Person:
Fernández López, Sixto Rafael

First Name

Sixto Rafael

Last Name

Fernández López

URI

https://hdl.handle.net/20.500.14352/75204

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Geológicas

Department

Geodinámica, Estratigrafía y Paleontología

Area

Paleontología

Identifiers

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Now showing 1 - 10 of 20

El Jurásico Medio de la Cuenca Catalana: unidades litoestratigráficas y elementos paleogeográficos.
(Revista española de paleontología, 1996) Fernández López, Sixto Rafael; Aurell, Marcos; García Joral, Fernando; Gómez Fernández, Juan José; Henriques, María Helena Paiva; Martínez Gutiérrez, Gemma; Meléndez Hevia, Guillermo; Súarez Vega, Luis Carlos
The palaeogeography and facies distribution of the Catalan Basin during the Middle Jurassic are reconstructed, on the basis of outcrops and logs data. A new lithostratigraphic classification valid for the Catalan Basin is defined and its equivalence with the correlative units in the lberian Basin and Majorca is discussed. A system of arched, listric-shaped faults dipping towards the Mediterranean sea was a major factor determining the differentiation of the subsident Platform of Tortosa. From a palaeobiogeographical point of view, the ammonite and brachiopod recorded associations from the Platform of Tortosa are taxonornically similar to the associations of the epicontinental European basins. The Catalan Basin and Majorca were two geographically separate areas, maintaining separate biogeographical and taphonomic dispersal ways in the Middle Jurassic. Yet in the Catalan Basin expanded, outer shelf sections were developed during the Garantiana Biochron (Upper Bajocian). During this episode the basin reached the maximum bathymetric values and acted as a biogeographical dispersal area for some taxonomic groups characteristic of the West-Tethys.
Fossilization of ammonites and sedimentary events in deep environments of carbonate platform (highest Middle to lowest Upper Oxfordian, Iberian Range, Spain).
(Rivista italiana di paleontologia e stratigrafia, 2004) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo
In the Ricla area (Zaragoza, Aragonese Branch of the Iberian Range), at the top of the Yátova Formation, grey-reddish wackestone limestones grade into yellow-green siliciclastic limestones of the Aldealpozo Formation. These changes of facies between the two successive formations are associated with syndepositional palaeoreliefs developed during the Late Oxfordian. The uppermost deposits of the Yátova Formation represent an Oxfordian condensed section, from the upper Bifurcatus Zone (Middle Oxfordian) and Hypselum Zone (Upper Oxfordian). These deposits are interpreted as developed in an open marine, moderately deep carbonate platform, showing uniform lowenergy conditions with extremely reduced carbonate and terrigenous background sedimentation, and very low sedimentation rates. The low diversity of the benthic fauna, scarce development of sponge bioherms and ammonite populations inhabiting the platform are palaeobiological criteria which corroborate these palaeoenvironmental conditions. Ammonite assemblages are composed of Sub-Mediterranean taxa. Over 900 ammonite specimens have been collected from the upper Bifurcatus and Hypselum zones. Oppeliidae (45,2%) and Perisphinctidae (37,9 %) are dominant. Aspidoceratidae (14,3%) are common. Haploceratidae (2,2%) are scarce. Two phylloceratids and a lytoceratid have been found. Ammonoids are commonly preserved as concretionary calcareous internal moulds of reelaborated elements. Resedimented shells are scarce. The degree of packing of ammonite remains and the stratigraphical persistence display high values. Taphonomic features indicative of sedimentary starving in deep carbonate platform environments are: 1) high concentrations of reelaborated ammonites, 2) taphonic population of type two, 3) phragmocones completely filled with sediment, and 4) homogeneous concretionary internal moulds, bearing no signs of abrasion, bioerosion or dense encrusting by organisms (such as serpulids, bryozoans or oysters). In conclusion, the occurrence of these ammonite associations confirms the development of an advanced deepening phase, within a 3rd order deepening/shallowing cycle, in the Aragonese platform, during the late Bifurcatus to Hypselum zones.
La Plataforma de Tortosa (Cuenca catalana) durante el Jurásico Medio: unidades litoestratigráficas, paleogeografía y ciclos ambientales
(Cuadernos de geología ibérica, 1998) Fernández López, Sixto Rafael; Aurell, Marcos; García Joral, Fernando; Gómez Fernández, Juan José; Henriques, María Helena Paiva; Martínez Gutiérrez, Gemma; Meléndez Hevia, Guillermo; Súarez Vega, Luis Carlos
