Stratigraphic sequence characteristics and geochronology research progress of the Cenozoic in the arcuate tectonic belt on the northeastern margin of the Tibet Plateau

Abstract

The Cenozoic tectonic deformation and sedimentary processes in the arcuate tectonic belt along the northeastern margin of the Tibetan Plateau have been influenced by the remote effect of the subduction of the Pacific Plate as well as controlled by the northeastward extension of the Tibetan Plateau. Determining the sedimentary age of the Cenozoic strata is an essential prerequisite for understanding these tectonic deformation and sedimentary processes. However, the sequence and depositional age of the Cenozoic strata in the arcuate tectonic belt is still controversial. This paper systematically studied the Paleoproterozoic to Neoproterozoic sedimentary sequences and stratigraphic ages in the arcuate tectonic belt. The results show that the sedimentary ages of the Sikouzi Formation, the Qingshuiying Formation, the Zhang'enbao Formation, and the Ganhegou Formation in the arcuate tectonic belt are the Middle to Late Oligocene, the Late Oligocene–Early Miocene, the Middle Miocene–Late Miocene, and the Late Miocene-Pliocene, respectively. We systematically analyzed the two unconformities of the Paleocene to Neoproterozoic and refined their formation age as well as geotectonic significance. The first unconformity developed between the Qingshuiying Formation and the Zhang'enbao Formation in the Early-Middle Miocene, which indicates the appearance of the remote effect caused by the northeastward extrusion of the Tibet Plateau at about Early Miocene. The second unconformity developed between the Zhang'enbao Formation and the Ganhegou Formation, which implies the summit of tectonic activities caused by the northeastward extrusion of the Tibet Plateau at about the Late Miocene. It is concluded that the Cenozoic basins have evolved through three stages based on the coupling relationship between the sedimentary process and the tectonic evolution. From the Middle Oligocene to the Early Miocene, the tectonic stress field of the arcuate tectonic belt was controlled by extension under the remote effect of the rollback of the subducted Pacific Plate. The tectonic stress field changed into compression under the effect of the northeastward extrusion of the Tibet Plateau from the Middle to Late Miocene; Significant and sustainable tectonic uplift developed in the arcuate tectonic belt from the Late Miocene to Pliocene, and the Cenozoic basins were divided by the strike-slip fault systems.

Keywords

• eogene–neogene
• geochronology
• sedimentary sequence
• unconformity
• the arcuate tectonic belt along the northeastern margin of the tibet plateau