At Site 1134, archive halves of all APC and XCB cores were measured using the 2-G 760-R magnetometer, except for those core sections obviously disturbed by drilling, or with inadequate recovery for meaningful measurements. The cores were routinely measured at 5- to 10-cm intervals at natural remanent magnetization (NRM) and after 20-mT demagnetization. These analyses were performed using the methods described in "Paleomagnetism" in the "Explanatory Notes" chapter. Four whole-core sections were measured to compare with standard archive half-core measurements, in connection with the experimental coring using nonmagnetic cutting shoes and APC assemblies. In addition, a comparison between the effects of the cutting shoe (Hole 1134A) and the complete core-barrel assembly (Hole 1134B) was made. Discrete samples were taken to compare the orientation they yield with that of the Tensor tool and to establish the rock magnetic characteristics of the core. Discrete sample analysis will be largely shorebased.
The results of long-core measurements of the nannofossil ooze cores from Holes 1134A and 1134B were only partially successful. The NRM is dominated by a vertically downward coring contamination that was largely removed by 20-mT demagnetization. After this, the signal was almost uniformly reduced to near the noise level of the instrument (Fig. F6). The long-core measurements did give an interval between 0 and 30 mbsf of negative inclination. However, the signal was very weak, with intensities falling from on the order of 10-4 A/m near the top of the core to on the order of 10-5 A/m near 120 mbsf. The intensity then increased substantially, which appeared to coincide with the first appearance of chert in the hole. At 160 mbsf, the intensity again decreased. A continuous interval from ~120 to ~145 mbsf gave a sequence of reversals that could be correlated within the Miocene segment of the geomagnetic polarity time scale (GPTS).
Analysis of Sample 182-1134A-10H-CC showed that there is a stable normal moment in the upper weakly magnetized section. (Fig. F7). Further work with these samples will be performed postcruise.
In Core 1134A, the late Pleistocene magnetostratigraphy is defined to ~40 mbsf, with the Brunhes/Matuyama boundary at 32 mbsf, although the data quality in this interval is only marginal (Fig. F8). In Core 1134B the Brunhes/Matuyama boundary is at 38 mbsf. Poor data precluded further long-core interpretations in the interval from ~50 to 90 mbsf. However, below this interval, although the intensity remains low, reversals were again apparent. The availability of an estimate of age and sedimentation rate from biostratigraphic data permitted a possible correlation with the GPTS in Cores 182-1134A-13H through 17X, which corresponds to an interval of high remanence intensities that are nearly two orders of magnitude higher than in the shallower cores. The sequence of reversals is not long enough to give unequivocal magnetostratigraphic data, but a possible correlation is given in Figure F8.