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

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 [mu]m 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 d6collement within the downgoing sediments.

Department dc:contributor.department

Joint Program in Oceanography/Applied Ocean Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2003

Author dc:creator

• Kelly, Robyn K

Advisor dc:contributor.advisor

• Peter Clift.

• Joint Program in Oceanography/Applied Ocean Science and Engineering.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/59656

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/59656