engleski

Sources of modern beach sands from two islands in the eastern Adriatic (Croatia)

The study of heavy mineral associations in modern sands provides useful insights regarding sources and supply pathways by which beaches receive their detritus. A systematic study of beach sand compositions was performed on the Islands of Hvar and Rab (Croatian Adriatic Coast), with comparison to older clastic sediments which are considered to represent important sources of detritus. The heavy mineral associations of beach sands from Hvar Island are characterized by a dominance of amphiboles, epidote/zoisite and pyroxenes. The predominant sources of this material are Pleistocene sands and sandstones. Airborne volcanic supply is supposed for the abundant augite found in some of the beach sands from the southern side of the island, similar to bottom sediments of the southern Adriatic (Pigorini, 1968). On Rab Island garnet and ZTR are the dominant heavy minerals. Two differing end member compositions can be identified based on a garnet/ZTR ratio, reflecting different sourcing for individual beaches. The considerable variations observed in the heavy mineral associations among the studied beach sands of two spatially distant islands, but also among nearby beaches of the same island reflect the indented character of the coastline which hinders significant longshore transport and sediment mixing along the coast. Similar trends have been observed in other parts of the Croatian coast (Pavicic et al., 2000). A better understanding of the composition and sources of beach sands from individual beaches should enhance our ability to manage and preserve the coastal zone environment in Croatia which represents an important resource of the country. This work is part of the projects « From ancient sedimentary basins to modern sediments» , and « Evolutionary changes of the Dinarides from subduction to modern Adriatic beaches» , both supported by the Ministry of Science, Education, and Sport of the Republic of Croatia.

modern beaches; sand; provenance; heavy minerals

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