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Composite section

Cores were depth-shifted on the basis of magnetic susceptibility data collected with the “Fast Track” magnetic susceptibility core logger (MSCL) soon after recovery. Magnetic susceptibility proved most useful for correlating between holes at Site U1307 (Fig. F18). There were only two holes cored at Site U1307, and, with poor recovery of several intervals in Hole U1307A, it was impossible to construct a complete spliced record for the entire recovered section. There were, however, several long intervals of overlap between holes where cores could be correlated. The correlated segments have been appended to one another in the record. The offsets and composite depths are listed in Table T14. Correlation between Holes U1307A and U1307B was generally good down to the bottom of Core 303-U1307B-6H (56.5 mcd). Core 303-U1307A-6H was disturbed, had low recovery, and could not be correlated to Core 303-U1307B-6H. Consequently, Core 303-U1307B-7H was appended to Core 303-U1307B-6H. It correlated with Core 303-U1307B-7H but covered an almost identical interval, so Core 303-U1307B-8H was further appended and correlated with Core 303-U1307A-8H.

The tie between Core 303-U1307A-8H and Core 303-U1307B-9H at 76.4 mcd is tenuous but is supported by application of the average growth factor for Site U1307. Core 303-U1307A-9H was a partial APC stroke that recovered only 2.2 m and could not be correlated with any of the rest of the section. Correlation between holes is good from 76.4 mcd to 104.7 mcd. There is another tenuous correlation at 104.7 mcd (i.e., the base of Core 303-U1307B-11H to the top of Core 303-1307A-12H). Another good floating splice extends from Core 303-U1307A-12H to the base of Core 303-U1307B-15H (146.2 mcd), which cannot be matched to the top of Core 303-U1307A-17H.

The bottom few cores from each hole are poorly matched, but there is reasonable correlation between the middle segments of Cores 303-1307A-17H and 303-1307B-16H. Natural gamma ray (NGR) data suggest a correlation between the bottom of Core 303-U1307B-16H and the top of Core 303-U1307A-18H.

The sections of core used for the splice are identified in Table T15. We avoided using the first (top) section of each core wherever possible because it was often disturbed and contained gravel-sized ice-rafted debris. The cores from Site U1307 provide a discontinuous stratigraphic sequence to ~160 mcd with the problematic intervals described above.

A growth factor (GF) of 1.06 is calculated by linear regression for both holes at Site U1307, indicating a 6% increase in mcd relative to mbsf (Fig. F19). We used this value of GF to calculate corrected meters composite depth (cmcd) presented in Table T14 to aid in the calculation of mass accumulation rates.

We calculated sedimentation rates using paleomagnetic and biostratigraphic datums. Linear regression provides a mean sedimentation rate of 4.9 cm/k.y. for the entire section cored at Site U1307 (Fig. F20). Using only paleomagnetic datums, interval sedimentation rates are still relatively uniform, varying between 2.7 and 7.6 cm/k.y., with a short interval between 148.3 and 148.9 mcd having a sedimentation rate of only 0.5 cm/k.y. (Table T16).