IODP

doi:10.2204/iodp.sp.329.2010

Site summaries (continued)

Site SPG-2A

Priority: Primary
Position: 26°03.0953′S, 156°53.6566′W (WGS 84) (26.0516°S, 156.8943°W)
Water depth (m) 5127
Target drilling depth (mbsf): 17 m
Approved maximum penetration (mbsf): Until basement is encountered
Previous drilling in area: DSDP Leg 91 Site 596, 500 nmi away
Comments: International waters; 255 nmi from Mangaia Island, Cook Islands Preferred weather window: November–December
Survey coverage (track map, seismic profile): High-resolution seismics:
• Primary line(s): MCS Line 1 - Shotpoint 2911 (Fig. AF4)
• Crossing line(s): MCS Line 3 - Shotpoint 3608 (Fig. AF5)
• Subbottom profile, 3.5 kHz: Line 1 - JDay 358 at 02:20 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF6)
Sediment cores: Two piston cores, two trigger cores, one gravity core, and five cores of an eight-barrel multicore taken at site location
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 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.
Drilling/Coring program: • Quadruple APC to basement
• Temperature measurements: APCT-3
Downhole logging program: None specified
Anticipated lithology: Homogeneous dark brown clay; manganese nodules recovered from core tops