. Collected reprints, Essa Institute for Oceanography. Oceanography MAGNETIC ANOMALIES IN THE GULF OF MEXICO 523. 930 92° 91" 90" 89° 88° 87° 86° 85° Fig. 4. Magnetic total intensity anomalies of the Campeche bank area. On some cruises seismic reflection and magnetic data were acquired simultaneously. The reflec- tion data indicate few sub-bottom horizons under the magnetic trends and those horizons are essentially horizontal. To seaward of the magnetic trends seismic reflection profiles show sub-bottom dome-like structures which are now believed to be ridges [Ewing and
. Collected reprints, Essa Institute for Oceanography. Oceanography MAGNETIC ANOMALIES IN THE GULF OF MEXICO 523. 930 92° 91" 90" 89° 88° 87° 86° 85° Fig. 4. Magnetic total intensity anomalies of the Campeche bank area. On some cruises seismic reflection and magnetic data were acquired simultaneously. The reflec- tion data indicate few sub-bottom horizons under the magnetic trends and those horizons are essentially horizontal. To seaward of the magnetic trends seismic reflection profiles show sub-bottom dome-like structures which are now believed to be ridges [Ewing and Antoine, 1965]. These structural features have no magnetic ex- pression. In an attempt to define the configura- tion of the materials producing the small-ampli- tude anomalies, magnetic anomalies were com- puted for various two-dimensional models by the procedure of Tahvani and Heirtzler [1964]. These calculations suggest that bodies about 30 km wide with a susceptibility contrast of no more than 2 X 10"* cgs and magnetized by in- duction could be the source. The depth to the upper surface of these bodies could not be ac- curately determined because of the difficulty in fitting the computed slopes to the observed slopes of the small-amplitude anomalies, but it seems likely that the depth of burial is greater than 5 km. Campeche bank area. Magnetic anomalies of Campeche bank are shown in Figure 4. The deep water areas to the north and west of the bank are relatively free of sharp magnetic variations. The Sigsbee knolls are a unique topographic feature, located in the vicinity of 25°45'N and 92°30^. These knolls and adjacent buried dome structures have no magnetic expression. It has recently been shown that this character- istic is not unique to the Sigsbee knoll area but that many buried dome-like features have little or no magnetic effect [Windisch et al., 1965]. The most distinct magnetic features of the Campeche bank north of Yucatan are the elongated closed con
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