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| Titel |
A new small-mammal biostratigraphy and high-resolution chronostratigraphic model for the Upper Freshwater Molasse of the eastern part of the North Alpine Foreland Basin (Bavaria, Germany) |
| VerfasserIn |
M. Boehme, H. Abdul Aziz, V. Bachtadse, J. Prieto, A. Rocholl, A. Ulbig, J. R. Wijbrans |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029082
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| Zusammenfassung |
| A detailed integrated stratigraphic study (lithostratigraphy, biostratigraphy, magnetostratigraphy,
40Ar/39Ar dating) was carried out on twelve sections from the eastern part of the Upper
Freshwater Molasse of the North Alpine Foreland Basin (NAFB), improving greatly the
chronostratigraphy and the temporal resolution (up to 100 kyr) of these sediments. The
sections contain 19 new small-mammal bearing levels. Based on this material and 24 already
published localities we propose a new taxon-range-zonation for the Late Ottnangian to the
Early Badenian, consisting of nine zones or subzones respectively. Radiometric ages obtained
for glass shards from tuff horizons are used together with the new biostratigraphic
information for confirming the magnetostratigraphic correlation to the Astronomical Tuned
Time Scale (ANTS04). This correlation implies that the Brackish- to Freshwater
Molasse transition already occurred during the latest Ottnangian. The pre-Riesian
hiatus, a remarkable feature in both the central and eastern part of the basin and the
southern Bohemian Massif, occurred during the latest Karpatian and lower Early
Badenian in Eastern Bavaria and Bohemia and during the Late Karpatian and earliest
Badenian in Western Bavaria. The geochemical and Ar-Ar data of volcanic ashes
suggest that highly evolved silicic magmas from a single volcano or volcanic centre,
characterized by a uniform Nd isotopic composition, erupted repetitively over the course
of at least 1.6 myr. Four phases of eruptive activity were identified at 16.1 ± 0.2
Ma, 15.6 ± 0.4 Ma, Â 14.9 Ma, and 14.5 ± 0.2 Ma. The correlation of the local
biostratigraphic zonation to the ANTS04 enables further the characterization of both the
Ottnangian-Karpatian and Karpatian-Badenian boundaries in the NAFB by mammals.
According to these results the Ottnangian-Karpatian boundary is contemporaneous
with the last appearance dates of Ligerimys florancei, Melissiodon dominans and
Prodeinotherium bavaricum and the first appearance date of Megacricetodon cf. bavaricus.
The Karpatian-Badenian boundary is characterized by a further size increase of the
large Megacricetodon lineage and possibly a re-immigration of Prodeinotherium
bavaricum. |
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