Middle Triassic) Benthic Faunas from the Schlern and Seiser Alm (South Tyrol, Italy

See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/321167653 Palaeoecology of Late Ladinian (Middle Triassic) benthic faunas from the Schlern and Seiser Alm (South Tyrol, Italy) Conference Paper · November 2017 CITATIONS READS 0 122 5 authors, including: Evelyn Friesenbichler Michael Hautmann Walo Bertschinger Central AG University of Zurich 14 PUBLICATIONS 69 CITATIONS 75 PUBLICATIONS 2,294 CITATIONS SEE PROFILE SEE PROFILE Alexander Nützel Hugo FR Bucher Bayerische Staatssammlung für Paläontologie und Geologie University of Zurich 200 PUBLICATIONS 3,385 CITATIONS 284 PUBLICATIONS 8,161 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Quantitative biostratigraphy / biochronology View project Taxonomy and palaeoecology of Early Jurassic (Pliensbachian) bivalves from Buttenheim, Franconia (Southern Germany) View project All content following this page was uploaded by Evelyn Friesenbichler on 30 November 2017. The user has requested enhancement of the downloaded file. 161 3.7 Palaeoecology of Late Ladinian (Middle Triassic) benthic faunas from the Schlern and Seiser Alm (South Tyrol, Italy) Evelyn Friesenbichler1, Michael Hautmann1, Alexander Nützel2 Max Urlichs3, Hugo Bucher1 1 Paleontological Institute and Museum, University of Zurich, Karl-Schmid-Strasse 4, 8006 Zurich ([email protected]) 2 SNSB-Bayrische Staatssammlung für Paläontologie und Geologie, Department of Earth and Environmental Sciences, Palaeontology & Geobiology, Geo-Bio-Center LMU, Richard Wagner Straße 10, 80333 Munich 3 Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191 Stuttgart The rich benthic fauna of the Schlern and Seiser Alm area, which is one of the few places in the world where the platform- Symposium 3.+ 4.: Palaeontology + Stratigraphy slope-to-basin transitional zone is preserved in its primary setting (Keim 2008; Brander et al. 2016), is known for more than 100 years but its palaeoecology has been insufficiently known. We present a detailed palaeoecological study based on quantitative faunal data of the fauna from the Schlernplateau beds (late Ladinian to early Carnian) and the more or less time-equivalent Pachycardientuffe (late Ladinian). The Schlernplateau beds yield a diverse fauna with more than 50 species. The ecology of the fauna, which is dominated by shallow infaunal suspension feeders, epifaunal grazers/detritivores and free-lying epifaunal suspension feeders, as well as the geological context leave no doubt that the Schlernplateau beds represent lagoonal sediments. The unusually high diversity for this environment and the locally restricted fossil occurences indicate an open lagoonal setting palaeogeographically close to an oceanic inlet. The high evenness of the fauna is best explained with time averaging. The fauna of the Pachycardientuffe is highly diverse, with more than 220 species; however, in contrast to the Schlernplateau beds, it is clearly dominated by two species of the eponymous bivalve genus Pachycardia. Several lines of evidence, such as the lack of fossils that were preserved in life position, the lack of bivalves that are preserved with conjoined valves, frequent fragmentation of fossils and poorly sorted sediment, indicate that the fauna of the Pachycardientuffe is allochthonous. By means of ecological features of the fauna and palaeogeographic reconstructions three possible source areas for the fauna of the Pachycardeintuffe were identified; (1) the lagoon of the Schlernplateau beds, (2) the reef fringing the lagoon of the Schlernplateau beds and (3) a shallow clastic coast of a nearby volcanic island and/or submarine high dominated by Pachycardia. The different context of the faunas requires different interpretations of their diversities: whereas the Schlernplateau fauna provides an estimation of the alpha-diversity in shallow-marine tropical seas ca. 15 Ma after the end-Permian mass extinction, the fauna of the Pachycardientuffe represents an integral of the diversity from different environmental settings and as such an approximation of the gamma-diversity of the region. Apart from the sheer increase in richness in comparison to Early Triassic benthic faunas, where alpha-diversity seldom exceeds 15-20 species and gamma diversity is usually lower than 30-40 species even at the end of this epoch, a larger variety of modes of life and a significantly higher proportion of gastropod species are notable features of the more fully recovered faunas of the late Middle Triassic. Swiss Geoscience Meeting 2017 Platform Geosciences, Swiss Academy of Science, SCNAT 162 Symposium 3.+ 4.: Palaeontology + Stratigraphy Figure 1. Rank-abundance distributions and guild-structure of the fauna of the Schlernplateau beds (A) and Pachycardientuffe (B). n = total number of individuals. REFERENCES Brandner, R., Gruber, A., Morelli, C., Mair, V. 2016: Pulses of Neotethys-Rifting in the Permomesozoic of the Dolomites. Geo. Alp., 13, 7-70. Keim, L. 2008: Geologie im Gebiet Schlern-Seiser Alm: vom Tethysmeer zum Gebirge. Gredleriana, 8, 25-46. Swiss Geoscience Meeting 2017 Platform Geosciences, Swiss Academy of Science, SCNAT View publication stats.

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