Deciphering seasonal to decadal climate variability during the Oligocene: an integrated approach based on bivalve sclerochronology and palynology

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The last time in Earth history characterized by a unipolar glaciation followed by a significant reduction of polar ice sheets was during the Oligocene. Hence, the Oligocene world may serve as a fossil analog for the climatic boundary conditions of the future, which will be initially characterized by a loss of Northern Hemisphere ice sheets. The resulting climate shifts will include changes in seasonality as well as in the frequency and intensity of decadal climate oscillations. However, the mode and tempo of these changes are as yet poorly constrained. In light of the above, our joint project will reconstruct short-term climate dynamics in Central Europe during the Oligocene following a combined sclerochronological and palynological approach. We will focus on shallow marine successions from the Mainz and Kassel Basins, which yield both excellently preserved bivalves (including extremely long-lived species) and palynomorphs. The growth patterns and isotope geochemistry of mollusk shells will open century-long windows into the Oligocene climate and provide coherent data on seasonal to decadal climate oscillations. Besides yielding age control, dinocysts and sporomorphs will allow to (qualitatively and quantitatively) reconstruct paleoenvironmental parameters for marine and terrestrial settings. Specifically, the project will address questions on the frequency and intensity of oceanic and atmospheric climate modes, temperature trends, and the relative strength and duration of precipitation events in the NE Atlantic sector during the Oligocene. Furthermore, we will study the reasons for the increased amounts of cold-water mollusks, low diversity and extraordinary thickness of shells in certain stratigraphic levels.