Site 1159 was located based on 1996 SCS site survey data and confirmed by a short 3.5-kHz PDR and SCS presite survey from the JOIDES Resolution (JR). Onboard instrumentation included a precision echo sounder, gyrocompass, seismic system, and GPS receivers.
Site selection for Site 1159 was based on a SCS survey conducted during the R/V Melville cruise Boomerang 5 in 1996. A 22.1-hr SCS and 3.5-kHz PDR survey was conducted all the way from Site 1158 to Site 1159 (JR SCS line S7; see Fig. F13) to locate potential new drill sites. This survey line terminated soon after crossing the prospectus site AAD-2b. The ship's average speed was 5.8 kt, and the course was 160° when the SCS survey approached Site 1159 (AAD-2b). The water gun was triggered at shot intervals of 12 s, equivalent to ~36 m at 5.8 kt. Data acquisition and processing parameters are described in "Underway Geophysics" in the "Explanatory Notes" chapter. We marked the position of Site 1159 near seismic shotpoint 6425 of line S7, where the water depth is 4504.2 m (see Fig. F14). Although there are significant out-of-plane reflectors, the sediment cover (Fig. F14) extends from 6.2 to 6.35 s in two-way traveltime, equivalent to at least 150 m of sediment. Hole 1159 was drilled through 145.6 m of sediment before basement was reached.
Three new proposed sites (AAD-38a, 39a, 40a) were located near shotpoints 1200, 2425, and 5050 (Figs. F15, F16, F17). Sediment thicknesses estimated from the SCS profile are 150, 280, and 280 m, respectively. Sites AAD-38a and 39a were subsequently drilled as Sites 1161 and 1162.