Development Features of Triassic Strata and Analysis of Original Sedimentary Pattern in North China

Based on the study on characteristics of vertical development and lateral distribution of Triassic in North China, and with the analysis of lithological characteristics, changes of strata thickness, strata contact relationships, as well as the research about the denuded thickness of strata, the influence of the Indosinian movement exerted on the sedimentation of North China during Triassic was analysed, and the original sedimentary pattern in North China during this period was studied and discussed. The research shows that there was a large-scale sedimentary basin inside the North China Plate during Early and Middle Triassic. It inherited the structural pattern and sedimentary characteristics of the Late Hercynian, and mottled sediments of fluvial-lacustrine facies developed. Beginning from the Late Triassic and caused by the Indosinian orogeny, the strata in the east of North China were uplifted and the Lower and Middle Triassic were denuded. In some areas, the Paleozoic was also denuded, and the intermountain basins were developed only in restricted areas. There still was a basin with sediments of fluvial-lacustrine facies under warm and humid climate in the southeast of North China, but its scale became smaller.