Physical Chemist

My work focuses on the interface between chemistry and two other disciplines, geology and archaeology. A relatively new way of determining the age of materials is to look at radiation damage caused by radioisotopes in the material itself and in its surroundings. Oversimplified, the longer something has been buried, the more damage should be found. The extent of damage can be measured with electron spin resonance (ESR), a technique that looks at the unpaired electrons often found when a stable bond is broken.

Geological applications have included following the rise and fall of sea levels due to ice ages by dating shells of species known to live in shallow water, and clarifying the development of soils in the Mississippi Valley. Other sites have ranged from the coral reefs of the Bahamas to ancient sea shores in Australia. Usually the geologist has a broad sense of probable scenarios, and ESR dating allows one to choose the best one.

Applications to archaeology (and paleoanthropology) cover the time range from New World flint artifacts to teeth and bones from million-year old sites associated with human evolution. The usual samples are teeth of large mammals found in the same site as hominid remains and/or artifacts. Hominid teeth themselves are generally too rare and too small to yield good results.

Interesting problems are found worldwide. Sites I have studied include Olduvai Gorge in Tanzania, Mesmaiskaya Cave in Russia, the Narmada River in India and Sao Raimundo in Brazil.