Contribution on the knowledge of the Kaštela Bay geology
Abstract
The Kaštela Bay is the biggest bay in the coastal area of the central Dalmatia. It is edged by the Čiovo Island, slopes of the Mount Kozjak and with the peninsula of Split. By its origin the Kaštela Bay is a sindinal fold which was transgraded in Pleistocene and submerged. The geological structure of the hinterland consists of the cretaceous limestone of the Mount Kozjak at foot of which the flysch sedimenlts of eocene formation are developed. Paleogene strata build up the Split peninsula, whereas the Čiovo Island is also of cretaceous limestone.
The bay itself shows different bathymetric and morphometric properties thus that two separate parts of the bay are clearly distinguished, the deeper eastern one and the shallower western one. Sedimentary cover of different sediment types, distinguished by their mechanical composition, follows the bathymetric distribution. These different sediment types are mainly distributed by a regular granulometric selection.
Both terrigeneous and biogene components take part in sediment formation. Terrigeneous elements are mainly transported from the adjacent cretaceous strata, and partly from the submarine springs. »Terra rossa« is found close to the submarine springs. It is sign of the transport of alohtone material by underground communications through which the intensive circulation of underground waters takes place in the littoral Karst area. In addition to the mass proportion of shells of Foraminifera the biogene elements contain also special types of »bruchschill« and »schill« sediments, which come of the smithereens or the whole shells of different organisms deposited on the sea bottoms. The submarine springs of the bay count among the most prolific ones in the Adriatic. Due to the submarine springs, the bay has an exceptional hydrographic significance. Under extreme conditions they even cause the ice to occur in the bay.
