PRELIMINARY CLASSIFICATION OF OKINAWA'S COASTS

Using Francis P. Shepard's morphological classification, preliminary work was conducted on Okinawa's coasts. Evidence of primary and secondary coasts was found.

On the eastern side of Okinawa, Camp Schwab is provisionally classified as a primary diastrophic coast. Quaternary dunes and beach material have been folded, faulted and are unconformably overlain by flat lying, younger beach material. Older mudstone is exposed along the fold and extends into the water where the rocks are covered. A thin-bedded, alternating red and cream, sand-sized unit crops out that may represent a tide cycle.

The western side of Okinawa has examples of secondary organism-built coasts, including the coral reef coasts at Bolo Point, Manzamo and Onna Point. Features such as sea caves, sea arches and sea stacks, are common along the 100-foot cliffs. Tidal action has developed pedestals in shallow depths.

Located at the northern-most point of Okinawa, site of the confluence of the East China Sea and the Pacific Ocean, Cape Hedo is an example of a secondary wave erosion coast. The coast's cliffs consists of deformed phyllite with kink and chevron folds that are overlain by folded Mesozoic (?) limestone. These basement rocks have been uplifted and represent a former wave-cut platform. Today, wave action is eroding the beach cliff and forming sea caves, sea arches and stacks. Undercutting of the beach cliff has resulted in mass wasting and is forming a present day, wave-cut platform.