Depósitos de brechas intraformacionales y slum ps en el Jurásico Medio del Subbético Medio oriental (Sierra de Ricote, provincia de Murcia)

Abstract

Stratigraphical and sedimentological analysis of early Bajocian hemipelagic deposits in the Bermeja Unit (eastern part of the Subbetic basin) is presented. Two distinct episodes of tectonic instability are recorded during the early Bajocian: (!) intraformational breccias and fine-grained turbidites (developed during the Walked Subzone) and (2) slumps (occurring at the top of the Blagdeni Subzone). Debris-flow deposits (slumps and intraformational breccias) and fine-grained sediments are linked to episodes of low sea-level, during which two important episodes of ammonite faunal turnover took place. A sharp onset of carbonate turbidites is recorded just after the intraformational breccias deposit, mostly in the pelagic part of the Unit. This later event occurred during an episode of high sea-level, simultaneously with the major ammonite radiation of the early Bajocian (Laeviuscula Zone). Our study stressed how important was the control imposed by the new regional tectonic configuration acquired in the western Tethys as response to the central Atlantic opening, as reflected by both the tecto-sedimentary record and the marine biota.