Geological map of the broader Trnovski gozd area.
Red colors on the picture are showing that from upper triassic limestone (7) and dolomite (8, 9) only the northern summits of Trnovski gozd are made - those above Belica and Trebuščica. The highest summits of our area are made of jurassic limestones (6), of lower cretacious limestones (5) and of upper cretacious limestones (4). Almost around the whole mountain group in lower areas there is younger, eocena flysch (2), plus some paleocene limestones (3).
Source: J. Janež, J. Čar, P. Habič, R. Podobnik: Vodno bogastvo Visokega krasa. Geologija d.o.o., Idrija, 1997.