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

Abstract

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 δ13C(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 δ18O(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 δ18O(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.