CONCLUSIONS

During Leg 190, we successfully cored six sites, meeting most of the leg objectives and also revealing some surprising new findings. We demonstrated that there is a large contrast among the various properties, including the lithologic and geochemical (including microbial activity) character of the incoming sequences at the Muroto and Ashizuri Transects. In spite of such contrast, we found that the décollement at both transects stays at the level of an almost identical horizon (6—7 Ma). We also documented the accretionary history of the Nankai Trough prism for the first time and revealed a phenomenally rapid rate of growth of the prism during the Pleistocene. Our results will provide a basic framework for further mechanical, hydrogeological, and geochemical studies of this accretionary prism.

Leg 190 results will also be useful for understanding the tectonics of accretionary prism evolution providing a link between prism-toe processes and highly deformed accretionary complexes, which are the dominant components of orogenic belts.