Person: Díaz Molina, Margarita
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First Name
Margarita
Last Name
Díaz Molina
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Area
Estratigrafía
Identifiers
9 results
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Now showing 1 - 9 of 9
Item Chert in bioturbated sediments of Sabkha paleoenvironment(Abstracts: Flint production and exchange in the Iberian Southeast, III Millennium B.C : VI International Flint Symposium, post-symposium field trip, OCtober 5th-10th,1991, Granada-Almería / by A. Ramos Millán ... [et al.], 2001) Arribas Mocoroa, José; Bustillo Revuelta, María Ángeles; Díaz Molina, Margarita; Bustillo Revuelta, María Ángeles; Ramos Millán, A.Item Efectos de la separación de flujo en las secuencias de barras de meandro. Ejemplos del Oligoceno Superior de la Cuenca de Loranca(Geotemas, 2008) Muñoz García, María Belén; Díaz Molina, MargaritaEl registro estratigráfico del Eoceno-Mioceno de la cuenca de Loranca está formado por sedimentos fluviales, aluviales y lacustres. Durante el Oligoceno Superior los depósitos de ríos meandriformes del abanico fluvial de Tórtola se extendieron por el centro de la cuenca y su margen oeste. Las barras de meandro del abanico de Tórtola presentan diferencias con el modelo de facies básico, en el que la secuencia de estructuras sedimentarias está producida por una disminución de la velocidad de la corriente. Las secuencias fining-upwards graduales no son las más frecuentes en las barras de meandro del Oligoceno de la cuenca de Loranca. La estructura sedimentaria más abundante es la estratificación cruzada de pequeña escala rellenando surcos erosivos, que puede presentarse en toda la sección de la barra de meandro. La estratificación cruzada de ripples compone a su vez otras formas del lecho que se caracterizan por una morfología de crestas longitudinales. Estas formas compuestas se interpretan como formas del lecho generadas por vórtices espirales en zonas de separación de flujo.Item Ichnofauna from coastal meandering channel systems (Upper Cretaceous Tremp Formation, South-Central Pyrenees, Spain): delineating the fluvial-tidal transition(Journal of paleontology, 2016) Díez Canseco, Davinia; Buatois, Luis A.; Mángano, M. Gabriela; Díaz Molina, Margarita; Benito Moreno, María IsabelThe Upper Cretaceous “redbeds” of the lower Tremp Formation (South-Central Pyrenees, Spain) contains an ichnofauna consisting of Taenidium barretti, Taenidium bowni, Loloichnus isp., Arenicolites isp., Planolites isp., and Palaeophycus isp. This ichnofauna occurs in deposits formed in tide-influenced meander loops and their associated overbank mudflats. Evaluation of the taphonomic controls on the Tremp ichnofauna shows that (1) two morphotypes of Taenidium barretti are controlled by the substrate consistence, (2) Arenicolites may be enlarged by erosion processes, and (3) Taenidium barretti and Planolites isp. are not the same ichnotaxa showing different types of preservation. The meniscate fill in Taenidium barretti suggests that this structure was produced by deposit feeders. The Tremp ichnofauna is grouped into two trace-fossil assemblages, a depauperate subaquatic monospecific Planolites suite and an assemblage representing the Scoyenia Ichnofacies.Trace-fossil distribution reflects paleoenvironmental changes in the meandering channels along the stratigraphic section with the Planolites suite in the lowermost part of the lower interval and the Scoyenia Ichnofacies in the middle and upper intervals. The lowermost suite may be likely formed seaward of the maximum salinity limit, under extreme brackish-water conditions, whereas the Scoyenia Ichnofacies records a freshwater assemblage that was formed landward of the maximum salinity limit, reflecting deltaic progradation.Item Sedimentary facies and three-dimensional reconstructions of upper Oligocene meander belts from the Loranca Basin, Spain(AAPG Bulletin, 2010) Díaz Molina, Margarita; Muñoz García, María BelénIn this article, we reconstruct and explore the three-dimensional (3-D) architecture of superimposed meander-belt sediments as an analog of subsurface reservoirs. Two exposures, named the Huete anticline and Garcinarro, were selected from the Loranca Basin, central Spain. In both of them, deposits are dominated by meandering river sediments of Oligocene age. Some point bars show fining-upward sequences of sedimentary structures and grain size typical of the helicoidal flow, but most of them present multiple vertical changes in grain size and are characterized by the occurrence of small-scale cross-stratification filling scours. The origin of these structures is related to oppositely rotating spiral vortices associated with flow separation along the convex bank of the meander bends. The 3-D architecture of superimposed meander-belt