During the Cenozoic era, the southeastern edge of the Qinghai Tibet Plateau underwent clockwise rotational deformation and southeast escape in response to the collision between the Indian and Eurasian plates. This process absorbs a large amount of north-south shortening and vertical growth of the plateau lithosphere, playing an important role in regulating the uplift and deformation process of the plateau structure. Studying the tectonic evolution history of the southeastern margin of the Qinghai Tibet Plateau during the Cenozoic era is of scientific significance for exploring the uplift evolution process, patterns, and dynamic mechanisms of the entire Qinghai Tibet Plateau.

Existing paleomagnetic studies indicate that the southern regions of the southeastern edge of the Qinghai Tibet Plateau, such as Lanping Simao, Tengchong, and Baoshan, experienced clockwise rotational deformation and southeast escape mainly after the Early Oligocene, later than the widely believed collision time of the Indian Eurasian plate, which occurred approximately 60-50 million years ago. The northern region of the southeastern edge of the plateau, such as Nangqian and Gongjue, recorded a complex history of rotational deformation during the Eocene. It is currently unclear whether the southern region of the southeastern margin underwent rotational deformation before the Oligocene, and whether the entire southeastern margin of the plateau responded to the collision mechanism of the Indian Eurasian plate in time and space. Around these problems, Yan Maodu, a researcher of the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, and his collaborators selected the Yunlong Formation strata in the Yunlong Basin in the northern part of the Lanping Simao block to carry out a systematic study of paleomagnetic rotation and deformation.

Rock magnetism, petrography, and field testing indicate that the Yunlong Formation samples record the direction of primary residual magnetism; The comprehensive comparative analysis of magnetic stratigraphy and regional chronology reveals that the stratigraphic age of the Yunlong Formation is approximately 79-61 million years old; The analysis of characteristic remanent magnetization direction indicates that the Yunlong Basin underwent approximately 45 ° clockwise rotation deformation after 79-61 million years. By comprehensively comparing the existing paleomagnetic data of the early Cretaceous and late Eocene in the Lanping Simao Basin, researchers found that the basin underwent approximately 20 ° clockwise rotation deformation during the Eocene, and the time and magnitude of rotation deformation were basically consistent with those of the Gongjue Basin in the northern southeastern margin. In addition, the structural trace from north to south on the southeastern edge of the plateau has a good linear relationship with the rotation after the Late Eocene, that is, the deformation of the bent mountain structure occurred after the Late Eocene. This study proposes a two-stage tectonic evolution model for the southeastern edge of the Qinghai Tibet Plateau in the Cenozoic era: in response to the collision of the Indian Eurasian plate, the southeastern edge of the Qinghai Tibet Plateau underwent a clockwise rotation deformation of about 20 ° in the early stage of the collision (during the Eocene period); After the Late Eocene, as the Indian Plate continued to wedge northward in the Himalayan East tectonic zone, different parts of the southeastern edge of the Qinghai Tibet Plateau underwent rotational deformation with varying degrees in the form of bent mountain structures.

Recently, the related research results were published in the Geological Society of America Bulletin under the title of Moderate magic clockwise rotation of the Yunlong Basin: Implicitations for synchronous Eocene rotation of the Southern Titanium Plateau. The research work has been supported by the National Key R&D Program, the National Natural Science Foundation of China, and the Second Comprehensive Scientific Expedition to the Qinghai Tibet Plateau.



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