Contact Between the Emeishan Basalt and Maokou Formation:Implication for the Geodynamic Model of the Emeishan Mantle Plume

It is still controversial about the lithospheric uplift prior to the Emeishan mantle plume, among which the key issue is the contact relationship between the Emeishan basalt and the underlying Maokou Formation. Therefore, it is crucial to re-examine the contact relationship. Based on the data of regional geological survey in the Emeishan large igneous province(ELIP), the contact between the Emeishan basalt and the Maokou Formation is unconformity(eruption unconformities), rather than faulted contacts. There are brecciola, basal conglomerate, paleosol, clay in the boundary,which resulted from the geological events in the end of the Late Permian. All these suggest that the Maokou Formation may have been uplifted over the sea level by the Emeishan mantle plume and then denudated differentially.Hydromagmatic deposits, submarine basaltic extrusions and local preservation of complete biostratigraphic zone can be attributed to the rapid subsidence followed the plume-induced domal uplift, as well as the complexity of plume-crust interaction. Therefore, the unconformity between the Emeishan basalts and the Maokou Formation is confirmed, which provides evidence for the geodynamic model of the Emeishan mantle plume.