Fig. 4

a–f Microphotographs of sandstones from the studied formations: a Calcareous litharenite dominated by ophiolitic rock fragments including serpentine fragments, chlorite flakes and altered mafic clasts with intersertal texture. A large metamorphic rock fragment can be seen in the upper part of the image; Oštrc Formation, sample 05-H/O-313/1. b Lithic wacke in which chlorite flakes have been “squeezed” between framework grains to form a pseudomatrix; Oštrc Formation, sample 05-H/O-309. c A silicified test of a foraminifera; Oštrc Formation, sample 05-H/O-318. d An orbitolinid foraminifera composed of agglutinated quartz grains within a litharenite; Bistra Formation, sample 05-H/B-207. e Radiolarite rock fragment with visible outlines of radiolarian; Bistra Formation, sample 05-H/B-207. f Litharenite dominated by metamorphic rock fragments; Glog Formation, sample 05-H/G-102. g Back-scattered electron image of a zoned tourmaline with a detrital core and multiple growth rims; Oštrc Formation, sample 05-H/O-318. h Heavy mineral separate dominated by zircons, many of which are at least slightly rounded; Glog Formation, sample 05-H/G-102