Lenz, O. K. ; Wilde, V. ; Mertz, D. F. ; Riegel, W. (2014)
Palynology as a high resolution tool for Paleogene cyclostratigraphy – the outstanding record of Lake Messel (Germany).
In: GeoFrankfurt 2014 / Abstract volume
Artikel, Bibliographie

Kurzbeschreibung (Abstract)

The Upper Rhine Graben is the prominent central segment of the Cenozoic Central European Rift System. Initial crustal weakness along the incipient Upper Rhine Graben is indicated by Paleogene phreatomagmatic volcanism sometimes leaving behind isolated sinks where sedimentation started prior to the onset of major rifting and graben formation. The best known of about half a dozen isolated occurrences of Paleogene sediments on the Sprendlinger Horst which flanks the Upper Rhine Graben to the northeast, is Messel. As most of them it represents the filling of a maar structure.

A continuous core from Messel revealed a complete reference section of the Eocene lake deposits (Messel Formation), including 90 m of clastic lake sediments overlain by 140 m of the classical “Messel oil shale”, a continuous succession of finely laminated bituminous claystones. The lamination was caused by annual algal blooms in the meromictic lake forming light layers alternating with the dark layers of the terrigenous background sedimentation (Lenz et al., 2010). These oil shales provide a unique high-resolution archive for palaeoenvironment and palaeoclimate of a time interval of ~640 ka during the Paleogene. The character of the annually laminated sediments allows studies at an unprecedented resolution within the most recent greenhouse period on Earth. As a consequence of orbitally controlled changes of the vegetation in the vicinity of the lake (Lenz et al., 2011) the lacustrine laminites can now be astronomically tuned. The correlation is based on the eccentricity amplitude modulations of the regional pollen rain and their correlation to the astronomical La2010a/d solutions in combination with a revised 40Ar/39Ar plateau age between 48.26 and 48.11 Ma ± 0.22 Ma (2-sigma) for the eruption at Messel. This allows for the first time the exact correlation of a Paleogene lacustrine sequence to the marine record. The Messel oil shale therefore becomes slightly older than previously assumed and includes the Ypresian/Lutetian boundary which moves the base of the European Land Mammal Age (ELMA) Geiseltalian (MP 11) into the Lower Eocene. Astronomical tuning in combination with refined radioisotopic ages now enables to establish an independent chronostratigraphic framework for Paleogene terrestrial records and their correlation to the marine realm. Furthermore, astronomical tuning of Messel reveals that higher amounts of pollen from “wet” and thermophilous plants indicate increased precipitation and slightly higher temperatures during a well expressed eccentricity minimum.

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