Continental palynomorphs from the Dabaa Formation, North-Western Desert, Egypt: a contribution to the reconstruction of the vegetation on the southern shores of the Tethys Ocean during the Early Oligocene

Abstract

The Eocene–Oligocene transition period was marked by one of the most abrupt and severe global environmental changes in the Cenozoic record, and this had a marked influence on the evolution of a number of animal and plant groups and entire ecosystems. This study documents continental palynomorphs recovered from the sedimentary rocks of the Dabaa Formation (Qattara area, North-Western Desert, Egypt) located on the southern shore of the Tethys Ocean and dated as Late Eocene–Early Oligocene. The botanical affinities, (phyto)ecology and distribution of the vegetation during the Eocene–Oligocene of the study area are discussed. The recorded assemblages are well preserved and comprise diverse lineages of algae, spores and pollen. They were identified, illustrated and assigned to 46 families encompassing chlorococcalean algae, lycopods, ferns, gymnosperms and angiosperms. The studied assemblages demonstrate the development of tropical vegetation, including tropical deciduous forest, grassland and (semi-)arid tropical shrubland, in which angiosperms were one of the main representatives; additionally open, drier habitats might have existed in the hinterland. Our data have been combined with previous megafossil and palynological evidence to assess and refine vegetation changes during the Early Oligocene time window in Egypt and across North Africa. Vegetation was a mosaic of different vegetation belts that ran more-or-less parallel to the coastline of the Tethys Ocean under the variable geographical influence of lagoons and streams. It is assumed that the belt of tropical forest along the coast of the Tethys Ocean narrowed during the Oligocene in parallel to climatic deterioration following the Eocene–Oligocene boundary, which may have also led to the fractionation of forest habitats.