Figure F5 shows the quality control logs for Hole 808I. A target ROP of 50 m/hr was chosen, and the averaged ROP throughout the whole section was 34 m/hr. To record one sample per 15 cm, the ROP must be maintained at 65 m/hr or lower. This was achieved for 99% of the total section in Hole 808I (Fig. F5). Although RAB image resolution would improve with even slower drilling rates, the quality of RAB images is still high (~3-cm pixel) and no significant reduction in resolution is observed.
Time-after-bit (TAB) measurements are <1 hr for 99% of the resistivity and gamma ray logs and <3 hr for 90% of the density and neutron porosity logs throughout the whole section (Fig. F5). Density TAB values of 10-20 hr at 728-750, 967-989, and 1003-1028 mbsf coincide with hole conditioning operations (see "Operations"). The differential caliper (DCAL) is the best indicator of borehole conditions. In typical logging applications a standoff of <1 in between the tool and borehole wall indicates high-quality density measurements with an accuracy of ±0.015 g/cm3. The differential caliper values are <1 in over 65% of the total section in Hole 808I. The differential caliper values in the long TAB intervals at 728-750 and 967-989 mbsf are significantly higher than adjacent intervals. Apparently, the long TAB measurements directly resulted in borehole enlargements and low-quality density measurements. The differential caliper values are <1 in over 30% of the 268- to 530-mbsf interval (log Units 1 and 2; see "Definition of Log Units and Lithologic Interpretation"). This interval corresponds to zones of borehole breakouts and the frontal thrust (see "Logs and Structural Geology"). The bulk density correction (DRHO) shows a trend similar to the differential caliper log and varies from 0 to 0.1 g/cm3 below 530 mbsf and from 0 to 0.2 g/cm3 above 530 mbsf (Fig. F5). Comparisons to core data clearly show that enlarged sections of the borehole yield unreliable density and associated porosity data (see below). Thus, these density and porosity results should be used cautiously until more complete correction and editing is completed postcruise.
As in Holes 1173B and 1173C, raw waveforms from the ISONIC tool were successfully recorded with high signal-to-noise ratios in Hole 808I. Preliminary waveform processing and evaluation of P-wave velocities were carried out by Anadrill-Schlumberger in Houston, Texas, during and after Leg 196. The preliminary P-wave velocity log (Fig. F29) does not correspond closely with core and other independent values and may be subject to significant errors in P-wave phase identification. This log will require continued processing and may be substantially modified postcruise (see "Logs and Physical Properties").