SEM pollen analysis of Miocene deposits of Entrischenbrunn (Bavaria, Germany) reveal considerable amounts of pollen of subhumid and sclerophyllous together with azonal water plants reflecting the vegetation mosaic of a braided river system

Abstract

The 1 m thick intercalated marly sediments of Entrischenbrunn represent a floodplain pond within a braided fluvial system of late Langhian age. The organic rich upper part of the marls that are characterized by the presence of numerous plant macrofossils, are investigated for palynomorphs with SEM. The results reveal that many typical azonal broad leaved forest elements were present (e.g., Fraxinus and Liquidambar) and some of the common macrofossils, such as Hemitrapa, Podocarpium, Platanus sp., Quercus spp. etc. However, because of non-resistant pollen walls, the two dominant components of the macroflora, Daphnogene and Populus are not represented in the palynoflora. In contrast, plants not known from macrofossils or rare for this locality are present: several aquatic plants (e.g., Callitriche sp., Ludwigia sp., Decodon sp.), and a large portion of more subhumid and sclerophyllous plants such as Celtis “tournefortii-type”, two Ephedra spp., two Erica spp. affiliable with Mediterranean species, Quercus sp. section Ilex, a Sapoteae, Sideroxylon sp., Rehderodendron sp., Ulmus sp. section Foliaceae Zelkova “abelicea/serrata-type”, and Ziziphus “mucronata/mauritania/jujube-type”, whereas Diospyros sp. and cf. Royena sp. can be interpreted to present humid to subhumid conditions. The reasons for this mixture might be threefold: 1. localized well-drained substrates and water loss on particularly pebbly, gravelly and sandy deposits of the braided river system or 2. presence of a geographically controlled localized lower humidity in that area, or 3. because of a generally drier period within the Middle Miocene.