Basic lithofacies-succession model for the wumishan cyclothems; their Markov chain analysis and regularly vertical stacking patterns in the third-order sequences

摘要

The Mesoproterozoic Wumishan Formation in the Jixian section of tianjin of Tianjin is a succession of 3300-m-thick carbonate strata formed in a period of about 100 Ma(1310±20 Ma-1207±10 Ma). In this succession of strata, the carbonate metre-scale cyclic sequences belonging to peritidal type with an approximately symmetrical lithofacies- succession are best developed. The wide development of 1:4 stacking patterns shows that these metre-scale cyclic se- quences are genetically related to the short-eccentricity cycles, which are called the Wumishan cyclothems that could truly represent sedimentary cycles.