Gas hydrate appears to occur as traceable stratigraphic horizons between sites as denoted by a combination of downhole logging measurements, seismic structure (BSR), and chlorinity anomalies. Other site-localized gas hydrate indicators from direct observations are also suggested but do not continue to other sites. Recovered gas hydrate occurrences cannot be correlated from site to site. At Site 997, a massive gas hydrate vein was interpreted to be a near-vertical fault-filling feature and is depicted as a steeply dipping feature.
Gas hydrate is thought to occur wholly within the interval of about 180-460 mbsf based on shipboard data; however, two occurrences of soupy sediment documented in the core photos suggest that gas hydrate may have been present (Sections 164-994C-4H-5 through 7, 29.8-32.9 mbsf, and Section 164-997B-15P-1, 501.0 mbsf). Both suspected gas hydrate occurrences are found within the measured gas hydrate stability field but outside the interval of about 180-460 mbsf, as determined by the shipboard scientists (Paull, Matsumoto, Wallace, et al., 1996). If these cores did contain gas hydrate, then the area of gas hydrate occurrences can be expanded to the 30-501 mbsf interval and could significantly increase gas hydrate mass estimates of the Blake Ridge.