Stable isotope analysis of the tooth enamel of Chaingzauk mammalian fauna (late Neogene, Myanmar) and its implication to paleoenvironment and paleogeography

The tooth enamel of a mammalian fauna from the uppermost Miocene/lower Pliocene Irrawaddy sediments at Chaingzauk, west-central Myanmar were analyzed using stable carbon and oxygen isotopes. The δ13C values of porcupines, tragulids, rhinocerotids, suids and proboscideans show that these mammals preferentially consumed C3 plants in a wooded environment, whereas the δ13C values of bovids and hippopotamids indicate that they were grassland-adapted grazers to mixed feeders. In contrast to the thorn scrub, grassland and shrubland vegetation of present-day central Myanmar, stable carbon isotope results of the Chaingzauk fauna suggest a presence of wooded environment in the Chaingzauk area at that time. Present-day arid conditions are likely to have been caused by the uplift of the Indo-Burman Ranges due to the Himalayan Orogeny during the late Miocene to Pliocene, resulting in a rainshadow effect in central Myanmar. Furthermore, southward marine regression due to the rapid influx of sediments from the Indo-Burman Ranges, Eastern Himalayan Ranges and Sino-Burman Ranges into the Central Myanmar Basin in the Miocene to Pliocene might have played an important role in the aridification of this region since the lower Pliocene.