Lithology of sediments from the Arabian Sea, supplement to: Calves, Gerome; Clift, Peter D; Inam, Asif (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

• Main Authors: Calves, Gerome, Clift, Peter D, Inam, Asif
• Format: Article in Journal/Newspaper
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2008
• Subjects: Drilling/drill rig; Leg24; Glomar Challenger; Deep Sea Drilling Project DSDP; Newfoundland
• Online Access: https://dx.doi.org/10.1594/pangaea.717633; https://doi.pangaea.de/10.1594/PANGAEA.717633

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.