Distribution of Opal Phytoliths in Coastal Region

Case Study in the Estuary of the Obitsu River

Abstract

Transportation and preservation of phytoliths were discussed, based on a relationship between the distribution and weathering degree of phytoliths in surface sediments and that of mother plant, in the estuary of the Obitsu River along the Tokyo Bay. Nine types of phytoliths obtained from surface sediments were identified : Carex pumila, Ischaemum anthephoroides, Calamagrostis epigeios, Phragmites australis, Carex scabrifolia, Lolium perenne, Imperata cylindrica var. koeni'gii, Bromus unioloides, and Phacelurus latifolius types. The distribution pattern showed that the first 5 types had a characteristics efficient transportation, and that the rest to be less efficient. It was suggested that most of phytoliths were transported by wind after a disintegration of leaves, to low places such as break of slope points and salt pond, and with silt and very fine sand particles of sediments.