Surface-ship gravity measurements in the Agulhas bank area, south of South Africa

In 1962 reconnaissance gravity measurements were made in the South Indian Ocean immediately south of South Africa with a Graf-Askania surface ship gravimeter with automatic beam control. A free-air gravity anomaly chart with an average standard deviation of about 7 mgal is presented. Errors due to the response of the meter, instrumental drift, imperfect navigation, platform deviation, the Harrison effect and cross-coupling are discussed. It is concluded that the Harrison, cross-coupling, and navigational errors should generally be less than 6 mgal each but may occasionally be much larger. Other errors are insignificant by comparison. A crustal profile, calculated by the technique of Talwani and others (1959) suggests that the structure of the Agulhas Bank is not markedly dissimilar from other published continental shelf-slope profiles but the Agulhas Plateau may not be typically oceanic.