Correlation of Crustal Kinematic Characteristics and the Uplift of the Southeastern Tibetan Plateau During the Paleogene.

The mechanism of the uplift of the southeastern Tibetan Plateau during the Cenozoic is much debated. To address this problem, we conducted a paleomagnetic study of the Eocene sedimentary strata in the Relu Basin, in the southeastern Tibetan Plateau. Two primary magnetic components of Ds = 24.0°, Is = 26.8°, k = 156.8, α95 = 3.5° acquired during ∼48.0–43.0 Ma and Ds = 172.2°, Is = −38.0°, k = 38.6, α95 = 9.8° during ∼43.0–35.0 Ma were isolated. The results combined with previous Paleocene and Eocene paleomagnetic and paleo‐altimetry data sets from the southeastern Tibetan Plateau, revealed a spatio‐temporal correlation between crustal movement and the uplift process of the southeastern Tibetan Plateau. The results showed that the final collision between India and Asia at ∼53.0–47.0 Ma immediately triggered the latitudinal crustal convergence and rotational deformation within the southeastern Tibetan Plateau. Since ∼47.0 Ma the southeastern Tibetan Plateau underwent a coherent crustal rotational pattern, and by at least ∼43.0 Ma, it finished the substantial latitudinal crustal convergence. The crustal movement transformations coincided with the major uplift of the southeastern Tibetan Plateau during ∼47.0–35.0 Ma and the eruption of extensive mafic magmatic rocks across the southeastern Tibetan Plateau and its margin during ∼43.0–33.0 Ma. These spatio‐temporal relationships suggest that the integral uplift of the southeastern Tibetan Plateau was mainly associated with the asthenospheric mantle upwelling and convection resulting from the tearing of the mantle lithosphere of the India Plate beneath the southeastern Tibetan Plateau. Plain Language Summary: We obtained primary magnetic components, which were combined with paleo‐altimetry data sets from Paleogene basins in the southeastern Tibetan Plateau and its margin. The results showed that since ∼47.0 Ma, the southeastern Tibetan Plateau underwent a coherent crustal rotational pattern, and by at least∼43.0 Ma, it completed the primary phase of major latitudinal crustal convergence. These transformations of crustal movement characteristics occurred at the same time as the major uplift process of the entire southeastern Tibetan Plateau during ∼47.0–35.0 Ma, and were also accompanied by the eruption of magmatic rocks resulting from the fractional crystallization of mantle‐derived mafic magmas across the southeastern Tibetan Plateau and its margin. Thus, the tectonic deformation and crustal thickening related to folding and thrusting in the southeastern Tibetan Plateau were significantly weakened, during the major uplift process of the southeastern Tibetan Plateau. This indicates that the substantial uplift of the southeastern Tibetan Plateau was not primarily driven by crustal shortening and thickening, or by the eastward flow of weakened lower crust, but rather that it was mainly associated with the asthenospheric mantle upwelling and convection resulting from the tearing of the mantle lithosphere of the India Plate beneath the southeastern Tibetan Plateau. Key Points: Since 47.0–43.0 Ma the southeastern Tibetan Plateau underwent a coherent crustal rotational pattern and completed crustal convergenceThe transformation of crustal movement was simultaneous with the main phase of uplift of the southeastern Tibetan Plateau since ∼47.0 MaAsthenospheric mantle upwelling and convection related to tearing of subducted India slab uplifted the southeastern Tibetan Plateau [ABSTRACT FROM AUTHOR]