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.