Grantee Research Project Results
Paleoecology of the Great Plains 2 to 10 Million Years AgoEPA Grant Number: U915039
Title: Paleoecology of the Great Plains 2 to 10 Million Years Ago
Investigators: Smith, Francesca A.
Institution: University of Chicago
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 1996 through January 1, 1999
Project Amount: $41,500
RFA: STAR Graduate Fellowships (1996) RFA Text | Recipients Lists
Research Category: Fellowship - Geology , Academic Fellowships , Ecological Indicators/Assessment/Restoration
The objective of this research project is to use the carbon isotope signature of organic material contained in fossil phytoliths (microscopic silica bodies produced by grasses) to reconstruct the proportion of C3 and C4 grasses during the Late Miocene and Pliocene (2 to 10 million years ago).
Phytoliths are extracted from ancient soil horizons dating back to the Late Miocene and Pliocene, 2-10 million years ago. This is conducted through a series of washes to remove carbonate and organics, followed by a heavy liquid separation on the silt size fraction. The carbon isotope ratio of organic matter trapped within the phytoliths is analyzed. The signature provides a mixing ratio between end-member values of pure C3 and pure C4 grass phytoliths, yielding a proportion of C3 to C4 grasses. Previous measurements have been taken exclusively on bulk carbon contained within phytoliths. This technique has the disadvantage of providing a compressed isotopic scale and reduced resolution. To improve resolution, I am developing a means of measuring the carbon isotopes in only a subset of organic compounds. This method will then be applied to the fossil phytoliths to provide a record of grassland ecosystem change with changing climate and atmospheric CO2 over the period from 2-10 million years ago.