Figure F4. Photomicrographs of clast types in gravel (Sample 316-C0007D-12R-CC, 51–55 cm). A, B. Impure chert with quartz veins. C, D. Chert with quartz veins and poorly preserved radiolarians. E, F. Chert with radiolarian tests. G, H. Vein quartz. A, C, E, and G are under plane-polarized light and B, D, F, and H are under cross-polarized light.