Variety of physical-chemical characteristics of Holocene sediments from the middle Adriatic Sea (Croatia)

Abstract

       Grain size, organic matter and carbonate content were analyzed in 5 Holocene sediment cores from the middle Adriatic. Fine-grained, non-carbonate particles settling prevailed in the investigated area. The differences among the stations were influenced by location and hydrodynamic conditions at the sampling sites, by the weathering of the surrounding areas partly under anthropogenic influence and the presence of the remains of the organisms with carbonate skeleton. Even though the east Adriatic coast is mostly carbonate, at the stations near the east Adriatic coast, the presence of the Eocene flysch deposits results in the lower carbonate content (40.27-48.88%) in the sediment with the predomination of silt-sized particles (33.12-56.83%). At the station near Vis Island the sediment is mostly carbonate (67.36-76.5%), with the highest sand content (67.07-70.63%). The source of this sediment are the skeletal remains of the organisms which lived on the seabed, the pre-Holocene sediments and the carbonate rocks from surrounding islands. At the deepest station located closer to the west Adriatic coast clayey particles prevail (52-70%), while carbonate content is low (31.7-40.5%). These clayey particles are the result of the erosion in the Alps and the Apennines. These particles have been supplied to the Adriatic Sea mostly by rivers, and subsequently redistributed by the sea current, which carries them along and off the west coast.