VOLCANIC BEACH SEDIMENTS, THEIR TRANSPORT, AND THE DEVELOPMENT OF SHORE PLATFORMS AT THE BASE OF THE CALDERA WALL ON THE SANTORINI ISLANDS,SOUTHERN GREECE

The texture, composition, provenance, and transport of volcanic sedime nts on four beaches and the development of small shore platforms at th e base of the caldera wall were studied on the coasts of the volcanic Santorini islands in southern Greece. All the beaches are composed mos tly of volcanic sediments, which consist mainly of coarse sand and gra nule gravel, moderately well-sorted, symmetrical, and mesokurtic or sl ightly leptokurtic. Lithic-fragment and mineral compositions are close ly related to nearby sea-cliff exposures of pyroclastic rocks with lav a fragments. Texture and composition show some local variation. The se diments of Monolithos Beach differ most from those of the other beache s: they are finer and negatively skewed, and the mineral-grain proport ion is largest. This indicates somewhat longer transport of sediments on this windy shore and, above all, disintegration of lava and pyrocla stic fragments into mineral grains. The direction of seasonal drift is determined mainly by the predominant waves approaching from the direc tion of the greatest fetch, but in the swash zone it is related to the direction of the resultant onshore wind. The latter also determines t he direction of net littoral drift. The small shore platforms at the b ase of the caldera wall are caused by breaking waves, wave quarrying, and abrasion. Variations in the platforms are related mainly to struct ural and lithological variations of the caldera wall.