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Present Address: Amoco Prod. Res., P.O. Box 591, Tulsa. OK 74102

Twenty-six single-channel seismic reflection profiles across the continental margin of Peru south of Lima are used to describe the shallow structures of this portion of the Nazca-South America convergence. The aseismic Nazca Ridge intersects the trench in the center of the study region, and the axis of the trench plunges away on either side of this intersection, more steeply to the south than to the north. The lower continental slope generally has a steep wall, backed by an unfilled bench, except opposite the ridge. Large upper-slope basins are found in the northern and southern portions of the survey area but not opposite the ridge where the slope and shelf are the narrowest. These few relationships are the only ones found in this study that may possibly reflect the interaction of the ridge with the continental margin, and even these may be noncausal. In any event, the limited extent of possible Nazca Ridge effects on the margin is noteworthy, at least for those effects evident in the morphology and shallow structure.

Structural highs that bound the seaward side of the two upper-slope basins are thought to result from a combination of imbricate thrusting and internal flow of material within the accretionary wedge. We argue that the continental margin of southern Peru exhibits characteristics of both processes, based on the character of lower-slope benches and the existence of upper-slope basins.

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