Paleosols as Indicators of Paleoclimates: Oxygen and Carbon Isotopes in Pedogenic Carbonate

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This grant permits Dr. Cerling to examine the extent to which soil carbonates contain useful climatic information. It is possible that the stable isotopic composition of paleosol carbonate may provide a direct measure of climatic and ecological conditions for non.marine sites. Since oxygen isotope composition in rainwater is affected by temperature and may vary by almost 20 per mil if this is perserved in paleosol carbonate it may provide a potential climatic indicator. The isotopic composition of soil carbon varies by about 15 per mil and is primarily a function of the proportion of C4 plants in the local setting. Since this vegetation is also influenced by climate carbon isotope ratio of soil carbonate may also reflect climate. Dr. Cerling will collect samples along both latitudinal and altitudinal transcents to document variation in the isotopic composition of modern soil carbonate which is due to ecological and climatic factors. He will also measure the isotopic composition of soil organic matter and respired soil carbon dioxide to document important controlling processes. Finally he will analyze a series of anthropologically significant soils from both Africa and Asia. This research is important because, if successful, it will provide an important anthropological tool. To understand how humans developed it is essential to understand the environments in which they lived and how these changed over time. While techniques are well established for marine sediments, terrestrial materials are much more difficult to interpret and very little work has been done. This project should help to remedy the situation.***//