A methodology was developed that can be used to derive rebound coefficients for the correction of rebounded core physical properties (density, porosity, and void ratio) and spliced meters composite depths (mcds) to in situ values. The increasing-with-depth mismatch between logging depths (density curves were used in this instance) and mcd depths are treated as consolidation tests, only somewhat larger. Core physical properties and mcd depths are first corrected for hydraulic rebound (here almost 4 m of offset at 190 meters below seafloor [mbsf]); the remaining offset is attributed to mechanical (porosity) rebound. The offset between the hydraulic rebound-corrected depths and logging depths are used in conjunction with hydraulic rebound-corrected discrete core sample physical properties to obtain rebound coefficients (Cr values) for the nannofossil and radiolarian oozes at Ocean Drilling Program (ODP) Sites 1218 and 1219. Using the nannofossil ooze rebound coefficients, the Site 1218 mcds are corrected upcore from a tie point at 80 mbsf, allowing derivation of a linear compression for the overlying pelagic clay unit. The three relationships derived from these two sites can then be used to correct the core physical properties and mcds for the other sites cored during ODP Leg 199. The corrected Site 1219 spliced density curve is presented as an example of this process. This method can also be applied to other ODP and Deep Sea Drilling Project sites where unlithified pelagic sediments were cored, a stratigraphic splice can be/has been constructed, and downhole logging was undertaken. Using this approach, it may be possible to produce locally to regionally applicable rebound-correction relationships for a number of pelagic sediments.
|Journal||Proceedings of the Ocean Drilling Program: Scientific Results|
|Publication status||Published - 1 Nov 2004|