Early Miocene deposits of fresh-water environments are characteristic in the Kalnik Mountain area, at the SW marginal zone of the Pannonian Basin System. Alluvial and lacustrine sediments varying from gravel to marl accumulated by different depositional processes during the Ottnangian. In the early, alluvial phase pebbly braided rivers developed. Deposition was characterized mostly by bar conglomerates and flood plain siltstones. Alluvial deposition was controlled by both autocyclic and allocyclic processes, in a semi-arid climate. During the later, lacustrine phase, sedimentation was mostly represented by marls and occasional coarser material, in a humid climate. Fresh-water deposition was terminated by marine transgression during the Karpatian. Lower Miocene fresh-water deposits of the Kalnik Mountain can be correlated with similar deposits in the wider area of Northern Croatia. The Kalnik Mountain represents the boundary area between two Early Miocene basins, the north-western one being characterized by marine deposition, and the south-eastern by contemporaneous fresh-water deposition, both belonging to the Central Paratethys.