From a geological point of view, in the Uz River basin two different areas can be differentiated:
- Cretaceous and Palaeocene flysch area which is very common and which occupies the entire mountain area;
- Neocene area found in the lower sector of the valley, most precisely in the post-tectonic intra-mountain Dărmăneşti depression.
From the geological sketch map of the area the following geological formations can be observed, taking into account the age and their stratification:
- The curbicortical flysch canvas: consists of deposits of lower and higher Cretaceous flysch, including: calcareous and marl sandstones, green and grey marls;
- The black shale canvas: clay shale, siliceous sandstones with black shale interlayering, red and green clays;
- Tarcău canvas: consisting of Cretaceous and Palaeocene deposits unevenly spread; composition: black shale, glauconitic sandstones with siliceous, tufacee shale marl;
The unit borderline: it generally consists of Cretaceous, Palaeogene and Miocene deposits, represented by green shale conglomerates, calcareous sandstones, green and white clays.