Estructura de la Cuenca de Jaca en el sector occidental de las Sierras Exteriores Aragonesas

Abstract

In the western part of the Sierras Exteriores Aragonesas the southern Pyrenean front is not a southvergent large thrust, but an isoclinal detachment fold (Santo Domingo anticline), whose core is occuppied by the Upper Triassic (Keuper facies). Twenty kilometers far from the western end of the Sierras the Santo Domingo anticline is defined at surface by the steep-dipping beds of the Eocene-Oligocene molasse (Campodarbe and Uncastillo fms.). At depth, the Upper Triassic is still the detachment level for this fold. Nevertheless, the anticline increases its amplitude and tightness toward the upper part, due to the existence of multiple detachments in the Tertiary fluvial deposits. Toward the North a series of WNW-ESE folds, showing lengths up to 80 km are the most consplcous compressive structures within the Jaca basin. In the studied area, the Botaya anticline is cross-cut by a high-angle south-vergent thrust, contemporary with folding, which joins the regional detachment level toward the North