Henry P. Schwarcz

University Professor of Geology
School of Geography and Earth Sciences (also, Dept. of Anthropology)
McMaster University
Tel. (905) 525-9140 ext. 24186
Fax (905) 522-3141
Email: schwarcz@mcmaster.ca

Research Interests

Stable isotope geochemistry, uranium series dating, electron spin resonance (ESR) dating, archaeological geology, paleoanthropology, paleodiet of ancient populations, Quaternary paleoclimate, isotopic ecology of corals, land mammals, fish, application of stable isotopes to medical research.

Current Research Projects:

ESR dating of prehistoric archaeological sites
Grad student: Vito Volterra (Anthropology)
In collaboration with W. Jack Rink, we are determining the age of prehistoric archaeological and anthropological sites in the Old World, in Africa, the Middle East, Europe, China, and Indonesia. ESR signals detected in fossil mammal teeth found at these sites are used to monitor the radioactive dose that these teeth have acquired since burial; the ratio of this does to the environmental dose rate at the site gives us the age. We are calibrating the transition from earlier forms of the genus Homo to modern humans. We have shown that some Homo erectus skulls from Java, previous thought to be almost 1 million years old, actually dated to less than 50,000 y, and were contemporaries of modern humans. This research is carried out in collaboration with archaeologists and anthropologists around the world. These studies make use of the McMaster Nuclear Reactor, and an ESR spectrometer housed in the Chemistry Dept.

ESR Paleoseismology
The ESR method (see above) can be used to determine the last time there has ben motion on a fault. We are using this technique to evaluate the risk of renewed activity on faults in California and elsewhere.

Mass-spectrometric uranium series dating of archaeological sites
We are using the decay of uranium-234 to thorium-230 to determine the age of calcium carbonate deposited in caves and fossil springs, to determine the age of associated human remains and artifacts. We are now studying sites in Israel, France, Egypt, South Africa. Thermal ionization mass spectrometry allows us to obtain dates with a precision of 1% of the age, comparable to the best C-14 dates. This method is also used by us to date samples studied by ESR (see above) to monitor the uptake of uranium by the teeth being dated.

Gamma-ray spectrometric U-series dating
Generally we determine the age of fossil humans by destructive analysis of non-critical samples of teeth, etc., from the sites where the fossils were found. Some key fossil specimens of early human ancestors cannot be dated by this means because the sites have been destroyed or the fossils were not collected in situ. In collaboration with Dr. John Simpson (Physics, U. of Guelph) we are using high-sensitivity gamma-ray spectrometers to determine the radioactivity of some of these key specimens, brought to Guelph by their curators from around the world. Their gamma spectra can be used to determine the age by U-series methods. We are working on samples from Israel, England and Africa, in collaboration with researchers from the British Museum of Natural History (London).

Isotopic Paleodiet Studies
Grad students: Tosha Dupras, Tracy Prowse (Dept. of Anthropology)
We can determine the amounts of different foods in the diets of ancient people, through analysis of the ratios of the stable isotopes of carbon and nitrogen (¹³C/¹²C, ¹⁵N/¹⁴N) in collagen extracted from their bones. This method is being used to determine the past diest of people of the time of ancient Rome, and originating in two localities: the Dakhleh Oasis in central Egypt; and Portus Romanus, the ancient port of the city of Rome. Isotopic modelling studies are being used to calculate the relative roles of different nutrients in determining the isotope ratios of collagen.

Isotopic paleoclimate studies
The climate of the past can be recovered from variations in the ratios of the stable isotopes of oxygen, carbon and hydrogen as preserved in shells, bones and cave-deposited stalagmites. Various projects on this theme are under way:

1. Isotopic analysis of cod otoliths:
Grad students: Yong Wen Gao, Robyn Jamieson
Cod and other teleost fish grow stony deposits in their ears (otoliths) which are in isotopic equilibrium with the blood of the fish and indirectly with seawater. We are analysing sequential deposits (growth zones) which trace the environmental conditions experienced through the life of the fish. We are studying cod from Atlantic Canada to test whether environmental change contributed to the collapse of the cod stocks in 1991.We also can learn about changes in the diet and metabolic acitivity of the fish through their life, and trace sources of recruitment.

