Abstract: The bedded siliceous rocks of this study occur in the Gufeng Formation of the Middle Permian in the Pingdingshan area, Chaohu region, Anhui Province. The origin and depositional environments for the siliceous rocks have been debated for a long time. In this paper, we report the detailed field and petrographic observation, Combined with the data of major elements,rare earth elements and oxygen isotopic compositions of these rocks. our results show that in the Al-Fe-Mn ternary, and the SiO2-(K2O+Na2O)，SiO2-Al2O3，SiO2-MgO，Al2O3-(K2O+Na2O) binary discriminant diagrams, these rocks fall in the biochemicallydeposited area. These siliceous rocks show an average K2O/Na2O ratio of 1.32, slightly negative Ce anomaly, and a comparatively enrichment of LREE, which indicate a biochemically-deposited origin for these rocks. The siliceous rocks have the total REE contents of 19.87~63.95 μg/g, with an average of 44.59μg/g. Their δCe values are 0.72~0.97, with an average of 0.84, and their Ceanom values are -0.174~-0.011, with an average of -0.088. The average (La/Yb)N and (La/Ce)N values are 1.01 and 1.16,respectively. All these geochemical characteristics suggest that these siliceous rocks were deposited in a continental margin setting where the sea water during deposition was under an anoxic condition. We found volcanic hairs in the mudstones interbedded with the siliceous rocks, which indicates that some of the silicon in the siliceous rocks might come from the volcanic rocks.