Estudi geològic de la vall d'Alinyà i la seva rodalia (Pirineu català, Espanya)

Abstract

Geological study of the Alinyà Valley and its surroundings (Catalonian Pyrenees, Spain).
This study is the explanatory account of the original geological cartography to scale 1:25.000 of the Alinya Valley and its surroundings, presented here. It corresponds to an area of 130 km² approximately. The Alinyà Valley, a natural protected region in the Catalonian Pyrenees, is of particular interest due to its complexity. It corresponds to NE border of the strike slip Segre fault, and joins two very differents stratigraphic and paleogeographic compartments: to the W, the eastern border of the N half of the South Pyrenean Central Unit; to the E the Port del Comte Unit, that belongs to the Pedraforca Unit s. l. The stratigraphic analysis is the main part of this work. We identified a total of 24 main stratigraphical units with 13 secondary distinctions. Ultra a modest representation of the Triassic and the Jurassic terrains, the Cretaceous terrains on one side and the Eocene terrains on the other, occupy almost all the region. New findings have been described in the field of stratigraphy and paleogeographical evolution. The tectonic analysis is relatively brief and is accompanied by a schematic chronology of the main structural events which affected this region from Upper Cretaceous to Upper Paleogene times, all considered in a much more extensive regional setting. A final comment on the morphology and groundwater hydrology is presented.