The study of the structure and composition of passive continental margins provides an insight into the mechanisms of continental rifting and its evolution to seafloor spreading. Wide-angle and normal-incidence seismic data acquired during July-August, 1995 (RRS <I>Discovery</I> cruise 215), has been used to determine the structure of the ocean-continent transition in the southern Iberia Abyssal Plain. A basement and mantle velocity structure is derived by P-wave travel-time and synthetic seismogram modelling along a 320 km long wide-angle seismic profile coincident with the pre-existing deep seismic reflection profile IAM-9 located at ~40°20'N. A series of five short (~60 km) wide-angle profiles and coincident MCS reflection sections constrain the structure of the peridotite ridge, an enigmatic basement feature identified to form part of the ocean-continent transition along the West Iberia Atlantic margin. The structure of thinned continental crust, close to its suspected oceanward limit, is imaged along four intersecting depth migrated MCS seismic profiles that lie close to the Ocean Drilling Program (ODP) Legs 149 and 173 transect of basement drill sites. On the IAM-9 wide-angle profile, a 190 km wide ocean-continent transition zone (OCT) is observed. The OCT includes a pair of overlapping peridotite ridges, and is bounded by oceanic crust and landward by fault bounded blocks of continental crust. The continental crust thins from 28 km to 7 km below the continental slope, over a lateral distance of 80 km.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:598475 |
| Date | January 1999 |
| Creators | Dean, S. M. |
| Publisher | University of Cambridge |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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