CONCLUSIONS

Sieving and heavy-liquid treatment has enabled us to produce a pure aragonite separate from the mixed-carbonate bulk sediment of the Bahamas slopes and to remove detrital material. This solves the problems of initial Th for these samples and allows use of U-Th techniques to learn about their age.

Sediments recovered during Leg 166 have suffered diagenesis that has altered their U-Th systematics. This diagenesis varies from site to site, probably reflecting the different fluid-flow regimes experienced at various distances from the platform. Samples from Site 1005 have experienced U loss while those from Sites 1006 and 1003 have experienced U gain. Samples from all sites have also suffered continuous loss of pure ²³⁴U due to -recoil. Correcting sample ages for both U loss/gain and for ²³⁴U loss does not allow precise ages to be assigned, but does enable each aragonite-rich sediment package to be matched with the sea-level highstand that formed it. Site 1005 has a complete sequence of highstands, equivalent to marine oxygen isotope Stages 1, 5, 7, 9, and 11. Hole 1006A is missing only the Stage 7 highstand (but this is present in Hole 1006B). Site 1003 has only the Stage 1 and Stage 11 highstands and is missing all those in between. Site 1007 still has sediment from the present day highstand but features sediments older than the U-Th age range immediately beneath that.

No aragonite-rich sediment packages are identified for Stage 3, or Substages 5a and 5c, even in the basin-located Site 1006. Unless somewhat unusual erosion has occurred, this suggests that the banks were not flooded during these periods and that sea level was therefore at least ~10 m lower than today.