We built a composite depth scale (as defined in "Composite Section" in the "Explanatory Notes") that ranges from the top of Core 202-1235C-1H to the bottom of Section 202-1235A-20H-7 (0.00-214.38 meters composite depth [mcd]) (Table T2) and a splice (as defined in "Composite Section" in the "Explanatory Notes" chapter) for the upper 151.42 mcd. The splice ranges from the top of Core 202-1235A-1H to the bottom of Section 202-1235B-17H-7 (0.00-188.55 mcd). The splice is continuous to 63.97 mcd. Below this, we constructed four intervals of a floating splice. The mcd scale and splice are based on the stratigraphic correlation of whole-core magnetic susceptibility data from the ODP multisensor track (MST-MS) sampled at 2.5-cm intervals and data from the Oregon State University Fast Track (OSUS-MS) collected at 5-cm depth intervals (Tables T3, T4, T5). These data were complemented by other data from the multisensor track (MST) and by gamma ray attenuation (GRA) bulk density, natural gamma radiation (NGR), color reflectance (measured on the archive-half multisensor track), and magnetic intensity measurements from the cryogenic magnetometer track. The composite section and splice of MST-MS are illustrated in Figure F5.
It is likely that a complete sediment section was recovered in the three holes drilled at Site 1235. However, significant ship heave, combined with gas expansion of cores recovered at Site 1235, led to poor correlation between MST data from adjacent holes in some intervals, and this made the construction of a composite section and a spliced record somewhat uncertain. In two intervals within the splice, precise correlation is problematic using available shipboard data. The first is at 4-16 mcd (between the top and bottom of Core 202-1235A-2H; Fig. F5A). The second is at ~45-49 mcd (between the base of Core 202-1235A-5H and the top of Core 6H; Fig. F5B). Core 202-1235B-5H may span this gap. In these two intervals, splice tie points are somewhat uncertain because of the poor correlation of the shipboard data between holes. Below Core 202-1235B-6H (63.97 mcd) there is a gap in the splice. The first section of floating splice begins at the top of Core 202-1235B-8H (76.54 mcd) and ends at the bottom of Core 202-1235B-9H (95.44 mcd) (Fig. F5C). The second section of floating splice begins at the top of Core 202-1235A-11H (103.87 mcd) and extends to the bottom of Core 202-1235B-11H (117.23 mcd) (Fig. F5D). The third section of floating splice begins at the top of Section 202-1235A-15H-1 (150.12 mcd) and ends at the bottom of Core 15H (163.93 mcd) (Fig. F5E, F5F). The fourth section of floating splice begins at the top of Core 202-1235A-17H (175.55 mcd) and extends to the bottom of Section 17H-7 (188.55 mcd) (Fig. F5F, F5G). Tie points (Table T6) were then used to construct representative spliced records for MST track magnetic susceptibility (MST-MS), GRA bulk density data, and NGR attenuation (Fig. F6). Although the susceptibility in cores covering the interval 90-100 mcd is low (~30 instrument units), careful inspection of these data combined with other MST data supports the correlations shown in Figure F5C and F5D. Below Core 202-1235B-17H (~189 mcd) we cannot confirm continuous recovery (Fig. F5G).
To aid in the construction of the composite section, as a first approximation we assumed an expansion factor of 13% to the top depth of all cores drilled at Site 1235. In the upper interval, where continuous recovery was documented, we found an expansion factor of 20%. The final expansion of 20% (Table T2) was applied to all cores below 172 mcd that could not be correlated (Fig. F5).
To facilitate the calculation of mass accumulation rates (MARs), we provide corrected meters composite depth (cmcd) in Table T2. The mcd growth factor for the composite interval at Site 1235 is 1.20 (Fig. F7).