STRUCTURE OF THE OCEAN CONTINENT TRANSITI ON ON A PASSIVE CONTINENTAL-MARGIN - MULTICHANNEL SEISMIC-REFLECTION IN THE IBERIA ABYSSAL-PLAIN (PORTUGAL)

We present a multichannel reflection seismic line crossing the Iberia Abyssal Plain from the Atlantic oceanic crust to the Portuguese contin ental margin. The transition between the oceanic domain and the contin ental slope spreads over a 150 km-wide zone, where some horizontal or low-dipping reflectors occur in the acoustic basement. These reflector s are interpreted as syn-rift tectonic contacts where the superficial normal faults connect at depth. Consequently to lithospheric extension , periodotite and gabbro drilled during the Leg ODP 149 have been empl aced on the seafloor in a tectonic window at the end of the continenta l rifting, after the final break-up of the crust.