IODP

doi:10.2204/iodp.sp.329.2010

Site summaries (continued)

Site SPG-3A

Priority: Alternate
Position: 27°56.5189′S, 148°35.3969′W (WGS 84) (27.9420°S, 148.5899°W)
Water depth (m) 4852
Target drilling depth (mbsf): 106 m, including 100 into basement
Approved maximum penetration (mbsf): Up to 100 m basement penetration. EPSP requested that TAMU considers the steepness of the slope.
Previous drilling in area: Closest drilling:
• IODP Expedition 310 Site 15, 610 nmi away (drilling of corals on Tahiti Platform)
• DSDP Leg 33 Site 318, 800 nmi away (Tuomotu Ridge volcanics)
Comments: International waters; 230 nmi from Rapa, French Polynesia Preferred weather window: November–December
Survey coverage (track map, seismic profile): High-resolution seismics:
• Primary line(s): MCS Line 3 - Shotpoint 5072 (Fig. AF7)
• Crossing line(s): None (Fig. AF8)
• Subbottom profile, 3.5 kHz: Line 3 - JDay 360 at 22:08 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF9)
Sediment cores: Two piston cores, two trigger cores, one gravity core, and five cores of an eight-barrel multicore
Objectives (see text for complete details): • Document the habitats, metabolic activities, genetic composition, and biomass of microbial communities in subseafloor sediments with very low total activity.
• Test how oceanographic factors (such as surface ocean productivity) control variation in sedimentary habitats, activities, and communities from gyre center to gyre margin.
• Quantify the extent to which these sedimentary communities may be supplied with electron donors by water radiolysis, a process independent of the surface photosynthetic world.
• Determine how the basement habitats, potential activities, and communities vary with crust age and hydrologic regime (from ridge crest to abyssal plain).
Drilling/Coring program: • Quadruple APC to basement
• RCB upper 100 m of basement
Downhole logging program: None specified
Anticipated lithology: Homogeneous dark brown to very dark brown clay; manganese nodules recovered from core tops