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

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.