Figure F14. Comparison of chloride distribution (solid circles) with sites drilled during Leg 146 (open circles) at Site 1251. All sites show a decrease in dissolved chloride with depth, reflecting the influence of a deep-seated fluid source. Site 888, which was drilled west of the deformation zone during ODP Leg 146, represents a background chloride distribution (Kastner et al., 1995). Estimates of gas hydrate amounts based on deviations in chloride (Cl-) concentration from the linear Cl- decrease reveal that gas hydrate occupies ~20% of the pore space in sediments at the bottom of the GHSZ. The lack of any other significant deviation in chloride concentration indicates that there is very little gas hydrate present above the deep hydrate layer just above the bottom-simulating reflector (BSR).