High-resolution regional vegetation analyses for Eocene records on the Sprendlinger Horst in Southwest Germany.

The lacustrine fillings of four small early to middle Eocene lakes at Messel, Offenthal, Groß-Zimmern and Grube Prinz von Hessen on the Sprendlinger Horst in SW Germany are compared using a principal component analysis of palynological data from 791 samples. Except for the pull-apart basin of Lake Prinz von Hessen, the other basins represent maar lakes which were formed by phreatomagmatic eruptions. Statistical analysis revealed different pollen and spore assemblages for each maar lake, but similar general trends in the evolution of the vegetation, which can be attributed to successional stages during the recolonisation of the disturbed habitats under the greenhouse conditions of the Palaeogene. Four different phases can be distinguished at these sites during progressive reestablishment of the vegetation: (1) an initial phase, (2) a recolonisation phase, (3) a recovery phase, (4) a climax phase. An initial phase is only recovered at Offenthal and Groß- Zimmern and represents the phase immediately after the eruptions, when the vegetation had been destroyed. In the recolonisation phase that is documented in all maar lakes, the recolonisation of the devastated areas by a pioneer vegetation started. Pollen assemblages of the following recovery phase are preserved in Messel and partly in Offenthal and indicate the re-establishment of the forest vegetation in the crater areas. The succeeding climax phase is only documented at Messel and characterised by a robust thermophilic climax vegetation. The composition of the vegetation at Lake Prinz von Hessen was similar compared to the vegetation around the maar lakes. However, the habitat remained undisturbed and the different phases of recolonisation did not occur. [ABSTRACT FROM AUTHOR]