Multisensor track (MST) and spectral reflectance (L*) data collected from Holes 1170A, 1170B, and 1170C were used to align equivalent features between cores from different holes and determine the depth offsets in the composite section. Magnetic susceptibility, gamma-ray attenuation (GRA) bulk density, and spectral reflectance measurements were the primary parameters used for core-to-core correlation at Site 1170. GRA bulk density and magnetic susceptibility data were collected at 2-cm intervals on all APC cores recovered from Holes 1170A, 1170B, and 1170C. Spectral reflectance data were collected at 2-cm intervals on most of the APC cores from Holes 1170A, 1170B, and 1170C (see "Physical Properties" and "Lithostratigraphy" for details about MST and spectral reflectance data).
The data used to construct the composite section and determine core overlaps are presented on a composite depth scale in Figure F24. The depth offsets that comprise the composite section for the APC sections of Holes 1170A, 1170B, and 1170C are given in Table T15.
Many of the cores in the APC section in Holes 1170A, 1170B, and 1170C contain significant intervals of flow-in or are highly disturbed (See "Lithostratigraphy" and the "Core Descriptions" contents page). This ubiquitous core disturbance, especially between 40 and 120 mcd (Cores 6H-13H in Holes 1170A, 1170B, and 1170C), made the construction of a composite APC section very difficult. Between 0 m composite depth (mcd) (top of the section) and 75 mcd (Core 8H in Holes 1170A, 1170B, and 1170C) all the cores could be placed into a composite framework, but often only one or two sections of a core could be utilized for the composite construction. In the lower portion of the APC section, all other cores were either too highly disturbed (e.g., Cores 12H and 13H in Holes 1170A, 1170B, and 1170C) or the MST and color reflectance data did not have sufficient or coherent signal amplitude to definitively tie features together between adjacent cores (e.g., Cores 14H-18H in Holes 1170A, 1170B, and 1170C). These cores were left in their original alignment with only a cumulative composite depth correction added to the original mbsf depth.
The construction of the composite section shows that, in general, cores from Hole 1170A were several meters shallower than equivalent cores in Hole 1170B (Table T15) and, thus, needed to be depth-shifted downward with respect to Hole 1170B. Cores from Hole 1170C, however, were several meters deeper than equivalent cores in Hole 1170B and were adjusted upward with respect to Hole 1170B (Table T15). Core 189-1170C-3H, although highly disturbed, appears to be a near duplicate of Core 189-1170C-2H and was depth shifted upward nearly 11 m in the composite section. Such duplication of section is not unexpected considering the rough sea state (large heave) during APC coring operations at this site (see "Operations" for details) and the system of APC core extraction and advancement utilized by the drillers. Only after a third APC core does the drill pipe always remain in the original hole (especially in rough seas). The combination of a large heave and the pipe entering a new hole could easily result in the recoring of the upper sedimentary section.
The depth offsets determined for the upper 70 mcd of Holes 1170A, 1170B, and 1170C are consistent with paleontological evidence. Most nannofossil, radiolarian, and foraminiferal datums (see "Biostratigraphy") present in all three APC holes fall within the same 9.5-m interval (the resolution of the datums) in the composite section. Exceptions include the FO of the radiolarian Pseudocubus vema and the FO of the foraminifer Globorotalia truncatulinoides. No amount of reasonable depth shifting of cores resulted in the alignment of these datums in the composite section. The FO of G. truncatulinoides is problematic at this site, though, often yielding ages that are discordant with the calcareous nannofossils. Specimens of G. truncatulinoides are very rare and, when present, are diminutive with thin, transparent shells (see "Biostratigraphy").
Paleontological evidence also supports a rough composite section alignment for Cores 14H through 17H in Holes 1170A, 1170B, and 1170C (Table T15). Radiolarian (the last consistent occurrence of Stichocorys delmontensis), foraminiferal (the FO of Globorotalia puncticulata), and nannofossil (the LO of Discoaster loeblichii) datums present in cores in all three holes in this part of the section are in good agreement when the cores are aligned using the cumulative composite depth correction added to the original mbsf depth. Multisensor track data and spectral reflectance data, however, do not have sufficient signal amplitude or coherency to definitely tie the cores together. Thus, the alignment of cores in this section may be off by as much as 1-3 m.
Stretching and compression of sedimentary features in aligned cores indicate distortion of the cored sequence. Because significant distortion occurred within individual cores on depth scales of <9 m, it was not possible to align every feature in the MST and color reflectance records accurately by simply adding a constant to the mbsf core depth. Core-scale changes will require postcruise processing to align smaller sedimentary features. Only after allowing variable adjustments of peaks within each core can an accurate estimate of core gaps be made.
Following construction of the composite depth section for Site 1170, a noncontinuous spliced section was constructed for the upper 71 mcd. Cores from Hole 1170A were used as the backbone for the splice, with cores from Hole 1170B and, to a lesser extent, Hole 1170C used to cover intervals between gaps in cores from Hole 1170A. Intervals having significant disturbance or distortion were avoided when possible. The moderately disturbed portions of Core 189-1170B-3H, however, were used in the splice. Gaps between Cores 189-1170A-3H and 4H and between Cores 189-1170A-5H and 6H could not be spanned by cores from Holes 1170B and 1170C. Below 70 mcd, core disturbance or low signal variability precluded construction of a spliced section. The Site 1170 splice (Table T16) does not represent a continuous section and should only be used as a crude sampling guide for high-resolution studies conducted on the upper portion of the APC interval.