AstroGeo seminar.
Pre-Cenozoic paleoclimate responses to astronomical forcing
David De Vleeschouwer
Westfälische Wilhelms-Universität (WWU) Münster
Institute of Geology and Paleontology, Germany
Astronomical insolation forcing is now well-established as the underlying metronome of Quaternary ice ages and Cenozoic climate carbon-cycle feedback mechanisms. However, its effects on earlier Eras (Mesozoic, Paleozoic, and pre-Cambrian) are less understood. During this seminar, I will evaluate various pre-Cenozoic modes of response to astronomical forcing, and provide an overview of the Earth System components that were particularly sensitive to astronomical forcing under evolving boundary conditions. Subsequently, the role of astronomical forcing in pacing the global carbon cycle in the Devonian warmhouse and Cretaceous hothouse worlds is discussed. Both periods are characterised by recurrent ocean anoxia and remarkably similar hypotheses exist regarding how astronomical forcing could have amplified a nutrient surplus (from chemical weathering and volcanism, respectively) to tip the ocean system into anoxia. The Triassic-Jurassic boundary cyclostratigraphy illustrates the importance of precession-scale time-control to understand feedback mechanisms and cause-and-effect chains at a resolution that is relevant for making analogies with the present-day. Finally, I will provide an outlook on the need for a coordinated approach, using so-called astrochronozones, to establish a fully astronomically-calibrated timescale for the Phanerozoic. Overall, the aim of the seminar is to highlight the need for a more comprehensive understanding of the role of astronomical insolation forcing in shaping Earth's climate over geologic time. After all, such comprehensive understanding constitutes a crucial pre-requisite before one can use the geological record to reconstruct solar system fundamental frequencies and Earth-Moon dynamics.
