Abstract

Integrated Ocean Drilling Program (IODP) Expedition 334 to southern Costa Rica, Central America, documented unprecedented subduction erosion in an area of active seismic slip. Widespread subduction erosion of the upper plate initiated when the Cocos Ridge, an overthickened aseismic ridge, arrived at the Middle America Trench. Subduction erosion was coeval with the rapid formation of deposition centers on the forearc of the upper plate. The completely recovered shelf sequence constrains a short (<2 m.y.) interval of extreme subsidence (∼1200 m) with a rapid pulse occurring during the first ∼0.3 m.y. This event removed an estimated 1.2 × 106 km3 of forearc material at a rate of ∼1690 km3/m.y./km of trench during a time of rapid (∼1035 m/m.y.) shelf sediment accumulation. At this erosive margin, a sediment-starved trench persisted, in spite of abundant sediment supply, because subduction erosion led to the creation of forearc basins. Similar rapid pulses of subduction erosion may punctuate the evolution of many margins, contributing disproportionately to crustal recycling at subduction zones with implications for the evolution of continental crust and mountain belts, and recycling of continental material into the mantle.

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