Biostratigraphy and sedimentology of the Fluviatile Untere Serie (Early and Middle Miocene) in the central part of the North Alpine Foreland Basin: implications for palaeoenvironment and climate

Abstract

The Early to Middle Miocene Fluviatile Untere Serie lithostratigraphic unit of the Upper Freshwater Molasse (UFM) in the North Alpine Foreland Basin (NAFB) crops out in a 40 m long section at Untereichen-Altenstadt (central part of the NAFB). This section yields a unique superposition of two vertebrate assemblages belonging to different biostratigraphic units: early part OSM C + D (Karpatian) and OSM E (Early Badenian). Detailed taxonomic analyses reveal different diversity patterns in the two assemblages. Nine small mammal and six ectothermic vertebrate taxa occur in the older level UA 540 m, while 20 small mammal and 23 ectothermic vertebrate taxa are recorded for the younger level UA 565 m. From the latter locality comes a small-sized representative of the biostratigraphically significant Megacricetodon lappi lineage. This evolutionary level has not been documented previously for the eastern part of the NAFB. Bioclimatic analysis combined with lithofacies and architectural element analysis indicates that significant changes in the fluvial sedimentation style, surface-water runoff and tectonics occurred between the Early Karpatian and Early Badenian. A meandering fluvial system (marly unit) is erosively overlain by sandy braided river deposits (sandy unit). Overbank deposits of the marly unit revealed that the older vertebrate fossil assemblage (UA 540 m) is deposited in an animal burrow that was presumably produced by owls. Both reptilian and mammalian taxa are indicative of a relatively open environment and dry, probably semi-arid climate. Conversely, vertebrates from the sandy unit (UA 565 m), which are accumulated in channel fill deposits, suggest closed as well as open habitats with a subtropical humid climate and mean annual rainfall of about 1,000 mm. According to the sequence stratigraphic analysis the marly unit is interpreted as a highstand-system-tract of the TB 2.2 global 3rd order sequence. The new results add support to the hypothesis that the erosional unconformity between both sedimentary units spanning the KarpatianBadenian transition corresponds to the pre-Riesian hiatus, which has been interpreted as part of the Styrian Tectonic Phase, and was previously identified only in the eastern and northeastern part of the NAFB. The biostratigraphic data further indicate that this hiatus lasted longer in the eastern than in the central part of the basin.

Early Miocene gastropod and ectothermic vertebrate remains from the Lesvos Petrified Forest (Greece)

“…The complete fauna from Lapsarna is presented in Table 2. (Prieto et al 2009). In general, species of the two genera seem to coexist in the western Paratethys during the Karpatian (upper part of MN 4b to lower part of MN 5), and during the early Badenian (middle part of MN 5) Cyprinion vel Capoeta is also present .…”

“…Böhme 2002;Prieto et al 2009). The absence of complete pharyngeal bones from the LRN material hinders detailed comparisons and the allocation of Fossil Barbus species are mostly interpreted as indicators of streaming waters and fluvial environments (Prieto et al 2009). …”

Gratkorn: A benchmark locality for the continental Sarmatian s.str. of the Central Paratethys

“…Bones and teeth are generally very well preserved, most often only insignificantly corroded and mainly beige coloured (Prieto et al 2010a). Prieto et al (2009Prieto et al ( , 2010a) explain such extreme local concentration of small vertebrate remains as the result of pellet accumulations at feeding/resting places of birds of prey, in more detail of owls. In contrast to, e.g., diurnal raptors or mammalian carnivores, owls cause only minor effects of digestion (Mayhew 1977;Denys et al 1995;Terry 2007).…”

A new Late Agenian (MN2a, Early Miocene) fossil assemblage from Wallenried (Molasse Basin, Canton Fribourg, Switzerland)

“…The palaeoecological value of the species of European ochotonids and stem lagomorphs has not been defined yet, though in the Middle Miocene of western and central Europe, the relative abundance of Prolagus vs. Lagopsis has been used as an indicator of relative temperature and humidity changes (Lòpez-Martìnez 1977, 1984Angelone 2009;Prieto et al 2009). If applied to the Early Miocene deposits of Wallenried, the higher abundance of Prolagus vs. Lagopsis in WallA would suggest a rather cool and wet environment, which conflicts with the analysis below.…”