Interpretation Of A Magnetic Anomaly On Continental Rise Off Cape Hatteras

A magnetic profile off Cape Hatteras has been analyzed. The reconstruction of the geologic structure below the sedimentary layer has been attempted, by comparing the theoretical profiles of two magnetic models with the field data. Magnetic reversals seem to fit the seismic section better than a model based purely on induced magnetism. A proton precession magnetometer profile between the continental sl. ope off Cape Hatteras and the Bermuda rise [Rona and Clay, 1967] indicates the presence of a deep-seated magnetic structure [Drake et al., 1963] about 10 km under the continental rise between 80 and 300 km southeast of Cape Hatteras. Regionally the magnetic field over both the lower continental rise and the Hatteras abyssal plain off Cape Hatteras was observed to be smooth relative to the disturbed magnetic field )ver the Bermuda rise [Heirtzler and Hayes, 1967]. The magnetic profile shows a trough, bordered by two peaks of roughly 200-gamma amplitude on either end, situated between the 2000-meter isobath off Cape Hatteras and the physiographic transition between the upper and lower parts of the continental rise (Figure 1). This anomalous trough is broken by two smaller features of 50- to 100-gammas amplitude (Figure 1). The northwestern peak of the trough coincides with one portion of the 'slope anomaly' discussed by Drake et al. [1963]. It has been shown that a magnetic peak is associated with a basement ridge under sections of the c.ontinental slope [Drake et al., 1959, 1963; Worzel, 1965]. Qualitatively, it may be expected that the magnetic structure off Cape Hatteras could be produced either by a shallow sediment-filled trough with a seaward ridge [Drake et al., 1963] or by reversals in the magnetic field below the sedimentary layers [Vine and Matthews, 1963]. To determine the configuration of the base