On isostasy at Atlantic-type continental margins

The concept of isostasy describes the manner in which topographic features on the earth's surface are compensated at depth. The present investigation is concerned with the isostatic mechanism at Atlantic-type continental margins. Particular attention is given to the question whether the flexure model of isostasy, which has successfully been used at other geological features in oceans, is applicable at margins. Cross-spectral techniques are used to analyze the relationship between free air gravity and topography at Atlantic-type continental margins. The relatively old eastern North America is found to be associated with the highest value of the effective elastic thickness in the range 10-20 km, while the relatively young Coral Sea/Lord Howe rise is associated with the lowest value of less than 5 km. The differences in estimates of effective elastic thickness between margins can be explained by a simple model in which the flexural strength of the basement increases with age.