Figure F23. Geological and wireline observations of the problematic zone between 910 and 970 mbsf in Hole 1256D. A. Penetration rate and recovery, along with core and unit numbers. B. Caliper log from the end of Expedition 312. The zone from 920 to 930 mbsf is strongly out of gauge (>20 inches; i.e., larger than the diameter of the caliper tool, as indicated by the dashed curves). There is no clear relationship between the trouble zone, lava flow type, core recovery, or penetration rate. C. Caliper log from the end of Expedition 335. The intervals cemented during Expedition 335 are indicated on the right side. Comparison of Expedition 335 and 312 caliper logs shows that cementing has improved the interval from ~930 to 970 but widely out-of-gauge hole persists above that. D. Wireline temperature measurements show a strong negative inflection at ~920–940 mbsf, indicating the return of cold drilling fluids from the formation following the cessation of drilling operations. EDTCB = enhanced digital telemetry cartridge, MTT = Modular Temperature Tool, TAP = Temperature/Acceleration/Pressure tool.
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