Abstract

We report the results of a multichannel seismic study on eastern Central Atlantic oceanic crust. Unmigrated and migrated sections have been used to identify the main seismic boundaries within the crust. The upper crust generally is seismically transparent except for a 20-km-long continuous reflection, which we interpret as associated with a long-lived normal fault in the basement and with hydrothermal circulation. Short and discontinuous reflections in the upper crust have also been observed. The lower crust is either transparent or variably reflective in form of subhorizontal layered reflection packages and/or dipping reflections. The reflectivity patterns are interpreted as magmatic in origin except for the dipping reflections that affect the whole crust, which are interpreted as expressions of extensional faults. The reflections dipping ridgeward are thought to have acted as detachment surfaces where plate separation took place. The Moho has been identified along most of the length of the seismic profiles either as the base of the reflective lower crust or as a sharp single reflection. The igneous crust shows large variations in thickness sometimes associated with fracture zones in the Cretaceous crust. Fracture zones in the Jurassic crust do not show, in general, a crustal thinning. This may be due to different accretionary processes during Jurassic and Cretaceous times.

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