Abstract
Planar stratification and anisotropic hummocky cross-stratification commonly occur in prograding lower shoreface deposits of the lower Mandano Formation (ca. 0.6 Ma) on the Boso Peninsula, Japan. On the basis of migration directions and grain fabric, we investigated the interaction between oscillatory and unidirectional currents that were responsible for the formation of these stratifications. The formation of planar stratification is interpreted to have mainly been influenced by offshore-directed downwelling currents in association with oscillatory currents. In contrast, the formation of anisotropic hummocky cross-stratification is interpreted to have been influenced by flow conditions more variable than those of planar stratification, and along-shoreline currents, which superimposed on oscillatory currents.
