Figure F21. Thin section photomicrographs of a Turonian nannofossil limestone/chalk with radiolarians (Sample 198-1207B-18R-CC, 10-11 cm). Opaline tests of radiolarians have been recrystallized and filled with chalcedony and microquartz. Small tripartite and thin white rods are radiolarian spicules/spines. The chalk/limestone matrix looks relatively pristine with no authigenic quartz. The upper view is under plane-polarized light, whereas the lower view is with nicols crossed.

Figure F21. Thin section photomicrographs of a Turonian nannofossil limestone/chalk with radiolarians (Sample 198-1207B-18R-CC, 10-11 cm). Opaline tests of radiolarians have been recrystallized and filled with chalcedony and microquartz. Small tripartite and thin white rods are radiolarian spicules/spines. The chalk/limestone matrix looks relatively pristine with no authigenic quartz. The upper view is under plane-polarized light, whereas the lower view is with nicols crossed.