sediments allowed the reconstruction of meandering channel orientations and meander wavelength, calculation of the net/gross sandstone content, and the fraction of interconnected sandstone bodies. The 3-D architecture revealed that the interconnection areas are nearly absent when the orientations of the superimposed meander belts were perpendicular and that interconnection areas are more abundant and larger where a coincidence in the orientations of superimposed meander belts is observed. Horizontal projections of the highly interconnected areas allow calculation of the area fraction where one or more sandstone bodies could be intersected by vertical drilling. Differences in sandstone fraction between the two studied exposures were caused by the proximity to the Altomira Sierra thrust belt, which forms the western margin of the Loranca Basin.Item Acercamiento a la muerte de un renacuajo en el Mioceno a través de una trama policíaca(Sin ciencia no hay cultura: III Congreso sobre Comunicación Social de la Ciencia. Libro de actas, 2006) Bustillo Revuelta, María Ángeles; Aparicio, H.; Rodríguez Talavera, María del Rosario; López Martínez, Mª J.; Díaz Molina, MargaritaItem Bioestratigrafía y paleogeografía del terciario al E. de la Sierra de Altomira (Cuenca)(2015) Díaz Molina, Margarita; Aguirre, Emiliano; Vilas Minondo, LorenzoItem Depositional setting and early diagenesis of the dinosaur eggshell-bearing Aren Fm at Bastus, Late Campanian, south-central Pyrenees(Sedimentary geology, 2007) Díaz Molina, Margarita; Kälin, Otto; Benito Moreno, María Isabel; López Martínez, María Nieves; Vicens, EnricThe Late Cretaceous Aren Fm exposed north of Bastus in the Tremp Basin (south-central Pyrenees) preserves an excellent record of dinosaur eggs laid in a marine littoral setting. Different from other cases reported in literature, at the Bastus site the preferential nesting ground was original beach sand. The coastal deposits of Aren Fm can be grouped into four facies assemblages, representing respectively shoreface, beachface, beach ridge plain and backbarrier lagoon environments. Shoreface deposits include fine- to coarsegrained hybrid arenites and subordinate quartz-dominated conglomerates with ripple structures of wave and wave-current origin. Beachface deposits are mainly storm beach conglomerates, but parallel-laminated foreshore arenites locally occur. Backbarrier lagoon deposits comprise of washover sandy conglomerates that grade laterally into sandy lime mudstones, biomicrites and marls. Beach ridge sediment, wherein the bulk of dinosaur eggs and eggshell debris occurs, predominantly is a reddish hybrid arenite that has undergone a complex early diagenetic evolution, including marine and meteoric cementation followed by soil development. The reddish arenites overlie wave-dominated shoreface deposits and in places pass laterally into lagoonal deposits. They originally formed shore ridges, that became stabilized during progradational episodes by pedogenesis (beach ridge, sensu[Otvos, E.G., 2000. Beach ridges—definitions and significance. Geomorphology 32, 83–108.]), which also affected the dinosaur eggs. The eggshell-bearing beach ridge arenites are typically preserved at the top of parasequences forming the systems tracts of a third-order sequence. Thick packages of this facies resulted from aggradation of barrier/beach ridge deposits, whose preservation below surfaces of transgressive erosion was favoured by incipient lithification.Item Dinosaur nests at the sea shore(Nature -London, 2002) Sanz , J.L.; Moratalla, J.J.; Díaz Molina, Margarita; López Martínez, María Nieves; Kälin, Otto; Vianey-Liaud, M.Item Stream mouth deposits in the palaeontological site of Somosaguas, Middle Miocene, Madrid Basin(Revista española de paleontología, 2012) Díez Canseco, Davinia; López Martínez, María Nieves; Díaz Molina, Margarita; Benito Moreno, María IsabelThe Middle Miocene sediments exposed in Somosaguas contain an excellent record of mammal fossil remains preserved in debris and mudfl ow deposits. In the sedimentary sequence of Somosaguas three facies associations are distinguished, representing alluvial fan and shallow lake margin environments. Alluvial fans are composed of mud and debris fl ow deposits. The whole of the lacustrine deposits are interbedded between debris and mud fl ow deposits. The shallow lake deposits are devoid of fossil remains, and they consist of well-sorted micaceous sandstone bodies with water flow structures, interbedded with thin mudstone beds. These sandstone bodies are interpreted as stream mouth lobes. Three integrated stratigraphic sections show that the lacustrine bedset overlain an erosion surface, probably scoured by flood waters. Palaeocurrent measurements indicate that the sediment filling the shallow lake came from the west and the north.