At Site 1249, five individual holes were drilled, but only three were used for physical property analyses. Holes 1249B and 1249C had very poor core recovery and are combined with Hole 1249F to describe the physical property results. Hole 1249F had almost complete core recovery, and therefore, data gaps in Holes 1249B and 1249C were filled when the equivalent intervals were cored in Hole 1249F. Physical properties were acquired following the standard procedures (see "Physical Properties" in the "Explanatory Notes" chapter). IR thermal imaging of all cores was done in Holes 1249B and 1249F, but only the top two cores of Hole 1249C were imaged to speed up the sampling of gas hydrates on the catwalk.
IR imaging of cores recovered at Site 1249 enabled the on-catwalk identification of hydrate zones in each core, as described in "Physical Properties" in the "Explanatory Notes" chapter. This information was used to facilitate hydrate sampling and preservation for most cores. The IR thermal anomalies are catalogued in Table T12, which includes an interpretation of the overall hydrate texture for each anomaly. Half of the hydrate detectable by IR imaging of Hole 1249F is present as nodular or massive textures (43% nodular and 8% massive). Apparently, disseminated hydrate accounts for 28% of the presence and vein structures for 21%. Core recovery is poor in Holes 1249B and 1249C above 40 mbsf. Core liners partially filled with hydrate fragments result in a nodular appearance even if the original material is massive or highly concentrated hydrate (Fig. F20A). For this reason, nodular and massive hydrate presence in the upper part of Hole 1249C is considered to be a single category. Textures differ systematically from the upper to the lower parts of the holes cored at this site, with massive and nodular textures dominating the upper part of Hole 1249F and all of Hole 1249C. Below ~47 mbsf in Hole 1249F, disseminated zones and veins or lenses become the dominant textures of hydrate. Figure F20B is a representative example of a steeply dipping relatively thick hydrate vein. In Hole 1249F, below 47 mbsf, five veins (23% of hydrate below 47 mbsf) appear to crosscut bedding, indicating that a significant amount of hydrate has been emplaced in fractures or faults. From this observation, we infer that stratigraphic control may be of less importance at Site 1249 than at other sites (e.g., Site 1245). Successive thermal images were used to produce downcore thermal profiles for each core recovered in Holes 1249B, 1249C, and 1249F (Fig. F21). Extensive cold anomalies are present in Holes 1249B and 1249F above 40-50 mbsf. The temperature anomalies created by hydrate have been extracted from the downcore temperature data and from direct examination of IR images for Hole 1249F. Figure F22 shows the magnitude of the temperature anomalies as a function of depth for Hole 1249F plotted against pore water saturation (Sw) calculated from LWD (see "Downhole Logging"). Results are consistent and show the decrease in IR anomalies at depths mirrored by the change in Sw . Poor recovery in the upper part of Hole 1249F makes precise assignment of IR anomaly depths impossible. This uncertainty explains the apparent presence of IR anomalies in zones of no core recovery in Figures F21 and F22. The assignment of depth to intervals of unfilled core liners is somewhat arbitrary; however, depth assignment of IR anomalies are in their appropriate stratigraphic sequence, and actual depths are certainly within 9.5 m (length of cored interval) of their estimated in situ depth.
The sediment density trend, which combines data from all of the available holes cored at this site, shows a normal compaction-related downhole increase (Fig. F23). Sediment density is ~1.55 g/cm3 at the seafloor and increases to ~1.65 g/cm3 at a depth of ~90 mbsf (Table T13). Porosity decreases downhole with increasing depth, from values of ~65% at the seafloor to 50% at 90 mbsf. The GRA density record is highly scattered because of gas cracking and is offset by 0.2 g/cm3 to the LWD and MAD data. The LWD data indicate an increase in sediment density at a depth of ~55 mbsf that is associated with seismic Horizon Y (Fig. F24); however, neither the MAD nor the GRA data show a similar trend across this interval.
