Tertiary geology of the Quebrada Huaricangana area, East Pisco Basin, southern Peru: Late Paleogene to Neogene transgressive sedimentation within a forearc basin

Clastic packages studied in the southern East Pisco Basin represent the transgressive Late Eocene to earliest Oligocene Paracas Group, with questionable presence of the latest Oligocene to Early Miocene Chilcatay formation. Syndepositional faulting and rugged topography protected Late Eocene sediment from direct wave attack. Fluvial systems were poorly developed in this arid environment, where sediment gravity flows provided poorly sorted sediment to fan deltas in proximal and inner shelf areas. Shelf facies contain evidence of storm-dominated sand transport and variable rates of bioturbation and suspended sediment input. In conjunction with compositional increases in igneous derived sediment, the preservation of wave induced structures increased between Paleogene and Neogene time. Factors associated with these changes include higher rates of transgression and lower sediment supply during the Late Eocene, less protected depositional areas, arid climates, and a dramatic increase in the supply of sand-sized volcanic sediment in Neogene time