ANDES 129 been influenced by clockwise rotation of the Atlantic Peninsula initiating spreading of the Weddell Sea between 175 and 155 Ma This rifting was well underway when a subduction regime was diachronically established along the western margin of South America in the Early to Middle Jurassic The Jurassic to Early Cretaceous history of this system is dominated by a complex series of forearc, intra-arc, and retro-arc basins in which extension was associated with subduction zone rollback and oblique convergence Middle Jurassic to Early Cretaceous thermal subsidence in the back-arc began at different times in different places The expansion of marine sedimentation in the Early Cretaceous reflects the thermal subsidence that followed this rifting and a long-term rise in global sea-level In the Southern Andes, extensional faulting in the Neuguen Basin was interrupted by inversion in the Jurassic (Araucanian Event) This inversion was followed by rifting along the east coast of northern Argentina, Uruguay and Africa at about the same time that the Late Jurassic magmatic arc in central Chile migrated $30–40 km to the east and the Atacama intra-arc strike-slip fault system became active Extension reached a height in the Southern Andes with the Late Jurassic formation of the oceanic Rocas Verdes Basin in southernmost Patagonia that incorporates the Sarmiento and Tortuga ophiolites In the Northern Andes, Jurassic extension precipitated thermal sag that led to extensive shallow marine embayment by the end of the middle of the Early Cretaceous (Neocomian) The Early Cretaceous (130–110 Ma) marks the opening of the South Atlantic Ocean off the shore of Brazil and rapid westward drift of South America relative to the underlying mantle Active extension was most pronounced in Bolivia, northern Argentina and Chile as the central South Atlantic Ocean began opening at $130 Ma at the time of the eruption of the Parana flood basalts in Brazil Intracratonic extension occurred in the southern Altiplano and in the Salta Rift system and Pampean ranges where it was associated with basaltic volcanism To the west, the Atacama intra-arc strike-slip fault system became transtensional at $132–125 Ma and the Aptian period ($121–112 Ma) brought increased negative trench rollback velocity causing the intra-arc and back-arc extension that produced the marine sediment-filled aborted marginal basin in Peru associated with Casma volcanism (after $112 Ma), the Sierra de Fraga low-angle detachment faults near 27 S, and the aborted marginal basin linked with the eruption of the extensive $119–110 Ma Veta Negra and related volcanic groups in central and south central Chile (29 to 33 S) In the Southern Andes, intracratonic rifting had essentially ceased by the Aptian as shown by the terminal stages of the Rocas Verdes Basin in southern Patagonia, a peak in the emplacement of the Patagonian batholith, and the end of marine sedimentation in the Neuque´ n Basin In the Northern Andes, the presence of blueschist and high-pressure metamorphic rocks ($130 Ma) along the Romeral and Peltetec faults can be associated with the obduction of small island-arc systems to the Colombian Central Cordillera and western side of the Ecuadorian Cordillera Real The Cretaceous (112–90 Ma) drowning of the Barinas–Apure Basin can be attributed to thermal subsidence Stage 2: Basin Inversion and Formation of the Early Andes The main compressional stage that built the Andes began after 10 Ma as active spreading in the South Atlantic accelerated the separation of South America from Africa, and South America began to actively override the trench A series of compressional events of variable intensity occurred all along the margin as foreland basins responded to flexural loading Compressional events took place in the Late Cretaceous near $105–95 Ma (Mochica Phase), near 85–75 Ma (Peruvian Phase), at the beginning of the Paleocene near 65–50 Ma, and during the Eocene (Incaic Phase) These are all times of changes in plate convergence rates and directions along the margin Late Cretaceous compression in Peru and Bolivia is marked by tectonic inversion in the Mochica Phase at $105 Ma In Chile, the final phase of pluton emplacement in the Coastal Cordillera took place at 106 Ma, after which the intra-arc Atacama Fault system was largely abandoned In Patagonia, the Late Cretaceous (98–85 Ma) marks the closure of the Rocas Verde Basin a peak in production, of the Patagonian Batholith, and the formation of the thrustloaded Magallanes foreland basin An inversion at $99 Ma marks the change from an extensional to a foreland setting for the Neuque´ n Basin The Peruvian phase corresponds with the final emplacement of the Late Cretaceous Coastal Batholith in Peru and the end of marine sedimentation in the large back-arc marine basin to the east in Peru and Bolivia In Chile, a new arc and fault system was established at $86 Ma in what is now the Central Valley, some 50 km east of the old Atacama system The protoCordillera de Domeyko was uplifted at this time In the Northern Andes, Late Cretaceous closure of an ocean basin led to accretion of the Cretaceous oceanic Pin˜ on–Dagua Terrane to the Colombian and Ecuadorian Western Cordilleras between $80 and 60 Ma (Calima Orogeny) The collision is generally