Beach Sediments of Crete: Texture, Composition, Roundness, Source and Transport

Mauri Pyokari

Abstract


The texture, composition, provenance, and transport of beach sediments and the roundness of sediment grains were studied on 22 beaches on the coasts of Crete in southern Greece.

The studied beaches range from low-carbonate to high-carbonate beaches, where the texture and mineral composition of beach sediments and roundness of sediment grains display some degree of local variation. Beach sediments consist mainly of medium and coarse sand, being moderately well or well-sorted, symmetrical or negatively skewed and mesokurtic or leptokurtic. On beaches where no rivers enter the sea the mineral composition is closely related to nearby exposed coastal formations (sea cliffs, bluffs and rocks), the grain-size frequency distribution of beach sediments being nearly normal, and the roundness of sediment grains rather good. Where rivers discharge on to the beach or near to it, the mineral content of these beaches is related both to the coastal formations and the formations situated inland in the catchment basins of the rivers. Coastal abrasion and fluvial sediments on shores are mixed by waves and littoral drift, causing somewhat poorer sorting and roundness. Low-Mg calcite and quartz are the most common minerals (altogether 50-90%) in the beach sediments on Crete. The other common minerals are dolomite, feldspars, epidotes, pyroxenes, amphiboles, tourmaline, zircon, titanite and magnetite; the sources being mainly dolomites, phyllite-quartzites, ophiolites, flysch, and sandstones on the mountains and coasts of Crete.

The direction of net littoral drift is determined mainly by the predominant wind and waves approaching from the direction of the greatest fetch, while the onshore winds and waves (the directions of the fetches arranged according to the length of the fetch) greatly determine the direction of seasonal littoral drift. These two wind factors together determine, to the large extent, the direction of seasonal littoral drift in the surf zone, whereas in the swash zone the direction is determined only by the onshore winds and waves. On the other hand, the prevailing wind and waves have a little effect on the direction of sediment movement on the coasts of Crete.

Keywords


Beach sediments; texture; composition; roundness; provenance; littoral drift; fetch; predominant and prevailing waves; Crete; Greece.

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