One 5-cm whole-round core was taken from Hole 1129A for interstitial water analysis. Similar whole-round samples were taken from Hole 1129C at a rate of one sample per section from the upper 15 cores and every other core thereafter, recovery permitting. Samples were analyzed according to the procedures outlined in "Inorganic Geochemistry" in the "Explanatory Notes" chapter. These data are presented in Table T7 and Figures F16, F17, and F18.
Salinity exhibits no change over the upper five cores, to a depth of 40.3 mbsf. This same trend of invariant change is exhibited in all conservative and nonconservative tracers, and is considered to be equivalent to the flushed zone discovered during Leg 166 on the margin of Great Bahama Bank (Eberli, Swart, Malone, et al., 1997) (see "Discussion"). Below the flushed zone, the concentrations of Na+, Cl-, and K+ all increase steadily to the base of the cored interval. The Na+/Cl- ratio exhibits a midprofile maximum of 1.05 at a depth of 135.2 mbsf (Fig. F16).
As mentioned previously, the upper 40.3 mbsf is characterized by essentially constant concentrations of the nonconservative elements, including Mg2+, Ca2+, Sr2+, Li+, and H4SiO40. Below this depth, the concentrations of Mg2+ and Ca2+ exhibit significant decreases in the upper 300 mbsf, with Mg2+ falling to 14.6 mM and Ca2+ to 3.9 mM at 201.7 mbsf (Fig. F17). With increasing depth, the concentrations steadily rise to the base of the cored interval, although ratios relative to Cl- remain lower than in normal seawater (Fig. F18). The concentration of Sr2+ shows two principal increases below the flushed zone, the first between 40.3 and 87.7 mbsf, and the second between 201.7 and 305.4 mbsf (Fig. F17). The first increase in Sr2+ is associated with a decrease in the concentration of high-Mg calcite (HMC) and the appearance of dolomite, whereas the second is associated with increasing amounts of cementation (see "Lithostratigraphy") and a decreasing amount of aragonite. Note that in the flushed zone, there is no measurable concentration of dolomite.
Although there is no net deficit of SO42- in the upper 116.2 mbsf, alkalinity increases downward substantially and H2S is abundant over the same interval (see "Organic Geochemistry"). This suggests that H2S is diffusing upward from underlying sediments and is being oxidized to SO42- (Fig. F18). Below 116.2 mbsf, the normalized concentration of SO42- decreases to a minimum at 268.3 mbsf. Over the same interval, the concentrations of NH4+ reach 26.7 mM (Table T7).
Alkalinity shows a maximum value of 97.28 mM at a depth of 28.6 mbsf. Toward the bottom of the hole, alkalinity decreases to a value of 29.51 mM. Values for pH and pH determined using the push-in electrode (ppH) are relatively consistent, decreasing to 5.9 at a depth of 427.3 mbsf (Fig. F18).
The sediments at Site 1129 are composed of low-Mg calcite, HMC, quartz, aragonite, and dolomite (Fig. F19; Table T8, also in ASCII format). High-Mg calcite is the dominant mineralogy at the top of the cored interval, but it decreases rapidly to zero coincident with the boundary between lithostratigraphic Units I and II (see "Lithostratigraphy"). This boundary marks the transition between bryozoan mounds and the underlying bioclastic packstones. The decrease in HMC is concurrent with the increase in dolomite, which reaches sustained concentrations of ~20% and has a maximum concentration of 30%. At the base of Unit II, the concentration of aragonite decreases to ~5%.
Sites 1129, 1131, and 1127 form a depth transect from shallow water (200 m) to deeper water (480 m) and present an ideal opportunity to examine pore-water geochemistry in a transect from the platform margin toward deeper water and to understand the origins of the saline fluids, high alkalinities, and sulfate reduction observed at these three sites.
