This work presents the sedimentological study of the Upper Miocene-Pliocene Oko Limestones, exposed in the Antzin-Murieta Basin, in Navarre. Two stratigraphic sections of the carbonate unit have been studied: the Oko cemetery and Ega road sections. The former exposes facies that characterize a fluvial carbonate environment, with a distinct development of microbial oncolitic deposits. The coeval deposits exposed in the Ega road section, instead, largely represent a palustrine-lacustrine setting that evolved under alternating conditions of ponding and desiccation. Data integration from these sections and the intermediate areas, allows the interpretation of a fluvial to palustrine-lacustrine wetland with a marked east-southeast trend, which developed coevally to the uplift of the Piedramillera thrust sheet.