Los depósitos aluviales sintectónicos de la Pobla de Segur: alogrupos y su significado tectonoestratigráfico

Abstract

Detailed structural and stratigraphic studies in the late Eocene and Oligocene alluvial fan, fan-delta and lacustrine deposits of La Pobla de Segur Conglomerates (Collegats Formation) in the south-central part of the Pyrenees have indicated a close link between tectonics and sedimentation. The conglomerates unconformably overlie apreviously deformed Mesozoic substratum and are organized : into a series of stacked wedge-shaped bodies reaching an accumulative thickness of about 3500 m. The presence of basinwide mappable i unconformity surfaces allowed the definition of five main allogroups (Pessonada, Ermita, Pallaresa, Senterada and Antist) internally
I subdivided into alloformations or sequences. Structural relationships between the conglomerates and its Mesozoic substratum allowed to establish the relative chronology of the late stages of the alpine deformation in the south Pyrenean Chain and the tectonic origin of the bounding surfaces of the allogroups