ML20151P767

Radiocarbon Age of Probable Coseismic Buried Soil Layers from State of Wa, Presented at 880506-08 Meeting in Seattle,Wa

ML20151P767
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Site:	Trojan File:Portland General Electric icon.png
Issue date:	05/06/1988
From:	Amy Hull CALIFORNIA, UNIV. OF, SANTA BARBARA, CA
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References
NUDOCS 8808100181
Download: ML20151P767 (1)

Text

7 RADIOCARBON AGE OF PROBABLE COSEISMIC BURIED SOIL LAYERS FROM WASHINGTON STATE ALAN G.

HULL UNIVERSITY OF CALIFORNIA, SANTA BARBARA Stratigrdphic and sedimentological data from exposures in coastal Washington have been interpreted to indicate that repetitive cycles of estuarine mud and thin organic horizons result from sudden burial of subaerial wetlands during Cascadia Subduction

ene earthquakes.

Regional synchroneity of these buried soils is an important requirement to establish sudden burial.

91 radiocarbon dates from peat, twigs, cones, and roots have been measured from eight distinct organic layers.

Each layer has from 3 to 27 dated samples taken from the uppermost part of up to 18 correlated exposures.

Large radiocarbon age ranges from each lajer indicate that instrumental and calibration errors are small compared to the variance in the population of sample ages and calculation of weighted mean ages.

Assuming minimal prevent correlation, instrumental, and calibration errors the following mean ages for buried soils are obtained:

LAYJ.3 sAw tr a m N Act g; g 1

27 263 +/-144 535 2

2 1730 +/- 90 180 3

27 1694 +/-185 810 4

8 2496 +/-117 382 5

10 2924 +/-234 720 6

7 3187 +/-108 250 COL /2 3

1027 +/-112 260 WTCH/1 7

1210 +/-256 900 Simple satistical analyses show that the population of radiocarbon ages two layers are significantly differentfor each layer has the same variance and all but (99.9% level) in mean age.

Layers 2 and 3, and COL /2 and WTCH/1 cannot be separated by dating alone.

Radiocarbon dating does not directly support sudden burial of scil layers, but does show that regional stratigraphic correlations are valid.

High standard errors reduce the accuracy of age determination for each layer and probably reflect range of organic materials preserved in the forest /wetlandthe natural age envirement.

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