Entschlüsselung der Dynamik des Eozänen Treibhausklimas: Hochauflösendes XRF-Scannen eines Bohrkerns aus der Grube Messel
Zusammenfassung der Projektergebnisse
Within the framework of this project, we refined the chronostratigraphy of the Messel oil shale by means of astrochronology using gamma-ray logging data. The refined stratigraphy revealed that the recovered 450 kyr interval of oil shale belonging to the Middle Messel Formation contains three medium-scale hyperthermals, with temperature increases of up to 4°C. From the FB2001 drill core, we generated a 90-meter-long, high-resolution XRF scanning record, which helped us to better understand the sedimentological processes during oil shale deposition and the evolution of the lake system. We further used prominent siderite layers, indicated by Fe/Ti peaks in the XRF record, which were interpreted as markers of anomalous precipitation events, to reconstruct the variability of pluvial extremes. The results show strong orbital forcing on extreme precipitation acting independently during both, summer and winter. Numerical model data suggest that strengthened westerlies during winter, resulting in heavier winter precipitation, account for much of the observed at least 5-fold fluctuations in heavy precipitation event frequency. Two of the three hyperthermals stand out with maximum frequencies of extreme precipitation events. The amplitude of these extremes aligns with thermodynamic forcing occurring mostly during winter. Additionally, we observed that such changes in hydrology, likely causing lake-level fluctuations and varying degrees of eutrophication strongly impacted fish communities. However, the lake’s ecosystem showed a remarkable resilience, as it returned to its pre-hyperthermal state after the end of the environmental disturbance. Unexpected was the magnitude of fluctuations of the extreme precipitation events in response to orbital forcing. The insight that the independent influence on precipitation extremes during winter and summer lead to the presence of half-precession cycles is certainly a major outcome of the study. Compared to orbital forcing, the impact of elevated greenhouse gas concentrations during hyperthermals was smaller than expected. Further, the resilience of the lake’s ecosystem to external perturbation was surprising.
Projektbezogene Publikationen (Auswahl)
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Eocene maar sediments reveal hyperthermal temperature history. Communications Earth & Environment 5, 471.
Schmitt, C., Vasiliev. I., Meijer, N., Brugger, J., Kaboth-Bahr, S., Bahr., A. & Mulch, A.
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Orbital forcing of past climates. GeoMin Köln. (Poster)
Schandl, J., Bahr, A., Zeeden, C., Wonik, T., Wedmann, S., Lenz, O. & Kaboth-Bahr, S.
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Improved chronostratigraphy for the Messel Formation (Hesse, Germany) provides insight into early to middle Eocene climate variability. Newsletters on Stratigraphy, 57(2), 153-170.
Kaboth-Bahr, Stefanie; Schmitt, Clemens; Bauersachs, Thorsten; Zeeden, Christian; Wonik, Thomas; Schandl, Jonas; Lenz, Olaf; Wedmann, Sonja; Vasiliev, Iuliana; Mulch, Andreas; Lourens, Lucas; Pross, Jörg & Bahr, André
