2007 December 23 (Day 5)
Weather: Fine but Cloudy
Site: C0004 (NT2-01I) (33°13’ N, 136°43’ E)

Due to a storm, there was a wait on weather between 1:00 AM and 6:00 AM, and another short wait on weather between 8:00 AM and 11:00 AM this morning. Except for minor Wait on Weather (excessive heave was making coring essentially impossible), we spent the entire day and night collecting RCB cores. The core quality and core recovery have been quite variable: highly fractured and faulted accretionary prism material has been causing quite a few problems with core jamming, heavy drilling disturbance and some bit plugging, requiring several trips with the deplugger and some minor halts in operations to clear the bit with increased drilling fluid flow. Coring is being conducted with 4.5 meter advance to minimize lost section and maximize recovery and quality, and there has been a recent increase in both recovery and quality. Close work with the core technicians, drillers, and operations groups, including core inspections and XCT inspections of cores has proven to be quite useful.

Recovery problems related to condition of material at depth, Core Technicians and drillers suggest jamming as the most likely cause. Current material recovered is quite fragmental and disturbed by drilling, however, some pieces large enough for detailed description indicate that we are sampling sheared/faulted accretionary prism material.

Lab work is moving along quite well: core processing, description and sampling have been keeping up with coring. Report writing (methods and initial introductory materials) is now underway, with the editing cycle starting to move along.