Archive halves of APC (to 140 mbsf) and XCB (to 218 mbsf) cores recovered at Site 1101 were measured at 5-cm intervals. Measurement of the natural remanent magnetization (NRM) of all cores was done at the 0- (NRM), 10-, 20-, and 30-mT alternating field (AF) demagnetization steps (Tables T4, T5, T6, T7, T8, all also in ASCII format in the TABLES directory). The distribution of inclination values obtained after demagnetization at 30 mT confirms the very good quality of the magnetic record, as the two lobes of the log-normal distribution are centered at -75º and +78º, in agreement with the value of ±76º expected at this latitude (Fig. F17). The four discrete samples that were progressively demagnetized (0-80 mT) gave linear demagnetization paths, and their inclinations agree well with the split-core inclinations (Tables T9, T10, both also in ASCII format in the TABLES directory).

Results obtained from Hole 1101A provide a near-continuous paleomagnetic data set down to 218 mbsf. The magnetostratigraphy has been constructed from records of the inclination and intensity of remanence (Fig. F18; Table T11). Declination was not used in the magnetostratigraphic record, as the cores were not azimuthally oriented. The Brunhes/Matuyama (0.78 Ma) boundary is recorded at ~55 mbsf. The Jaramillo (0.99-1.07 Ma) Subchron is seen between 71.2 and 76 mbsf and the Olduvai (1.77-1.95 Ma) between 121.2 and 127 mbsf. The oldest full polarity zone that is unambiguously recorded in the sediments is Chron C2An.1n (2.581-3.04 Ma), between 166 and 209.4 mbsf. Assuming constant sedimentation rates between geomagnetic polarities, the two short intervals of normal polarity observed at 81.4 and 136.4 mbsf seem to correspond to the Cobb Mountain and Reunion Events, respectively.

From 209.4 mbsf to near the base of the hole, the sediments are reversely magnetized. At the very base of the hole, the inclination is shallow, possibly indicating a polarity transition zone (Fig. F18). If this is the Chron C2An.1r-C2An.2n reversal boundary, the age of the sediments at the bottom of the hole becomes 3.11 Ma. Alternatively, an age of 3.13 Ma is obtained by assuming a constant sedimentation rate from the Chron C2An.1n interval to the base of the hole.