Abstract On the eastern margin of the Panama Basin, the Nazca oceanic plate converges towards the continental plate of South America at approximately 53 mm a −1 . Subduction processes are accompanied by the presence of anomalous bathymetric elements including the Sandra Ridge. This east–west-orientated ridge is catalogued as an aborted rift derived from a magmatic spreading axis that was active between 12 and 9 Ma. Seismic activity within this structure is considered evidence of fault reactivation and tectonism. Once the structure reached the subduction trench several submarine landslides were triggered. Run-out lengths of these submarine landslides are perpendicular to the convergence of the structure with some units spreading and forming a wide fan that reaches tens of kilometres to the north and south of the trench. The area affected by the three main landslides varies between 130 and 300 km 2 approximately, with relatively superficial earthquakes (<33 km) and with magnitudes that reach up to M w 7.2. The morphology of the landslides suggests a retrogressive nature with younger events proximal to shore. This paper presents estimates of the age of these landslides and discusses sources of uncertainty regarding these times of occurrence.

ABSTRACT Forearc topography and inferred paleotopography are key constraints on the processes acting at plate interfaces along subduction margins. We used along-strike variations in modern topography, trench sediment thickness, and instrumental seismic data sets over >2000 km of the Chilean margin to test previously proposed feedbacks among subducted sediments, plate interface rheology, megathrust seismicity, and forearc elevation. Observed correlations are consistent with subducted sediments playing a prominent role in controlling plate interface rheology, which, in turn, controls the downdip distribution of megath-rust seismicity and long-term forearc elevation. High (low) rates of trench sedimentation promote long-term interseismic coupled offshore forearc uplift (subsidence) and onshore forearc platform subsidence (uplift). Low trench sedimentation rates also promote deeper megathrust seismic slip, enhancing short-wavelength coastal zone uplift. Shallowing of subducting slabs contributes to a reduction in coastal zone–onshore forearc relief, in turn preventing formation of onshore forearc basins. The extremely low denudation rates of hyperarid northern Chile have allowed better reconstructions of the histories of paleoel-evations and paleoclimate compared to other sections of the forearc. Even if these histories are not sufficiently resolved to unequivocally assign causality among climate variability, changes in plate interface frictional properties, and forearc elevation, they are consistent with the onset of hyperaridity in the coastal zone at 25–20 Ma (1) triggering long-term, long-wavelength offshore forearc subsidence and onshore forearc uplift, and (2) accelerating short-wavelength coastal zone uplift.

ABSTRACT This study is focused on the Salaverry Basin, in the forearc of the Peruvian Andes, which contains three oil seeps sampled and analyzed, suggesting at least one active petroleum system within the basin. The development of the basin is controlled by the interaction between the Nazca-Farallon and South American plates, together with Nazca ridge subduction. Seismic stratigraphic analysis calibrated with available well and core data was carried out to understand the spatial-temporal evolution of Cenozoic depositional systems in the basin. As a result, the Cenozoic succession is best subdivided into five second-order sequences (2S1–2S5) composed of nine third-order sequences (3S1–3S9). Subsequently, 3-D seismic geomorphologic analysis afforded images of depositional elements from mapped seismic sequences. Further analysis of these images enhanced interpretation of depositional systems and lithological predictions. Hence, this study adds new potential reservoir rocks into the 2S1, 2S2, 3S2, 3S3, 3S5, and 3S6 sequences and seal rocks into the 3S1, 3S4, 3S5, and 3S7–3S9 sequences, for the petroleum systems previously defined in the basin. These new petroleum system elements are related to the potential plays proposed in this study, which in turn, through a follow-up assessment, could become very attractive exploratory prospects located in the central portion of the Salaverry Basin, shallow water offshore Peru (west South America).