Explaining the Mumbai High offshore negative gravity anomaly, India

Abstract

The large negative free-air gravity anomaly in the Mumbai offshore (Mho) is located on the inner shelf of the West Coast Continental Margin of India (WCMI). It overlaps the giant Mumbai High oil field (MHf) which rests on a huge anticlinal Archean basement high. This is intriguing as such a structural feature would normally be expected to show a positive, and not a negative anomaly. While many workers have put forward hypotheses explaining gravity anomalies of major morphological features located beyond the shelf in the WCMI, the Mho on the inner shelf remains unstudied till date. This paper presents, for the first time, a hypothesis explaining the Mho, based primarily on the interpretation of well data from MHf, which provides crucial insights into the complex nature and composition of the basement. The observations and evidence from studies by previous workers that helped construct the hypothesis are cited. The study concludes emplacement of localized magma pond below a down-warped Moho as the causative for the pronounced negative gravity anomaly (Mho).