Abstract
A large number of ancient wood pieces appeared at the sea bottom just after the Niigataken Chuetsu-oki earthquake in 2007, off the town of Izumozaki, in Niigata Prefecture, Japan. Most of the wood pieces were formed at 7000–2000 cal BP. Half of the wood pieces had their edges well-ground, probably by water and sand. Among 54 wood samples, fourteen taxa, mostly of deciduous broad-leaved trees, were identified by observing microscopic characters. The identified taxa were thought to have grown near water, such as in ravines, near rivers, and in wetlands, in the cool-temperate (or partly warm-temperate) zone. The relatively warm climate in the area during the middle to late Jomon periods implied that these trees grew in the upper to lower streams of rivers. These ancient wood pieces were thought to have resulted from repeated huge natural disasters.
