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doi:10.2204/iodp.proc.303306.113.2006

Stratigraphic correlation

The upper 10–12 cores of all holes drilled at Site U1314 were measured for magnetic susceptibility at 5 cm resolution using the “Fast Track” magnetic susceptibility core logger (MSCL) soon after recovery. Initial correlation based on these data was used to monitor the coring breaks and ensure that they did not coincide for any two holes. It was confirmed that depth offsets between the holes were large enough to fill coring gaps, and subsequently, correlation based on MSCL measurements did not influence coring operations.

The final meters composite depth (mcd) scale (Table T19) and a spliced stratigraphic section (Table T20) were constructed after gamma ray attenuation (GRA) density, natural gamma radiation (NGR), magnetic susceptibility, magnetic intensity and inclination, and color reflectance data became available. Coring deformation as the result of large ship heave experienced during operations was severe in much of the upper portion of Hole U1314A, particularly in Cores 306-U1314A-2H, 5H, 6H, and 12H, but also in other intervals (Table T21). Weather conditions were more favorable during coring in Holes U1314B and U1314C, resulting in excellent core quality.

Prior to uploading the data into Splicer for correlation, we removed those intervals that contained coring disturbance or voids. Each of these cleaned data sets shows prominent amplitude variations related to changes in lithology. For depth-shifting the cores from Site U1314, we relied mainly on between-hole correlation of distinctive magnetic susceptibility and NGR variations (Figs. F21, F22, F23). These correlations were confirmed to be consistent with geomagnetic polarity reversals recorded in the paleomagnetic inclination (Fig. F20).

Apart from a single problematic interval with a tenuous tie between Core 306-U1314C-3H and Core 306-U1314B-4H at 25.90 mcd, correlation was straightforward, the mcd scale was well resolved, and the spliced section was complete to 281 mcd. Because of the core disturbance in the upper part of Hole U1314A, the splice in the interval 0–188.30 mcd was built from Holes U1314B and U1314C, with the exception of a short interval (65.80–69.50 mcd), where an undisturbed section of Core 306-U1314A-8H was incorporated into the composite section (Table T20). From 188.30 to 300 mcd the splice was constructed from Holes U1314A and U1314B because Hole U1314C was drilled only to 222 mcd. The two deepest cores, 306-U1314B-29H and 30H (interval not cored in Holes U1314A and U1314C), were appended to the splice (Figs. F21, F22, F23). A growth factor of 1.08 is calculated by linear regression for the three holes at Site U1314, indicating an 8% increase in mcd relative to mbsf.

Unlike the previous two sites, the lightness variations do not correlate as well with the oxygen isotope stack of Lisiecki and Raymo (2005), nor do the sediments at Site U1314 have the large changes in lightness that were obvious at Sites U1312 and U1313. Instead, the color varies mainly through shades of greens and grays with some lighter intervals (cycles) occurring mainly in the upper 70 mcd.

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