Site summaries (continued)

Proposed Site LOUI-4B (Seamount 168.6°W - Koko equivalent)

Priority: Primary site
Position: 38°10.98′S, 168°38.26′W
Water depth (m): 1248
Target drilling depth (mbsf): ~410 (60 m sediment; ≥350 m basement)
Approved maximum penetration (mbsf): 420 (350 m basement; additional basement penetration must be reviewed by the operator during drilling operations)
Survey coverage: • AMAT02RR (Fig. AF10)
• Line AMAT 168.6-0 (CDP 22417) (Fig. AF11)
• Line AMAT 168.6-1 (CDP 23158) (Fig. AF12)
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): • 0–8: pelagic ooze
• 8–60: lithified limestones, volcaniclastics, and minor lava flows(?)
• >60: basalt (~50 m.y. old)
Site characterization: Dredge sample AMAT10D2 yielded a preliminary age of 50.1 ± 0.4 Ma, making this seamount very similar in age to Koko Seamount (49 Ma) in the Emperor Seamount Trail. Only a small 8 m thick patch of pelagic sediment cap is calculated at the location of this proposed drill site. Also, the presumed volcaniclastic sequence underneath the pelagic cap is relatively thin (~52 m) on this seamount. A detailed magnetic survey of this small guyot during the AMAT02RR cruise yielded an unreasonable paleopole position (Fig. F9), but the complexity of the anomaly pattern suggests dual polarities, which (if sampled) could provide a more robust paleolatitude estimate.