Lithified paleokarst turbidite deposits in Okno Cave, Demanovska Valley occur in cavities intersected by the main relict fluvial passages of the cave. The deposits show a degree of diagenesis not normally associated with lithified cave sediments with the development of spar-lined voids and diagenetic chalcedony. This indicates a period of post-depositional burial before their exposure in the walls of the present cave. The deposits indicate the existence of an ancient period of cave development and filling after the folding of the limestone but before the incision of the Demanovska Valley. This is likely to have taken place in the Paleocene.