El presente trabajo constituye una guía de campo de un transecto de la Plataforma de Tortosa, en dirección SW-NE, desde el Estrecho de Beceite hacia las proximidades del Alto de Tarragona. Los afloramientos situados en las proximidades de Alfara, Tivenys, Llaberia y Cap Salou permiten reconocer las sucesivas unidades litoestratigráficas, así como las variaciones de espesor y facies en los distintos sectores, facilitando la reconstrucción paleogeográfica y secuencial de la Cuenca Catalana para este intervalo temporal, entre el Toarciense y el Oxfordiense. Los materiales del Jurásico Medio en la Cuenca Catalana forman una potente sucesión carbonática que sobrepasa los 350 m de potencia, y muestran una fuerte reducción de espesor hacia el norte (área de Llaberia) y el nordeste (el llamado Alto de Tarragona). Estos materiales han sido estudiados a partir de los datos de superficie (más de 30 perfiles estratigráficos) y de subsuelo (más de 30 sondeos petrolíferos). Se han reconocido tres formaciones que habían sido previamente definidas: la Fm. Sant Blai, preferentemente carbonatada (Toarciense inferior a Bajociense inferior), la Fm. Cardó, preferentemente margosa (Bajociense inferior a Bajociense superior), y la Fm. La Tossa, formada por calizas y dolomías (Bajociense superior a Calloviense medio). En la Fm. Sant Blai se distingue a su vez cinco miembros estratigráficamente sucesivos. Por encima de la Fm. La Tossa se desarrolla la Fm. Serra de la Creu, formada por calizas bioclásticas y peloidales (Oxfordiense medio a superior). Las variaciones de facies y de espesor son indicativas de que la sedimentación estuvo controlada por fracturas de basamento, que condicionaron el desarrollo de diversas plataformas carbonáticas así como sucesivos cambios relativos del nivel del mar. No obstante, las discontinuidades de mayor amplitud, localizadas en el Aaleniense (Biozona Murchisonae), en el límite Batboniense - Calloviense (Biozona Discus) y en el límite Calloviense - Oxfordiense, se encuentran también en la Cuenca Ibérica y fueron debidas a factores alocíclicos. Las profundidades relativas de estas áreas de plataforma epicontinental alcanzaron valores mínimos durante el desarrollo de estas tres discontinuidades mencionadas, que localmente pudieron corresponder a episodios prolongados de exposición subaérea. Los máximos valores batimétricos se alcanzaron durante el Bajociense superior (Biocrón Niortense) y durante el Oxfordiense medio (biocronos Schilli y Rotoides). Durante estos intervalos de máxima profundización relativa se registraron las únicas evidencias de colonización generalizada de la Cuenca Catalana por poblaciones de ammonites.
La configuración paleogeográfica de la Cuenca Catalana durante el Jurásico Medio
(Comunicaciones de las X Jornadas de Paleontología : Madrid 3,4 y 5 de noviembre de 1994, 1994) Fernández López, Sixto Rafael; Aurell, Marcos; García Joral, Fernando; Gómez Fernández, Juan José; Henriques, María Helena Paiva; Martínez Gutiérrez, Gemma; Meléndez Hevia, Guillermo; Súarez Vega, Luis Carlos; Fernández López, Sixto Rafael
Trimarginia and trimarginites (Ammonoidea) from the Iberian basin.
(De la biostratigraphie à la paléobiogéographie : réunion spécialisée APF-SGF, Lyon, 27-28 novembre 1997 : résumés, 1997) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo; Enay, Raymond
Depositional sequences and ammonite fossilization on deep carbonate platform environments (upper Oxfordian, Iberian Range, Spain)
(Volumina Jurassica, 2006) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo
El Dogger y Malm en Moscardón (Teruel).
(Guía de las excursiones al Jurásico de la Cordillera Ibérica : 4-8 de octubre 1978, 1978) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo; Súarez Vega, Luis Carlos
Abrasion surfaces on internal moulds of ammonites as palaeobathymetric indicators
(Palaeogeography, palaeoclimatology, palaeoecology, 1994) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo
Some abrasion surfaces displayed by internal moulds of ammonites, such as annular abrasion furrows formed on the venter surface and ellipsoidal abrasion facets preferentially developed on the last third part of the preserved whorl, are diagnostic criteria of taphonomic reworking. These taphonomic criteria indicate that the internal moulds have been exhumed and moved before their final burial. We explain the origin of these abrasion surfaces by the action of directional (non oscillatory) currents in very shallow water, most probably in intertidal environments. The distribution of ammonite moulds displaying such preservational features is correlated with the changes in the facies and the trend of the sedimentary sequences. Taphonomic analysis of Jurassic ammonites of the Iberian Range underlines the importance and usefulness of taphonomic gradients in sequence stratigraphy and palaeogeographic reconstructions.
