Paleomagnetic Evidence of Internal Rotation in the Eastern Qiangtang and Its Relation to Distributed Strike-Slip Faulting in the Southeastern Tibetan Plateau

Abstract

The southeastern Tibetan Plateau has undergone complex deformation due to the India-Eurasia collision. Although late-stage internal rotations are documented in the Lanping-Simao Terrane to the south, it remains unclear whether similar processes have affected the north. This study presents new paleomagnetic data from Eocene red beds in Baizha of the northern region. Fourteen sites yield primary ChRMs, with mean of Ds = 51.6°, Is = +33.3° (k = 28.2, α95 = 7.6°), suggesting a ∼40° clockwise rotation occurred after the late Eocene. This rotation includes both a regional oroclinal bending component and an additional local rotation. We interpret the local rotation as resulting from early Miocene left-lateral motion on the Lancang and Ganzi-Yushu faults. Combined with existing evidence, our findings support a three-stage Cenozoic tectonic evolution for the southeastern Tibetan Plateau and further suggest that the distributed strike-slip faulting and widespread local rotations since the early Miocene were facilitated by pincer-like convergence between the Chuandian and Burma terranes.