CONCLUSIONS

1. No significant rebound effects have been demonstrated in the porous, upper soft sediment section of Sites 999 and 1001, whereas a rebound in porosity of ~2% is estimated for the cemented, deeper sections below 572 mbsf at Site 999 and below 352 mbsf at Site 1001.
2. By a modified strategy for determination of preconsolidation from consolidation tests, preconsolidations matching the present burial stress were obtained for the upper 550 m of soft sediments at Site 999, in accordance with the conservative burial history indicated for this site by paleontological data (Sigurdsson, Leckie, Acton, et al., 1997).
3. By applying the same strategy to compaction curves from Site 1001, and from interpretation of the present in situ burial stress -depth curve, 400 m of section is estimated to be missing at the hiatus at 166 mbsf at Site 1001. This interpretation of previous burial at Site 1001 brings the occurrence of wispy laminations with respect to burial depth in agreement with their occurrence at Sites 999 and 807. Based on this interpretation, the burial depth for the first appearance of wispy lamination at the three sites is ~500 mbsf.
4. At Sites 999 and 1001, wispy laminations are observed over the same depth ranges as cementation is observed, and a direct link between dissolution and precipitation might be suggested. Data from Site 807 suggest no direct link because dissolution seams and stylolites are observed ~500 and ~300 m, respectively, above the depth where cementation is found. These observations indicate that the formation of wispy lamination and stylolites is governed by burial depth, whereas the onset of cementation is governed by other factors (e.g., temperature and chemical composition of the pore water).
5. The slopes of the compaction curves are similar for the relatively carbonate-rich samples studied and are comparable to calcareous sediments from Site 807. Each compaction curve has a distinct shift along the porosity axis. This is interpreted to be because of microfossils playing only an insignificant passive role during compaction. Despite the generally high clay content of these Caribbean samples (8%-43% insoluble residue), the compaction curves are controlled by the fine-grained calcite, so that the fine-grained clay fraction appears to be moving dispersed in the pore fluid between the calcite grains.
6. Two relatively clay rich (47% and 50% insoluble residue) and microfossil poor samples underwent relatively large porosity loss during loading. This is probably a consequence of the bimodal distribution of fine carbonate particles and clay. The compaction of these samples appears to be controlled mainly by the fine-grained clay fraction.