Seismic Stratigraphy of the Peruvian Forearc Drifts from 3° to 7°S: Identification and Influence of Lower Layers of the Humboldt Current System

Abstract The seafloor morphology and subsurface geometry of a late Neogene contourite drift located along the Peru margin is documented for the first time using multibeam bathymetry, two‐dimensional and three‐dimensional seismic data. Along the margin several submarine canyons incise the shelf and slope. Between these canyons, interfluves are characterized by the occurrence of undulating sediment waves and mounded features. We quantify these features to understand the processes that could have caused their formation. This analysis allows us to define a contourite depositional system, present between 70 and 4,280 m water depth, and to relate it to the main oceanographic currents acting in the study area. The Humboldt Current is a key element in shaping the margin, and resulted in various processes related to bottom currents, ranging from erosion to deposition. We propose that the Humboldt Current System intensified at ∼10 Ma based on age calibrated hiatuses and sedimentation trends of the eastern Pacific Ocean. The initiation of the Humboldt Current System marks a prominent erosion surface on the continental slope. This surface is also observed in the Talara Basin associated to the uplift driven by subduction of the Inca Plateau. The identification of this contourite sequence has implications for the understanding of this active margin (e.g., sediment distribution and winnowing) and in the structural geology (unloading of tectonic structures by seafloor erosion) of its forearc basins. This also implies an external control that could be climatic over the pace of ocean currents, particularly in strength and depth.