All three sites are influenced by the presence of high-salinity fluids within and beneath the cored intervals. A contour plot of the Cl- (Fig. F20) data reveals that contours of equal Cl- concentration crosscut sequence boundaries (i.e., they are subhorizontal). This observation is consistent with emplacement of the brine during previous sea-level lowstands, under the influence of a hydraulic head from the adjacent continent. The present concentrations in the pore waters are derived from the diffusion of cations and anions from a region of high concentration (the brine) to a region of low concentration (overlying seawater and underlying sediments). The Na+/Cl- ratio also changes between the proximal and the distal sites (Fig. F21). At Sites 1129 and 1131, there is a pronounced maximum in the ratio, although at Site 1127, this ratio has decreased (Fig. F21). The presence of fluids with a high Na+/Cl- ratio suggest that the sediments were also influenced by a brine that had either dissolved Na+/Cl- or had been involved in the precipitation of evaporite minerals. The higher Na+/Cl- in the proximal sites is consistent with origination of this brine on the continent. The location of the fluids with high Na+/Cl- within the Pleistocene constrains the timing of the brine emplacement.
Although the maximum amount of sulfate reduction occurs in the sediments from Site 1129 (Fig. F22), Site 1131 shows the maximum increase in alkalinity (Fig. F23) and exhibits the highest concentrations of H2S and CH4 (see "Organic Geochemistry," "Organic Geochemistry" in the "Site 1127" chapter, and "Organic Geochemistry" in the "Site 1131" chapter). Although the connection between the degree of sulfate reduction and alkalinity remains to be precisely defined at these sites, the high alkalinity at Site 1131 is a combination of SO42- supply, the amount and nature of organic material, and the amount of mud in the sediment. At Site 1127 for example, the sediment appears to be somewhat finer grained than at the two more proximal sites (see "Lithostratigraphy" in the "Site 1127" chapter). This allows the pore fluids at Site 1127 to act as a closed system and to become more depleted in SO42- near the sediment/seawater interface. In contrast, SO42- is never completely depleted at the other sites and the zone of lowest SO42- concentration is much deeper at Sites 1129 and 1131 than at Site 1127 (Fig. F22). At all three sites, the relatively steep SO42- concentration gradient in the lower portion of the cored intervals allows the higher than normal rates of diffusion of SO42- to the zone of organic material oxidation. At both proximal sites (Sites 1129 and 1131), the upper profile of SO42- in the sediments is modified by oxidation of H2S in the upper portion of the profile.
Of the three sites in this transect, Site 1127 exhibits the lowest amount of carbonate recrystallization. This conclusion is supported by observations of the degree of cementation (see "Lithostratigraphy" and "Biostratigraphy," "Lithostratigraphy" and "Biostratigraphy" in the "Site 1127" chapter; and "Lithostratigraphy" and "Biostratigraphy" in the "Site 1131" chapter) and the nature of the Sr2+ profile in the pore waters. At Site 1127, the concentration of Sr2+ exhibits a very small increase over the upper 180 mbsf, before rising rapidly to 600 µM between ~180 and 220 mbsf. Preservation of carbonate microfossils is good at this site, with minimal amounts of overgrowth and dissolution. At Site 1131, an initial rapid rise in Sr2+ not seen at Site 1127 indicates shallow carbonate recrystallization. At Site 1129, the presence of a flushed zone in the upper 43 mbsf eliminates any gradients in the concentration of Sr2+. Below this depth, the Sr2+ concentration increases to between 400 and 500 µM. In this interval, the concentration of dolomite increases and HMC decreases (Table T8). A second rapid increase occurs between 201.7 and 305.4 mbsf, with Sr2+ values exceeding 2000 µM. The gradual decrease in aragonite toward the base of the Pleistocene can be interpreted as being the result of the increasing recrystallization of carbonate with depth. The loss of HMC at both Sites 1131 and 1129 appears to be mainly a facies-dependent signal (see "Lithostratigraphy" and "Lithostratigraphy" in the "Site 1131" chapter). However, the absence of HMC in the lower portion of the cored interval at both Sites 1131 and 1129 probably reflects the recrystallization of fine amounts of HMC, which is more soluble than aragonite (Morse and Mackenzie, 1990). In contrast, the persistence of HMC to deeper intervals at Site 1127 is a result of the complete removal of sulfate, which produces a pore-water environment supersaturated with respect to aragonite and HMC (Ben-Yaakov, 1973).