Summary
To understand the timing and emplacement processes of giant Hawaiian submarine landslide, a series of piston coring was performed in the area adjacent to the Hawaii islands by R/V KAIREI, JAMSTEC in the summer of 2001. Long-distance volcaniclastic sediment transport generated by Hawaiian submarine landslides has been suggested by several previous studies (e.g. Garcia and Hull, 1994). Stratigraphical, sedimentological, and geochemical studies on the cores obtained by systematic sampling will help to understand the origins and ages of volcaniclastic emplacement to the ocean-floor.
Nine cores were collected from five regions around the islands: northeast and south of Oahu, and northeast, southeast, and southwest of Hawaii Island. The major lithology of all the cores is brown pelagic clay with abundant volcanic sand layers. Off the Hawaiian Arch northeast of Oahu, pelagic clay with a distinct 195cm-thick volcanic sand layer was recovered. The thick sand is likely related to Nuuanu landslide, an enormous debris avalanch derived from Oahu Island. Northeast of Hawaii, alternating layers of brown clay and volcanic sand were obtained. Hana ridge and Polulu and Laupahoehoe slumps are possible origins for these frequent occurrences of volcanic sand. To the south of Hawaii Island, we recovered alternations of volcanic sand and pelagic clay. Previous results from the 1998 JAMSTEC cruise suggest that volcaniclastic material in this area were derived from Kilauea, as well as older volcanoes of Hawaii Island. The obtained cores will provide better stratigraphic information and time constraints for the volcanic history of Hawaii Island. The base of one of the two cores contains radiolarian ooze, Eocene in age as suggested by on-board inspection. A single core west of the southern end of Hawaii contains a massive black sand layer at its base that may be a deposit from the South Kona landslide. Finally, two piston cores were obtained southwest of Oahu. These two contain scarce volcanic sand layers in their upper sequence, and massive clay in the lower.
Figure pc2. Simplified lithology of sediment cores PC7 through 15.
Onboard-Sampling proceduresColumnar cores were vertically split into two sections; working and archive halves. Magnetic susceptibility and color reflectance were measured@on the archive sections (see section 4-5&6). The texture and structure of sediment were described to identify lithologic features; a summarized lithology was illustrated in Figure 2, detail records are attached to the appendix. Representative or distinct lithology in sections were sampled for smear slide observation (Table 5).
