Structure of the frontal part of the Andean Convergent Margin


  • R. Von Huene,

  • L. D. Kulm,

  • J. Miller


A multichannel seismic reflection record across the central Peru margin and trench was improved by processing 24 rather than the 12 channels previously processed and by thorough migrating to reject the strong diffractions that obscured weaker primary reflections. The increased resolution clarifies the structure of the 15-km-wide frontal accretionary complex and the adjacent truncated continental framework against which the trench sediment was imbricated. Resolved are individual thrust slices and packets adjacent to the trench axis, subducting sediment-filled graben in the ocean crust beneath the lower slope, and a Tertiary stratigraphic section of the upper slope Yaquina Basin which is cut by normal faults. The resolution in this multichannel record provides criteria for reinterpreting single-channel data off Chile with increased confidence. The previously proposed truncation of the South American continent along much of the Peru-Chile Trench is confirmed and the development of an accretionary complex in front of the truncated continental crust appears to vary with the amount of sediment seen in the trench axis. The Andean margin frontal structure is similar to that off Central America, the Aleutian Trench, and the Japan Trench which suggests common truncation as well as accretion at the front of convergent margins.