Chile triple junction

Tectonic plate movement

The Antarctic plate started to subduct beneath South America 14 million years ago in the Miocene epoch forming the Chile triple junction. At first the Antarctic plate subducted only in the southernmost tip of Patagonia, meaning that the Chile triple junction lay near the Strait of Magellan. As the southern part of Nazca plate and the Chile Rise became consumed by subduction and the more northerly regions of the Antarctic plate begun to subduct beneath Patagonia so that the Chile triple junction advanced gradually to its present position in front of Taitao Peninsula at 46°15'. The South American plate is moving away from the Nazca plate and moving in a direction to the north of the Chile ridge spreading center, while the Nazca plate is subducting under the South American plate at a rate of about 80–90 mm/a north of the triple junction. The triple junction of the Chile Ridge, the Chile Trench and the Antarctic plate collided about 14 Ma ago near the latitude of Tierra del Fuego. Since then it has migrated north, with the actual triple junction now located at 46°12'S. The Chilean margin consists of the Nazca-Antarctic spreading center, the Chile Rise or Chile Ridge, and the Chile Ridge, with the Nazca-Antarctic spreading center being at 46.5° S, the Chile Rise or Chile Ridge being more prominent in the south. Additionally around 14 Ma, the Chile Rise collided with the South American continental plate. The high relief topography caused the trench to be devoid of sediment at the Chile-South America junction.

Subduction

Subduction accretion is an important process that leads to mountain building and the growth of continents, but it is also associated with the destruction of forearc material. The impact of topographic features, such as topographic features of mountain ranges and faulting, is one important mechanism. An impact between a spreading ridge and a continental forearc can result in a thermal pulse within the forearc. This thermal pulse can be quantified using apatite fission track data and the thermal maturity of organic carbon in the forearc sediment. Several authors have suggested that subduction erosion or slip during earthquakes may be responsible for the uplift of the Coastal Cordillera, a trench-parallel morphostructural system in north Chile.