Meso- and Neoproterozoic sedimentary sequences in Jixian, Tianjin, northern China: division of the first-order sequences of the Cambrian strata (1800-600 Ma) and their correlation with the Phanerozoic strata

The strata in the famous Meso- and Neoproterozoic Jixian section, Tianjin, northern China range in age between 1800-600 Ma, with the thickness less than ten thousand metres. These Cambrian strata have been grouped, on the basis of sedimentary facies sequences and stacking patterns of depositional sequences, into 63 third-order sequences, or 22 second-order megasequences and 4 first-order supersequences, of which the latest ones represent the depositional cycles with the periods of 200-400 Ma during 1800-600 Ma. These cycles plus two first-order cycles in the Phanerozoic successions have disclosed that a genetic link may be postulated for individual Earth shells and galactic precessional cycles. The stratigraphic records of the above-mentioned cycles are significant especially for the division of the Precambrian strata with lower stratigraphic resolutions.