Crustal Magnetization in the South Atlantic from Inversion of Magnetic Anomalies.

摘要

A method for inverting magnetic anomalies in the presence of topography is used to analyze and describe crustal magnetization along 12 profiles in the South Atlantic. The profiles are approximately 2000 km long and are almost perpendicular to the trend of the magnetic anomalies. A bandpass filter is used to remove long-wavelength anomalies unassociated with seafloor-spreading processes. A filter that pases only wavelengths between 200 and 3 km produces a magnetization that approximates the positive and negative aspects of the geomagnetic reversal sequence, the positive aspects originating from normally magnetized portions of the crustal source. A 6-km thick crust is assumed in order to produce magnetizations consistent with dredged oceanic rocks. A long-wavelength pattern is evident in the magnetization solutions. The highest magnetization are associated with the ridge crest (1.35-1.74 A/m). Within the western section of the study area, a sharp decrease in magnetization occurs within 100 km of the ridge crest (4.5 Ma). A minimum in magnetization is reached at 400 km from the axis or at 18 Ma (0.51-0.57 A/m). The magnetization then gradually increases out to 1100 km or 86 Ma (0.34-0.43 A/m). Keywords: Oceanic crust; Geodynamics; Geomagnetism/paleomagnetism. Reprints. (edc)