Las asociaciones de ostrácodos en secuencias aluviales como indicadores de cambios ambientales holocenos (Bardenas Reales de Navarra, Cuenca del Ebro, NE Península Ibérica)

Abstract

In this paper, the ostracod assemblages identified in three alluvial units preserved in Bardenas Reales de Navarra (Ebro Basin, NE Iberian Peninsula) have been studied, with the aim of reconstructing the palaeoenvironmental evolution of this area during the late Holocene. The most common ostracod species in the studied samples are Ilyocypris bradyi Sars and Paralimnocythere aff. psammophila (Flossner), accompanied by Pseudocandona albicans (Brady). Variations in their relative abundance along these alluvial units allow us to characterize internal changes in the depositional environment. Thus, the unit deposited between 4763±87 and 2848±55 years cal. BP is dominated by I. bradyi , indicating the presence of small streams with running water developed probably in fluvial flood plains. Nevertheless, from 2848±55 to 836±65 years cal. BP Paralimnocythere aff. psammophila is the dominant species, representing the establishment of an ephemeral and stagnant aquatic environment, mainly related with more arid climatic conditions (Medieval Warm Period). Finally, the ostracod assemblage identified in Recent times (191±97 to 127±82 years cal. BP) is mainly dominated by I. bradyi , which indicates the presence of running waters. This later assemblage probably defines the influence of cold and wet climatic phase (Little Ice Age) during Recent times in this area. The palaeoenvironmental evolution identified from the late Holocene according to ostracod assemblages in Bardenas Reales de Navarra shows good correlation with rapid climatic changes deduced from other continental records of the NE Iberian Peninsula.