40Ar¯39Ar age of the St. Marys Islands volcanics, southern India: record of India¯Madagascar break-up on the Indian subcontinent

The new compilation of aeromagnetic data of the Arabian Shield has made possible the analysis of the direction of magnetization. The method adopted consists of examining the behavior of the autocorrelation function calculated on sub-zones of the total map. In general, it is possible to reach the direction of magnetization through some iterations. In the case of the Arabian Shield, the goal is reached easily and, surprisingly, it appears that the magnetization of sources is vertical and, consequently, remanent. Although of relative precision, this technique provides strong indications in favor of a polar position for the Arabian Peninsula because only in a such position can the magnetization be vertical. In addition, it can be seen that the major part of the vertically magnetized rocks are the deepest ones. A discussion on the age of this polar position suggests a probable date around 650¯630 Ma.