8 research outputs found
Continental response to active ridge subduction
[1] Apatite fission track ages from a ā¼2000 m elevation transect from the Patagonian fold and thrust belt (47.5Ā°S) allow us to quantify the denudational and orographic response of the upper plate to active ridge subduction. Accelerated cooling started at 17 Ma, predating the onset of ridge collision (14ā10 Ma), and was followed by reheating between 10 and 6 Ma. Thermal modeling favors reheating on the order of 60Ā°C at ā¼28Ā°C/Ma due to east-migration of a slab window after the ridge-trench collision. Final rapid cooling since 4 Ma of ā¼18Ā°C/Ma (geothermal gradient of 14Ā°C/km) correlates with the presence of an orographic barrier and >1 km rock uplift in this region between 17.1 and 6.3 Ma. Increased precipitation and erosion since 4 Ma caused asymmetric exhumation, with 3ā4 km on the leeside. Repeated crustal unroofing in response to active ridge subduction can explain the positive gravity anomaly south of the Chile Triple Junction