CONCLUSIONS

In summary, Leg 190 sands and sandstones consist of three main petrofacies:

1. Volcaniclastic sand rich in mafic to intermediate rock fragments present in the upper Pleistocene section at Sites 1173 and 1174 and derived from the Izu collision zone at the eastern end of the Nankai Trough,
2. Quartzose sandstone with abundant quartz, less common feldspar, and lithic fragments present in the lower-middle Miocene section at Site 1177 and the Pliocene-lower Pleistocene sections at Sites 1175 and 1176, and
3. Sedimenticlastic sand and sandstone with abundant sedimentary lithic fragments present in the upper Miocene section at Sites 1177 and 1178.

A transverse delivery of sediment from northwestern sources (southwest Japan) is implied for the Miocene-lower Pleistocene quartzose and sedimenticlastic sand and sandstone at Leg 190 Sites 1175-1178, whereas the upper Pleistocene sands at Sites 1173 and 1174 are derived by lateral transport from the east along the Nankai Trough. These conclusions are limited because of the reliance on sandstone petrography and can be tested by analysis of the geochemistry of minerals, mud/mudstone and sand/sandstone samples, and radiometric dating of selected minerals from Leg 190 sections and comparison with inferred sources in southwest and central Japan.