Well-preserved stratigraphic sequences composed of radiolarian chert and basalt were found in Pha Som metamorphic complex in Nan suture zone, northern Thailand. Bedded chert contains Follicucullus porrectus, fossils from late Middle Permian to early Late Permian. These cherts have high SiO2(>92.5%), low Al/(Al+Fe+Mn) ratio (0.51 on average), and high Ce/Ce ratio(1.14 on average). These geochemical characteristics mentioned above indicate that the cherts deposited on continental margins.