Place: 4421 Sterling Hall, Coffee and cookes 3:30 PM. Talk begins at 3:45 PM
Speaker: Stephen Meyers, Department of Geoscience, UW Madison
Abstract: Quasiperiodic variations in Earth’s orbit and spin vector influence the distribution of sunlight on Earth’s surface, causing cyclic climate change on time scales >10,000 years. The geologic record preserves evidence of these astronomical-climate rhythms, which are expressed as physical, chemical and paleobiologic variability in sedimentary strata. In this seminar, I will discuss how these “fossilized” astronomical signals can be used to test hypotheses about the behavior of the Solar System, and its evolution over the past several billion years. One of the most fundamental questions that we can address with the geological archive pertains to the proposed chaotic dynamical nature of the Solar System that is predicted by numerical and analytical models of the planetary orbits. New geological data from the Cretaceous period (~86 million years ago) provides the first unambiguous confirmation of this chaotic motion. Another question that the geologic record is uniquely poised to address is the history of the Earth-Moon system, including changes in Earth-Moon separation and length of day. To address this research problem, I will present results from a new Bayesian inversion approach that uses the astronomical signals preserved in very ancient strata (> 1 billion years old) to reconstruct the Earth-Moon history, as well as the fundamental frequencies of the Solar System. A byproduct of this work is the development of high-resolution geological time scales that can be used to assess rates of Earth system processes, including climate change and biological evolution. Taken together, these examples highlight the close interlink between geology and astronomy, and how these fields can fundamentally inform each other.