Oxygen isotopes in living mammal's bone phosphate: Further results

Abstract

The potential use of oxygen isotopes in mammal bone phosphate to study paleoclimates has been recognized since a few years. It has been proven that the δ 18O(PO 4 3−) of some mammal species is related to the mean δ 18O of local meteoric water, each species showing a specific linear relationship. We report here some measurements of the oxygen isotopic composition of bone phosphate from living specimens of deer, mice, cattle and sheep coming from different areas with different mean annual values of local meteoric water. The oxygen isotopic composition of body water (blood water) of some of these specimens has also been measured. Linear relationships between the δ 18O of bone phosphate, the δ 18O of blood water and the mean δ 18O of local meteoric water have been found, as in the case of the previously studied specimens of humans, pigs and rats. The slopes of the calculated equations for the bone phosphate-meteoric water relationships are the following: 0.79 (wood mice), 1.01 (cattle), 1.13 (deer) and 1.48 (sheep). The calculated phosphate-water fractionation factors are quite homogeneous, ranging from 1.0172 to 1.0175. These values are very close to those which may be calculated for isotopic equilibrium conditions between bone phosphate and body water. Fossil bones from the studied species may now be used for paleoclimatological and paleohydrological studies.