Figure 4. Profiles related to the TOBI deep-tow magnetometer profile. A. Total-field magnetic anomaly recorded by a near-surface magnetometer. B. Total- field magnetic anomaly recorded by the TOBI magnetometer. The noise on the profile east of 120 km is principally instrumental in origin. C. Computed total- field magnetic anomaly caused by relief at the top of two-dimensional basement uniformly magnetized (1 A/m) in the direction of the present field. Relief was obtained from a coincident multichannel seismic reflection profile (see text and Fig. 4E). Note different vertical scale from the rest of the figure. D. Computed total-field magnetic anomaly based on the two-dimensional model shown below. E. Two-dimensional model used to compute the profile in Figure 4D. Seafloor spreading was assumed west of the peridotite ridge (PR) with intensities of magnetization of nent magnetization was I = +58°, D = -43° (after Galdeano et al., 1989); induced magnetization was assumed east of the peridotite ridge (values in A/m). Sites 898, 900, and 901 are indicated.

Figure 4. Profiles related to the TOBI deep-tow magnetometer profile. A. Total-field magnetic anomaly recorded by a near-surface magnetometer. B. Total-field magnetic anomaly recorded by the TOBI magnetometer. The noise on the profile east of 120 km is principally instrumental in origin. C. Computed total-field magnetic anomaly caused by relief at the top of two-dimensional basement uniformly magnetized (1 A/m) in the direction of the present field. Relief was obtained from a coincident multichannel seismic reflection profile (see text and Fig. 4E). Note different vertical scale from the rest of the figure. D. Computed total-field magnetic anomaly based on the two-dimensional model shown below. E. Two-dimensional model used to compute the profile in Figure 4D. Seafloor spreading was assumed west of the peridotite ridge (PR) with intensities of magnetization of

A/m, except for the J anomaly block (4 A/m); direction of remanent magnetization was I = +58°, D = -43° (after Galdeano et al., 1989); induced magnetization was assumed east of the peridotite ridge (values in A/m). Sites 898, 900, and 901 are indicated.