We built a continuous meters composite depth (mcd) scale and a splice (as defined in "Composite Section" in the "Explanatory Notes chapter) that range from the top of Core 184-1144C-1H to the bottom of Section 184-1144A-23H-7. The splice and the continuous portion of the mcd scale extend from 0.0 to 235.41 mcd. Splice construction below this interval was precluded by incomplete core recovery and alignment of core gaps. As described below, however, we were able to construct a discontinuous ("floating") mcd scale (see "Composite Section" in the "Explanatory Notes" chapter) for cores below 235 mcd.
The mcd scale and the splice are based on the stratigraphic correlation of whole-core multisensor track (MST) and split-core color spectral reflectance (CSR) data (lightness, L*) collected at 4- to 8-cm intervals (see "Physical Properties" for details). From the MST, we used magnetic susceptibility (MS), gamma-ray attenuation (GRA) bulk density, and natural gamma radiation (NGR) data. These data and the splice constructed from them are presented on the mcd scale in Figures F1, F2, F3, and F4 (also as Synergy Software KaleidaGraph plots and Microsoft Excel data files [see the "Supplementary Materials" contents list]; the spliced records are also available in ASCII format). The depth offsets that comprise the mcd scale are given in Table T3 (also in ASCII format). The splice tie points (Table T4, also in ASCII format) should be used as a guide for detailed postcruise sampling.
Magnetic susceptibility was the most useful stratigraphic tool for correlation. Color spectral reflectance and NGR were helpful in intervals where MS structure was ambiguous or the signal amplitude low. Failure of the NGR recorder on the MST resulted in the loss of NGR data over much of Hole 1144B. Gamma-ray attenuation was the least useful for correlation because intracore squeezing and stretching (resulting from the coring process as well as gas expansion) degraded the signal significantly. We constructed the mcd scale by assuming that the uppermost sediment (the "mudline") in Core 184-1144B-1H was the sediment/water interface. However, based on a preliminary comparison of the MS structure in this core with that from core MD97-2146 (collected during the IMAGES III cruise in the same general vicinity but in water 300 m shallower), we suspect that the upper 2 m of the sedimentary section was not recovered at Site 1144.
Core 184-1144C-1H, the "anchor" in the composite depth scale, is the only core with depths that are the same on the mbsf and mcd scales. From this anchor we worked downhole, correlating the stratigraphy on a core-by-core basis. Stratigraphic misalignment was evident in the cores with the highest gas (and thus void) content, such as those in the upper 50 mcd of the section. The core-splitting process, which involves pulling a cutting wire lengthwise along the section, can dislodge sediments and reposition voids, thus offsetting the split-core CSR and whole-core MST data (see "Composite Section" in the "Explanatory Notes" chapter). Thus, stratigraphic correlations based on CSR may differ slightly from those based on MST data. Fortunately, many of the voids were removed on the catwalk by drilling gas-escape holes in the liner and manually pushing together sedimentary intervals within the core liner.
Correlation of the intervals spanning 18 to 40 mcd, 122 to 150 mcd, and 180 to 196 mcd were especially challenging because of low amplitude in the MS signal. Here we relied more on CSR and NGR data to construct stratigraphic ties, although alternative correlations are possible. In the splice, we chose to append successive cores from Hole 1144B at two locations (Table T4), rather than to incorporate short intervals from other holes. Independent verification of stratigraphic continuity across these ties is required.
Although the cores below 235 mcd could not be tied directly to the composite depth scale (and thus the splice), they could be correlated with each other. We placed the cores in a relative, or discontinuous, composite depth scale. This "floating" scale is not tied to the overlying mcd scale (and thus back to the mudline). Instead, the positions of the cores are adjusted such that correlative features match. At other Leg 184 sites, we chose a single hole (keeping core offsets within it constant below the splice) and mapped cores from the other holes to the chosen hole. This approach was not possible at Site 1144 because of inadequate core quality in the lower section.