We present new multibeam bathymetric and multichannel seismic data on the Middle American Trench, between 17 and 19°N. These data show, north of the present tip of the East Pacific Rise, unsedimented seafloor with an abyssal hill fabric bare of sediments at the outer wall of the trench (18 3/4 0'N). Two multichannel seismic profiles orthogonal to the Middle American Trench display clear oceanic crust extending more than 20 km beneath the overriding plate. These seismic images suggest that the subducting oceanic crust along the Middle American Trench is younger than previously proposed. This result, therefore, implies a new location for the East Pacific Rise termination in relation to the trench. The subduction of this young oceanic crust off western Mexico provides new constraints on the deformation and magmatism of the western Mexican mainland. (C) 2000 Elsevier Science B.V. All rights reserved

This study was supported by the CICYT Spanish project ANT94-0182-C02-01/02, INSU-France, IRD, Spanish–France bilateral co-operation program (ref. HF1997-077). Additional funding was provided by agreement CSIC/CONACYT and by CIRIT (Project 1997SGR 00020)

Contribution 303 of ‘Géosciences Azur.-- 14 pages, 5 figures