UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Seismic evidence for crustal underplating beneath a large igneous province: The Sierra Leone Rise, equatorial Atlantic

Jones, EJW; McMechan, GA; Zeng, X; (2015) Seismic evidence for crustal underplating beneath a large igneous province: The Sierra Leone Rise, equatorial Atlantic. Marine Geology , 365 (C) pp. 52-60. 10.1016/j.margeo.2015.03.008. Green open access

[thumbnail of 1-s2.0-S0025322715000870-main.pdf]
Preview
Text
1-s2.0-S0025322715000870-main.pdf

Download (3MB) | Preview

Abstract

Wide-angle seismic profiles reveal anomalously thick crust with a high-velocity (> 7.3 km s− 1) zone under the Sierra Leone Rise, a major mid-plate elevation in the Atlantic lying between the Cape Verde platform and the Cameroon Volcanic Line. A profile recorded over the crest using an ocean-bottom seismometer and surface sonobuoys shows that beneath a 3 km water layer and 1 km of sediments, the basement extends to 16–20 km below sea level. Most velocity-depth values fall outside the expected range for Mesozoic–early Cenozoic ocean floor and stretched continental crust. The detection of 7.3–7.5 km s− 1 material beneath thick, lower-velocity volcanics suggests that magmatic underplating of the crust has occurred. A prominent change in velocity gradient 10–12 km below sea level may mark the transition to underplated material emplaced during the late Cretaceous–early Cenozoic. A pronounced change in Moho depth lies on the line of a long offset fracture zone extending from the African margin, implying underplating was influenced by a pre-existing discontinuity in the lithosphere. Other seismic lines show 7.0–7.2 km s− 1 basement above the underplated zone extending into water depths of almost 5 km. This is probably the intrusive foundation of early-formed crust over a mantle hot-spot. It is suggested that the development of the Sierra Leone Rise is distinct from other Atlantic hot-spot features to which it has been linked because of its setting in a region of intense lithospheric shear.

Type: Article
Title: Seismic evidence for crustal underplating beneath a large igneous province: The Sierra Leone Rise, equatorial Atlantic
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.margeo.2015.03.008
Publisher version: http://dx.doi.org/10.1016/j.margeo.2015.03.008
Language: English
Additional information: © 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: Large igneous province; Seismic structure; Crustal underplating; Magmatic underplating; Hot-spots; Atlantic Ocean
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/1471632
Downloads since deposit
118Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item