天津蓟县雾迷山组高频旋回沉积特征研究

he Mesoproterozoic Wumishan Formation in Jixian, Tianjin represents a succession of 3300m carbonate strata, in which Wumishan cyclothems with approximately symmetrical lithofacies successions are best developed. The Wumishan cyclothems consist of tidal-flat dolomites and muddy dolostones, stromatolite biostromes and thrombolite bioherms. So they are particularly meter-scale cyclic sequences of peritidal type. Based on the analysis of types and association of rock genetic units of the Wumishan cyclothems, the general model and sedimentary model of the Wumishan cyclothems were established. The magnetic susceptibility of the rock genetic units and its relationship to the high frequency cyclothems were discussed. It is believed that Wumishan cyclothems were formed in the sedimentary environment change, i.e. water depth change from shallow to deep, to shallow then, and instantaneously exposed at last .So it is possible real sedimentary cycle. According to the vertical stacking patterns rock genetic units of the Wumishan cyclothems , it is concluded that the Wumishan cyclothems was probably formed by autocyclical deposition that was controlled by high frequency sea-level change related to the Milankevitch cycle.