Tunjice Hills are located west of the town of Kamnik, central Slovenia. Due to the rich fauna and microflora, as well as the structural and stratigraphic importance of the area, Tunjice Hills were being investigated since the second half of the 19th century. Tertiary stratigraphic succession of the Tunjice Hills, which includes more than 1500 m of various sedimentary rocks, is of Oligocene to mid-Miocene age, and paleogeographically belongs to the Central Paratethys domain. Tertiary deposits form a syncline with normal southern limb and an overturned northern limb. I have explored and analysed sedimentary and petrographical characteristics of sedimentary rocks of mid-Miocene Govce and Laško formations. I have mapped the area and logged 12 sections. I collected samples from the sections and outcrops which were then used for microfacies studies. Nine different microfacies were described: 1) recrystallized biomicrite with detrital quartz, packstone; 2) recrystallized biomicrite with detrital quartz, floatstone; 3) pebbly sandy biosparite; 4) sandstone with micrite matrix; 5) sandy mudstone; 6) sandy quartz mudstone with plant remnants; 7) muddy quartz sandstone with quartz-sericite epi-matrix; 8) quartz sandstone; 9) conglomerate. I analysed the geometry of the Tunjice syncline by analysing bedding attitudes and have determined that the syncline axis is nearly horizontal with a plunges of 3 degrees towards the west (dip azimuth of 259 degrees). I constructed a structural section in a N-S orientation accross the mapped area which suggests that the formation thicknesses change from the southern limb to the northern limb. In the southern part of the Tunjice Hills the Govce, Laško and Dol formations are thicker than in the north, and beds are gently dipping. In the northern part, bedding is steeply dipping towards the north and is in overturned position, or is vertical in places. Shortening direction implied from the bedding attitudes suggests that the Tunjice syncline was formed in dextral transpression due to the right-lateral activity of the Sava strike-slip fault.