Climatic controls on travertine deposition in southern Tibet during the late Quaternary

Large volumes of travertine deposits are preserved at hydrothermal spring sites on the Tibetan Plateau (TP). Yet, most of these deposits are under-researched with respect to their diagenetic and depositional history and there is still very limited understanding of the tectonic and climatic influences on travertine precipitation in the arid high-altitude setting of Tibet. In this study, a detailed uranium-series dating campaign was carried out for the Qiusang travertine (~4270 m above sea level), southern Tibet that has been previously dated back to 486 thousand years ago (ka). Based on 42 new ²³⁰Th/U ages, combined with geomorphological and sedimentological investigations, several travertine zones were identified and distinct travertine depositional phases constrained: 11.7–6.8 ka and ~ 13.4 ka (zone 1), 128–122 ka (zone 2), ~193 ka (zone 3), ~292 ka and 324 ka (zone 4), >317 ka (zone 5), ca. 415 to 470 ka (zone 6) and ca. 419 to 445 ka (zone 7). Comparison of these depositional phases with local and regional proxy records suggests that travertine accumulation at Qiusang occurred during main interglacials when monsoon precipitation peaked on the TP. This coincidence, together with a sensitive response of Tibetan hydrothermal spring activity to meteoric recharge, implies that climate controls the precipitation of large travertine volumes on orbital timescales on the plateau. We propose that (i) tectonic activity is of subordinate importance and influences travertine precipitation on the TP only episodically and on significantly shorter (i.e. centennial to millennial) timescales related to the recurrence rates of large earthquakes and that (ii) intensive monsoonal-driven groundwater recharge is required on top of tectonic activity for generating volumetrically significant travertine accumulations. Because of the high precipitation rates typical for hydrothermal spring carbonates, we conclude that travertine deposits on the TP could be utilized as valuable high-resolution proxy records of peak monsoon conditions in the currently arid to semi-arid landscape. Furthermore, the Qiusang travertine zone 7 is terraced and the travertine layers adjusted to a paleo-riverbed elevation ~30 m above the current river, allowing us to constrain fluvial incision to ~0.07 m/ka for the south-central sector of the TP since the Mid-Pleistocene. The abundant travertine occurrences in Tibet in combination with uranium-series dating can thus also provide detailed insights into earth surface dynamics and landscape evolution on the world highest plateau.