Applied Geochemistry, Vol. 4, pp. 261-270. 1989 11883-2927/89 $3,00 + .DO Printed in Great Britain Pergamon Press plc Molecular preservation and crystallographic alterations in a weathering sequence of wildebeest bones N. TUROSS* Geophysical Laboratory, 2801 Upton Street, N.W. Washington, DC 20008, U.S.A. A. K. BEHRENSMEYER Department of Paleobiology, NHB-E207 MRC 121, Smithsonian Institution, Washington, DC 20560, U.S.A. E. D. EANES and L. W. FISHER Bone Research Branch, National Institute for Dental Research, Bethesda, MD 20892, U.S.A. and P. E. HARE Geophysical Laboratory, 2801 Upton Street, N.W. Washington, DC 20008, U.S.A. Abstract--The changes that occur in bone after the death of an animal are important because they control whether the bone becomes a fossil and what information is retained concerning the original biology of the animal. Taphonomic study of two 10-year longitudinal samples of wildebeest bones subjected to natural weathering in Amboseli Park, Kenya, provides evidence for progressive change in both the organic and inorganic components of mammalian bone. These changes correspond to weathering stages described on macroscopic structural features. The bone samples were subjected to well-established techniques of protein extraction from mineralized tissue, protein identification by gel electrophoresis and reactivity to antibodies of noncollagenous proteins, as well as X-ray defractometry of the mineral component. Both adult and juvenile bones show progressive increase in hydroxyapatite crystal size and increased protein degradation over the 10-yearperiod. Noncollagenous proteins persist at their original molecular weight in diminished amounts relative to modern controls. In the study area, 10 years or less of natural surface weathering altered the extractability of collagen, indicating peptide and crosslinking cleavage in this protein. Increased hydroxyapatite crystal size may reflect a tendency of crystals to enlarge in situ once the organic matrix begins to breakdown, without the addition of external minerals. INTRODUCTION MINERALIZED vertebrate tissue is transformed in the taphonomic transition from the biosphere to the lithosphere. Although it is clear that replacement of inorganic mineral components and destruction of the organic components have commonly occurred in the process of fossilization, the mechanism, rate and predictability of these changes is poorly understood. Analyzing the end product of fossilization does not necessarily lead to an understanding of the changes that have occurred, especially those that happen soon after the death of an animal. In 1975, BEHRENSMEYER initiated a long-term study of bone weathering (BEHRENSMEYER, 1978) in order to document macroscopic and microscopic changes that occur during the breakdown of vertebrate remains. Two of the carcasses monitored for macro- scopic characterization of weathering were used in the present study to examine biochemical and crystal- lographic changes that accompany the progressive weathering stages. While the time frame of this 10- *Current address: Smithsonian Institution, CAL/MSC, 2/210 Silver Hill Road, Suitland, MD 20746, U.S.A. 261 year study applies most directly to ecological or forensic concerns, we will also use it as a model for interpreting early, post-death taphonomic history in more ancient archaeological and paleontological bone. Understanding the biochemical and micromineral- ogical correlatives of structural changes seen in the weathering stages provides information on the pro- cesses that destroy mineralized tissue and the nature of decomposition in a natural environment. Corre- lation of the morphological, organic and inorganic changes should ultimately prove useful in assessing rates and conditions of burial for bones that are "well preserved" and the diagenetic history of bones in various stages of preservation. From a paleontologi- cal perspective, understanding early taphonomic his- tory in recent bones is important in establishing environmental conditions necessary for the preserv- ation of fossils. Such information may also suggest which sedimentary environments and taphonomic pathways could preserve organic components, rela- tively intact, for long periods of time without diagene- tic alteration. From a biochemical point of view it is important to establish diagenetic processes that alter organic and