Calcium distribution in soils and stream sediments in Istria (Croatia) and the Slovenian littoral

For experimental geochemical mapping soil was sampled in 5×5 km regular grid in Istria and the Slovenian littoral (Croatia and Slovenia). The territory consists predominantly of karstified limestones and dolomites, and of flysch beds exposed in two basins, Istrian and Brkini. In addition to soil, stream sediment was also collected in the flysh area. Sampling was performed according to an analysis of variance design that permitted one to estimate the effects of the sample medium, geographic position, sampling error and analytical error. The analysis of variance of chemical variables indicated that soil and stream sediment as sampling media lead to similar results in producing geochemical maps. The largest differences with respect to the lithologic substrate of soil is indicated by calcium. As shown by the geochemical map, calcium in soil is high on the Istrian flysch beds, and low on limestones as well as on the flysch beds of the Brkini basin. The two soils also differ in mineralogy. The reason for this difference seems to lie in soil genesis on limestone and on flysch, and in the variable calcium content of flysch beds. The results of Q-mode factor analysis confirmed the adherence of soil and stream sediment of the two flysch basins to two differing groups. This difference was discovered by geochemical mapping. The hypothesis of differing calcium content in the rocks of the two basins was confirmed by the investigation of fresh and weathered rocks and soils in eight profiles sampled in the Brkini and Istrian flysch basin. It was found that the sandstone and calcarenitic samples from the Istrian basin contain an average factor of 3.5 more Ca than those of the investigated Brkini basin, and the samples of Istrian marls 4 times more Ca than those of the Brkini siltstones. Furthermore, the investigated weathered rocks and soils that originated from these rocks in the Istrian basin contain considerably more Ca than in the Brkini basin. In comparison with sandstone and siltstone samples of the Brkini basin, sandstone, calcarenite and marl samples of the Istrian flysch basin contain less clay minerals, quartz and feldspars and more calcite.