Evolution of a Holocene delta driven by episodic sediment delivery and coseismic deformation, Puget Sound, Washington, USA


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dc.contributor.author Barnhardt, Walter A.
dc.contributor.author Sherrod, Brian L.
dc.date.accessioned 2007-05-01T19:47:46Z
dc.date.available 2007-05-01T19:47:46Z
dc.date.issued 2006-08-16
dc.identifier.citation Sedimentology 53 (2006): 1211-1228 en
dc.identifier.uri http://hdl.handle.net/1912/1596
dc.description This paper is not subject to U.S. copyright. The definitive version was published in Sedimentology 53 (2006): 1211-1228, doi:10.1111/j.1365-3091.2006.00809.x. en
dc.description.abstract Episodic, large-volume pulses of volcaniclastic sediment and coseismic subsidence of the coast have influenced the development of a late Holocene delta at southern Puget Sound. Multibeam bathymetry, ground-penetrating radar (GPR) and vibracores were used to investigate the morphologic and stratigraphic evolution of the Nisqually River delta. Two fluvial–deltaic facies are recognized on the basis of GPR data and sedimentary characteristics in cores, which suggest partial emplacement from sediment-rich floods that originated on Mount Rainier. Facies S consists of stacked, sheet-like deposits of andesitic sand up to 4 m thick that are continuous across the entire width of the delta. Flat-lying, highly reflective surfaces separate the sand sheets and comprise important facies boundaries. Beds of massive, pumice- and charcoal-rich sand overlie one of the buried surfaces. Organic-rich material from that surface, beneath the massive sand, yielded a radiocarbon age that is time-correlative with a series of known eruptive events that generated lahars in the upper Nisqually River valley. Facies CF consists of linear sandbodies or palaeochannels incised into facies S on the lower delta plain. Radiocarbon ages of wood fragments in the sandy channel-fill deposits also correlate in time to lahar deposits in upstream areas. Intrusive, sand-filled dikes and sills indicate liquefaction caused by post-depositional ground shaking related to earthquakes. Continued progradation of the delta into Puget Sound is currently balanced by tidal-current reworking, which redistributes sediment into large fields of ebb- and flood-oriented bedforms. en
dc.description.sponsorship This study was supported by the Coastal and Marine Geology Program, and the Earthquake Hazards Program of the U.S. Geological Survey. en
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Blackwell en
dc.relation.uri http://dx.doi.org/10.1111/j.1365-3091.2006.00809.x
dc.subject Earthquake en
dc.subject Ground-penetrating radar en
dc.subject Mount Rainier en
dc.subject Multibeam bathymetry en
dc.subject Puget Sound delta en
dc.title Evolution of a Holocene delta driven by episodic sediment delivery and coseismic deformation, Puget Sound, Washington, USA en
dc.type Article en
dc.identifier.doi 10.1111/j.1365-3091.2006.00809.x

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