We built a meters composite depth (mcd) scale to 222.89 mcd and a splice (as defined in "Composite Section" in the "Explanatory Notes" chapter) that ranges from the top of Core 202-1236C-1H to the bottom of Section 202-1236C-12H-7 (0-129.72 mcd) (see Tables T2, T3). Below Core 202-1236C-12H, little correlation exists between multisensor track (MST) measurements of magnetic susceptibility (MS), natural gamma ray (NGR), gamma ray attenuation (GRA) bulk density, or archive multisensor track (AMST) measurements of reflectance made in cores from different holes. Therefore, below Cores 202-1236A-12H, 202-1236B-12H, and 202-1236C-12H (131.44-223.19 mcd), cores were appended according to the cored interval, if nominal recovery was <100%, or to the recovered interval, if recovery was >100%.
The mcd scale and the splice are based on the stratigraphic correlation of split-core reflectance (a*) collected at 2.5-cm intervals using the AMST and whole-core MS measurements collected at 2.5-cm intervals using the MST. Measurements of magnetic susceptibility were also made with the OSU Fast Track (OSUS) using a 10-s integration time (Tables T4, T5), but because of some technical problems the MST-MS data were used here. No OSUS data are available from Hole 1236A, and partial data are available from Hole 1236B, starting at Section 202-1236B-7H-1. MS and a* data for Holes 1236A, 1236B, and 1236C and the splice constructed from them are presented on the mcd scale in Figures F7 and F8, respectively. The splice tie points (Table T3) were then used to construct representative spliced records for reflectance (L*, a*, and b*), MST-MS, and GRA bulk density data. The spliced records of reflectance (a*), GRA, and MS are presented in Figure F9.
Reflectance (a*) was the most useful stratigraphic tool for correlation at Site 1236. We assumed that the uppermost sediment (the "mudline") in Core 202-1236C-1H was the sediment/water interface. A mudline was also recovered in Core 202-1236B-1H, which confirmed the fidelity of the top of the recovered section. Core 202-1236C-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 records on a core-by-core basis. A comparison of the mcd and mbsf depth scales (Fig. F10) shows that the mcd scale is on average 14% longer than the mbsf scale.
To facilitate the calculation of mass accumulation rates (MARs), we provide corrected meters composite depth in Table T2 and in Table T3 for depths within the splice. The mcd growth factor for the spliced interval at Site 1236 is 1.14.