As a radiogenic isotope geochemist, I use the decay of radioactive elements in natural materials as clocks to determine the ages of those materials. I work with many different types of materials and radioactive parent-daughter element pairs. With the Middle Stone Age NSF REU project, I will be using U-series dating to determine the ages of ostrich egg shell fragments from the research site. Ostrich eggs were a common food source of early humans and the shells may have been used for tools and jewelry. The age of the egg shells found at the archeological site will provide the age of the human activity at that site.
U-series dating uses the radioactive decay of 238U to 230Th. Because the rate of decay is constant through time, we can measure the amount of 238U and the amount of 230Th created by the decay of 238U in the egg shell fragment and can calculate the age of the egg shell, if the system has not been disturbed. In our lab, this dating method is used regularly to date stalagmites, the calcite domes that form from dripping water in caves. However adapting this method to ostrich egg shells has interesting complications. Work of the MSA REU will help to test some of our hypotheses with respect to these complications and attempt to determine the ages of several shell fragments. Students who work on this portion of the project will work with me and Dr. Jay Banner in his clean chemistry laboratory and analyze U and Th isotopes using a TIMS (thermal ionization mass spectrometer) in the Department of Geological Sciences at UT Austin.