IODP

doi:10.2204/iodp.sp.329.2010

Site summaries (continued)

Site SPG-6A

Priority: Primary
Position: 27°55.0017′S, 123°9.6568′W (WGS 84) (27.9167°S, 123.1609°W)
Water depth (m) 3738
Target drilling depth (mbsf): 115–123 (including 100 m into basement)
Approved maximum penetration (mbsf): Up to 100 m basement penetration
Previous drilling in area: Closest drilling:
• DSDP Leg 92 Site 598, 550 nmi away
Comments: International waters; 210 nmi from Ducie Island, United Kingdom Preferred weather window: November–December
Survey coverage (track map, seismic profile): High-resolution seismics:
• Primary line(s): MCS Line 2 - Shotpoint 10020 (Fig. AF16)
• Crossing line(s): MCS Line 4 - Shotpoint 10708 (Fig. AF17)
• Subbottom profile, 3.5 kHz: Line 2 - JDay 004 at 05:37 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF18)
Sediment cores: Two piston cores, two trigger cores, one gravity core, and six 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: • Triple to quadruple APC to basement; RCB upper 100 m of basement
• Temperature measurements: APCT-3
Downhole logging program: Wireline logging: triple combo, FMS-sonic
Anticipated lithology: Stiff dark yellowish brown clay grading to yellowish brown foraminifer-bearing clayey nannofossil ooze