Geological manifestations of ridge collision: Evidence from the Golfo de Penas-Taitao Basin, southern Chile

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