Paleoecology, biostratigraphy and paleoclimatology of the lacustrine fossiliferous beds of the Izarra Formation

Abstract

This paper reports the results of the palynological analysis of three miospore assemblages from the non-marine deposits of the Izarra Formation (Basque-Cantabrian Basin, Álava province). This unit represents the sedimentary infill of a small diapiric basin (the Izarra Basin) developed during the Lower Miocene as an endorreic basin where complex sedimentary systems established sequentially; initially a stream dominated alluvial fan (Lower Clastic Member), then a palustrine floodplain (Middle Marly-Calcareous Member), and finally, a permanent lake (Upper Clayey Member). The palynological analysis allowed the identification of 87 taxa (bryophytes, clubmosses, ferns, gymnosperms and angiosperms). The landscape of the region was mainly characterized by mixed riparian with laurophilous elements, mesophytic and coniferous forests, though non-arboreal open vegetation characterized by Poaceae had relevance during deposit of sediments of the Middle Marly-Calcareous Member. The composition of the palynological assemblages is similar to these from Lower and Middle Miocene of the Western Mediterranean Region and East Iberian Peninsula. A subtropical climate was inferred using the socalled �coexistence approach�. The palynological results were also contrasted with the data obtained from the study of a megafloral assemblage associated to carbonate concretions found in the Upper Clayey Member.