Abstract: The elevation evolution history of the southeastern Tibet Plateau is of great significance for examining the deformation mechanism of the plateau boundary and understanding the interior geodynamic mechanics. It provides an important window to inspect the uplift and deformation processes of the Tibet Plateau, and also an important way to test two controversial dynamic end-element models of the Plateau boundary. In recent years, some breakthroughs have been made in the study of paleoaltitudes in the southeastern Tibet Plateau, which allows us to have a clearer understanding of its evolution process and dynamic mechanism. By reviewing and recalculation of the latest achievements of paleo-altitude studies of the basins in the southeastern Tibet Plateau from north to south, including the Nangqian Basin, Gongjue Basin, Mangkang Basin, Liming-Jianchuan-Lanping Basin, Eryuan Basin, Nuhe Basin and Chake-Xiaolongtan Basin, we discuss the surface elevation evolution framework of the Cenozoic geomorphology and dynamics in the southeastern Tibet Plateau. The results show as follows:
(1)There was an early Eocene-Oligocene quasi plateau with an altitude of at least 2.5km from the north to middle of the southeastern Tibet Plateau(north of Dali), while the surface elevation in the south(south of Dali to Yunnan-Guizhou Plateau)was relatively low, even close to sea level. Until Miocene, the north to middle of the southeastern Tibet Plateau reached the present altitude, while the southern part of the Tibet Plateau showed a differential surface uplift trend, which established the present geomorphologic pattern. But it cannot be completely ruled out that this trend was probably caused by the accuracy of the calculation results.
(2)The quantitative constraints on the uplift process of the southeastern Tibet Plateau during Cenozoic provide certain constraints for the dynamic mechanism of geomorphic evolution in the southeastern Tibet Plateau. The northern and central parts of the southeastern Tibet Plateau can be well explained by the plate extrusion model. In this model, the collision and convergence between India and Eurasia plate or Qiangtang block and Songpan-Ganzi block resulted in the shortening and thickening of the upper crust in the region, and making the early stage(early Eocene)surface uplift. Subsequently, due to delamination or the continuous convergence between the Qiangtang block and the Songpan-Ganzi block resulting in the shortening and thickening of the crust, the plateau continued to grow northward and rose to its present altitude around Miocene. In the Eocene, the area from the south of the southeastern Tibetan plateau to the Yunnan-Guizhou Plateau mainly showed a low altitude. It seems that it may be in the peripheral area not affected by the shortening and thickening of the upper crust during the early stage India-Eurasia plate collision or plate extrusion and escape. In addition, as proposed by the lower crustal channel flow model, the lower crust material made the low-relief upland surface extending thousands of kilometers in the region uplift gradually towards the southeast, which seems to explain the low elevation landform of the region in the early stage, but it could not explain the whole uplift process of the southeastern Tibet Plateau. Therefore, a single dynamic model may not be able to perfectly explain the Cenozoic complex uplift process of the southeastern Tibet Plateau, and its process may be controlled by various dynamic processes.
(3)According to the paleoaltitude reconstruction results, if most areas of the ancient southeastern Tibet Plateau, especially the area to the north of Jianchuan Basin, had been uplifted in a certain scale and became part of the early plateau in the early Cenozoic, and reached to the current surface altitude around Miocene, the widely rapid surface erosion in this area since Miocene probably would be a continuous lag response to the finished surface uplift process, and the lag time may correspond to the sequential response process of surface uplift, the decline of river erosion base level and the gradual enhancement of river erosion capacity. Therefore, it is not proper to regard the rapid denudation and rapid river undercutting as the starting time of plateau uplift, as proposed in the previous thermochronological study.

Key words: southeastern Tibetan plateau, Cenozoic basins, paleoaltitude reconstruction, plateau uplift, lower crustal flow

摘要： 掌握青藏高原的高程演化历史对检验高原边界的变形机制和理解深部地球动力学具有重要意义。 文中对青藏高原东南缘的囊谦盆地、 贡觉盆地、 芒康盆地、 黎明-剑川-兰坪盆地、 洱源盆地、 怒河盆地和岔科-小龙潭盆地等不同区域的典型新生代盆地的古高度重建研究成果进行了系统梳理、 总结以及部分重新计算后, 恢复了青藏高原东南缘新生代隆升过程的时空分布历史, 讨论了青藏高原东南缘新生代期间的主要隆升阶段与幅度。 综合分析表明, 青藏高原东南缘北段—中段地区存在始新世—渐新世准高原, 而南段地区的地势相对较低。 中新世期间, 南段地区呈现出差异化的隆升趋势。 在此基础上, 文中进一步定量化约束了高原东南缘新生代的隆升过程, 为青藏高原东南缘构造、 地貌演化的动力学机制探讨提供制约。

关键词: 青藏高原东南缘, 新生代盆地, 古高度重建, 高原隆升, 下地壳流