Mesozoic-Cenozoic Evolution of the Western Margin of South America: Case Study of the Peruvian Andes

Based on the structural style and physiographic criteria, the Central Andes of Peru can be divided into segments running parallel to the Pacific coast. The westernmost segment, the Coastal Belt, consists of a Late Jurassic-Cretaceous volcanic arc sequence that was accreted to the South American craton in Cretaceous times. The Mesozoic strata of the adjacent Western Cordillera represent an ENE-vergent fold-and-thrust belt that formed in Eocene times. Tight upright folds developed above a shallow detachment horizon in the West, while more open folds formed above a deeper detachment horizon towards the East and in the neighboring Central Highlands. A completely different style with steeply dipping reverse faults and open folds affecting the Neoproterozoic crystalline basement is typical for the Eastern Cordillera. The Subandean Zone is characterized by mainly NE-vergent imbricate thrusting which occurred in Neogene times. A quantitative estimate of the shortening of the orogen obtained from balanced cross-sections indicates a total shortening of 120-150 km (24%-27%). This shortening was coevel with the Neogene westward drift of South America, occurred at rates between 3 and 4.7 mm/year and was responsible for the high elevation of the Peruvian Andes.