Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE

dc.contributor.author Kelly, Robyn K.
dc.coverage.spatial Middle America Trench
dc.date.accessioned 2008-10-01T18:37:09Z
dc.date.available 2008-10-01T18:37:09Z
dc.date.issued 2003-09
dc.description Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003 en
dc.description.abstract The cosmogenic radionuclide 10Be is a unique tracer of shallow sediment subduction in volcanic arcs. The range in 10Be enrichment in the Central American Volcanic Arc between Guatemala and Costa Rica is not controlled by variations in 10Be concentrations in subducting sediment seaward of the Middle America Trench. Sedimentary 10Be is correlated negatively with 143Nd/144Nd, illustrating that 10Be concentrations varied both between and within cores due to mixing between terrigenous clay and volcanic ash endmember components. This mixing behavior was determined to be a function of grain size controls on 10Be concentrations. A negative correlation of bulk sedimentary 10Be concentrations with median grain size and a positive correlation with the proportion of the sediment grains that were <32 μm in diameter demonstrated that high concentrations of 10Be in fine-grained, terrigenous sediments were diluted by larger grained volcanogenic material. The sharp decrease in 10Be enrichment in the Central American Volcanic Arc between southeastern Nicaragua and northwestern Costa Rica correlates with changes in fault structure in the subducting Cocos plate. Offshore of Nicaragua, extensional faults associated with plate bending have throw equal to or greater than the overlying subducting sediment thickness. These faults enable efficient subduction of the entire sediment package by preventing relocation of the décollement within the downgoing sediments. Offshore of Costa Rica, the reduction of fault relief results in basement faults that do not penetrate the overlying sediment. A conceptual model is proposed in which the absence of significant basement roughness allows the décollement to descend into the subducting sediment column, leading to subsequent underplating and therefore removal of the bulk of the sediment layer that contains 10Be. Basement fault relief was linearly related to plate curvature and trench depth. The systematic shoaling of the plate from southeastern Nicaragua to northwestern Costa Rica is not explained by changes in plate age for this region. Instead, it is hypothesized that the flexural shape of the plate offshore of southeastern Nicaragua and northwestern Costa Rica represents a lateral response to a buoyant load caused by the thick crust and elevated thermal regime in the Cocos plate offshore of southeastern Costa Rica. en
dc.description.sponsorship Funding for this work was provided by the National Science Foundation Graduate Research Fellowship, the WHOI Ocean Ventures Fund, the WHOI Deep Ocean Institute Graduate Fellowship, and Geological Society of America Graduate Research Grant #7179-02. en
dc.format.mimetype application/pdf
dc.identifier.citation Kelly, R. K. (2003). Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE [Doctoral thesis, Massachusetts Institute of Technology and Woods Hole Oceanographic Institution]. Woods Hole Open Access Server. https://doi.org/10.1575/1912/2458
dc.identifier.doi 10.1575/1912/2458
dc.identifier.uri https://hdl.handle.net/1912/2458
dc.language.iso en_US en
dc.publisher Massachusetts Institute of Technology and Woods Hole Oceanographic Institution en
dc.relation.ispartofseries WHOI Theses en
dc.subject Subduction zones en_US
dc.subject Seismic prospecting en_US
dc.subject Marine sediments en_US
dc.subject Beryllium en_US
dc.subject Isotopes en_US
dc.subject Radioisotopes in oceanography en_US
dc.subject Maurice Ewing (Ship) Cruise EW0005 en_US
dc.subject Maurice Ewing (Ship) Cruise EW0104 en_US
dc.subject Sonne (Ship) CruiseSO76 en_US
dc.subject Fred H. Moore (Ship) Cruise FM3502 en_US
dc.subject Ida Green (Ship) Cruise IG2402 en_US
dc.title Subduction dynamics at the middle America trench : new constraints from swath bathymetry, multichannel seismic data, and 10BE en
dc.type Thesis en
dspace.entity.type Publication
relation.isAuthorOfPublication 616d2f38-9ab6-4b9e-b066-475e8b0451a9
relation.isAuthorOfPublication.latestForDiscovery 616d2f38-9ab6-4b9e-b066-475e8b0451a9
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