Full length articleTectonostratigraphic evolution of the Mohe-Upper Amur Basin reflects the final closure of the Mongol-Okhotsk Ocean in the latest Jurassic-earliest Cretaceous

- Stratigraphic correlation, depositional ages, and provenance of the Mohe-Upper Amur Basin were refined.
- Middle Jurassic-Early Cretaceous paleogeographic evolution of the Mohe-Upper Amur Basin was reconstructed.
- Final closure of the Mongol-Okhotsk Ocean in the latest Jurassic-earliest Cretaceous was constrained.

The Mohe-Upper Amur Basin to the south of the eastern Mongol-Okhotsk Suture Zone contains important stratigraphic records for understanding the closure of the eastern Mongol-Okhotsk Ocean. The basin is crossed by the Russia/China border, and its Chinese and Russian parts are known as the Mohe Basin and Upper Amur Basin, respectively. Using most up-to-date data on stratigraphy, sedimentology, petrography, and detrital zircon U-Pb geochronology, this study establishes the stratigraphic correlation between the two, Mohe and Upper Amur parts of the basin, and analyzes depositional ages, provenance, and paleogeography of their Jurassic-Lower Cretaceous strata. The adopted Middle-Late Jurassic ages for the Xiufeng, Ershierzhan, Emuerhe, and Kaikukang formations in the Mohe Basin, are revised and constrained to late Kimmeridgian, Tithonian, Berriasian-early Valanginian, and late Valanginian ages, respectively. During the late Kimmeridgian-Tithonian, extension occurred in the Mohe-Upper Amur Basin, and sediments were mainly sourced from areas to the south of the basin. Later, in the Berriasian-early Valanginian, the northern margin of the Mohe-Upper Amur Basin was uplifted and started furnishing sediments into the basin. In the late Valanginian, regional uplift of the northern part of the Mohe-Upper Amur Basin transformed the basin into a compressional intermountain basin, with sedimentation localized in its southern part. After the Valanginian, extension and associated volcanism occurred in the basin. We suggest that the evolution of the Mohe-Upper Amur Basin reflects the gradual closure of the eastern Mongol-Okhotsk Ocean and associated collision of the Siberia Craton and the Amuria Block, that occurred from the Kimmeridgian-Tithonian, to the west of the basin through to the Berriasian-Valanginian, to the north and northeast of the basin. The final closure of the Mongol-Okhotsk Ocean to the north of the Mohe-Upper Amur Basin in the earliest Cretaceous significantly affected the sedimentological, structural and tectonic evolution of Northeast Asia.

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