Cenozoic paleoaltimetry of the SE margin of the Tibetan Plateau: Constraints on the tectonic evolution of the region

- We report lacustrine carbonate δ18O from three basins in SE Tibet and Yunnan.
- Basin paleoelevation was model-based calculated from δ18O.
- SE Yunnan reached its current elevation (∼1.6 km) by ∼13 Ma.
- Lower crustal flow in SE Yunnan occurred >13 Ma.

An improved understanding of the elevation history of the Tibetan Plateau is crucial in discriminating among the various tectonic models for the evolution of the India-Asia continental collision. We reconstruct the paleoelevation history for three Cenozoic sedimentary basins from SE Tibet and Yunnan, China, to provide more constraints on the tectonic processes for raising the SE margin of the Tibetan Plateau. The results presented here, together with those of previous studies, indicate that (1) the plateau margin of NW Yunnan was near its elevation (∼2.6km) by the latest middle Eocene (∼40Ma); (2) the plateau margin of SE Yunnan reached its current elevation (∼1.6km) by the middle Miocene (∼13Ma). Interpretations of the tectonic processes responsible for this inferred surface uplift of the region are made in the context of well-documented surface geology. We conclude that high landscape (∼2.6km elevation) in NW Yunnan may represent the remnants of the Eocene Tibetan plateau that originally formed in the northeastern Qiangtang Block by crustal thickening associated with the India-Asia continental collision. The near-modern elevation of SE Yunnan since ∼13Ma probably reflects the initiation of lower crustal flow in this area by at least that time. Collectively, our paleoaltimetric interpretations disagree with previously proposed models of middle Miocene to Pliocene crustal flow acting as a sole tectonic process for raising the SE margin of the plateau, but support a protracted history of surface uplift that most likely involved crustal thickening during the Eocene, southeastward extrusion of a portion of Eocene Tibetan plateau during the Oligocene to early Miocene, and lower crustal flow beneath this region since at least the early Miocene.