Lehre@GEO Award 2024 for Haodong Chen and Lukas Wildgruber

Haodong Chen and Lukas Wildgruber‘s research project dealt with the "Stratigraphy and micropaleontology of the younger Neuhofen Formation in the Mitterdorf clay pit." The basis and preparatory work were their bachelor theses, for which they had already received the 1st and 2nd prize for the best bachelor thesis from the ‚Freunde der Geologie München e.V.’ The project was the students' own idea, demonstrating a high level of commitment and motivation. They secured the necessary project funding independently via the StudForschung@GEO funding program of the Faculty of Geosciences. The project was supervised by Prof. Bettina Reichenbacher.

The award winners Haodong Chen and Lukas Wildgruber.

For their research project, Haodong and Lukas pursued three specific research topics and questions related to the deposition and paleoenvironment of the Lower Miocene Upper Marine Molasse using the outcrop of the Neuhofen Formation in the Mitterdorf clay pit near Passau:

1. the origin and chronology of a previously unknown channel structure in the Neuhofen Formation
2. possible causes for the occurrence of unusually large planktonic foraminifera in the Neuhofen Formation
3. interpretation of the regional paleoenvironmental conditions in the uppermost section of the Neuhofen Formation (at the transition to the overlying glauconitic sands and marls)

In November last year, Haodong and Lukas took public transport to the Mitterdorf clay pit to take samples at short intervals, 18 in total. They then washed the samples in the lab and picked all the microfossils from the residue under the microscope. Their methodology also included the taxonomic identification of the numerous benthic foraminifera and analysis of the planktonic foraminifera using a scanning electron microscope (SEM). As the foraminifera found were very well preserved, Lukas and Haodong also carried out isotope analyses (O¹⁸/O¹⁶, C¹³/C¹²) on both the benthic and planktonic foraminifera in the laboratory of Prof. Michael Joachimski at the University of Erlangen.

Large planktonic foraminifera from the Neuhofen Formation. Image taken with a scanning electron microscope.

The results show that well-preserved (not reworked) index fossils of the Neuhofen Formation are present in the channel sediments. This indicates that the formation and filling of the channel was contemporaneous with the deposition of the Neuhofen Formation (question 1). SEM images showed that the "large" planktonic foraminifera are not artifacts due to taphonomic overprinting (aggregation crystallization), but were primarily that large; the isotope analysis results also show that their "gigantism" is not related to specific environmental parameters (question 2). Furthermore, the isotope values indicate a significant stratification of salinity in the water column, with the surface water in the older part of the sampled profile having a relatively low salinity. This indicates a climate with high precipitation and consequently increased fluvial input into the sea. In the younger part of the profile, on the other hand, no more stratification of the water column can be detected, which could indicate increasingly drier climatic conditions (question 3).

Such a clear climatic signal in the Neuhofen Formation and the younger Upper Marine Molasse was previously unknown. It is interesting to note that this coincides with a global warming event around 17.67 million years ago. The results of Haodong Chen and Lukas Wildgruber’s research thus provide the first reliable data to answer the long-standing question of whether global climate changes, in addition to active tectonics, were significant factors for the paleoenvironment of an Alpine foreland basin such as the South German Molasse Basin. A publication of the results is in preparation.