Daily Report for IODP Expedition 311, October 26, 2005
LOCATION: Sites U1326 (CAS-03C)
SCIENCE UPDATE: Throughout the morning we continued coring in Hole U1326D. The last core of this expedition was on deck at 09:00 hr. Due to reports of deteriorating weather conditions, it was decided to stop coring at a depth of 271.4 mbsf and deepen the hole to a total depth of 300 mbsf by drilling to gain time and complete logging, rigging down, and securing the rig flooor before the expected arrival of forecasted storm. Because heave conditions had slightly improved through the night and early morning, we did attempt three deployments with the DVTP tool (at 252.2 mbsf, 271.4 mbsf, and 300 mbsf). All three deployments yielded only marginally useful data but may be sufficient to establish a simplified linear temperature gradient for this site. The last three cores in Hole U1326D showed unexpectedly strong IR imaged cold-spot anomalies at depths below the seismically inferred BSR at ~230 ± 5 mbsf. Uncertainty remains in the position of the BSR until the velocity data from the planned wireline logging survey and the data from the deep DVTP surveys are completely processed and analyzed postcruise. After completing coring operations we started to rig up for downhole logging. It was decided to conduct a single novel downhole log run with a non-standard IODP tool string, which included the Scintillation Gamma Ray (SGT) Tool, Phasor Dual Induction (DIT) tool, and the Dipole Sonic Imager (DSI). Logging operations started at ~23:00 hr and continued throughout the night. All of the labs continued to process the remaining cores throughout the afternoon and into the night. Pore fluid salinity measurements were completed and showed an unexpected trend with depth, where salinity and chlorinity remain almost constant from the seafloor to the base of the cored interval (271.4 mbsf). Pore-water freshening from gas hydrate dissociation showed an unexpected inverted profile with depth, with the strongest anomalies at shallower depths and decreasing towards the predicted depth of the BSR.