Integrated Precambrian Stratigraphy of the Quanji Massif: A Review

The Quanji Group and Xiaogaolu Group in the Quanji Massif of the northern Tibetan Plateau recorded a series of important geological events, such as the Neoproterozoic glacial events, Supercontinent cycle and Great Unconformity (GU), thus offering an important window to review the Precambrian geological evolution of this tectonic unit. Recent investigations on the biostratigraphy, chronostratigraphy, and event stratigraphy indicate that: ① The new finding Ediacara-type fossils and associated tubular organisms provide the new sight into our understanding on the origin of modern-looking marine ecosystem, and constraint the upper age limit of Xiaogaolu Group to the late Ediacaran (551～543 Ma). ② The scale of Ediacaran-Cambrian unconformity in the Quanji massif has been suggested to be the approximately 25～50 Ma with missing stratigraphic successions of Terreneuvian Series (Cambrian), which is broadly correspond to the magnitude of GU at the western-southwestern margins of North China Craton. ③There is a significant unconformity between the Hongzaoshan Formation (Quanji Group) and the overlying succession Heituopo Formation (Xiaogaolu Group). Chronostratigraphic investigation revealed that the age of Hongzaoshan Formation (Quanji Group) is the late Paleoproterozoic (1640～1646 Ma), rather than the Ediacaran period (635～539 Ma) as previously thought. ④ The Quanji massif contains a unique Neoproterozoic glaciation unit, the Hongtiedou diamictite, which is roughly equivalent to the Ediacaran glacial deposits of Zhengmuguan and Luoquan Formation from the western-southwestern margins of North China Craton. ⑤ Both of the Quanji massif and North China Craton have been proposed to be the mid-high latitude region during the late Ediacaran period, rather than the low latitude as previously thought. The common tectonostratigraphic characteristics suggest that the Quanji massif shares the closely tectonic-sedimentary evolution with North China Craton during the Ediacaran-Cambrian transition.