The U-channels were easily demagnetized by AF techniques and exhibited very satisfactory demagnetization behavior. Most of the NRM intensity is removed by peak fields of 50–60 mT, as shown by the intensity decay curves (Fig. F2A). Orthogonal vector component diagrams and stereographic projections reveal only one single component of magnetization. The demagnetization behavior and other magnetic properties (see below) are consistent with magnetite as the primary magnetic carrier. Magnetic parameters including magnetic inclinations and intensity from Hole 1202A are shown in Figure F3. The NRM inclinations are mostly positive and reach their highest values in the intervals between 108 and 112 mbsf and between 117.6 and 118.5 mbsf. The suspected geomagnetic excursion (Shipboard Scientific Party, 2002) could not be confirmed.
In the upper part of the sequence (0–69.4 rmbsf), orthogonal vector component diagrams of the NRM again exhibit very satisfactory demagnetization behavior (Fig. F2B). A secondary NRM component, imprinted by the coring or sampling process, is removed after the 20-mT demagnetization step, and the characteristic remanent magnetization (ChRM) can be readily determined. In the interval from 69.4 to 86.5 rmbsf, the NRM has a relatively low intensity (Fig. F4) that is unstable during demagnetization. Both broad directional variations and remagnetizations at higher demagnetization steps have been observed in this interval (Fig. F2C). In the remainder of the section, the NRM usually demagnetizes well up to peak fields of 50 or 60 mT, but some remagnetization occurs in higher fields (Fig. F2D). Similar behavior has been observed at other locations (e.g., Shipboard Scientific Party, 2001) and may provide evidence for the presence of iron sulfides, which can acquire a gyromagnetic remanence during the AF demagnetization (Snowball, 1997; Sagnotti and Winkler, 1999). We cannot exclude the possibility that the remagnetization is caused by a spurious component during the demagnetization process.
The magnetic parameters from Hole 1202B are shown in Figure F4. The NRM inclinations are mostly positive, but shallow and negative values occur in intervals 50–62, 73–81, and 103–110 rmbsf. The NRM inclinations are distinctly noisier below 114 rmbsf, which is the depth at which the coring system was changed from APC to XCB.
The geomagnetic field at the latitude of Site 1202 (24.8°N) has an inclination of 42.7°, assuming a geocentric axial dipole model that is sufficiently steep to determine magnetic polarity in the APC and XCB cores, which lack azimuthal orientation.
Positive magnetic inclinations indicate that only the Brunhes (C1n) normal polarity chron (Berggren et al., 1995) is recorded in these sediments. Whether the Brunhes Chron is complete cannot be determined from the magnetostratigraphy.