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doi:10.2204/iodp.pr.320T.2009

Discussion and conclusions

The main objectives of Expedition 320T were testing the WHC and the refurbished drilling and coring systems. In addition, the expedition provided an opportunity for assessing the overall readiness of all science systems before the start of international scientific operations. Many of the instruments and applications are entirely new or upgraded, and all of them are newly installed in the renovated ship's laboratories. The cores recovered during this expedition are allocated as USIO cores (rather than IODP) and will be used primarily for education and training.

All routine shipboard analytical measurements and descriptive observations made on the recovered core material and the corresponding data were uploaded to the new LIMS. Litho- and biostratigraphic observations are essentially consistent with findings previously reported for Site 807 (Kroenke, Berger, Janecek, et al., 1991). A Holocene/upper Pleistocene calcareous ooze extends from the sediment/water interface to the ooze–chalk transition at 293 mbsf, about three times deeper than the cored depth of the two holes drilled during this expedition. Coarse examination of the planktonic foraminifer assemblages recovered from core catcher samples yielded average sediment accumulation rates that are very similar to the rates calculated based on several microfossil groups and paleomagnetic polarity data for Site 807.

The downhole logging program during Expedition 320T was specifically designed to determine the efficiency of the new WHC system by using uphole (surface) and downhole acceleration data to evaluate the efficiency of the heave compensation and by comparing the new logging data with the data collected from Site 807. As with the core data, the new logging results correspond well with the previously reported data. As expected, the sediment section logged in Hole U1330A is characterized by generally low natural radioactivity and resistivity. The relatively uniform composition and the limited data collected did not allow the definition of distinct logging units. However, the three defined subunits, based on slight variations in resistivity and gamma ray values, correspond to the lithostratigraphic subunits defined by the Leg 130 scientific party (Kroenke, Berger, Janecek, et al., 1991). Performance testing of the WHC both in pipe and in open hole in Hole U1330A proved satisfactory. This is also confirmed by the high-resolution FMS images (sensitive to heave conditions) that showed excellent agreement of layering and sedimentary features recorded during different runs. However, further fine-tuning and testing of the WHC will need to continue over the next few years to evaluate the system's response under varying heave conditions.

In conclusion, the successful deployment of the APC and RCB coring systems and the retrieval of ~103 m of drill core (with an average recovery rate of 93%), the full onboard processing of the cored material and subsequent scientific examination (largely confirming the results reported for Site 807), and the successful runs of new and standard logging tools using the new WHC during Expedition 320T have proven the operational readiness of the drillship and its analytical systems. The crew and IODP personnel are looking forward to the beginning of international operations on 5 March 2009.

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