THE PRESERVATION OF GLACIAL-INTERGLACIAL CLIMATIC SIGNATURES IN THE OXYGEN ISOTOPES OF ELEPHANT SKELETAL PHOSPHATE

Phosphate deltaO-18 values (deltaO-18(p)) of modern elephant bone and teeth are found to vary linearly according to the deltaO-18 of local meteoric water (deltaO-18(mw)), a parameter with close ties to regional and local climatic conditions. Enamel, dentine, cementum and bone separates from individual fossil elephant specimens, of Late Pleistocene age, have deltaO-18(p) values which vary by up to 1.4 parts per thousand, despite the fact that differences in deltaO-18(p) values of only 0.6 parts per thousand are observed between equivalent phases for specific modern elephant specimens. The larger spread in the deltaO-18(p) values of the various skeletal phases for the fossil samples is interpreted as evidence for post-depositional alteration of primary deltaO-18(p) signatures of some, if not all, of these fossil skeletal components. In the fossil samples investigated, enamel and dentine phases have systematically lower deltaO-18 values than associated bone and cementum phase. Differential re-equilibration with soil waters, either by the wholesale replacement of primary apatite or by processes of isotopic exchange, is suggested as a mechanism to account for the observed spread in the fossil phosphate deltaO-18 data.