The common frame for research at the Palaeobotanical Section in Frankfurt includes aspects of both, sedimentology/facies and systematic (palaeo)botany and may therefore be summarized under the heading of “Terrestrial Palaeoecology”. This is a direct expression of the interdisciplinary tradition of Senckenberg palaeobotany between geo- and biosciences. Therefore, most of the present research projects consequently are a continuation and further development of traditional research programs at Senckenberg in Frankfurt. The may be assigned to the following major fields.
Plant remains of Paleogene age and their sedimentological context, especially within Germany, are a major research focus of Palaeobotany at Frankfurt. Running projects mainly comprise sediments of Eocene age in terrestrial and marginal marine settings, such as the lacustrine deposits of Messel and Eckfeld and the lignite-bearing successions of the mining districts of Helmstedt and the Geiseltal. Projects include systematic work on individual taxa of pollen/spores, fruits/seeds, flowers, leaves and, sometimes, wood fom Messel and Eckfeld which is done in close cooperation with external and internal experts and specialists. There are milestone publications on pollen from Messel (Thiele-Pfeiffer 1987) and Eckfeld (Nickel 1996), leaves from Messel (Wilde 1989) and fruits/seeds from Messel (Collinson, Manchester & Wilde 2012).
For Eckfeld, there is a long-term cooperation with the University of Mainz and the Natural History Museum Mainz/State Collections for Natural Sciences Rhineland-Palatinate (Herbert Frankenhäuser). Present work mainly includes Juglandaceae, conifers, ferns and some selected taxa of unknown affinity. The pollen which is preserved in-situ in flowers at Messel and Eckfeld is used in another project as a base for comparisons with dispersed pollen taxa and may help in refining their systematic assignment, especially by applying Scanning Electron Microscopy.
Systematic palynological studies at Messel and Eckfeld allowed for a reconstruction of climate and vegetation around the maar lakes and their surroundings (Thiele-Pfeiffer 1987 and Nickel 1996, respectively). Supported by a grant from the German Research Foundation (DFG) Olaf Klaus Lenz later started high-resolution studies on a research core from the Messel pit (“Messel 2001”) which led to a series of pioneering papers. They were designed to resolve changes in the vegetation with time by the help of modern statistical methods. In a first step reconstruction of the re-occupation of the area devastated by the eruption ca. 48 Millio years ago by the vegetation became possible. Analyzing quantitative changes in the composition of the pollen and spores as recovered from the oil shale of the Middle Messel Formation clearly revealed orbital and suborbital cyclicity as the driving force for changes in climate and vegetation. Furthermore, varve countings for the first time directly revealed ENSO-cyclicity for Eocene lacustrine sediments. Statistical analyses of plant biodiversity which were based on pollen and spores as proxies recently revealed fluctuations in the same ranges. Altogether this proves in high resolution that surprisingly similar mechanisms acted for climate change in greenhouse and icehouse systems of the Cenozoic.
Another famous lagerstätte for the terrestrial Middle Eocene in Germany is the former lignite mining district of the Geiseltal near Halle (Saale). Prior to final flooding of the mining area five field campaigns were conducted here between 2000 and 2003 in close cooperation with the Geiseltalmuseum in Halle. They mainly served for securing data and samples from remnant sections spanning much of the middle Eocene land mammal stage “Geiseltalian”. Most of the >1500 individual samples and a number of plant fossils have not yet been studied in detail and form a base for ongoing and future research. Inspired by previous work of WALTER RIEGEL the opencast mine Schöningen-Southfield of the Helmstedt Lignite Mining District became an important research focus. Several thousand samples have been collected here in a great number of individual sections. Altogether they span more than 10 million years from the uppermost Paleocene to the middle Eocene and therefore include the critical episodes of the so-called Paleocene-Eocene Thermal Maximum (PETM) and succeeding climate excursions. Detailed palynological analyses of selected parts of the section are now studied with respect to vegetation, climate and palaeoecology. It is important here that the taxonomic resolution for the study is greatly enhanced by the combination of light microscopical techniques and scanning electron microscopy. Initial results are promising, but, a great number of samples and some more sections still remain to be studied. The German Research Foundation (DFG) recently provided the funds for a statistical study of plant (palyno) biodiversity throughout the whole section by Olaf Klaus Lenz.
