Development of the negative gravity anomaly of the 85 degrees E Ridge, northeastern Indian Ocean – A process oriented modelling approach

• Main Authors: Sreejith, K.M, Radhakrishna, M, Krishna, K.S, Majumdar, T.J
• Format: Journal Article
• Language: English
• Published: Indian Academy of Sciences 2011
• Subjects: gravity anomalies; lithosphere; plate tectonics; sediments; seismic reflection profiles

The 85 degrees E Ridge is associated with two contrasting gravity anomalies: negative anomaly over the north part (up to 5 degrees N latitude), where the ridge structure is buried under thick Bengal Fan sediments and positive anomaly over the south part, where the structure is intermittently exposed above the seafloor. Ship-borne gravity and seismic reflection data are modelled using process oriented method and this suggest that the 85 degrees E Ridge was emplaced on approximately 10–15 km thick elastic plate (Te) and in an off-ridge tectonic setting. Gravity anomalies for different crust-sediment structural configurations of the ridge existing at three geological ages, such as Late Cretaceous, Early Miocene and Present were simulated. The gravity anomaly of the ridge in the north has changed through time from its inception to present. During the Late Cretaceous the ridge was associated with a significant positive anomaly with a compensation generated by a broad flexure of the Moho boundary. By Early Miocene the ridge was approximately covered by the postcollision sediments and led to alteration of the initial gravity anomaly to a small positive anomaly. At present, the ridge is buried by approximately 3 km thick Bengal Fan sediments on its crestal region and about 8 km thick pre- and post-collision sediments on the flanks. This geological setting had changed physical properties of the sediments and led to alter the minor positive gravity anomaly of Early Miocene to the distinct negative gravity anomaly