Events between the Mid-Eocene Climatic Optimum and the Eocene-Oligocene Transition as reflected in vegetation dynamics of riparian forest in central Europe during late Eocene
Abstract
The Cenozoic Weißelster Basin (Germany) and the North Bohemian basins (Czech Republic) have an extensive fossil record of riparian vegetation traceable from the middle Eocene to the early Miocene. Within this paper we focus on its evolution and gradual changes between the late Bartonian and the Eocene-Oligocene turnover, which is regarded to be a time interval of gradual global cooling.
For most of the time span a certain stasis in the development of azonal regional vegetation was previously observed resulting in the establishment of the Zeitz floristic complex ("Florenkomplex") that covers ca. 3.0-3.5 Ma contradicting the suspected global climatic trend. Herein we summarize results of investigations of several fossil floras of the Weißelster Basin that were conducted over the last decade and allocate them into the modern lithostratigraphic concept for central Germany.
Previously published floras from this basin that come from an unambiguous lithostratigraphic position are revisited. For comparison floras from the North Bohemia are included.
Our results show that the Zeitz floristic complex cannot be maintained in its original circumscription but needs a subdivision into three floristic stages based on immigration and disappearance of key vegetation elements. Stage 1, representing the type horizon and flora of the Zeitz floristic complex, is characterized by the presence of typical 'subtropical' species persisting since the middle Eocene, e. g.
Doliostrobus taxiformis, Laurophyllum syncarpifolium, Steinhauera subglobosa, and Rhodomyrtophyllum reticulosum. In stage 2 thermophilous deciduous elements such as Platanus neptuni and Taxodium dubium as well as new Lauraceae immigrate into the regional vegetation.
The stage 3 is typical with disappearence of the old 'subtropical' elements, whereas other evergreen warm-temperate or 'subtropical' elements such as Eotrigonobalaus furcinervis and Quasisequoia couttsiae persist.