No high Tibetan Plateau until the Neogene.

Area of Science:

• Paleontology
• Paleogeography
• Climate Science

Background:

• The Paleogene surface height and paleoenvironment of the Qinghai-Tibetan Plateau (QTP) are poorly understood.
• Existing models struggle to reconcile the plateau's current elevation with Paleogene climate conditions.

Purpose of the Study:

• To reconstruct the Paleogene topography and paleoenvironment of the central QTP.
• To challenge prevailing tectonic and paleoenvironmental models of the region.

Main Methods:

• Discovery and dating of fossil palm leaves from Late Paleogene paleolake sediments in the Lunpola Basin.
• Analysis of palm leaf anatomy to infer temperature and altitudinal constraints.
• Integration with paleoterrestrial lapse rate models.

Main Results:

• Discovery of the youngest fossil palm leaves in Tibet, dated to the Late Paleogene (Chattian, ~25.5 Ma).
• Palm leaf fossils indicate a low-elevation paleovalley (<2.3 km) in the Lunpola Basin, not a high plateau.
• The paleovalley was flanked by mountains exceeding 4 km, creating a highly varied landscape.

Conclusions:

• A high plateau did not exist in the core of the QTP during the Paleogene.
• The findings necessitate revisions to models of tectonic uplift, Asian monsoon dynamics, and biodiversity evolution.
• The study reveals a complex paleotopography that influenced regional climate and ecosystems.