inorganic carbon percentages to infer whether samples were likely to contain greater than

45 wt%/ of carbonates. Although grain size data were available for samples from ODP

Leg 112 Sites 679 and 681 (Peru), the scale used for the particle size criteria (Masters and

Christian, 1990) was different from the rest of the grain size data used in this study.

Thus, I excluded grain size data from Sites 679 and 681 in this part of the study. All

samples used in the grain size classification (marked with an asterisk) and values of

available weight percentages of CaCO3 are tabulated in Appendix A.

 All samples were categorized into the following four groups based on their grain

size distribution:

* Group 1, sediment containing more than 80% clay size material.

* Group 2, sediment containing 60-80% clay-size material.

* Group 3, sediment-containing silty-clays with less than 60% clay and less than 5%
 sand.

* Group 4, sediment-containing sandy-silts with less than 60% clay and more than
 5% sand.

 The following particle size criteria were used for classification: sand (>63 tpm), silt

(63-4 tpm) and clay (<4 tpm). The log linear relationships for each of the groups obtained

by least squares regression fit are given in Table 2-2. Group 4 was excluded from the

grain size classification as it only contained a total of four samples.

Table 2-2. Permeability-porosity relationships based on grain size analyses.
Group Description Permeability-porosity Permeability-porosity relationship
 relationship for Gulf of Mexico (Bryant
 2002)*
1 > 80% clay log (k) = -24.28 + 11.32n log (k) = -20.9 + 6.54n
 (R2 = 0.53)
2 60-80% clay log (k) = -19.73 + 4.49n (R2 log (k) = -20.53 + 6.16n
 = 0.56)
3 Silty-clays with log (k) = -19.91 + 5.45n (R2 log (k) = -20.59 + 6.77n
 <60% clay and = 0.43)
 <5% sand