Palynology, biomarker assemblages and clay mineralogy of the early Eocene climate optimum (EECO) in the transgressive krappfeld succession (Eastern ALPS, Austria)

Sediments of the Eocene Holzer Formation from the Pemberger quarry were analysed for palynomorphs, lipid biomarker distributions, and clay mineralogy. The palynoflora is rich in megathermal and mesothermal families and genera, but also contain abundant wind-derived pollen derived from temperate to mesothermal taxa. The co-existence of temperate to megathermal elements suggests a sub/tropical and seasonally controlled passat-like or monsoon-like climate, comparable with the extant forests of the zonoecotone I/II, an interpretation consistent with relatively high temperatures derived from soil bacterial glycerol dialkyl glycerol tetraether (GDGT) lipid distributions. The lithologies and palynomorph assemblages represent three different facies: (1) coal-bearing palm swamp characterized by Myricaceae, triporate pollen types, fern spores and several palm pollen types, (2) coastal near swamp with mangrove elements such as Nypa, Avicennia and Ceriops, and (3) shrubby back swamp dominated by Myricaceae, triporate pollen, fern spores and palm pollen types. All of these are consistent with a dominance of terrigenous lipids, including triterpenoids and leaf waxes, in all samples. Abundant kaolinite contents in all the sediment samples are consistent with the biomarker and pollen analyses, indicating long periods with deep weathering under a warm and humid climate.