Análisis isotópico (ó13C y ó180) de los depósitos carbonatados del sector de Borja-Tarazona: registro de cambio paleogeográfico en el Mioceno de la Cuenca del Ebro

• Autores: Marta Vázquez-Urbez, María Concepción Arenas Abad, Gonzalo Martín Pardo Tirapu
• Localización: Geotemas (Madrid), ISSN 1576-5172, Nº. 5, 2003 (Ejemplar dedicado a: V Congreso del Grupo Español del Terciario (Granada, 23-25 de septiembre, 2003)), págs. 237-242
• Idioma: español
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• Resumen

  • This contribution deals with the isotopic characterization of the Miocene carbonate deposits of the west central part of the Ebro Basin. The sequence studied has been divided into two sets: the lower one (middle Aragonian-Vallesian), formed of marls, bioclastic, bioturbated and nodulised limestones, mudstones and sandstones, and the upper one (¿Vallesian-?), mostly with oncolitic, tufa and intraclastic limestones, which constitute the “Muela de Borja limestones". The isotopic composition (-4.17> d'3C>-9.04 and -6 .13> d180>- 10.91 °/ooPDB) shows a wide dispersion and positive correlation between dl80 andduC in the lower set, whereas the upper set has very small isotopic variation and lacks correlation. These data, along with sedimentological interpretation, suggest that the upper set was deposited in a hydrologically open fluvio-lacustrine system, unlike the lower set, formed in closed lacustrine systems. Thus, the Muela de Borja limestones could represent the oldest record known related to the connection of the Ebro Basin drainage to the Mediterranean Sea. In that eontext, the dw0 values of the upper set were expected to be lower than those of the lower one. This could be caused by inputs of '80-enriched waters into the fluvio-lacustrine system, likely supplied by springs (probably favoured by fractures) from a regional aquifer in the Iberian Ranges.