Abundant Fe rich concretes have been discovered in the Jixian Section of the Mesoproterozoic Xiamaling Formation. The concretes are consisted mainly of siderite as determined by X ray diffraction, optical microcopy examination and energy dispersion spectrometry. The discovery of siderite concretes in the Xiamaling Formation is not only of potential economical significance, but implies that the seawater was reducing and not sulfidic during the Xiamaling Period.