Study Of Sequence Palaeogeography In The Late Palaeozoic In Eastern North China

Based on the analysis of wild outcrops, sequence stratigraphy of drills, and predecessors' research fruits, this paper combines related information, proceeds partition and comparison of sequence, and establishes unitive sequence stratigraphy structure of Huabei Basin. It divides the late Paleozoic of Huabei to be one first-grade sequence, two second-grade sequences, and seven third-grade sequences. The second-grade sequences respectively belong to the epicontinental sea type(Sq1-Sq3) and the offshore inland type(Sq4-Sq7). And it identifies five the sedimentary system:platform, tidal-flat, barrier-lagoon, shallow delta and rivers-lakes sedimentary systems, and analysis its evolution under the sequence structure.With the unit of sequence, this paper proceeds the paleogeographic restore of late Paleozoic in the research area, and at the same time studies the variation law of the sea level, combining the sequence palaeogeographic of maximum flooding surface. It is the evolutionary stages of the Epicontinental Sea during Sq1-Sq3, which is mainly to be the marine sedimentation. And it presents the paleogeographic pattern of lower in the north with higher in the south and tilt to the northeast and the transgression comes from the northeast during Sq1. However, it turns to be the paleogeographic pattern of lower in the south and higher in the north, with the transgression coming from southeast during Sq2. And all of the sequences basically inherits this pattern, but the scale of transgression gradually becomes smaller after Sq3. During Sq4-Sq7, it is evolutionary stages of the offshore inland basin, and the paleogeographic features are mainly delta deposit, with tidal-flat, lagoon coexistence; the evolutionary is mainly rivers deposition, with delta facies, tidal-flat, lagoon sedimentary system coexistence; and finally turns to be large rivers-lakes sedimentary system.This paper discusses the controlaction that the paleostructure, paleoclimate, sea-level change, and sediment supply make to the evolutionary of paleogeographic, and think the paleostructure to be the main control factor of paleogeographic evolutionary.