The rise of the Tibetan plateau — the largest topographic anomaly above sea level on Earth — is important for both its profound effect on climate and its reflection of continental dynamics. In this study published in GSA Bulletin, Katharine Huntington and colleagues employ a cutting-edge geochemical tool — “clumped” isotope thermometry — using modern and fossil snail shells to investigate the uplift history of the Zhada basin in southwestern Tibet.
|The Tibetan Plateau [Credit: NASA/Jeff Schmaltz, MODIS Rapid Response Team,
Goddard Space Flight Center]
Views range widely on the timing of surface uplift of the Tibetan Plateau to its current high (~4.5 km) over more than 2.5 square kilometers. Specifically, interpretations differ on whether the modern high elevations were recently developed or are largely a continuation of high elevations developed prior to Indo-Asian collision in the Eocene.
Clumped isotope temperatures of modern and fossil snail shells record changing lake water temperatures over the last nine million years. This is a reflection of changes in surface temperature as a function of climate and elevation change. A key to their Zhada Basin paleo-elevation reconstructions is that Huntington and colleagues were able to contextualize them with sampling of modern and Holocene-age tufa and shells from a range of aquatic environments.
Huntington and colleagues find that the Zhada basin was significantly colder from three to nine million years ago, implying a loss of elevation of more than one kilometer since the Pliocene. While surprising given the extreme (~4 km) elevation of the basin today, the higher paleo-elevation helps explain paleontological evidence of cold-adapted mammals living in a high-elevation climate, and is probably the local expression of east-west extension across much of the southern Tibetan Plateau at this time.
Huntington and colleagues note that future studies could improve on their own initial “calibration” work with year-round monitoring of water temperature and a focus on specific taxa and their micro-habitat preferences.
Source: Geological Society of America [August 29, 2014]