What controls the isotopic signature of terrestrial organic carbon? A biomarker study of the Paleocene and Eocene section in the Bighorn Basin (WY, USA)

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Earth's climate is warming at a pace and magnitude unprecedented in recent times, with profound (but not easily predicted) consequences for terrestrial ecology and hydrology. Carbon isotopic signatures are an important tool for geologists studying terrestrial environmental change on long time scales. However, carbon isotopic signatures can vary widely and work on modern plants reveals both environment and community composition can be equally significant influences. Although secular carbon isotope variations of atmospheric carbon dioxide are certainly transferred into ancient plant carbon, and thus soil carbon, so also are ecophysiological differences (e.g., phylogeny, leaf habit, water use)that modulate carbon isotope fractionation between plant biomass and carbon dioxide and as well as carbon from other inputs such as microbes or weathered carbon. Work supported by this grant will evaluate the relative importance of environment versus community composition as major mechanisms controlling carbon isotope values and molecular signatures of terrestrial plant inputs in the ancient soils and terrestrial sediments in the Paleocene and Eocene of the Bighorn Basin (WY, USA) across both short term (PETM) and more protracted (Eocene) global warming.