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doi:10.2204/iodp.proc.320321.109.2010

Stratigraphic correlation and composite section

Special Task Multisensor Logger data were collected at 5 cm intervals from Holes U1337B–U1337D and compared to the Whole-Round Multisensor Track (WRMST) data obtained at 2.5 cm resolution from Hole U1337A. In this way drilling was monitored in holes after Hole U1337A in real time to maximize the opportunity for the recovery and construction of a stratigraphically complete composite section. Cores from Holes U1337B to U1337D were measured on the WRMST for final correlation. After the cores were split and described, a composite section and spliced sequence were constructed.

Magnetic susceptibility, NGR, GRA bulk density, light reflectance (L*), and scanned images all contributed to correlation between holes at Site U1337. GRA and magnetic susceptibility are illustrated in Figures F37 and F38. Features between all records are well aligned to ~220 m CCSF-A. Offsets and composite depths are listed in Table T23.

Below 220 m CCSF-A, a confused interval of ~50 m was characterized by incomplete recovery in all holes (Fig. F39). A short gap may persist at 220 m CCSF-A and Core 321-U1337C-9H has been appended to the bottom of Core 321-U1337C-8H, suggesting another short break in recovery. At 265 m CCSF-A a definite break occurs apparently caused by poor recovery of a hard chert layer. Comparison of GRA records with downhole density logs (see "Downhole measurements") indicate that most of the section is represented in the cored material. Between 265 and 440 m CCSF-A a continuous correlation can be made although the amplitude of the variations in properties are such that there may be some incorrect tie points. A major gap occurs at 440 m CCSF-A where Core 321-U1337A-44X is appended to Core 321-U1337A-43X. Particularly puzzling is the large gap seen in Holes U1337C and U1337D at the same level. This "void" is the result of forcing the color change at ~445 m CCSF-A to the same level at all holes. It may be that this color change occurs higher in the section at the latter two holes than in Hole U1337A. This question is not resolvable using data available. Splice tie points are listed in Table T24.

A growth factor of 1.12 is calculated by linear regression of CSF versus CCSF-A for all Site U1337 cores, indicating a 12% increase in CCSF-A relative to CSF depth (Fig. F14). We used this value to calculate the CCSF-B scale presented in Table T23 to aid in the calculation of sedimentation and mass accumulation rates.

Sedimentation rates

All principal biostratigraphic datums and a set of 26 tentatively interpreted paleomagnetic reversals (restricted to the APC-cored sections) (Table T25; see also "Biostratigraphy" and "Paleomagnetism") were used in establishing age control (Fig. F40). The linear sedimentation rate at Site U1337 decreases from 21 m/m.y. in the middle Miocene to 17 m/m.y. in the late Miocene and stays relatively constant in the remainder of the section (Fig. F40).

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