Geophysical constraints on Washington convergent margin structure

Journal of Geophysical Research


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Gravity and magnetic maps of western Washington reveal the lateral structure and fabric of the Washington Coast Range, Puget Basin, and southern Washington Cascade Range. Two-dimensional gravity and magnetic modeling constrained with geological and other geophysical data indicate that the Coast Range Province rocks are about 1 km thick at the coast, thickening to as much as 30 km near their postulated eastern edge. A composition largely of basalt and gabbro with little interbedded sediments is suggested. Under these rocks may be mantle or a subduction complex composed of dense mafic, ultramafic, and sedimentary rocks like that proposed to underlie Vancouver Island. The Washington model requires that the proposed subduction complex be more dense than the trench sediments and, therefore, that material denser than sediments be incorporated within it. The absence of continental mantle and the modeled wedge shape of the Coast Range Province upper crust suggest that erosion of the bottom of the overriding plate by subduction processes may have occurred. -from Author

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Geophysical constraints on Washington convergent margin structure
Series title Journal of Geophysical Research
Volume 95
Issue B12
Year Published 1990
Language English
Larger Work Type Article
Larger Work Subtype Journal Article
Larger Work Title Journal of Geophysical Research