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In‐situ mass balance estimates offshore Costa Rica

December 21, 2020

The Costa Rican convergent margin has been considered a type erosive margin, with erosional models suggesting average losses up to −153 km3/km/m.y. However, three‐dimensional (3D) seismic reflection and Integrated Ocean Drilling Program data collected offshore the Osa Peninsula images accretionary structures and vertical motions that conflict with the forearc basal erosion model. Here we integrate such data to do an in‐situ accounting of material transfer at the plate boundary across the outermost 10 km of the forearc, characterized by active and inactive megathrusts. Our in‐situ budget finds an approximate balance between sediment recycling via accretion and underplating, 0.7–2.3 km3/km/m.y., and basal erosion, 0.7 km3/km/m.y., while subducting sediment volumes, 7.8 km3/km/m.y., greatly outpace either material transfer volumes. These budget results differ significantly from published estimates based on simple proxies of trench axis deflection and slope subsidence. These budget results are the summation of thin incoming hemipelagic sediments that variably accrete along the deformation front, underplating of hemipelagic sediments on the upthrown‐side and basal erosion on the downthrown‐side of active plate bending faulting landward of the trench axis, and sediment subduction primarily composed of pelagic sediments.

Publication Year 2021
Title In‐situ mass balance estimates offshore Costa Rica
DOI 10.1029/2020GC009190
Authors Joel Edwards, Jared W. Kluesner, Eli Silver, Rachel Lauer, Nathan Bangs, Brian Boston
Publication Type Article
Publication Subtype Journal Article
Series Title Geochemistry, Geophysics, Geosystems
Index ID 70218478
Record Source USGS Publications Warehouse
USGS Organization Pacific Coastal and Marine Science Center