JA Daily Science Report for Expedition 309, 16 August 2005
LOCATION: Site 1256
SCIENCE UPDATE: Cores 157R and 158R recovered 2.9 m of basalts from 1194.2 to 1203.8 mbsf (30.2 % recovery) that consist of aphyric cryptocrystalline to microcrystalline basalt (Unit 55A). In Section 157R-1 Piece 4, the host basalt (Subunit 55A) is intruded by an aphyric glassy to cryptocrystalline basaltic dike (Subunit 55B). Chilled contacts between the host basalt and the dike are also observed in Pieces 6, 8, and 13 of Section 157R-1. Section 157R-2 Pieces 7 and 9a are brecciated, with angular to subrounded cryptocrystalline basaltic clasts (2-6 mm), cemented by sulfides, chlorite, and anhydrite.
At 1045 the bit had accumulated 57.8 hrs of rotation and the pipe was tripped for a bit change. Bit #8 cored 58.6 m and recovered 19.96 m of basalts (34.06 % recovery) at an average ROP of 1.01 m/hr. The bit cleared the cone at 1340 and was on deck at 1945. The bearings in two of the cones were loose and several inserts were missing from the cones. A new CC-9 bit (#9) was made up and the pipe was tripped back to the seafloor.