Preliminary palynological data on floristic and climatic changes during the Middle Eocene-Early Oligocene of the eastern Ebro Basin, northeast Spain

Abstract

Variations in pollen spectra observed in sediments from the middle Bartonian-Lower Oligocene of Igualada, Ebro Basin (northeast Spain), have permitted the identification of general trends in floristic and climate change. Detailed investigations of the biological affinities of certain fossil pollen have revealed a number of plant genera previously unidentified in the fossil record. The floral diversity and ecological characteristics of the pollen taxa indicates that the middle Bartonian vegetation of the eastern Ebro Basin was characterised by a complex mangrove swamp reflecting warm climatic conditions. During the Priabonian, the greater variety of herbaceous plants suggests the existence of a more open vegetation correlated with the change to a climate with a dry season. During the Priabonian the diversification of Caesalpiniaceae indicates African influence. During the Late Eocene taxa interpreted as indicators of a dry climate are identified, while those indicating humid climatic conditions disappear. Dry climatic conditions characterise the Lower Oligocene, as indicated by the abundance of cupressacean pollen interpreted as evidence of a sclerophyllous forest. A slight climatic cooling is also revealed by the presence of some microthermal taxa.