Figure F6. Volcanic ash beds interbedded with silty clays from Unit II (upper Shikoku Basin facies; interval 190-1173A-13H-6, 100-124 cm). The lower ash bed has a sharp plane-parallel base, a gradational upper contact, and pale gray and green diffuse layers. The upper volcanic ash has a sharp, irregular bioturbated base, a gradational upper contact, and diffuse pale pink and brown layers.