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TitleCorrelated paleoseismic interpretation of turbidites from 3 distinct sedimentary environments in the Cascadia Subduction Zone off Vancouver Island Canada
 
AuthorHamilton, T S; Enkin, R JORCID logo; Rogers, G C
SourceAmerican Geophysical Union Fall Meeting 2014, abstracts; T43B-4720, 2014 p. 1 Open Access logo Open Access
LinksOnline - En ligne
Image
Year2014
Alt SeriesEarth Sciences Sector, Contribution Series 20140188
PublisherAmerican Geophysical Union
MeetingAmerican Geophysical Union Fall Meeting 2014; San Francisco; US; December 15-19, 2014
DocumentWeb site
Lang.English
Mediaon-line; digital
File formathtml; pdf
ProgramPublic Safety Geoscience Western Canada Geohazards Project
Released2014 12 01
AbstractSedimentary sequences containing turbidites can provide important paleoseismic records. We present sedimentary records from 3 distinct sedimentary systems which provide a reliable well-dated paleseismic record. All 3 sites are subject to strong ground shaking in the event of a megathrust earthquake along the Cascadia Subduction Zone near Vancouver Island, Canada. Effingham Inlet is an anoxic fjord on the west coast of Vancouver Island with an age model based on radiocarbon dates from terrestrial plant material (no marine correction), the Mazama Ash, and sedimentation rates constrained by annual laminations [Dallimore et al. 2008, Enkin et al., 2013]. Barkley Canyon [Goldfinger et al., 2012], 150 km SW, has been sampled at the abyssal plain fan in front of a submarine canyon. Slipstream Slump [ms submitted], 40 km north of Barkley Canyon, is a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge. At Slipstream, given the 2300 m water depth and the thin weak crust at the outer edge of the accretionary wedge, megathrust earthquake shaking is the most likely trigger for the turbidity currents, with sediments sourced exclusively from the exposed slide scar. Correlations based on sedimentology and physical property logging are made between turbidites observed at Barkley Canyon and Slipstream Slump, and a mutually consistent age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. A young marine reservoir age of delta-R=0 yr brings the top to the present and produces age correlations consistent with the thickest (>10 cm) Effingham Inlet turbidites. Correlations of physical property logs tie the Effingham Inlet record to the offshore, despite the extreme differences in the sedimentology. Having good marine geophysical data and well positioned core transects allows the facies analysis needed to interpret the turbidite record. This study provides a much needed link between the marine and terrestrial paleoseismic records. The combined paleoseismic record has 10 turbidites between 10.8 and 6.6 ka, after which the offshore sites became sediment-starved and only 2 or 3 more turbidites were deposited. The recurrence interval for the inferred Early Holocene megathrust earthquakes is 460 ± 140 years.
Summary(Plain Language Summary, not published)
Sedimentary sequences containing turbidites can provide important paleoseismic records. We present sedimentary records from 3 distinct sedimentary systems near Vancouver Island which provide a reliable well-dated paleoseismic record. This study provides a much needed link between the marine and terrestrial paleoseismic records and helps define seismic hazard for better definition of the building code.
GEOSCAN ID295143

 
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