Greater Siletzia and the Making of the Columbia Embayment, Northwest USA

Greater Siletzia and the Making of the Columbia Embayment, Northwest USA

Ray Wells

We will look at the history of the Columbia Embayment (CE); the area of anomalous low topography that lies inboard of the Cascadia subduction zone and is enclosed by the oroclinal bend in the Mesozoic arc. We think that the accreted coastal basalt terrane of Siletzia extends eastward beneath the Columbia Basin, and that the timing of its emplacement overlaps with northward transport of far-travelled British Columbia terranes (“Baja BC”) and Laramide deformation of the US Cordillera. We propose a model that links the origin of the Kula Plate to the Laramide orogeny, its subsequent role in rifting of BC terranes out of the CE, about 400 km south of its present location, and contemporaneous emplacement of Siletzia. The model may help reduce the misfit between large paleomagnetic and smaller geologic estimates of BC terrane displacements.

Please join us at:

Worthy Brewing (eastside location)

In the Hop Mahal Room

5:30 pm social hour

7:00 pm presentation

COGS talk are free and open to the public -- all are welcome! Please join us for the social hour before the presentation.

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