At Site 1083, four holes were cored with a maximum penetration of 206.15 mbsf. Physical properties and color reflectance data were measured at 2-cm (Hole 1083A) and at 4-cm (Holes 1083B, 1083C, and 1083D) intervals. The correlation of features present in the physical and visual properties measurements of adjacent holes was used to demonstrate the completeness of the local stratigraphic sequence drilled and to establish a depth scale in terms of meters composite depth (mcd) for Site 1083. The continuity of the stratigraphic sequence could be demonstrated between 0 and 218.1 mcd, with a gap between 46 and 47.5 mcd (Fig. 8; Table 8).
At Site 1083, magnetic susceptibility and wet bulk density (GRAPE) were used to establish the mcd scale. The data sets were extensively processed before being used for correlation. Suspect measurements were eliminated by thresholding the data. The resulting data were smoothed using a Gaussian filter with a length of 12 cm. All data shown in Fig. 8 and Fig. 9 were processed as described above.
The gap in the sedimentary sequence at 46 mcd results from only 28% recovery in Core 175-1083A-6H and 66% recovery in Core 175-1083B-5H. Stratigraphic correlation indicated that Cores 175-1083A-6H, 175-1083B-5H, and 175-1083D-5H (95% recovery) all end at the same depth. The length of the gap at 46 mcd between the two complete sections is unknown. Based on the driller's depth (in mbsf), at least 1.5 m of sediment are missing between Cores 175-1083D-5H and 6H.
Although Core 175-1083A-4H was recovered empty, the sedimentary sequence above 46 mcd is complete. Large gaps exist between Cores 175-1083A-1H and 2H (2.5 m), Cores 175-1083B-1H and 2H (6 m), Cores 175-1083B-2H and 3H (3 m), and Cores 175-1083B-4H and 5H (3 m). The most complete recovery is found at Hole 1083D.
The spliced record presented in Figure 9 and Table 9 is continuous to 46 mcd and from 47.5 to 218 mcd for magnetic susceptibility and GRAPE density. The selection of cores to be included in the spliced record and the placement of tie points were carried out mainly using the composite section of the magnetic susceptibility from Site 1083. Cores from Holes 1083A, 1083B, and 1083D had to be used in almost equal numbers to ensure completeness of the shipboard splice.
The resulting growth of the mcd scale compared with the standard ODP mbsf scale is ~13% (Section 175-1083B-21H-CC at 218 mcd and 192.8 mbsf). The growth of offsets applied to cores with meters below seafloor is not exactly linear (Fig. 10) but is always close to 10%. The offsets applied to cores from Hole 1083B are ~4 m larger because of an offset of 5.88 m applied to Core 175-1083B-2H.