IODP NanTroSEIZE Stage 1:
Expedition 316: NanTroSEIZE "Shallow Megasplay and Frontal Thrusts"
Weekly Report #3
Date 11/Jan/2008
Coring operations in Hole C0006E resulted in retrieval of Cores 37X-49X (286.8-409.4 meter below seafloor, or mbsf), with total recovery of 98.5 meters of core with recovery rate of 80.37%. After observing a drastically reduced rate of penetration, we determined that refusal had been reached, and Hole C0006E was completed at 409.4 mbsf, 19:30 PM on January 6. C0006E was completed, the Borehole Assembly pulled out of the hole, drill pipe tripped and the HPCS/ESCS Assembly was racked back.
Chikyu then relocated to Hole C0006F and the RCB Borehole Assembly was run down to the seafloor. Hole C0006F was tagged at 17:30 PM on January 7, at location 33° 1.6242’ N, 136° 47.6282’E, water depth 3875.5 meter. Conducted jet-in to 50 mbsf and washed down to 395 mbsf. RCB coring operations began, and since then cores C0006F-1R to13R have been collected from 395 to 514 mbsf for a total of 30.1 meters of recovery at a rate of 25%.
Drilling at Site C0006 continues within the accretionary prism; intensity of deformation is variable, and several generations of deformation have been observed. Possible repeated formations are consistent with stacking of thrust sheets, but currently biostratigraphy is unable to resolve any age reversals. The ESCS produced high recovery and was able to partially recover sand units. At ~400 mbsf, consolidation necessitated switching to RCB coring. Recovery using RCB has been lower and less representative of the formation; primarily more consolidated material is recovered.
Sampling for pore fluids, void gas (where appropriate), and head space gas was carried out in the core cutting area. XCT scanning, Multi-sensor core logging, and whole-round core sampling for geotechnical and physical properties analysis were carried out on whole round core sections, followed by core description (structural, sedimentological, stratigraphic), and physical properties measurements (thermal conductivity, moisture and density, P-wave velocity and electrical resistivity) were carried out on the split core section. This was followed by collection of a complete suite of samples for paleomagnetic, physical properties, paleontological, mineralogical, age-dating, geotechnical, and structural analyses. Following color and spectral scanning and paleomagnetic scanning, cores were packed for shipping to the core repository.
