Publication: Fluvial carbonate occurrences in high energy rivers: Examples from the Gállego River Tributaries, Pyrenees, Huesca
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2017
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Sociedad Geológica de España
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Abstract
En este trabajo estudiamos los depósitos carbonáticos que se forman en el lecho de dos arroyos de montaña, Oliván y Orós, afluentes del Río Gállego, en los Pirineos. Los arroyos drenan los terrenos formados por el flysch eoceno, cargándose en calcio y carbonato. Estos carbonatos fluviales, escasos en relación con los depósitos de gravas gruesas que cubren el lecho del río, tienen muchos rasgos en común con los de las tobas fluviales. Las principales facies carbonáticas que se forman sobre la carga de fondo y entre los clastos grandes son: grandes oncoides, pequeños parches de framestones y rudstones de fitoclastos. El carbonato, muy bien laminado, está formado por calcita e incluye numerosos restos vegetales y diatomeas. Las láminas están formadas por grandes cristales de calcita (bladed, fibrosa, en forma de abanicos y de arbustos) y micrita-microesparita. Los microbios tuvieron un papel importante en la formación de algunas de las microestructuras pero el principal mecanismo que favorece la precipitación de calcita en estos ríos fríos de montaña es la desgasificación mecánica de CO2 .
In this paper we study the carbonate deposits that form on the bed of Oliván and Orós mountain streams, which are tributaries of the Gállego River, in the Pyrenees. The streams drain the terrains formed by the Eocene Flysch, which provide calcium and carbonate to the rivers. These fluvial carbonates although scarce, in comparison with the dominant coarse gravel deposits of the streams, show similarities with fluvial tufa deposits. The main carbonate facies, formed on the bedload and between the large clasts, include: large oncoids, small framestone patches and rudstones of phytoclasts. The carbonate, very well laminated, is composed of calcite and includes vegetal debris and diatoms. The laminae are formed by coarse calcite crystals (bladed, fibrous, fan-like with filaments and bushes) and micritemicrospar. Microbes played an important role in the formation of some of the microstructures, however the main mechanism favoring carbonate precipitation in these mountain, cold-streams is mechanical CO2 degassing.
In this paper we study the carbonate deposits that form on the bed of Oliván and Orós mountain streams, which are tributaries of the Gállego River, in the Pyrenees. The streams drain the terrains formed by the Eocene Flysch, which provide calcium and carbonate to the rivers. These fluvial carbonates although scarce, in comparison with the dominant coarse gravel deposits of the streams, show similarities with fluvial tufa deposits. The main carbonate facies, formed on the bedload and between the large clasts, include: large oncoids, small framestone patches and rudstones of phytoclasts. The carbonate, very well laminated, is composed of calcite and includes vegetal debris and diatoms. The laminae are formed by coarse calcite crystals (bladed, fibrous, fan-like with filaments and bushes) and micritemicrospar. Microbes played an important role in the formation of some of the microstructures, however the main mechanism favoring carbonate precipitation in these mountain, cold-streams is mechanical CO2 degassing.