“Poop and plants from the Colorado Plateau” by: Jessica Metcalfe
Poop and plants from the Colorado Plateau
In the dry caves that line the walls Grand Canyon and Glen Canyon, ancient dung and plants that are more than 13,000 years old are preserved in near-pristine condition. In early 90s and earlier, Jim Mead and Larry Agenbroad among others collected and dated some of these poop samples, which belonged to mammoths, ground sloths, horses, shrub-ox, and other extinct megafauna. As part of my postdoctoral research at the University of British Columbia I am using isotopic compositions of dung and other materials from these sites to investigate the paleoecology of this ancient ecosystem. This past summer, 2015, a grant from the Larry D. Agenbroad Legacy Research Fund supported a PhD student research assistant (Christina Cheung) who prepared ancient plant samples for isotopic analysis. Typically, only charred plant remains are believed to retain their original isotopic compositions after thousands of years. Our results – just in – indicate that the carbon isotope compositions of these ancient uncharred plant remains are just as well-preserved as the macroscopic appearance of the samples! The spacing between δ13C values of ancient C3 and CAM plants from Glen Canyon are just what we would expect based on modern ecosystems. This has two important implications: (1) quantitative estimates of dietary components can be made by comparing the plant isotopic compositions with those of ancient animal tissues (e.g., bone collagen) or dung, and (2) aspects of ancient climatic conditions can be estimated from the isotopic compositions of the plants themselves. Few studies have explored the potential for using isotopic compositions of ancient plant remains for paleoenvironmental reconstruction, and these astoundingly well-preserved samples offer a unique opportunity for a pilot study in this area. I look forward to sharing more detailed results in the future.