The Salaverry forearc basin, offshore Peru: Neogene evolution based on seismic sequence stratigraphy

Abstract

Using integrated 3D seismic data and regional 2D seismic lines, this study establishes the seismic stratigraphic framework of the Miocene-Pliocene succession in the central Salaverry forearc basin, offshore Peru. The basin fill is divided into three megasequences: (1) R, characterized by alternating amplitude reflectors under underfilled conditions; (2) S, a thin, largely seismically transparent unit containing basal channel-levee complexes formed under sediment-starved conditions; and (3) C-MTC, comprising deltaic clinoforms and mass-transport deposits that record overfilled conditions during Pliocene uplift of the oceanward Outer Shelf High (OSH). The megasequences are further subdivided into depositional sequences (A to F) whose stratal terminations record the interplay of tectonic subsidence, basin inversion, and two distinct phases of OSH uplift. Seismic stratigraphic analysis indicates that erosion of sequences A and B along the seaward margin of the Salaverry Basin records the onset of OSH uplift. Overlying sequences C-F exhibit progressive changes in stratal architecture, including truncation, onlap, draping, and thickening across the eastern flank of the OSH into the adjacent Trujillo Basin. Thickening of sequences E and F reflects increasing subsidence from late sequence E onward, with deposition occurring during relative tectonic quiescence. Amplitude mapping delineates major sand fairways, including transgressive basal sands, sinuous channels and terminal splays (sequence B), isolated shelf sands (sequence E), and channel-levee complexes (sequence F). Basin fill was initially underfilled, with sediment supplied from the east. Axial sediment transport developed during the final stages of basin evolution, indicating increased basin confinement and overfilled conditions associated with continued uplift of the OSH.