IODP

doi:10.2204/iodp.sp.329.2010

Site summaries (continued)

Site SPG-7A

Priority: Alternate
Position: 27°44.2713′S, 117°37.1815′W (WGS 84) (27.7379°S, 117.6197°W)
Water depth (m) 3688
Target drilling depth (mbsf): <103 (including 100 m 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:
• DSDP Leg 92 Site 599, 500 nmi away
Comments: International waters; 450 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 3 - Shotpoint 11865 (Fig. AF19)
• Crossing line(s): MCS Line 1 - Shotpoint 11264 (Fig. AF20)
• Subbottom profile, 3.5 kHz: Line 3 - JDay 006 at 12:29 GMT
• Detailed bathymetry and site location (swath bathymetry: collected with SIMRAD EM120) (Fig. AF21)
Sediment cores: One piston core, one trigger core, one gravity core, one 4 inch jumbo 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.
• 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: Successions of brown foraminifer-bearing clayey nannofossil ooze grading to dark brown clay