The grain density does not show any downhole trend. The average grain density is 2.70 g/cm3. The anomalously low grain densities and bulk densities and associated high porosities at ~10 mbsf (e.g., in Sections 204-1249F-3H-1 and 3H-2) correspond to an interval where gas hydrate is present. The presence of gas hydrate in these core sections was inferred from the strong IR anomalies (Fig. F23) and mousselike textures, as described in the core descriptions (see "Lithostratigraphy"). As a result of the highly disrupted nature of the sediments and the high water content of the samples associated with dissociated hydrate, these samples are not representative of the general trend.
MS shows an irregular downhole trend with several MS peaks. These peaks correspond to individual turbidite layers or to intervals with abundant sulfides (see "Lithostratigraphy"). One example of a sulfide-related MS anomaly can be seen in Core 204-1249F-15H, at a depth of 78-86 mbsf. Another MS anomaly in Core 204-1249C-9H, at a depth of 55 mbsf, is correlated with seismic Horizon Y. Horizon Y is characterized by abundant turbidite sequences with sandy layers (see "Lithostratigraphy"), which may be the cause of these MS peaks.
No velocity measurements were carried out at this site because of poor core recovery and extensive gas-expansion cracks.
As a result of poor core recovery and overall poor core quality (abundant gas expansion cracks), only a few thermal conductivity measurements were made in Hole 1249C (Table T14). A more detailed profile was acquired in Hole 1249F.
No shear strength measurements were carried out at this site because of poor core recovery and/or abundant gas expansion cracks.
At this site, we conducted a second hydrate dissociation experiment similar to that performed on a core section from Site 1248. Section 204-1249F-9H-3 was used for this experiment, and it contained two different types of gas hydrate. Disseminated hydrate was inferred from IR thermal imaging throughout intervals 204-1249F-9H-3, 0-40 cm, and 95-130 cm (Fig. F25). Within interval 204-1249F-9H-3, 80-95 cm, hydrate was present in a vein-type structure. The experiment was conducted over a period of ~3 hr. During this time, the section was scanned six times with the X-ray line scanner and was measured five times with the MST (Non Contact Resistivity system, GRA, and MS). After the experiment was finished, the section was split open lengthwise and discrete samples were taken every 10 cm. The section was finally imaged and analyzed to examine structural controls on gas hydrate occurrence. The temperature increased from an initial average value of 10° to 21°C, which is the average ambient room temperature, over the duration of the experiment.
The electrical conductivity showed a significant change in the upper 40 cm during the 3-hr experiment (Fig. F25). GRA and MS did not change during that time. The change in conductivity is 10 times greater than can be accounted for by the temperature increase. The increase in conductivity over the upper 40 cm is similar to that found in an experiment at Site 1248 (see "Physical Properties" in the "Site 1248" chapter. It can most easily be accounted for by the dissociation of hydrate, in the shape of veins or veinlets rather than as multiple small nodules (disseminated hydrate). Vein structure of electrically insulating hydrate would provide significant resistance to current flow despite its relatively small volume, something that would not be expected from small nodules.
The IR anomaly in interval 204-1249F-9H-3, 80-95 cm, indicates a vein or layer of hydrate, confirmed by the X-ray images and the digital photograph taken from the split archive half after the experiment was finished (Fig. F26). The images show a fracture dipping across the liner at an angle of ~45°. The fracture appears as a sharp boundary in the X-ray image, taken just after the core was recovered on deck. The digital core photograph shows a mousselike texture of the sediments, typical for sediments that contained gas hydrates. Onshore analyses will be conducted to model the change in resistivity associated with various hydrate concentrations and the thermal anomaly.
Physical properties were acquired at Site 1249 from three different holes, which were combined to provide downhole profiles. The measurements were strongly affected by poor core recovery and gas expansion effects. Data interpretation and correlation to lithostratigraphic units is, therefore, limited. In general, the MAD samples provide the highest quality data and correlate well with the LWD data. IR thermal imaging provided the best method to detect the presence of hydrates in the core liners. A complete downhole temperature profile was acquired only in Hole 1249F.