Climate, volcanoes, and tectonic activity – Their influence on the lower to middle Eocene paleoenvironment on the Sprendlinger Horst (Southwest Germany)

The Sprendlinger Horst represents the northern extension of the Odenwald basement which is flanking the Upper Rhine Graben to the northeast. Several small, isolated basins filled by lacustrine sediments of Eocene age are known from the area. Most of them represent the filling of maar-type volcanic structures, such as the lakes at Messel, Offenthal and Groß Zimmern. Only Lake Prinz von Hessen near Darmstadt represents a small pull-apart basin. High resolution palynological analyses of drill cores from these four nearly coeval lake basins allows to reconstruct the vegetation during the last natural greenhouse system in Central Europe. Quantitative palynological data from the deposits of the four lakes prove that the vegetation generally shows the same succession with a recolonization phase at the beginning, followed by a recovery and a terminal climax phase. The record may be incomplete for some of the lakes, but an extensive data set including nearly 1000 samples shows that each basin has its unique story to tell. For example, in Messel the undisturbed record of about 600.000 years reveals the influence of orbital forcing on the climate and the composition as well as on the diversity of the climax vegetation during the early middle Eocene. In contrast, at lakes Prinz von Hessen and Groß Zimmern regional tectonic and seismic activity had a more pronounced influence on the paleoenvironment than orbitally controlled climate change.