Isotopic Composition of Paleosol Carbonates and Organic Matter

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Dr. Cerling will continue his NSF supported research and examine the extent to which soil carbonates contain useful climatic information. His preliminary research, under controlled modern conditions, has shown that carbon isotopes directly reflect the overlying plant community, and on this basis it is possible to determine the relative amounts of "C3" and "C4" species. C4 plants are adapted to water stressed conditions and thus provide a useful climatic indicator. Since oxygen isotope composition in rainwater is affected by temperature and may vary by almost 20 per mil, if this is preserved in paleosol carbonate it also may yield climatic information. Dr. Cerling has analyzed several series of fossil soils associated with anthropologically significant materials and has extracted useful climatic signals. In his new research, Dr. Cerling will continue his study of both modern and fossil soils. He will examine some modern soils to further understand the oxygen isotopic record in paleosol carbonates and continue to work on soils formed on limestones so that they may be used in paleoecologic reconstructions as well. He will also apply and evaluate these emerging techniques to paleoontologic and anthropologic sites in the Old World to shed light on climatic changes which occurred during the Miocene, Pliocene, and Pleistocene. 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.