Transform tectonics and thermal rejuvenation on the Cote d'Ivoire-Ghana margin, West Africa

Online Access: Get full text
doi: 10.1144/gsjgs.154.3.0483
Author(s): Clift, P. D.; Lorenzo, J.; Carter, A.; Hurford, A. J.
Ocean Drilling Program, Leg 159, Shipboard Scientific Party, College Station, TX
Author Affiliation(s): Primary:
Woods Hole Oceanographic Institution, Department of Geology and Geophysics, Woods Hole, MA, United States
University of Liverpool, United Kingdom
Louisiana State University, United States
University College London, United Kingdom
Volume Title: Tectonic, magmatic and depositional processes at passive continental margins
Volume Author(s): Roberts, Alan M., prefacer; Kusznir, Nick J.
Source: Journal of the Geological Society of London, Vol.154 (Part 3), p.483-489; Symposium on Geological processes at passive margins, London, United Kingdom, February 1996, prefaced by Alan M. Roberts and Nick J. Kusznir. Publisher: Geological Society of London, London, United Kingdom. ISSN: 0016-7649 CODEN: JGSLAS
Note: In English. 32 refs.; illus., incl. sect., sketch map
Summary: Formation of a pronounced basement ridge along many transform continental margins has been attributed to a variety of processes during continental break-up, including transpressional crustal thickening, and thermal rejuvenation and igneous underplating during passage of a spreading ridge. ODP drill holes on the Cote d'Ivoire-Ghana margin now provide the first opportunity to quantify the vertical motions along this type of margin. Apatite fission-track dating of detrital sands suggests that large amounts of erosion occurred on the flanks of an intra-continental wrench zone that predated margin formation. Rapid cooling of >120°C at 120-115 Ma corresponds to erosion of 3.5-5 km along the conjugate Brazilian margin, reflecting c. 1 km of tectonically driven uplift, subaerial erosion, and isostatic uplift due to unloading. Following rift initiation at 120 Ma (Aptian), an oceanic spreading axis passed adjacent to this part of the margin at 90 Ma (Cenomanian). Maximum uplift during the ridge-transform intersection was 390 m. considerably less than the 2000+ m predicted by heat conduction models in local isostatic equilibrium. The modern ridge is partially the product of thicker crust (22 km) underlying the ridge than the adjacent Deep Ivorian Basin (19 km), and partially related to flexural unloading of the transform ridge between the end of intra-continental wrenching and ridge-transform intersection. Flexural coupling between the continental and oceanic plates since ridge-transform intersection has caused a progressive depression of the offshore margin, estimated at about 650 m in the study area.
Year of Publication: 1997
Research Program: ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Africa; Apatite; Atlantic Ocean; Continental margin; Cretaceous; Crustal thickening; Erosion; Faults; Fission-track dating; Flexure; Geochronology; Geophysical methods; Geophysical profiles; Geophysical surveys; Ghana; Gulf of Guinea; Ivory Coast; Leg 159; Mesozoic; Multichannel methods; North Atlantic; ODP Site 959; ODP Site 960; ODP Site 961; ODP Site 962; Ocean Drilling Program; Offshore; Phosphates; Plate tectonics; Rifting; Seismic methods; Seismic profiles; Strike-slip faults; Subsidence; Surveys; Tectonics; Thermal history; Transform faults; Uplifts; West Africa
Coordinates: N030000 N040000 W0022000 W0033000
Record ID: 1997049337
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute.