In Holes 1131A and 1131B, the nonmagnetic cutting shoe was used with standard APC barrels for Cores 182-1131A-3H through 7H and 182-1131B-3H through 7H. The nonmagnetic cutting shoe had a nonmagnetic flapper valve. A standard 10-finger core catcher was incorporated because of earlier core loss. Sections 182-1131B-3H-3 and 3H-4 and 182-1131B-4H-3 and 4H-4 were measured both as whole cores and as archive halves.
Plots of declination are given in Figure F5 for Cores 182-1131A-2H through 7H for NRM and after 20 mT demagnetization. In the even-numbered cores, which were cored with the standard shoe, the declination is close to zero, whereas in the odd-numbered cores, which were cored with the nonmagnetic shoe, the direction of magnetization departs from 0°. Agreement with the tensor tool is not very good for any of the cores.
The lower panels of Figure F5 show the results for Hole 1131B. Scatter in the data is less than for Hole 1131A, and the distinction between the results for cores taken with the nonmagnetic shoe and those taken with the standard shoe is also less. The agreement between tensor tool and remanence for the cores taken with the nonmagnetic shoe is better for Hole 1131B than for Hole 1131A.
Tensor tool measurements were available for Cores 182-1131A-3H through 7H and for Cores 182-1131B-3H through 7H. The agreement between the direction of magnetization of the cores and the tensor tools was poor. The tensor tool orientations for the cores taken with the nonmagnetic corer in Hole 1131B were 329°, 336°, and 335°. One would expect tensor tool orientations to be very randomly between 0° and 360°; therefore, these orientations are suspect.
Figure F6 shows the comparison between the whole-core and archive measurements for Sections 182-1131B-3H-3 and 3H-4, and 182-1131B-4H-3 and 4H-4. In the top row of panels, declination, inclination, and intensity are shown for Sections 182-1131B-3H-3 and 3H-4, and below are the corresponding plots for Sections 182-1131B-4H-3 and 4H-4. In each plot, the values for the whole-core NRM, the whole core after 20 mT demagnetization, and the archive core are shown. There is no NRM plot for the archive-half core because it was already demagnetized as part of the whole core. The declination values after all three measurements are very similar for Sections 182-1131B-3H-3 and 3H-4, as are the demagnetized values for both the inclination and intensity. The pattern is a little different in Sections 182-1131B-4H-3 and 4H-4 in that the declination, inclination, and intensity of the archive half of Section 182-1131B-4H-4 differ significantly from the whole-core measurements. This is consistent with a larger radial moment in the cores taken with the standard corer but needs to be checked by discrete measurements from the cores to assess the radial moments present.
At Site 1131 as at Site 1128, there is a general tendency for cores taken with the standard cutting shoe to show declinations that are more closely aligned with 0° declination than are the declinations in the cores taken with the nonmagnetic shoe. The comparison between half-core and whole-core measurements revealed greater differences in the cores taken with the standard cutting shoe than with the nonmagnetic shoe, which is consistent with a greater radial moment in cores taken with the standard cutting shoe.