Construction of the composite and spliced section from Holes 1131A and 1131B followed the methods outlined in "Composite Depths" in the "Explanatory Notes" chapter. Table T3 (also in ASCII format) relates mbsf depth to meters composite depth (mcd) for each core and section at Holes 1131A and 1131B, and provides offset values for the conversion of mbsf depths to mcd. The composite section was constructed to a depth of 104 mcd and indicates that most of the sedimentary section down to this depth was recovered at Site 1131; however, several small gaps are apparent in the record.
The primary lithologic parameters used to create the composite section were NGR emission data collected by the multisensor track (MST) on whole-round cores, the 400-nm color reflectance data, and a ratio of the 700- to 400-nm color reflectance data measured on split cores (Fig. F10). For specifics regarding data collection procedures and parameters, see "Physical Properties". Because of the high sedimentation rates at Site 1131, biostratigraphic and paleomagnetic datums occurred below the total depth of Hole 1131B and could not be used in the construction of the composite section.
The composite section for Site 1131 is presented in Figure F10. The primary difficulty encountered in the construction of this composite section was the lack of obviously correlative small-scale features (<1 m) throughout much of the section in Holes 1131A and 1131B. This is the result of the general uniformity of the sediments on these scales (uniform wackestones to packstones over much of the section; see "Lithostratigraphy"). Larger scale (>1 m) distinctive events are also infrequent in the single-band color reflectance data but are more prevalent in the NGR data. The ratio of the 700:400 nm color reflectance data is marginally better than the individual 400- or 700-nm color reflectance data. These ratio data reveal cyclicity in the record in the form of long-wavelength (~10 m), low-amplitude oscillations that were correlated between holes. Core overlap between holes was reduced by significant core disturbance within the first sections of several cores.
The sediments comprising the composite section are entirely of Hol-ocene and Pleistocene age, based upon biostratigraphic data (see "Biostratigraphy"). The stratigraphic record within the range of the composite section is divided into two primary lithostratigraphic units. The upper unit, lithostratigraphic Unit I (0-32 mcd), is defined by the presence of unlithified bryozoan floatstone and rudstone, interbedded with wackestone, packstone, and grainstone. The floatstone and rudstone facies exhibit high color reflectance values (60%), which were relatively easy to correlate between holes. Lithostratigraphic Unit II (below 32 mcd) consists of a homogeneous light gray to light olive gray bioclastic packstone to grainstone, which yields a color reflectance data record with few obviously distinctive and correlative features (Fig. F10). Similarly, the characteristics of the NGR and gamma-ray attenuation (GRA) bulk density records are markedly dissimilar between holes, with the exception of some high-amplitude peaks in the NGR record. As a result, the record within lithostratigraphic Unit II was difficult to correlate between holes, and most ties rely upon long-wavelength oscilla-tions apparent in the 700:400 nm color reflectance data.
The composite and spliced sections indicate the existence of at least two unrecovered intervals in the record (Figs. F10, F11). Poor recovery in Cores 182-1131B-6H and 11X resulted in gaps in the record at 53.2-53.9 mcd and 76.9-77.2 mcd, respectively. Furthermore, although core overlap appears to occur between ~42 and 47 mcd (Cores 182-1131B-5H and 182-1131A-6H; Fig. F10), no significant statistical correlation could be found between the records, and the splice was appended at that point (Table T4, also in ASCII format). A similar situation occurs at ~68-69 mcd, between Cores 182-1131A-8X and 182-1131B-8X.