Sedimentología de un sistema de abanico deltaico dominado por flujos supercríticos (Formación La Peza, ¿Serravaliense?- Tortoniense basal, Cordillera Bética)
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Abstract
En este trabajo se ha llevado a cabo la caracterización sedimentológica
en afloramiento del miembro detrítico gris de la Formación
La Peza (¿Serravaliense?-Tortoniense basal, SO de la Depresión de
Guadix, Cordillera Bética). Se han diferenciado en los 135 m de potencia
del miembro detrítico 15 secuencias grano y estratocrecientes
de espesor métrico a decamétrico constituidas por cinco asociaciones
de facies (AF 1-5) características de otros tantos subambientes
deposicionales: (A) Llanura deltaica (canal distributario (AF-1) y barra
de desembocadura (AF-3), bahía interdistributaria (AF-2)); (B)
Zona infralitoral dominada por acción del oleaje (AF-4), y (C) Canales
de chute en un talud/frente deltaico de grano grueso (AF-5). Las
asociaciones de facies de gravas (AF-1,3,5) representan flujos de alta
concentración de sedimento de grano grueso (desde flujo hiperconcentrados
a turbiditas de alta densidad) con comunes estructuras
de formas de lecho asociadas a flujos supercríticos características de
zonas de pendiente con saltos hidráulicos. Estos rasgos son característicos
de sistemas sedimentarios inmaduros de corto recorrido y
alta pendiente del tipo abanicos deltaicos probablemente adosados
a un margen de cuenca con relieves emergentes próximos a costa
This sedimentological study focuses on the grey detrital member of the La Peza Formation (Serravalian?-Lower Tortonian, SW of the Guadix Basin, Betic Cordillera) on the basis of outcrop observations. The 135 m thick succession consists of 15 coarsening and thickening-upward meter to decameter thick sequences made up of five facies association (FA 1-5) representing different depositional subenvironments: (A) Delta plain (distributary channel (FA-1) and distributary mouth-bar (FA-3), interdistributary bay (FA-2)); (B) Wave- dominated shoreface (FA-4), and (C) Chutes along a deltaic slope (FA-5). Gravel facies associations (FA-1, 3, 5) consists of deposition of high-concentration coarse-grained flows (i.e. from hiperconcentrated to high-density turbiditic flows) with common structures and bedforms linked to supercritical conditions related to hydraulic jumps in slopes or channel-lobe transition zones. All these features fit to a non-mature, steep and short sedimentary systems (fan delta-type) attached to a basin margin with emergent reliefs close to the coast
This sedimentological study focuses on the grey detrital member of the La Peza Formation (Serravalian?-Lower Tortonian, SW of the Guadix Basin, Betic Cordillera) on the basis of outcrop observations. The 135 m thick succession consists of 15 coarsening and thickening-upward meter to decameter thick sequences made up of five facies association (FA 1-5) representing different depositional subenvironments: (A) Delta plain (distributary channel (FA-1) and distributary mouth-bar (FA-3), interdistributary bay (FA-2)); (B) Wave- dominated shoreface (FA-4), and (C) Chutes along a deltaic slope (FA-5). Gravel facies associations (FA-1, 3, 5) consists of deposition of high-concentration coarse-grained flows (i.e. from hiperconcentrated to high-density turbiditic flows) with common structures and bedforms linked to supercritical conditions related to hydraulic jumps in slopes or channel-lobe transition zones. All these features fit to a non-mature, steep and short sedimentary systems (fan delta-type) attached to a basin margin with emergent reliefs close to the coast
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