Hochauflösende Chronologie des Mittel- und Ober-Miozäns Süddeutschlands
Zusammenfassung der Projektergebnisse
A magnetostratigraphic study in the Upper Freshwater Molasse (UFM; Obere Serie lithostratigraphic unit) of the North Alpine Foreland Basin (NAFB) has been carried out on a 150 m long drill core near the village Irsee and on the fossil bearing site Hammerschmiede (Kaufbeuren area). ChRMs were identified in 91% of the sampled material carried by magnetite. The resulting polarity pattern of the drill core has three long normal polarity intervals and two reversed ones. Topographic correlation of Hammerschmiede and Irsee yield generally the same results. We correlate the normal polarity intervals with C5An1n, C5r.2n and C5r.2r-1n decreasing in age and document for the first time the Middle to Late Miocene boundary in the NAFB with precise magnetostratigraphic age constraint. The resulting sedimentation rate suggests two main phases of erosion at ~11.5 and ~11.8 Ma with durations of 150 kyrs and 300 kyrs, respectively. At least the younger phase has strong evidence in form of an erosion channel at the Hammerschmiede section. The identified hiatuses present in the Irsee drill core sediments are more or less isochronous with described sediment cessation in the Vienna Basin and might therefore suggest a more global importance for this feature. Additionally, we identify the youngest UFM sediments in the Bavarian part of the NAFB to be ~11.1 Ma old. We therefore constrain the age of the 122 m long UFM segment from Irsee to 12.2 to 11.1 Ma (late Sarmatian to Pannonian C). The total missing time of 450 kyrs in the Irsee drill suggest that only 60% of time is represented in the Obere Serie stratigraphy of the Kaufbeuren area. Assuming constant sedimentation rate and/or similar stratigraphic representation for the up to 300 m thick lithostratigraphic unit Obere Serie will put the initiation of their sedimentation, or the Geröllsandserie - Obere Serie transition at 13.8 Ma, contemporaneous with the Middle Miocene global climate transition at the onset of the Badenian salinity crisis and the Langhian-Serravallian boundary. It has further been shown here that ‘coal’ layers in the Obere Serie, enriched in organic matter, have little spatial coverage and can therefore not precisely be used as regional stratigraphic markers. Our results put crucial constraints on a straightforward mammal biostratigraphy of Central Europe and allocate the Hammerschmiede fossiliferous level as a continental chronostratigraphhic tie-point for the base of the Tortonian stage, respectively Pannonian regional stage. The precise age of the Hammerschmiede vertebrate level is 11.611 ±0.002 Ma, which postdates the base of the Tortonian by only 12 to 16 kyrs. The only partly studied Hammerschmiede vertebrate fauna include so far 84 taxa from 54 families, highlighting this locality as one of the taxonomically most diverse Late Miocene vertebrate localities on global scale. Furthermore, by lateral correlations we suggest ages of the nearby mammal localities Markt Rettenbach of 12.05 Ma and Hillenloh of 11.4 Ma, which are consistent with biochronologic data. It also appears that the lack of hipparionin horse fossils in the Bavarian part of the NAFM has a chronologic, rather than ecologic reason. According to our chronology and discussions the ‘Hipparion datum’ was a bioevent in western Eurasia at 11.1 Ma, synchronous in the Ukraine, Austria, and Spain. Finally, the late Sarmatian and early Pannonian climate in the NAFB was cyclic and experienced about 20% increased humidity at the Serravallian-Tortonian transition (11.64 to 11.61 Ma), but provide still significant water stress for continental ecosystems.
Projektbezogene Publikationen (Auswahl)
- 2011. First record of an autochthonous community of fluviatile freshwater molluscs from the Middle/Late Miocene Upper Freshwater Molasse (southern Germany). Archiv für Molluskenkunde: International Journal of Malacology 140 (1): 1-18
Schneider S, Prieto J
- Reappearance of Galerix (Erinaceomorpha, Mammalia) at the Middle to Late Miocene transition in South Germany: biostratigraphic and paleoecologic implications. Zoology 80 (3): 179-189
Prieto, J., Hoek Ostende, L.W. Van den, Böhme, M.
- 2015: Revision of the bovid Miotragocerus monacensis Stromer, 1928 (Mammalia, Bovidae) at the Middle to Late Miocene transition in Central Europe. Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen 276/3: 229-265
Fuss, J., Prieto, J., Böhme, M.
