Stable isotopes of modern herbivore tooth enamel in the Tibetan Plateau: Implications for paleoelevation reconstructions

Fossil tooth enamel from herbivores is considered one of the best proxies for paleoclimate and paleoelevation reconstructions, due to its low susceptibility to diagenetic alteration. A synthesis of oxygen and carbon isotope analyses of modern tooth enamel from herbivores such as Tibetan yaks, asses and antelopes is assessed. The average delta C-13(PDB) value of herbivore tooth enamel in the Lhasa and south Qiangtang terrains is -11.3% +/- 1.1%, whereas in the north Qiangtang and Hoh Xil terrains value is -10.2% +/- 1.4% consistent with the current C3-dominant ecotype in the Tibetan Plateau. In addition, the average delta O-18(PDB) values from tooth enamel show a northward systematic increase from -11.8% +/- 3.4% in the Gyirong Basin, to -11.1% +/- 1.1% in the Lhasa and southern Qiangtang terrains, and then to -9.0% +/- 1.1% in the northern Qiangtang and the Hoh Xil areas, similar to those of the local river water and precipitation variation trends. It is suggested that delta O-18(PDB) values of tooth enamel should not be used directly to evaluate the paleo-elevation of the Tibetan Plateau, because oxygen isotopic composition from tooth enamel is a combination of drinking water (precipitation- and river-sourced) and diet (plant-sourced). Moreover, an empirical relationship between oxygen isotope of tooth enamel and modern river water, and as well as elevation is recommended, which can be used in future studies of Tibetan Plateau paleoelevation.