2. Mesophytic and the transition Mesophytic/Cenophytic
Work on material and outcrops from this period of time is continued on a low level. The palynology of the Upper Triassic Kössen Beds from the orthern Calcareous Alps was successfully studied in a PhD-project by Björn Holstein (Frankfurt am Main); the project was funded by the German Research Foundation (DFG). Systematic work on selected plant fossils of Triassic/Lower Jurassic and Lower Cretaceous age, including megaspores, is going on. This especially includes the NW-German Wealden-facies which is of Berriasian age.
Most of the other scientists belonging to the Department for Palaeontology and Historical Geology have traditionally focussed their research towards the Palaeozoic, especially towards the Devonian of the Rheinisches Schiefergebirge. Several pioneering studies of Richard Kräusel and Hermann Weyland on Devonian plant fossils and a monograph of Tiwari & Schaarschmidt (1975) on Devonian palynology were part of this tradition. Following a recent re-organisation of the Devonian research group, palaeobotany and, especially, palynology became again included as an integral and important part of the ongoing interdisciplinary biostratigraphic and palaeoecologic studies of predominantly clastic successions. The present studies in the Devonian include actuogeologic comparisons in cooperation with the Research Station at Wilhelmshaven. Two major bilateral projects of the Department which were devoted to the Devonian of Turkey, especially to the Devonian of the Taurids included the Palaeobotanical Section. They were jointly funded by the International Bureau of the BMBF on the German side and the Tübitak on the Turkish side. Further inner-departmental cooperation is directed towards the Lower and early Middle Devonian of the Eifel (W-Germany).
There are only few palynological studies published on the famous Lower Devonian Hunsrück-Shale. Especially fired by Walter Riegel who has collected a large number of samples from the Hunsrück-area, a new project started. It has been realized now that SEM-techniques provide reasonable images of palynomorphs which are almost or even completely opaque when light microscopical techniques are applied, including infrared. This allows even for the determination (and stratigraphic interpretation) of specimens which were subject to very high thermal alteration.
It should be mentioned here that there are some subordinate activities with regard to permineralized material from the upper Palaeozoic. They especially include exceptionally preserved silicified material of early conifers from the Lower Permian (“Rotliegend”) of Schöneck-Kilianstädten in the Wetterau near Frankfurt, but much remains to be done here as far as time allows.
For some time the Section is now involved in cooperation projects with Geochemists. Some important studies have been carried out on the terpenoids of extant and fossil conifers from the Late Mesozoic and Cenozoic by Angelika Otto as a postdoc in cooperation with Wilhelm Püttmann (University of Frankfurt) and Bernd R. T. Simoneit, Corvallis, Oregon, USA. They showed a great potential for terpenoids as specific biomarkers of the different conifer families in turn allowing for unraveling the botanical affinity of some extinct conifers and the origin of amber. Another project initiated in cooperation with Wilhelm Püttmann (University of Frankfurt) and Stephan Hoernes (University of Bonn) dealt with the “Variation of chemofossils and stable isotopes in coals and plant remains from the Westphalian/Stephanian boundary of the Euramerican Carboniferous”. A major result was the recognition of cordaites as biological source for specific arborane/fernane derivatives in a PhD-thesis by Stephan Auras. Presently cooperation started at the Schöningen section with a working group around Richard Pancost (Bristol) and Margaret E. Collinson (London) on organic-geochemical proxies for changes in climate and peat-forming environments within the Paleogene greenhouse phase. Recently, a group in Frankfurt started isotope studies in combination with palynological analyses to unravel short-term climate events in the Paleogene.