Figure F3. The effect of a nonmagnetic core barrel, indicated by dashed lines, on the mean initial NRM intensities and mean AF demagnetized negative inclinations (25 mT) at Hole 1237B. Inclination means are taken only from the negative inclination values (normal polarity) of the upper 14 cores representing ~6.5 m.y. of geomagnetic behavior. The mean inclination prior to demagnetization is ~70° due to a significant drilling overprint. The expected geomagnetic inclination for normal polarity at this site latitude is -30° as indicated by the solid line. Shallower (less negative) inclinations during times of normal polarity indicate a bias caused by the drilling overprint. Sediment at Site 1237 is a pelagic nannofossil ooze and therefore represents a very different lithology than at the sites previously discussed. The weaker overprint observed in the nonmagnetic barrel cored sediments at Site 1237, though small, indicates that the use of a nonmagnetic core barrel will improve the probability of paleomagnetic success in a range of sediment types and intensity ranges.

Figure F3. The effect of a nonmagnetic core barrel, indicated by dashed lines, on the mean initial NRM intensities and mean AF demagnetized negative inclinations (25 mT) at Hole 1237B. Inclination means are taken only from the negative inclination values (normal polarity) of the upper 14 cores representing ~6.5 m.y. of geomagnetic behavior. The mean inclination prior to demagnetization is ~70° due to a significant drilling overprint. The expected geomagnetic inclination for normal polarity at this site latitude is -30° as indicated by the solid line. Shallower (less negative) inclinations during times of normal polarity indicate a bias caused by the drilling overprint. Sediment at Site 1237 is a pelagic nannofossil ooze and therefore represents a very different lithology than at the sites previously discussed. The weaker overprint observed in the nonmagnetic barrel cored sediments at Site 1237, though small, indicates that the use of a nonmagnetic core barrel will improve the probability of paleomagnetic success in a range of sediment types and intensity ranges.