1. College of Resources and Civil Engineering, Northeastern University, Shenyang 110819, China;
2. Northeastern University at Qinhuangdao, Qinhuangdao 066004, Hebei China

A series of volcanic-sedimentary rocks occurred in the Early Cretaceous Yixian Formation of Yixian Basin, of which the sedimentary rocks contain tuffaceous components. The petrology and geochemistry of the volcaniclastic marl rock (volcanic event strata), laminated marl interlayers in Zhuanchengzi layer, and laminated marl in Dakangpu layer have been studied, in order to understand the effect of volcanic activity on the sedimentary successions. The results show that large number of volcaniclastics exit in the sample of volcanic event strata (20% ±), and other layers contain tuffaceous components. The content of the major elements (e. g. CaO+MgO) is high, with great variations of SiO₂. The Al₂O₃ values is low. The ratio of the trace elements to the upper continental crust (UCC) elements is mostly less than 1, indicating the depletion of most trace elements (e.g. Rb, Th, Nb and REE). Li,Sc,As,Sr and Ag are enriched in volcanic event strata. The volcanic activity can influence the contents of SiO₂ and K₂O in the sedimentary layers, and it may lead to the enrichment of As element. The chemical index of weathering (CIW) range from 82 to 91 with gradually increasing trend in volcanic event strata, indicating strong weathering.