Phylloceratina ammonoids in the Iberian Basin during the Middle Jurassic: a model of biogeographical and taphonomic dispersal related to relative sea-level changes
(Palaeogeography, palaeoclimatology, palaeoecology, 1996) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo
Phylloceratina and Lytoceratina ammonoids in the Middle Jurassic of the Iberian Chain (E. Spain) represent less than 1% of the whole of Ammonoidea. There are two intervals, however, in which their occurrence is remarkably constant: within the Upper Bajocian and at the Lower/Middle Callovian boundary. These two dispersal episodes of Phylloceratina and Lytoceratina into the Iberian Basin are regarded to reflect changes in their palaeoecological and taphonomical behaviour, as a consequence of regional sea-level changes during the Middle Jurassic. A relative rise during the Late Bajocian favoured the immigration of juvenile phyllocerataceans. Phylloceras and Adabofoloceras immigrations gave rise to monospecific assemblages, where they soon died. They did not breed or ontogenically develop in this basin. In contrast, phyllocerataceans recorded at the Lower/Middle Callovian boundary constitute polyspecific assemblages, dominated by adult individuals. These Callovian assemblages were formed by nekroplanktonic drift, related to a relative sea-level fall and general homogenization of the shelf bottom, hence favouring the concentration of remains of organisms from more open marine and oceanic areas.
Dispersión biogeográfica y tafonómica de ammonoideos filoceratinos hacia la Cuenca Ibérica durante el Jurásico Medio
(Coloquios de paleontología, 1994) Fernández López, Sixto Rafael; Meléndez Hevia, Guillermo
Los Phylloceratina (Filoceratáceos y Litoceratáceos) representan menos dell% de los ammonoideos en las asociaciones registradas del Jurásico Medio de la Cordillera Ibérica. Sin embargo, su presencia es relativamente constante en los materiales del Bajociense superior y del Calloviense inferior/medio. Estos dos episodios de dispersión de filoceratinos hacia la Cuenca Ibérica representan cambios en su comportamiento paleoecológico y tafonórnico debido a cambios relativos del nivel del mar durante el Jurásico Medio. El aumento relativo del nivel del mar durante el Bajociense superior favoreció la dispersión biogeográfica de algunas especies y la llegada ocasional de filoceratáceos inmigrantes. Algunos individuos juveniles dePhylloceras y Adabofoloceras llegaron a la Cuenca Ibérica, pero no hay evidencias de que encontraran condiciones favorables para su desarrollo, y representan individuos miodémicos. En cambio, los filoceratinos de las asociaciones registradas en los materiales del Calloviense inferior/ medio corresponden en su mayoría a individuos adultos. El descenso relativo del nivel del mar durante el Calloviense inferior/medio, asociado al incremento en la homogeneidad del relieve del fondo de la Cuenca Ibérica, aumentó la accesibilidad de las conchas de ammonoideos por deriva necroplanctónica y favoreció la concentración de restos de filoceratinos adémicos procedentes de otras áreas marinas más abiertas u oceánicas. [ABSTRACT] Phylloceratid ammonoids (Phyllocerataceae and Lytocerataceae) in the Middle Jurassic of the lberian Chain represent less than 1% of the whole spectra of ammonoidea. Their presence is, however, remarkably constant in two intervals, at the upper Bajocian and at the lower/middle Callovian boundary. These two separa te episodes of dispersa} for representatives of Phylloceratina towards the lberian Basin are regarded to represent meaningful changes in theirpalaeoecological and taphonomical behavior, as a consequence of regional sea-level changes during the Middle Jurassic. A relative sea-level rise during the upper Bajocian favored the biogeographic dispersa! of sorne species and the occasional arrival of immigrant filocerataceans. Sorne juvenile individuals ofPhylloceras and Adabofoloceras reached the lberian Basin, though no evidence that they could develop and evolve there can be found, so they are rather regarded as miodemic individuals. On the other hand, phylloceratid associations recorded at the lower/middle Callovian boundary, mainly formed by adult, polyspecific assemblages, had a very different origin, resulting from a relative sea-level fall and to a general homogenization of the shelf bottom, which led to an in crease of the accessibility of ammonite shells by nekroplanktonic drift, hence favoring the concentration of ademic individuals from more open to oceanic marine areas.