Climate and vegetation dynamics during the Eocene greenhouse of Central Europe: Palynological investigation of lacustrine sediments from Lake „Prinz von Hessen“ (Southwest Germany)

Lacustrine sediments of a small pull-apart basin at Grube Prinz von Hessen, 5 km NE of Darmstadt (Southwest Germany), have been analyzed palynologically in order to reveal long- and short-term interaction of climate and environment across the last natural greenhouse system in Central Europe. The lacustrine succession includes 34 m of clastic sediments which are overlain by 54 m of finely laminated bituminous claystone and lignite. In a first step the complete section has been covered by samples in 2 m intervals. Based on palynological index fossils it can now be proven that the lake basin must have persisted for some millions of years from the latest Early Eocene into the Middle to Late Eocene. Statistical analyses of the diverse and well-preserved palynoflora reveal 5 distinct associations throughout the sedimentary record. There is a strong correlation between major changes in vegetation and lithology which was controlled by factors such as tectonics and climate. In a second high resolution study palynological data from a c. 13 m thick part of the succession which is characterized by a regular alternation of lignite layers and mudstones have been analysed. The results show a correlation to lake level fluctuations including short time establishment of an open lake. Nevertheless, since no rooting structures have been observed below the lignites and some of them show erosional structures at their base, an allochthonous origin for the organic material in the lignite layers is suggested. It has been redeposited from material which was eroded around the lake, probably due to tectonic activity. Therefore, an orbital control of lake level fluctuations responsible for the regular occurrence of lignites cannot be proven. Nevertheless, cyclic abundance fluctuations of palynomorphs indicate an orbital influence and therefore a climate control on vegetation changes independently of lake level fluctuations