Evidence for a remanent contribution in Magsat data from the Cretaceous quiet zone in the south Atlantic

Abstract

Indirect evidence for the presence of a TRM component in the MAGSAT elevation data in the South Atlantic is found through forward modeling of the prominent positive anomaly overlying the Walvis Ridge. The anomaly contrast between the Ridge and adjacent Angola and Cape Basins is too large to be easily explained by induced magnetization of even alkali basaltic crust. However, most of the Walvis Ridge and portions of the adjacent basins lie within the Cretaceous Quiet Zone where prolonged normal polarity may have produced enough volume of material to cause a measureable contribution at satellite elevation. An additional 3 A/m (spread over the entire layer 2 thickness) TRM contribution is required to account for the Walvis Ridge anomaly. This value is within the range found for the Cretaceous Quiet Zone anomalies in the MAGSAT data in the North Atlantic.