Site summaries (continued)

Proposed Site LOUI-6A (Seamount 28.6°S - Detroit equivalent)

Priority: Alternate site
Position: 28°33.93′S, 173°16.78′W
Water depth (m): 1480
Target drilling depth (mbsf): ~470 (120 m sediment; ≥350 m basement)
Approved maximum penetration (mbsf): 470 (350 m basement; additional basement penetration must be reviewed by the operator during drilling operations)
Survey coverage: • AMAT02RR (Fig. AF13)
• Line AMAT 28.6-3 (CDP 25887) (Fig. AF14)
• Line AMAT 28.6-4 (CDP 26684) (Fig. AF15)
Objective: (see text for details) 1. Core thin sediment cover and igneous basement until enough igneous units suitable to acquire accurate paleolatitudes and 40Ar/39Ar ages are recovered.
2. Study the geochemical evolution of this guyot.
Drilling, coring, and downhole measurement program: • RCB coring to TD.
• FFF deployment and two bit changes (two reentries).
• Wireline logging (triple combo, FMS-sonic, magnetometer, and possibly UBI).
Anticipated lithology (mbsf): • 0–10: pelagic ooze
• 10–120: lithified limestones, volcaniclastics, and minor lava flows(?)
• >120: basalt (~72 m.y. old)
Site characterization: This alternate drill site for primary proposed Site LOUI-1C is located ~2.1° south of Sites LOUI-1C and LOUI-1B on the 26.5°S guyot, which gives an interpolated age of ~72–73 Ma that is distinctly younger than the Detroit Seamount (76–81 Ma) in the Emperor Seamount Trail. A pelagic cap is present but is not >10 m thick based on 3.5 kHz CHIRP data. The sequence of volcaniclastics and lava flows is estimated to be at least 70–110 m thick (0.055–0.060 s two-way traveltime at 2.5–3.5 km/s in volcaniclastic sediment), but there only is evidence for minimal posterosional volcanism.