Shallow marine depositional sequences with stromatoporoids (lower Aptian, Prebetic, Sierra de Bedmar-Jódar)

Abstract

Se estudian dos secuencias deposicionales de la parte inferior de la Formación Llopis (Aptiense inferior) en la Sierra de Bedmar-Jódar. Entre estos materiales y los infrayacentes (Formación Los Villares) se ha detectado una discontinuidad estratigráfica con un hiato que abarca el Hauteriviense y el Barremiense. La primera secuencia deposicional está compuesta por sedimentos terrígenos y carbonatados depositados en medios de plataforma interna, muy someros y de aguas agitadas, próximos a la barrera, representada por calizas de estromatopóridos. En la segunda secuencia deposicional se observan también sedimentos terrígenos y carbonatados de plataforma interna que evolucionan hacia medios intermareales, que puntualmente tienen influencia continental; como en el caso anterior, estos ambientes están delimitados por bioconstrucciones de estromatopóridos. Cada secuencia puede interpretarse como el resultado de una somerización progresiva hacia techo. Entre ellas se detecta una ruptura sedimentaria que sugiere una caída relativa del nivel del marIn the Sierra de Bedmar-Jódar (Prebetic), between the Los Villares Formation (upper Valanginian) and Llopis Formation (lower Aptian), an unconformity with an associated Hauterivian-Barremian hiatus has been recognised. In the second lithostratigraphic unit, several depositional sequences have been identified. In this paper, we analyse the first and second sequences (Sd1 and Sd2) deposited in a siliciclastic-carbonate mixed marine platform. The Sd1 is made up by siliciclastics and oolitic-bioclastic grainstone deposited in inner platform environments, near to the barrier zone, with shallow and turbulent waters. The upper part of this sequence is composed of stromatoporoid limestones (floatstone). These limestones are interpreted as deposited in a shallow barrier environment with calcarenitic bars. The rocks that made up the Sd2 are also attributed to an inner platform, with more shallow and calm waters than the previous sequence, according to the miliolid wackestone with fenestral texture found. These shallow environments could have being be influenced by fresh waters, as the presence of charophytes suggests. The upper part of this sequence contains again stromatoporoid floatstones like the underlying one, deposited in a barrier environment. Each one sequences could be interpreted as shallowing upward. A sedimentary break is detected between them, interpreted as the consequence of a relative sea level fal