. The extinction boundary, located around the Tenuicostatum−Serpentinum zonal boundary, coincides with a marked increase in temperature in the Serpentinum Zone, on which average seawater temperatures of 22 °C have been calculated. Warming continued through part of the Middle Toarcian Bifrons Zone, reaching average temperatures of 24.7 °C. Readjustment of the ostracod population allowed recovery of these faunas in the upper Serpentinum Zone, although the extinction of a major ostracod group, the healdioids, was also recorded. The correlation between mass extinction and warming infers a causal relationship. Comparison of the results with the records of stable isotopes in belemnites and in bulk carbonates, as well as TOC and facies analysis suggests that the anoxia linked to the Early Toarcian oceanic anoxic event was not the main responsible for the ostracod mass extinction.
Base of the Toarcian Stage of the Lower Jurassic defined by the Global Boundary Stratotype Section and Point (GSSP) at the Peniche section (Portugal)
(International Union of Geological Sciences (IUGS), 2016-10) Bordalo da Rocha, Rogério; Mattioli, Emanuela; Duarte, Luís Vitor; Pittet, Bernard; Elmi, Serge; Mouterde, René; Cabral, Maria Cristina; Comas Rengifo, María José; Gómez Fernández, Juan José; Goy, Antonio; Hesselbo, Stephen P.; Jenkyns, Hugh C; Littler, Kate; Mailliot, Samuel; Veiga de Oliveira, Luiz Carlos; Osete López, María Luisa; Perilli, Nicola; Pinto, Susana; Ruget, Christiane
The Global Stratotype Section and Point (GSSP) for the base of Toarcian Stage, Lower Jurassic, is placed at the base of micritic limestone bed 15e at Ponta do Trovão (Peniche, Lusitanian Basin, Portugal; coordinates: 39°22’15’’N, 9°23’07’’W), 80km north of Lisbon, and coincides with the mass occurrence of the ammonite Dactylioceras (Eodactylites). The Pliensbachian/ Toarcian boundary (PLB/TOA) is contained in a continuous section forming over 450m of carbonate-rich sediments. Tectonics, syn-sedimentary disturbance, metamorphism or significant diagenesis do not significantly affect this area. At the PLB/TOA, no vertical facies changes, stratigraphical gaps or hiatuses have been recorded. The base of the Toarcian Stage is marked in the bed 15e by the first occurrence of D. (E.) simplex, co-occurring with D. (E.) pseudocommune and D. (E.) polymorphum. The ammonite association of D. (Eodactylites) ssp. and other species e.g. Protogrammoceras (Paltarpites) cf. paltum, Lioceratoides aff. ballinense and Tiltoniceras aff. capillatum is particularly significant for the boundary definition and correlation with sections in different basins. Ammonites of the PLB/ TOA are taxa characteristic of both the Mediterranean and Northwest European provinces that allow reliable, global correlations. The PLB/TOA is also characterized by other biostratigraphical markers (brachiopods, calcareous nannofossils, ostracods and benthic foraminifers) and by high-resolution stable carbon and oxygen isotopes, and 87Sr/86Sr ratios that show distinctive changes just above the PLB/TOA, thus providing additional, powerful tools for global correlations. The PBL-TOA lies at the end of a second (and third) order cycle of sea-level change, and the top of bed 15e is interpreted as a sequence boundary. Cyclostratigraphy analysis is available for the Lower Toarcian of Ponta do Trovão. Detailed correlations with the Almonacid de la Cuba section (Iberian Range, Spain) provide complementary data of the ammonite succession in the Northwest European Hawskerense and Paltum Subzones, and magnetostratigraphical data that allow supraregional correlations. The proposal was voted on by the Toarcian Working Group in June, 2012, and by the International Subcommission on Jurassic Stratigraphy in September, 2012, approved by the ICS in November, 2014, and ratified by the IUGS in December, 2014. With this Toarcian GSSP, all international stages of the Lower Jurassic have been officially defined.