Volcanic Beach Sediments, their Transport, and the Development of Shore Platforms at the Base of the Caldera Wall on the Santorini Islands, Southern Greece

Abstract

ABSTRACT The texture, composition, provenance, and transport of volcanic sediments on four beaches and the development of small shore platforms at the base of the caldera wall were studied on the coasts of the volcanic Santorini islands in southern Greece. All the beaches are composed mostly of volcanic sediments, which consist mainly of coarse sand and granule gravel, moderately well-sorted, symmetrical, and mesokurtic or slightly leptokurtic. Lithic-fragment and mineral compositions are closely related to nearby sea-cliff exposures of pyroclastic rocks with lava fragments. Texture and composition show some local variation. The sediments of Monolithos Beach differ most from those of the other beaches: they are finer and negatively skewed, and the mineral-grain proportion is largest. This indi ates somewhat longer transport of sediments on this windy shore and, above all, disintegration of lava and pyroclastic fragments into mineral grains. The direction of seasonal drift is determined mainly by the predominant waves approaching from the direction of the greatest fetch, but in the swash zone it is related to the direction of the resultant onshore wind. The latter also determines the direction of net littoral drift. The small shore platforms at the base of the caldera wall are caused by breaking waves, wave quarrying, and abrasion. Variations in the platforms are related mainly to structural and lithological variations of the caldera wall.