2. Oxygen isotope studies of bone and tooth mineral
Grad student: Tracy Prowse (Anthropology); Post Doctoral Fellow: Hilary Stuart-Williams
The oxygen isotopic composition of carbonate hydroxyapatite in teeth and bones reflects the ¹⁸O/¹⁶O ratio of the water and food that was consumed by the individual. Human teeth from a Roman cemetery are being used to trace the origin of the population living in Portus. Teeth from caves in Israel are studied to trace climate change during the last 200,000 y. Work on beaver teeth from Ontario has been used to test records of seasonal change in ¹⁸O/¹⁶O of precipitation. Analysis is both by pyrobromination of silver phosphate and reaction of enamel powder with phosphoric acid to liberate carbonate oxygen.

3. Speleothem studies
Post-doctoral fellows: Amos Frumkin and Hilary Stuart-Williams
In collaboration with Derek Ford, we are analysing the ¹⁸O/¹⁶O and ¹³C/¹²C ratios of calcite deposited in caves to learn about climate of the past. Using analyses of U-series-dated stalagmites from caves in North America and Israel, we have been able to refine the dates of the glacial/interglacial transitions of the last 400,000 y and to show how these climatic shifts were expressed on the continents. We have shown that there have been very large shifts in the ¹⁸O/¹⁶O ratio of rain falling on Israel, which we can also use as a marker to identify climate stages using other isotopic recorders such as teeth and bones. We have obtained an isotopic record for the past 500,000 years from a cave in South Dakota, that reveals the long-term climate shifts on this continent.

4. Corals of the deep sea and of reefs
Graduate students: Jodie Smith and Jeff Heikoop (now PDF)
Working together with Mike Risk, we are studying variations in the ¹⁸O/¹⁶O and ¹³C/¹²C ratios of coralline aragonite in corals from the deep sea. These species lack symbiotic algae like those found in reef corals, and are profoundly out of isotopic equilibrium with seawater. However, their isotope ratios show systematic patterns which allow us to recover paleoclimate data. Using these data, we discivered a record of very rapid climate change at the end of the Younger Dryas, 13,000 years ago. We are now pursuing similar studies of gorgonians which have similar potential for recording deep-sea climate shifts.

Isotopes in Marine Soft Tissues

As well as studying O and C isotopes in the carbonates of marine organisms, we are also studying the living tissues of some of these organisms, to learn about their metabolic histories, their diet, and the possible effects of pollution and climate change on their mode of living. Using corals from around the world, we have shown wide ranges in the ¹⁵N/¹⁴N ratio that are partly due to varying light levels, and partly reflecting the isotopic composition of local seawater. We also study the impact of human polltuants on Cand N isotopes in coral flesh.

Medical applications of stable isotopes

In collaboration with medical scientists at McMaster (S. Atkinson, M. Tarnopolsky, O. Bar-Or) we are using stable isotopes of C, N and H to trace various aspects of metabolism and tissue growth in humans. For example, we use ¹³C-labelled glucose to observe energy production during exercise in diabetic humans. The doubly-labelled water method (O and H isotopes) is being used to monitor energy consumption in infants. A new study is making use of rubidium in cells to determine the cell mass of infants and track cell growth.

Recent Publications

Cormie, A.B. and Schwarcz, H.P. (1995) Effects of climate on deer bone ð¹⁵N and ð¹³/C: lack of precipitation effects on ð¹⁵N. Geochimica et Cosmochimica Acta, 60:4161-4166.

Wright, Lori and Schwarcz, H.P. (1996) Infrared evidence for diagenesis of bone apatite at Dos Pilas, Guatemala: paleodietary implications. Jour. Archaeol. Sci., 23: 933-944.

Swisher, C.C. III, Rink, W.J., Antón, S C., Schwarcz, H.P., Curtis, G.H., Suprijo, A., and Widiasmoro, (1996) Latest Homo erectus of Java: potential contemporaneity with Homo sapiens in Southeast Asia, Science, 274:1870-1874.

Toyoda, S. and Schwarcz, H.P. (1996) The spatial distribution of ESR in fault gouge revealed by abrading technique. Radiation and Isotopes. 47:1409-1413.

Smith, J.E., Risk, M.J. Schwarcz, H.P. and McConnaughey, T.A. (1997) Rapid climatic change in the North Atlantic during the Younger Dryas as recorded by deep sea corals. o Nature, 386:818-820

Aharon, P., Schwarcz, H.P. and Roberts, Harry H. (1997) Radiometric dating of submarine hydrocarbon seeps in the Gulf of Mexico, Bull. Geol. Soc. America, 109:568-579

Stuart-Williams, H. Le Q. and Schwarcz, H.P. (1997) Oxygen isotopic determination of climatic variation using phosphate from beaver bone, tooth-enamel and dentine. Geochimica et Cosmochimica Acta, 61:2539-2550.