Stable isotope revealed hydroclimate transition and topography growth in the Northern Tibetan Plateau at ∼ 10 Ma

Abstract

The Middle to Late Miocene uplift of the northern Tibetan Plateau had been revealed in a large amount of studies, however, its effects on hydrological and climatic evolution in Asia remains unclear due to the lack of well dated direct hydrological records in this region. Here, we report a carbonate oxygen isotope record (δ18Oc) from the western Qaidam Basin, and compare it with the δ18Oc records of five different basins in the Northern Tibetan Plateau. These data reconstruct the hydroclimatic evolution in this region and show a divergence of δ18Oc variation pattern in different basins at ∼11.5–8.5 Ma, which is different with a consistent evolution pattern of them before and after this time interval. This divergence is characterized by a significant decrease of δ18Oc in the windward locations while an increase in the leeward locations. This δ18Oc divergence was decoupling with the concurrent stable global climate, but consistent with the contemporaneous uplift of the northern Tibetan plateau. This suggests a possible link between δ18Oc divergence and topographic growth, which is further supported by a ∼ 1000 m paleoelevation increase revealed by our δ18Oc paleoelevation reconstruction. We suggest that the topography growth of the northern Tibetan Plateau especially the surrounding mountains would have facilitated water vapor transport to the windward regions, resulting in isotopic depletion in the water vapor masses. Whilst, a blocking of water vapor masses would induce aridity and increased evaporation in the leeward slopes, thus enriching heavy isotopes in precipitation there. This study corroborates the extensive uplift of the Northern Tibetan Plateau during ∼11.5–8.5 Ma from an isotopic perspective. A comparison of the obtained δ18Oc records with modern ones further suggests an establishment of modern hydroclimatic patterns in northern Tibetan Plateau at ∼8.5 Ma.