A Latest Jurassic to Early Cretaceous Syn‐Collisional Trench Sequence in Central Tibet Recorded the Role of Microcontinents in Lhasa–Qiangtang Collision

Abstract As the most recent collisional event prior to the early Cenozoic India‐Asia collision, the suturing of the Lhasa‐Qiangtang terranes resulted in crustal accretion and the formation of lithospheric structures that greatly influenced subsequent Cenozoic rock uplift in central Tibet. The discovery of several microcontinents within the Bangong‐Nujiang suture zone between the Lhasa and Qiangtang terranes potentially implies multiple suturing stages, however, how and when the suturing of these terranes occurred are highly disputed. Here, we present a newly discovered latest Jurassic to Early Cretaceous deep‐marine gravity‐fan succession that is over 660 m thick in the Jienu Mountain region, south to the Cenozoic Lunpola basin. By employing multi‐proxy, single‐grain provenance analysis and forward modeling of sediment mixtures, we find the detritus was deposited in a syn‐collisional trench and was sourced from the Dongkaco microcontinent, the obducted ophiolite—subduction complex, the accreted seamounts, and the volcanic arc rocks. We interpret that this trench deposition occurred due to the latest Jurassic to Early Cretaceous collision of the Lhasa terrane beneath the Dongkaco microcontinent and other accreted components. The sutured Dongkaco microcontinent forms the basement to the Lunpola basin and is inferred not present beneath the narrower Nima, Gaize, and Awenco basins along strike to the west where these basins are either narrower or exhibit abrupt facies changes with time. This study highlights the importance of Mesozoic tectonic inheritance on subsequent Cenozoic uplift of the Tibetan Plateau.