| The Huaiyuan movement represents one of the most important geological events affecting the North China Craton during the Early Ordovician, and is widely regarded as being closely associated with regional strat-igraphic discontinuities. However, substantial controversies remain regarding its tectonic nature, temporal subdivision, and tectonic-paleogeographic responses. Based on the characteristics of Ordovician strati-graphic development in the North China Craton and adjacent regions combined with biostratigraphic evi-dence, this study presents a comprehensive analysis of the evolutionary history of the Huaiyuan movement. The results indicate that the Huaiyuan movement comprises two evolutionary stages. The initial stage oc-curred in the middle part of the Early Ordovician, mainly characterized by stratigraphic depositional hia-tuses in the southern North China Craton and the absence of conodont zones. The main stage occurred in the late Early Ordovician, during which tectonic uplift intensified markedly, resulting in the widespread in-completeness of Early Ordovician strata across the North China Craton. Stratigraphic loss was more pro-nounced in the south than in the north, and a parallel unconformity developed beneath the first member of the Middle Ordovician Majiagou Formation. Both stages were characterized by rapid regression followed by a relatively slow transgression, but the impact of the main stage was significantly greater than that of the initial stage. The post-main-stage transgression exhibited far-field characteristics. One consequence of this transgression was the southward migration of the conodont Polycaulodus similaris, which invaded seawater and evolved into Polycaulodus yuxianensis during deposition of Jiawang shale (early Middle Ordovician). Regional and global comparisons showed that both the initial and main stages of the Huaiyuan movement elicited varying degrees of response and correlation in platform areas in North America, Siberia, and Australia, indicating that the Huaiyuan movement was a global event. |