IODP

doi:10.2204/iodp.sp.329.2010

Site summaries (continued)

Site SPG-5A

Priority: Alternate
Position: 28°26.7840′S, 131°23.4215′W (WGS 84) (28.4464°S, 131.3904°W)
Water depth (m) 4221
Target drilling depth (mbsf): 22
Approved maximum penetration (mbsf): Until basement is encountered
Previous drilling in area: Closest drilling:
• DSDP Leg 92 Site 597, 600 nmi away
Comments: International waters; 240 nmi from Pitcairn Island, United Kingdom Preferred weather window: November–December
Survey coverage (track map, seismic profile): High-resolution seismics:
• Primary line(s): MCS Line 3 - Shotpoint 8705 (Fig. AF13)
• Crossing line(s): MCS Line 1 - Shotpoint 7871 (Fig. AF14)
• Subbottom profile, 3.5 kHz: Line 3 - JDay 001 at 14:12 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF15)
Sediment cores: Two piston cores, two trigger cores, one gravity core, and one 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
• Temperature measurements: APCT-3
Downhole logging program: None specified
Anticipated lithology: Very dark brown pelagic clay with mottles appearing in top meter, increasing downcore; changes to dark yellowish brown with depth and composition changes to nannofossil-bearing clay