Promjene fizikalno-kemijskih karakteristika holocenskih sedimenata iz srednjeg dijela Jadrana (Hrvatska)

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 influ¬ence 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 sedi¬ment 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 Apen¬nines. 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.Veličina zrna, udio organske tvari i karbonata određeni su u 5 jezgara holocenskih sedimenta iz srednjeg Jadrana. U istraživanom području prevladava taloženje sitnozrnatih i nekarbonatnih čestica. Na razlike između postaja utječe njihov geografski položaj i hidrodinamički uvjeti na njima, mehaničko trošenja okolnog područja djelomično pod antropogenim utjecajem ali i prisutnost ostataka organizama s karbonatnim skeletom u sedimentu. Iako je istočna obala Jadrana uglavnom karbonatna, na postajama u blizini istočne obale, prisutnost eocenskih flišnih naslaga smanjuje udio karbonata (40,27-48,88%) u sedimentu, a prevladavaju čestice veličine mulja (33,12-56,83%). Na postaji u blizini otoka Visa sediment je uglavnom karbonatan (67,36-76,5%), s najvećim sadržajem čestica veličine pijeska (67,07-70,63%). Porijeklo ovog sedimenta su skeletni ostaci organizama koji su živjeli na morskom dnu, pre-holocenski sedimenti i čestice nastale trošenjem karbonatnih stijena okolnih otoka. Na najdubljoj postaji koja se nalazi blizu zapadne obale Jadranskog mora prevladavaju čestice veličine gline (52 - 70%), a udio karbonata je nizak (31,7-40,5%). Ove glinene čestice su nastale erozijom Alpa i Apenina, a u Jadransko more su dospjele rijekama, te su morskim strujama pretaložene duž zapadne obale