Coring at Site 1259 extended to a total depth of 559 mbsf. Three discrete intervals were targeted for overlap and composite section construction: (1) the lower Eocene foraminifer nannofossil chalks of lithostratigraphic Subunit IIC (including the P/E boundary [~305–375 mcd]), (2) the Campanian–Maastrichtian nannofossil chalks and calcareous siltstones of lithostratigraphic Subunit IIIB (~440–505 mcd), and (3) the Cretaceous black shales (lithostratigraphic Unit IV—calcareous claystone with organic matter [~520–555 mcd]). Magnetic susceptibility and gamma ray attenuation (GRA) bulk density data were collected with the multisensor track (MST) at 2.5-cm intervals on all whole-core sections from Holes 1259A, 1259B, and 1259C. Natural gamma ray (NGR) data were collected at 7.5-cm intervals on all whole cores from Holes 1259A, 1259B, and 1259C. Noncontact resistivity (NCR) data were collected at 2.5-cm intervals on whole cores from Hole 1259A. No NCR data were collected from Holes 1259B and 1259C (see "Physical Properties" in the "Explanatory Notes" chapter for a discussion of problems associated with the calibration and accuracy of NCR data). Spectral reflectance data were collected at 2.5-cm intervals on all split cores. Magnetic susceptibility was the primary data set used to correlate between holes in the lower Eocene and the Campanian–Maastrichtian sections of Site 1259. Within the Cretaceous black shales, NGR and GRA bulk density data provided the most reliable core-to-core comparisons.
The depth offsets that compose the composite section for Holes 1259A, 1259B, and 1259C are given in Table T11. In the lower Eocene and P/E boundary section (~305–375 mcd) and from the K/T boundary to the top of the Cretaceous black shales (440–505 mcd), magnetic susceptibility is a sensitive indicator of the fluctuations in the carbonate/clay ratio in the calcareous chalks that compose these two intervals. These magnetic susceptibility data (Figs. F14, F15), combined with the good RCB recovery in all three holes, allowed the construction of a continuous composite section for both intervals. The quasiperiodic variability of the claystone and chalk/limestone composing the black shale unit resulted in strong signal-to-noise ratios in both the GRA bulk density and NGR data sets (Fig. F16). These data sets, combined with good RCB recovery over a significant portion of the black shale interval, allowed for the construction of a continuous composite section from ~520 to 555 mcd. Poor recovery from 495 to 520 mcd precluded the construction of a composite section in this upper interval of the Cretaceous black shales.
The composite depth scales constructed for each of these three intervals, however, cannot be tied to the intervals above and below because of gaps in the record resulting from poor recovery (e.g., the interval from 375 to 400 mcd). Thus, the absolute depth of these composite sections cannot be accurately determined. As at the other Leg 207 sites, these composite intervals "hang" in the composite depth scale linked only to correlative cores in other holes but not to the other discrete continuous intervals above or below.
The periodic variability in the lower Eocene and Campanian–Maastrichtian intervals at Site 1259 will provide a good basis for postcruise cyclostratigraphic studies. Age control is excellent, with well-defined paleomagnetic datums in both sections (e.g., Chrons C22n and C24 in the lower Eocene and Chrons C30n and C32n in the Campanian–Maastrichtian) (see "Paleomagnetism"). Preliminary investigation suggests the dominant periodicities of the magnetic susceptibility data are Milankovitch in nature.
Following construction of the composite depth section at Site 1259, three discrete splice records were assembled for the aligned cores in the intervals 305–375, 440–505, and 520–555 mcd (Table T12; Figs. F14, F15, F16). Hole 1259A cores were used as the "backbone" for each splice, with cores from Holes 1259B and 1259C used to span gaps between cores in Hole 1259A. Figure F17 provides a qualitative estimate of the confidence of the core-to-core correlations and the resultant splices between cores in Holes 1259A, 1259B, and 1259C. When utilizing these splices as sampling guides, it is advisable to overlap a few decimeters from different holes to accommodate anticipated postcruise revisions to the composite depth scale. The reason for this approach is that distortion of the cored sequence can lead to stretching or compression of sedimentary features. Because much of the distortion occurs in individual cores on depth scales of <9 m, it was not possible to align every feature in the MST and color reflectance records. However, at crossover points along the splice, care was taken to align highly identifiable features from cores in each hole. Postcruise work will establish a detailed correlation between holes by establishing a revised meters composite depth (rmcd) scale that allows differential stretching and squeezing in cores.