Terrestrial carbon isotope and paleomagnetic stratigraphy across the Paleocene/Eocene boundary: Constraining global biotic and environmental change

It has become clear that mankind is forcing changes in the earth's climate and ecosystems that may be of a severity above and beyond that characteristic of non-anthropogenic change. Anthropogenically-induced change will likely involve complex, dynamic responses within and among climatological, geochemical, and biological systems. The study of intervals of global change in the geologic record remains the primary method for generating understanding of the dynamic behavior of earth systems, which is used to inform earth-system models and to make predictions about future change.; In this thesis, I present studies of climate system and mammalian community response to a transient global warming event that occurred ∼55 million years ago, at the boundary between the Paleocene and Eocene epochs. In chapter one, I focus on constraining patterns of mammal origination and dispersal near the Paleocene/Eocene boundary. I use carbon isotope stratigraphy and magnetostratigraphy to correlate early Paleogene mammal faunas from Asia to the geomagnetic polarity timescale. I find support for the simultaneous appearance of several higher-level mammal clades on the holarcitc continents at the Paleocene/Eocene boundary. This finding is contra the hypothesis that these groups originated in Asia during the Paleocene and lived there for several hundred thousand years prior to the IETM. The second and third chapters focus on elucidating the details of IETM climate through the study of carbon isotope timeseries. In chapter two, I develop a model for soil organic matter and CO₂ concentration and stable carbon isotope composition (δ13C). In chapter three I apply this and other models to δ13C records spanning the Paleocene/Eocene boundary. I show that differences in the pattern of δ13C change in terrestrial and marine records can be attributed to the effects of elevated humidity on plant photosynthesis and to enhanced cycling of organic carbon within soils. These changes in the climate and carbon cycle constrain the feedbacks and mechanisms that contributed to the development of and recovery from global warming during the IETM.