Geological Origin of Divine White and Black Pebbles Paved Around the Main Palace of Ise Shrine, Central Japan

Ise Shrine is dedicated to the Japanese greatest deity, Amaterasu-Omikami, and is the most venerable and famous shrine in Japan. The main palace in the shrine is reconstructed every 20 years with a grand ceremony called Shikinen Sengu. The ceremony has more than 30 rituals, one of which is the Oshiraishi-mochi event. During the event, divine white pebbles termed Oshiraishi paved around the main palace in the main sanctuary are replaced by the deity’s envoys called Shinryomin. These envoys must collect more than 100,000 Oshiraishi from the Miyagawa River for the event. In the main sanctuary, divine black pebbles termed Kiyoishi are likewise paved outside the Oshiraishi area, although they do not have to be newly collected by Shinryomin. This study examines the origins of Oshiraishi and Kiyoishi. Oshiraishi originate predominantly from thick quartz veins developed in pelitic schist and subordinately from meta-chert of the high-P–low-T metamorphic Sanbagawa Belt on the Kii Peninsula. In contrast, Kiyoishi are composed of mudstone or very fine- to fine-grained sandstone from brackish-water/shallow-marine deposits and likely originate from the Lower Cretaceous Matsuo Formation in the middle zone of the Chichibu Belt on the eastern Kii Peninsula (Shima Peninsula) or the Miocene Kumano Group on the southern Kii Peninsula.