부산대학교 도서관

The timing and magnitude of the early Cenozoic surface uplift of the Tibetan Plateau is controversial due to a scarcity of unaltered terrestrial sediments required for palaeoaltimetry techniques. Such information is critical, however, for constraining the geodynamic and palaeoclimatic evolution of the Indian and Eurasian continents and for interpreting global climate, biodiversity and biogeochemical cycles since the Cenozoic. We find that substantial uplift occurred by 63 to 61 million years ago, before the collision of the Indian and Eurasian continental plates, based on comparison of triple oxygen isotopes of modern meteoric waters with epithermal Ag–Pb–Zn deposit quartz veins from the Palaeocene Gangdese Arc in southern Lhasa. Low δ18O and δ17O quartz values are consistent with precipitation from meteoric waters influenced by a large degree of topographic rainout. We show that by 63 to 61 Ma, the Gangdese Arc reached an elevation of ~3.5 km, suggesting that the Gangdese Arc achieved >60% of its current elevation before continent–continent collision. This uplift was probably caused by crustal shortening in response to low-angle subduction of Neo-Tethyan oceanic lithosphere. This early high palaeoelevation estimate for the Himalaya–Tibetan system challenges previous assumptions that southern Tibet uplift required continent–continent collision to achieve substantial topography.
The triple oxygen isotope composition of quartz veins indicates that the southern Tibetan Plateau was already around 3.5 km high by 60 million years ago, showing that substantial surface uplift started before collision of the Eurasian and Indian plates.