Sagar Kanya Bathymetric High Complex: An extinct giant submarine volcanic caldera in the Eastern Arabian Sea?

Abstract

The marine geophysical investigations carried out in the Eastern Arabian Sea revealed the presence of a bathymetric high feature, referred to as the Sagar Kanya Seamount. The preliminary morphology and geophysical characteristics of this feature were studied along a single transect by earlier researchers, however, a detailed geophysical mapping over the entire extent of this feature is still awaited. The present study aims for such a detailed investigation on the Sagar Kanya Seamount and its adjacent regions using newly acquired high-resolution multibeam bathymetry data, complemented with sea surface magnetic and gravity data. Bathymetric map reveals the presence of well-defined bathymetric high features constituting three seamounts connected with structural high/ridge-like features, together representing a large nearly elliptical bathymetric high complex surrounding a region of nearly flat seafloor, referred to as the Sagar Kanya Bathymetric High Complex (SKBHC). The overall morphology of this feature closely resembles with the shape of a submarine volcanic caldera. The gravity anomalies over this feature are mostly correlatable with topography; elliptical-shaped gravity highs are associated with bathymetric highs and gravity lows are associated with the enclosed flat seafloor. Some magnetic anomalies observed over the SKBHC are correlatable with the topographic highs, while others are observed over the flat seafloor. The magnetic anomalies are interpreted as features of post-caldera volcanism. In view of the proximity of this feature to the R�union hotspot track, and the tectonic framework of the region, the genesis of the SKBHC is attributed to the R�union hotspot volcanism.