Tectónica extensiva sinsedimentaria de la Fm Escucha en el sector meridional de la Subcuenca Cretácica de Oliete (Cadena Ibérica Oriental)

Resumo

The sedimentary record of the Escucha Fm in the southern sector of the Oliete Subbasin shows several synsedimentary extensional features developed due to the extensional tectonic regime that governed the sedimentation of this cretaceous unit during the Lower-Middle Albian. The stratigraphic and structural study of these synrift features has allowed the distinction of two extensional episodes developed during deposition of two lithosomes of the Escucha Formation. The first extensional episode produced during the sedimentation of the lithosome 2, which is formed by sandstones alternating with silts. The second extensional episode affected the lithosome 3, which is a sandy body that displays silt and clay intercalations. The geometrical relationship between lithosomes 2 and 3 is an angular unconformity defined by the erosive truncation of rotated and faulted beds of the lithosome 2 and by the onlap that deposition of the sandy lithosome 3 produced on this surface. Fossilization of extensional faults by the surface that defines the angular unconformity between both lithosomes determines the synsedimentary character of these faults. During the first episode deca- to hecto-metric NW-SE to NNW-SSE trending listric faults developed with a shallow detachment level (probably clays of the lithosome 1). Their evolution produced the development of rotated fault-blocks, internal angular unconformities and minor extensional faulting. During the second episode normal faults, with trends similar but with higher dips towards NE (65º-85º) to previous ones, with metric-scale offsets formed. These faults have been interpreted as blind faults propagating toward the surface, probably from a deeper major normal fault. The listric faults system developed during the sedimentation of the lithosome 2 probably branched down into this steep and deeper major fault. Faults described show an ENE-WSW to NE-SW principal extension direction.