Measurements from the MST of magnetic susceptibility and GRAPE density, sampled at 2- to 4-cm intervals, and color reflectance, discretely measured at 2- to 4-cm resolution, were used to establish interhole depth continuity at Site 1078. Sedimentary features in the MST and color reflectance data of adjacent holes were graphically and quantitatively adjusted to be at approximately the same relative depth, thus generating a composite depth scale (expressed as meters composite depth [mcd]). Working from the core top down, a constant is added to the meters below seafloor (mbsf) scale of each core to establish the mcd depth offsets for individual cores. Establishing continuity of the Site 1078 stratigraphic sequence was problematic because of insufficient intercore overlap of the first three cores and intervals of high scatter in the data. However, a composite section was documented between 16 and 91 mcd.
Magnetic susceptibility, GRAPE, and color reflectance (red/blue ratio [650 nm/450 nm] and chromaticity b*) data were all used to construct a composite section and to verify core gaps. Because of the presence of gas voids and scatter in the data, no single parameter was uniformly reliable through the entire hole to constrain intercore correlation; thus, all parameters were used where appropriate. In addition, core flow-in was identified in the bottom section(s) of a number of cores, particularly those at Hole 1078B (see "Lithostratigraphy" and "Paleomagnetism" sections, this chapter, for further discussion). Disturbed sections were avoided when correlating between cores. To reduce the scatter in the raw MST measurements, raw data were filtered. Details of the filtering process are documented in the "Composite Section" section, "Site 1075" chapter (this volume), with the exception that a nine-point Gaussian filter was used to smooth the color reflectance data, and a six-point Gaussian smoothing was used for the GRAPE data.
Continuity of the composite section record is documented between 16 and 91 mcd (Fig. 23; Table 7). Composite splices used to constrain core gaps ranged from fair to very good. Lack of overlap among Holes at Site 1078 at 7 and 16 mbsf precluded the determination of core gaps among the three top cores. Between 16 and 57 mcd, the composite section is very good; however, the magnetic susceptibility and GRAPE display high scatter between 42 and 52 mcd, which made us shift reliance to color reflectance data for constraining the splice over this interval. The postulated overlap at ~57 m should be regarded with caution. The splice relies on a small positive feature observed in color reflectance (chromaticity b* and red/blue ratio) in both Sections 175-1078A-6H-7 and 175-1078C-7H-1. The correlation is not supported by the GRAPE and magnetic susceptibility records. Below 57 m, generally high scatter in the data degrade the quality and confidence of the spliced intervals. Despite these caveats, there is good agreement found in establishing a composite section to 91 mcd. The growth of the mcd scale relative to the mbsf scale was ~7% (Fig. 24)
Upon completion of the composite depth sections, a single spliced record was assembled using overlapping cores from Holes 1078A, 1078B, 1078C, and 1078D for GRAPE, magnetic susceptibility, and color reflectance (red/blue ratio [650 nm/450 nm]; Fig. 25). Hole 1078C served as the backbone for the sampling splice. Adjacent holes, primarily 1078D, were used to splice across core gaps in the Hole 1078C sequence. Intervals of core flow-in and disturbance were avoided, where possible, in assembling the splice. The splice for Site 1078 (Table 8) can be used as a sampling guide.