Resumen de La ventana tectónica de Albuñol: estratigrafía y estructura (Complejo Alpujárride, Zona Interna Bética, provincia de Granada)
Carlos Sanz de Galdeano Equiza, Ángel Carlos López Garrido
- español
La ventana tectónica de Albuñol corresponde a parte de la unidad alpujárride de Lújar-Gádor. Esta unidad, afectada por un metamorfismo de bajo grado, tiene potentes secuencias de plataforma (del Ladiniense-Carniense) que muestran rasgos de inestabilidad tectónica durante el depósito. Es cabalgada por otras unidades alpujárrides y, particularmente en el techo de la ventana (donde se han formado brechas tectónicas) se conserva bien el sentido de desplazamiento de estas hacia el N. Ligados a los cabalgamientos hay grandes bloques de carbonatos y filitas que proceden de unidades inferiores, englobados en la base de la principal unidad cabalgante o cerca de ella. La estructura interna de la ventana es simple, formada fundamentalmente por un suave pliegue E-O. Además, existen otros pliegues posteriores de dirección N20-35ºE. En la unidad de Lújar-Gádor hay abundantes estructuras menores, muchas de ellas ligadas a la formación de pliegues, sobre todo boudines e infinidad de juegos de diaclasas. Localmente los boudines han sido algo rotados y desplazados en el sentido de la vergencia de los pliegues. Los rasgos de extensión posteriores ligados al levantamiento de la cordillera están menos marcados.
- English
The Albuñol tectonic window situated within the Alpujarride Complex is known from the beginning of the last century, but its stratigraphic series and structure have not been described in detail. Inside of this window, the Ladinian-Carnian stratigraphic series of the Lujar-Gador unit (with a low degree of metamorphism) crops out. This succession deposited in a shallow platform, which underwent tectonic instability, and consequently several episodes of intraformational breccias and slumps were formed. These sequences, including the breccias and slumps, can be correlated with those of the Lujar and Gador sierras, and correspond to the beginnings of the rifting process that affected the western part of the Tethys. Pseudo S/C structures existing near the bottom of the overthrusting units and also in the tectonic breccias formed in the surface of the window indicate a top to the north sense of displacements. To the NNE of the locality of Albuñol, there is another type of breccias, with the appearance of rauhwackes (carbonate breccias but also including in this case other types of rocks), probably linked to the process of tectonic superposition of the units. Also linked to the process of thrusting, great blocks (even exceeding a hundred metres) of carbonates and phyllites, are included in the overthrusting units, near their bottom. These blocks were formerly considered to be part of the upper units and attributed to the Palaeozoic. Later extensional features, linked to the regional uplift of the cordillera are less clearly expressed, this being surprising because of the abundant literature describing them as dominant in the region. The internal structure of the Albuñol tectonic window is simple, formed mainly by a kilometric open fold of approximate E-W strike, to which other smaller folds are related. N70ºE to EW folds were formed initially and other N20-35ºE ones were superposed over them. There are abundant minor structures, many linked to the limbs of folds. Some of the boudins have rotated and been displaced in the sense of the vergence of the folds. There is also a myriad of joint sets, formed very easily according to the change of the stress ellipsoid during the process of formation of every structure, under fragile conditions, but coexisting with certain ductility. The overthrusting of the units probably occurred during the Oligocene and then formed the N70ºE to E-W folds. At the end of the Oligocene- early Miocene the Internal Zone was expelled to the W and formed the N20-35ºE folds.
