Funding: National Science Foundation EAR-0319024 “ Collaborative/RUI Research: Stable Isotope Reconstruction of North American Terrestrial Environments during the Late Cretaceous." Our official collaborators are Ray Rogers and his students at Macalester College. Others folks that we bug a lot include Scott Sampson, Tony Fiorillo, Kirk Johnson, Kristi Curry, and Dean Pearson.
The most exciting aspect of this research is the use of carbon and oxygen isotope ratios of dinosaur tooth enamel to study terrestrial environments, ecological differences between dinosaur taxa, and dinosaur migration. Carbon isotope ratios of mammalian tooth enamel reflect those of ingested diet, and our combined study of sedimentary organic material and dinosaur tooth enamel indicates that the same was true for dinosaurs. In turn, carbon isotope ratios of C3 plants vary significantly with environmental conditions such as temperature, aridity, salinity, etc. Similarly, oxygen isotope ratios of dinosaur tooth enamel should be influenced by ratios of ingested water, and oxygen isotope ratios of water also vary greatly depending on temperature, aridity, rainfall, water source, etc. We take advantage of all these isotopic variations by (1) comparing isotopic data from a number of different kinds of dinosaurs living in one place and by (2) comparing isotope data from a single taxon living in different places.
At the present time we are studying several different time periods/areas: One is the Campanian/Maastrictian of Montana, where we are comparing isotope data from upland Two Medicine Fm. sediments of western Montana with data from contemporaneous coastal Judith River Fm. sediments of central Montana (~250 miles apart). Preliminary results indicate that dinosaurs from the two areas are isotopically distinct, and that no migration occurred between regions.
Our study of the latest-Maastrictian of North Dakotais different in that isotope data is being compared between different stratigraphic intervals of the local Hell Creek Fm. rather than comparing data between widespread localities of the same age. Preliminary results indicate that different dinosaur taxa can have isotopically distinct isotope ratios, and thus these animals partitioned food resources. Furthermore, the nature of this partitioning appears to change over time.
Although at a much earlier stage, we are planning to undertake similar isotopic investigations of dinosaur and other remains from late Cretaceous sediments in Utah and Alaska. Integral to all this research is the study of how isotope ratios (and other chemical signatures) may have been affected during diagenesis. |
