Site summaries (continued)

Proposed Site LOUI-8A (Seamount 36.9°S - Nintoku equivalent)

Priority: Alternate site
Position: 36°56.51′S, 169°46.90′W
Water depth (m): 970
Target drilling depth (mbsf): ~470 (120 m sediment; ≥350 m basement)
Approved maximum penetration (mbsf): 420 (a request for 470 m total penetration depth is pending). 350 m of basement penetration is approved; additional basement penetration must be reviewed by the operator during drilling operations.
Survey coverage: • AMAT02RR (Fig. AF7)
• Line AMAT 36.9-1 (CDP 19234) (Fig. AF19)
• Line AMAT 36.9-3 (CDP 22075) (Fig. AF20)
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, and magnetometer).
Anticipated lithology (mbsf): • 0–40: pelagic ooze
• 40–120: lithified limestones, volcaniclastics, and minor lava flows(?)
• >120: basalt (~54 m.y. old)
Site characterization: This alternate drilling site is located on the same seamount targeted for primary Site LOUI-3B on the 36.9°S guyot. Its interpolated age of 54 Ma is very close to the 56 Ma age of Nintoku Seamount in the Emperor Seamount Trail. The estimated pelagic cap is well layered and, at ~30–40 m thick, it is thicker than the cap at primary Site LOUI-3B based on 3.5 kHz CHIRP data (0.039 s two-way traveltime at 1.6–1.9 km/s). The intercalated sequence of volcaniclastics and lava flows is estimated to be at least 55–80 m thick (0.045 s two-way traveltime at 2.5–3.5 km/s in volcaniclastic sediment).