Publication: Efectos de la separación de flujo en las secuencias de barras de meandro. Ejemplos del Oligoceno Superior de la Cuenca de Loranca
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2008
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Sociedad Geológica de España.
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Abstract
El 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.
In the Loranca Basin the Eocene to Miocene stratigraphic record consists of fluvial, alluvial and lacustrine sediments. During Late Oligocene times meandering river deposits of the Tórtola fluvial fan extended on the central part of the basin and towards its western margin. Point bars of the Tórtola fan show departures from the basic facies model, where the sequence of sedimentary structures was generated by a decrease in flow velocity. Gradual fining-upward sequences are not frequent in the Oligocene point bars of the Loranca Basin. The most abundant sedimentary structure is small scale cross-stratification filling trough erosional surfaces, which can be present along the whole point bar section. Ripple cross-stratification in turn composed longitudinal ridges bed forms. These composite bed forms were probably generated by spiral vortices in flow separation zones.
In the Loranca Basin the Eocene to Miocene stratigraphic record consists of fluvial, alluvial and lacustrine sediments. During Late Oligocene times meandering river deposits of the Tórtola fluvial fan extended on the central part of the basin and towards its western margin. Point bars of the Tórtola fan show departures from the basic facies model, where the sequence of sedimentary structures was generated by a decrease in flow velocity. Gradual fining-upward sequences are not frequent in the Oligocene point bars of the Loranca Basin. The most abundant sedimentary structure is small scale cross-stratification filling trough erosional surfaces, which can be present along the whole point bar section. Ripple cross-stratification in turn composed longitudinal ridges bed forms. These composite bed forms were probably generated by spiral vortices in flow separation zones.