Early Miocene elevation in northern Tibet estimated by palaeobotanical evidence

Abstract

The area and elevation of the Tibetan Plateau over time has directly affected Asia’s topography, the characteristics of the Asian monsoon, and modified global climate, but in ways that are poorly understood. Charting the uplift history is crucial for understanding the mechanisms that link elevation and climate irrespective of time and place. While some palaeoelevation data are available for southern and central Tibet, clues to the uplift history of northern Tibet remain sparse and largely circumstantial. Leaf fossils are extremely rare in Tibet but here we report a newly discovered early Miocene barberry (Berberis) from Wudaoliang in the Hoh-Xil Basin in northern Tibet, at a present altitude of 4611 ± 9 m. Considering the fossil and its nearest living species probably occupied a similar or identical environmental niche, the palaeoelevation of the fossil locality, corrected for Miocene global temperature difference, is estimated to have been between 1395 and 2931 m, which means this basin has been uplifted ~2–3 km in the last 17 million years. Our findings contradict hypotheses that suggest northern Tibet had reached or exceeded its present elevation prior to the Miocene.

Low palaeoelevation of the northern Lhasa terrane during late Eocene: Fossil foraminifera and stable isotope evidence from the Gerze Basin

“…According to previous palaeoelevation study results, in the late Oligocene (~26 Ma), the Nima Basin had reached approximately 4,000 m 5 and the Lunpola basin had reached 3,190 ± 100 m5051. Combining these results with the results of our study suggests that the northern Lhasa terrane experienced surface uplift of at least 3,000 m over approximately 10 million years from the late Eocene to the late Oligocene.…”

Eocene to late Oligocene history of crustal shortening within the Hoh Xil Basin and implications for the uplift history of the northern Tibetan Plateau

“…For example, Eocene to late Oligocene crustal shortening and thickening of the Hoh Xil Basin likely contributed to surface uplift; however, palynological and paleoelevation data from the Hoh Xil Basin indicate that surface uplift continued after the Oligocene [ Q . Duan et al , , ; Wu et al , ; Polissar et al , ; Sun et al , ]. This suggests that crustal shortening alone may not be responsible for elevation gain in northern Tibet.…”

“…Duan et al , , ; Wu et al , ]. Paleobotanical evidence from Miocene Wudaoliang strata indicates that paleoelevation was between 1.4 and 2.9 km at 17 Ma [ Sun et al , ] and that the Miocene fossil assemblage was dominated by drought‐ and cold‐tolerant species [ Q . Duan et al , , ; Wu et al , ].…”

“…We postulate that crustal shortening in late Eocene to Oligocene time led to surface elevations of no more than 2.6 km. This is consistent with paleobotanical evidence from the Miocene Wudaoliang strata [ Sun et al , ] and the Eocene to Miocene elevation change derived from lipid biomarkers [ Polissar et al , ]. High elevations (3.4–4.2 km) may have been attained in late Miocene time but fall short of the 4.5–5.5 km elevations of the modern northern plateau and may be suggestive of post–late Miocene uplift [ Polissar et al , ].…”

“…The attainment of modern elevations (4.5–5.5 km) occurred after ~17 Ma [ Q . Duan et al , , ; Wu et al , ; Polissar et al , ; Sun et al , ], substantially later than any significant crustal shortening preserved in the region.…”