GEOMAR - Helmholtz-Zentrum für Ozeanforschung Kiel

We use new swath bathymetry data acquired during the RV Sonne cruise GEOPECO and complement them with swath data from adjacent regions to analyse the morphotectonics of the Peruvian convergent margin. The Nazca plate is not covered with sediments and therefore has a rough surface along the entire Peruvian trench. The styles of roughness differ significantly along the margin with linear morphological features trending in various directions, most of them oblique to the trench and roughness magnitudes of a few to several hundred meters. The lower slope is locally very rough and at the verge of failure throughout the entire Peruvian margin, as a result of subduction erosion causing the lower slope to over-steepen. Using curvature attributes to quantitatively examine the morphology in the Yaquina and Mendaña areas revealed that the latter shows a larger local roughness both seaward and landward of the trench. However, the amplitude of morphological roughness is larger in the Yaquina area. We identified a 125 km2 large slump on the Lima middle slope. Morphometric dating suggests an age of 74,500 years within 35 to 40% error. Estimated incision rates on the upper slope are between 0.1 and 0.3 mm/yr suggesting that landscape evolution on the Peruvian submarine continental slope is similarly slow than that in the Atacama desert.