Subduction erosion, and the de-construction of continental crust; the Central America case and its global implications

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doi: 10.1016/j.gr.2016.10.001
Author(s): Vannucchi, Paola; Morgan, Jason P.; Balestrieri, Maria Laura
Author Affiliation(s): Primary:
Royal Holloway University of London, Earth Sciences Department, Egham, United Kingdom
Other:
Istituto di Geoscienze e Georisorse, Italy
Volume Title: Gondwana Research
Source: Gondwana Research, Vol.40, p.184-198. Publisher: Elsevier on behalf of International Association for Gondwana Research, Amsterdam and Kochi, International. ISSN: 1342-937X
Note: In English. 120 refs.; 1 table
Summary: The relative rates of creation and destruction of continental crust at subduction zones are a key factor shaping the evolution of continental crust through time. Central America, arguably the best studied place where subduction erosion has been documented, is used here to assess past rates and modes of forearc recycling. Drilling from Guatemala to Costa Rica indicates that subduction erosion has been active since at least the early Miocene. Drilling also shows that the rates of subduction erosion have varied significantly both along strike and through time. The Integrated Ocean Drilling Program (IODP) Expedition 334 to southern Costa Rica documents unprecedented subduction erosion there--at rates larger than the fastest known rates of forearc accretion. In southern Costa Rica, accelerated subduction erosion of the upper plate initiated when the Panama Fracture Zone/Cocos Ridge, the latter being an over thickened aseismic ridge, arrived at the Middle America Trench. The forearc records this event with an unconformity at 2.2 ± 0.2 Ma. The recovered shelf sequence overlying the unconformity constrains a short (< 2 Myr) interval of extreme subsidence (∼ 1200 m) with a rapid pulse occurring during the first ∼ 0.3 Myr. This event removed an estimated 1.2 × 106 km3 of forearc material at a rate of ∼ 1125 km3/Myr/km of trench during a time of rapid (∼ 1035 m/Myr) contemporaneous shelf sediment accumulation. Detrital apatite fission-track thermochronology on the sediments above the unconformity indicates the pattern of surficial sediment transport during this subduction erosion event. The fission track data show that sediments from the extinct and exhumed volcanic arc--the Cordillera de Talamanca--were able to immediately access the growing forearc basin after the onset of the 2.2 Ma subduction erosion event. The onset of subduction of an aseismic ridge as occurred at 2.2 Ma in southern Costa Rica is a fairly common tectonic event along a subduction margin. We suggest that similar rapid pulses of subduction erosion may punctuate the evolution of many margins, contributing disproportionately to crustal recycling at subduction zones. The (poorly) preserved geologic record of paleoforearcs needs to be reassessed with this mechanism in mind. It also implies that continental forearc material may be significantly consumed during short local bursts along a subduction margin, and furthermore, that margins abutting regions of frequent subduction of aseismic ridges, like the regions in the Western Pacific where the Darwin Rise currently subducts, should face disproportionate pulses of future subduction erosion and forearc recycling.
Year of Publication: 2016
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Aseismic ridge; Bathymetry; Central America; Cocos Ridge; Continental crust; Controls; Costa Rica; Costa Rica Seismogenesis Project; Crust; Deep Sea Drilling Project; Deformation; Drilling; East Pacific; El Salvador; Equatorial Pacific; Erosion; Erosion rates; Expedition 301; Expedition 334; Expedition 344; Fission-track dating; Global; Guatemala; IPOD; Integrated Ocean Drilling Program; Juan de Fuca Ridge; Leg 170; Leg 205; Leg 66; Leg 67; Nicaragua; North Pacific; Northeast Pacific; Ocean Drilling Program; Pacific Ocean; Relative age; Subduction; Subduction zones; Trenches
Coordinates: N030000 N110000 W0820000 W0880000
Record ID: 2018065660
Copyright Information: GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands