Structural Model for the Columbia River Basalt Near Riggins, Idaho by
نویسنده
چکیده
Imnaha Basalt and Grande Ronde Basalt (RI) of the Columbia River Basalt Group form a small synclinal basin immediately west of Riggins, Idaho. The displacement of the margins of the basalt outcrop, of the synclinal axis, and of a dike of Saddle Mountains(?) Basalt define a pattern best explained by a model of west-northwest to eastsoutheast and north-northwest to south-southeast dextral strike-slip faults and east-northeast to westsouthwest sinistral strike-slip faults. The development of the syncline, downthrow on the east side of the easterly dipping Riggins fault, and the strike-slip displacement are regarded as broadly contemporaneous. Regional implications of significant westnorthwest strike-slip movement in the Riggins area and the possible displacement of the Columbia River dike swarm by such a movement farther west is noted.
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