Relación entre subsidencia y señal isotópica: un ejemplo en el límite Jurásico-Cretácico de la Unidad de Loma Solana (Subbético Externo, provincia de Murcia)

Resumen

The oxygen and carbon stable isotopes have been analysed within the Jurassic-Cretaceous boundary sucessions in the pelagic facies of the External Subbetic near Caravaca (External Zones of the Betic Cordilleras). Despite significant impact o f diagenesis, the observed changes in 813C can be correlated with deep-water sections from different tethysian basins. The values of 8iaO may be influenced not only by global factors (isotopic composition and temperature of seawater) but also by local tectonics: in the pelagic swells, subsidence and uplifts lead to changes in depth, and thus, in the rate of sedimentation and in the diagenetic conditions. The evolution of 8lsO values are compared in pelagic trough and pelagic swell during the late Tithonian-Berriasian. In deeper sites 8,80 depleted values could reflect cementation at higher burial temperatures. On the crest of tilded blocks heavier 8,sO values are preserved. The combined study of the facies, backstripping and isotopic evolution has enabled to show the importance of local or global factors in the boundaries and evolution of the genetic units.