Site location for Site 1162 was based on a Leg 187 SCS survey conducted during transit from Site 1158 to Site 1159 (JOIDES Resolution [JR] survey line S7; Fig. F24). The roughly north-south seismic profile between shots 1074 and 1283 shows a ~12-km-wide basin structure with sediment cover >300 m. (see site AAD-39a in Fig. F16 in the "Site 1159" chapter [AAD = Australian Antarctic Discordance]). The prospectus site AAD-39a is near shotpoint 2425, located slightly toward the northern side of the basin.
An additional 2.6-hr 3.5-kHz PDR and SCS survey was conducted on approaching the site (JR survey line S10; Fig. F24) from west to east, crossing line S7 at about shotpoint 380. The ship's average speed was 5.8 kt. The water gun was triggered at a shot interval of 12 s, equivalent to ~36 m at 5.8 kt. An asymmetric basin structure with a steeper basement reflector on the eastern side is revealed in the S10 seismic profile (Fig. F25). No distinct reflector signals can be found in the basin, implying that the sediment is relatively homogeneous. Site 1162 was located ~5.8 km west of the prospectus site AAD-39a at a position corresponding to shotpoint 214 of seismic profile S10. The scattering of basement signals, ranging from 7.55 to 7.73 s in two-way traveltime, indicates a complicated variation of basement relief in the vicinity of Site 1162. Sediment cover was estimated to be between 220 and 400 m (Fig. F25). We washed through 333.2 m of sediment in Hole 1162A before basement was reached, whereas Hole 1162B, about 200 m north, penetrated 348.4 m of sediment.