Anomalous subsidence on the rifted volcanic margin of Pakistan: No influence from Deccan plume
The role of hotter than ambient plume mantle in the formation of a rifted volcanic margin in the northern Arabian Sea is investigated using subsidence analysis of a drill site located on the seismically defined Somnath volcanic ridge. The ridge has experienced > 4 km of subsidence since 65 Ma and lies within oceanic lithosphere. We estimate crustal thickness to be 9.5-11.5 km. Curiously < 400 m of the thermal subsidence occurred prior to 37 Ma, when subsidence rates would normally be at a maximum. We reject the hypothesis that this was caused by increasing plume dynamic support after continental break-up because the size of the thermal anomalies required are unrealistic (> 600 °C), especially considering the rapid northward drift of India relative to the Deccan-Réunion hotspot. We suggest that this reflects very slow lithospheric growth, possibly caused by vigorous asthenospheric convection lasting > 28 m.y., and induced by the steep continent-ocean boundary. Post-rift slow subsidence is also recognized on volcanic margins in the NE Atlantic and SE Newfoundland and cannot be used as a unique indicator of plume mantle involvement in continental break-up. Crown Copyright © 2008.
Publication Source (Journal or Book title)
Earth and Planetary Science Letters
Calvès, G., Clift, P., & Inam, A. (2008). Anomalous subsidence on the rifted volcanic margin of Pakistan: No influence from Deccan plume. Earth and Planetary Science Letters, 272 (1-2), 231-239. https://doi.org/10.1016/j.epsl.2008.04.042