Recent geological and geophysical studies in the southern Andes adjacent to the intersection of the Chile Rise with the Peru‐Chile Trench (ANT‐NAZ‐SAM triple junction) have revealed a number of features and a Neogene geologic history that are unique along the Pacific margin of South America. This history includes (1) development of a Tertiary‐Quaternary marine basin with up to 3 km of sediment infill (Golfo de Penas‐Taitao basin, GTB), (2) disruption of the region by a series of faults with both normal and strike slip movements, and (3) localization of silicic, near‐trench volcanism and epizonal plutonism and related hydrothermal activity. The northern portion of the GTB began to subside in the Late Miocene (possibly earlier), and has subsequently been deformed, uplifted, and exposed. Gravity and seismic reflection data suggest that the basin continues offshore where it is still actively subsiding today (Golfo de Penas). Subsidence and uplift have thus occurred diachronously in the region, although it is unclear when subsidence began in the Golfo de Penas. Tectonic disruption of the region is likely related to the Liquiñe‐Ofqui fault (LOF), a major, NS‐trending, crustal shear zone that curves westward and terminates in the Golfo de Penas. The LOF has both down‐to‐the‐west and right lateral offset and separates the main Andean Cordillera on the east from a large crustal block (the Chiloe block) on the west. We hypothesize that the GTB has developed as a pull‐apart basin in response to northward movement of the Chiloe block along the LOF. We propose a dynamic model whereby a stress gradient that decreases longitudinally away from the Chile Rise/Peru‐Chile Trench intersection is set up because the youngest, most buoyant, oceanic lithosphere is being subducted at the triple junction. The Chile Rise is viewed as a type of indenter which is acting to drive the Chiloe block northward in front of the northward‐migrating triple junction. This model explains the unique set of geologic features found in the region, and suggests that ridge‐trench interactions may be an important factor in orogenesis at active continental margins.

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The Cordillera Darwin orogenic core complex is a structural and topographic culmination in the southern Andes, which underwent mid-Cretaceous penetrative deformation and metamorphism associated with the deformation and incipient obduction of a partly ophiolitic back-arc basin (Rocas Verdes) block along its southern boundary. Whereas structural evidence suggests uplift of the Rocas Verdes terrane relative to the Cordillera Darwin during this event, metamorphic assemblages reflect a greater net uplift of the opposite sense. New fission track ages together with existing K-Ar and Rb-Sr ages were used to estimate cooling and uplift histories and their relationships to foreland sedimentation and present-day topographic relief. The results suggest that, whereas initiation of uplift in the Cordillera Darwin and Rocas Verdes blocks may have accompanied mid-Cretaceous deformation, the major, rapid uplift (around 0.5-1.5 mm/y) occurred after the deformation. Also, uplift occurred earlier in the Rocas Verdes block than in the Cordillera Darwin block, the latter having experienced a greater net uplift since the mid-Cretaceous. The major, post-tectonic uplift of the Cordillera Darwin occurred at a slower rate (0.05-0.20 mmiy) and coincides with the deposition of thick flysch and conglomerates in the foreland basin

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