The Oxygen Isotopic Composition of Interstitial Waters: Evidence for Fluid Flow and Recrystallization in the Margin of Great Bahama Bank

This study investigates the δ O of pore 18 waters from Sites 1003-1007 collected during Leg 166 of the Ocean Drilling Program which drilled sites along the western margin of Great Bahama Bank. These data generally show a positive correlation between δ O and the 18 concentration of chloride with the exception of Site 1006 which exhibits non-linear behavior with respect to chloride. However, the correlation between Cl and δ O at most of 18 the sites is a coincidence as the increase in Cl is a result of diffusion of Cl from an underlying Cl rich source, while the increases in δ O result from recrystallization of 18 metastable carbonates in the presence of a geothermal gradient. The difference in behavior of δ O at Site 1006 is probably a 18 result of the relative absence of carbonate diagenesis and interactions between clay minerals, particularly abundant at this site. In contrast to the behavior of other conservative and non-conservative constituents in the pore water, which exhibited no change in the upper 30 to 50 meters of the cores, the oxygen isotopic composition exhibited greater variability in this upper interval. The δ O of 18 the pore waters in the upper 50 meters of the cores shows a similar pattern to the concentration of chloride in that the values become more enriched in O nearer the 18 platform, suggesting an input of saline and isotopically heavy water from the platform surface. 0.00 400.00 800.0