Based on existing data, the records of pre-Cryogenian sedimentation and paleontology are mainly concentrated in the Meso-Neoproterozoic, with relatively few records from the Paleoproterozoic or earlier. The oldest geological record is the Hadean detrital zircons in the metamorphosed sedimentary rocks of the Himalaya and Qamdo areas (ca. 4.0 Ga).