IODP

doi:10.2204/iodp.sp.329.2010

Site summaries

Site SPG-1A

Priority: Primary
Position: 23°51.0508′S, 165°38.6538′W (WGS 84) (23.8508°S, 165.6442°W)
Water depth (m) 5697
Target drilling depth (mbsf): 171 (including 100 m of basement)
Approved maximum penetration (mbsf): Up to 100 m basement penetration
Previous drilling in area: DSDP Leg 91 Site 596, <1 nmi away
Comments: International waters; 365 nmi off Palmerston Island, Cook Islands Preferred weather window: November–December
Survey coverage (track map, seismic profile): High-resolution seismics:
• Primary line(s): MCS Line 1 - Shotpoint 1167 (Fig. AF1)
• Crossing line(s): MCS Line 3 - Shotpoint 2280 (Fig. AF2)
• Subbottom profile, 3.5 kHz: Line 1 - JDay 354 at 19:48 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF3)
Sediment cores: Two piston cores, two trigger cores, one gravity core, and one 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 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 to 100 m of basement
• Temperature measurements: APCT-3
Downhole logging program: Wireline logging: triple combo, FMS-sonic
Anticipated lithology: Dark brown to dark yellowish brown clay; manganese nodules present at top