Tectonic Development of Columbia Plateau

Stephen B. Reidel, Michelle A. Chamness, Karl R. Fecht, Michael C. Hagood, Terry L. Nolan

The Columbia Plateau can be subdivided into two structural subprovinces: the Palouse, characterized by the Blue Mountain anticlinorium, and the Yakima foldbelt, characterized by generally narrow, asymmetric (faulted) anticlinal ridges separated by broad basins.

The tectonic features of the Columbia Plateau result from (1) north-south compression during and following the emplacement of the Columbia River Basalt (CRB); (2) the subsidence of the Yakima foldbelt subprovince relative to a stable Palouse subprovince; (3) the growth of the Yakima folds superimposed on a subsiding basin; (4) the growth of major northwest-trending strike-slip faults on the western side of the plateau; and (5) the influence of regional structures that trend into the Columbia Plateau.

Subsidence of the Yakima foldbelt subprovince began prior to the eruption of the CRB and has continued from the Miocene to the present. The rate of subsidence kept pace with CRB emplacement, decreasing as eruption rates waned. Simultaneously, anticlinal fold growth within the Yakima foldbelt occurred under north-south compression, and decreased as the rate of subsidence and CRB eruptions declined. Paleomagnetic data indicate fold growth was accompanied by a component of clockwise rotation that occurred on a local scale and only in anticlines. The development of these tectonic features is consistent with oblique subduction along a converging plate margin.

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.