We made the 51-nmi northeast transit between Sites 1163 and 1164 at average speed of 11.3 kt. At 1130 hr on 3 January, we slowed to 6 kt and ran a southwest-to-northeast single-channel seismic (SCS) survey over the prospectus site to confirm sediment thickness. We dropped a positioning beacon on the prospectus Global Positioning System (GPS) coordinates.
The corrected precision depth recorder (PDR) depth referenced to the dual-elevator stool at this site is 4809.4 m. The nine-collar bottom-hole assembly employed at the previous sites was reassembled with a new C-4 four-cone rotary bit made up to a refurbished mechanical bit release. We initiated Hole 1164A at 2145 hr on 3 January. After washing through 138.5 m of sediment and recovering a wash barrel (Core 187-1164A-1W; Table T1), we cored to 146.7 meters below seafloor (mbsf) before drilling conditions forced us to abandon the hole. We recovered four cores (Cores 187-1164A-2R to 4R), although the last core was probably material recovered during our attempt to ream the hole and clear several meters of fill. A bag with fluorescent microsphere tracers was deployed in the core catcher of Core 187-1164A-2R. The bit cleared the seafloor at 1115 hr, and we offset 200 m back along our survey track to the southwest.
Hole 1164B was spudded with the rotary core barrel at 1230 hr on 4 January. We washed down to 150.4 mbsf at 50 m/hr and retrieved the core barrel (Core 187-1164B-1W) when the driller noted a hard contact. We advanced the hole by rotary coring to 216.1 mbsf, recovering nine cores (Cores 187-1164B-2R to 10R). Microsphere tracers were deployed on Cores 187-1164B-2R and 10R. Hole conditions and recovery were not ideal, but we continued operations until we reached our nominal depth objective. The drill string cleared the seafloor at 0045 hr and the rotary table at 0845 on 6 January, ending operations for Leg 187.