engleski

Clay minerals in the sediments from the Croatian Adriatic shelf

Clay minerals are carried into the Adriatic Sea mostly by Italian rivers entering from the west, and less by Albanian rivers coming from the east. Their longitudinal dispersion is governed by general cyclonic circulation. Based on the data obtained on the samples collected primarily on the Italian side of Adriatic main clay minerals are illite and smectite, with minor amounts of chlorite, kaolinite and sometimes serpentine (Tomadin, 2000). The Croatian Adriatic shelf receives small amounts of terrigenous fine-grained sediments due to the largely carbonatic coast with poorly developed network of mostly karstic rivers. Consequently, this region is covered by mixed carbonate-siliciclastic sediments, mostly sands. In order to supplement the knowledge of sources and clay-mineral composition in sediments of the Adriatic, 33 samples of uncommon muddy surface sediments (containing 8 to 46% of <2 μm fraction and 23 to 90% of carbonates) from the Croatian Adriatic shelf were investigated by XRPD. Semiquantitative mineral analysis, illite and montmorillonite “crystallinity” indices determination were performed in order to obtain data complementary to those of Tomadin (2000) for the western part of the Adriatic. Observed differences in clay and carbonate mineral content of <2 μm fraction of muddy surface sediments reflect hydro-geographic characteristics of sampling area (i.e. sea currents, bathymetry, closeness of river mouths and Italian volcanoes). Based on observed differences, four areas can be distinguished: Northern Adriatic, Middle-Adriatic Depression, Southern Adriatic and the channel area. Obtained data for the Croatian part of the Adriatic correlate well and complement those obtained by Tomadin (2000) for the western part of the Adriatic.

clay minerals; Adriatic shelf

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