Estimating the age of volcanism in Seamount Provinces of the Northeast Indian Ocean

Abstract

The breakup of Australian landmass from Greater India, part of the late dispersal of Gondwana, started around 136 Ma. Concurrent with this breakup was the eruption of significant volumes of volcanics, on both the continental margins of Australia and India, including the North-West shelf, and in the ocean basin separating the two. Later submarine volcanism occurred within the Christmas Island Seamount Province (ChrISP), or which Christmas and Cocos (Keeling) Islands are two subareal examples. These volcanic events significantly impacted the thermal evolution of these margins, but the ultimate cause for this disparate volcanism, and the relationship between margin volcanics and later submarine volcanic events, remains unclear. The study tries to establish a relation between the volcanic activities and look for any evidence of these volcanic episodes. The study uses gravity, magnetic, and subsidence modelling to attempt to constrain the structure and ages of seamount volcanism within the Christmas Island Seamount Province, including the Wharton Basin and Argo Abyssal Plain. Gravity modelling helps to determine the crustal structure and constrains the depth of limestone cap, which further helps in calculating when the seamount was sub aerially exposed and approximates the time since it was last exposure. The relationship between the volcanism observed in the ChrISP (Late Cretaceous to Eocene) and that recorded earlier on the NW shelf continental margin, remains ambiguous, and will be better constrained with forthcoming geochemical analysis. But the results presented here point to a rich and complex history of volcanism within the Indo-Australian plate.