LATE QUATERNARY TECTONIC DEFORMATION IN THE CAPE ARAGO-BANDON REGION OF COASTAL OREGON AS DEDUCED FROM WAVE-CUT PLATFORMS

The style of late Pleistocene deformation along the Cascadia forearc near Cape Arago is well expressed by the altitudinal variation of a set of five uplifted wave-cut platforms. These platforms record open folding as well as late Quaternary offset on flexural-slip reverse faults that parallel bedding in the underlying bedrock. Quantitative analysis of the mechanism of flexural slip folding for the South Slough syncline near Cape Arago indicates that the late Quaternary strain rate has decreased in the last 200 kyr. Evidence of past great subduction-style earthquakes is lacking in the region. Instead, the deformational style is controlled by folding. Though localized folding is dominant, the occurrence of great subduction-style earthquakes is not precluded because localized folding could occur concurrently with regional coseismic deformation. -from Authors