Information published in U.S.G.S. Professional Papers 445 and 478 indicated to the writer that the structure of the Coeur d'Alene District in northern Idaho were developed by slumping along a rift graben that formed during late Precambrian time while the sediments were more or less semi-consolidated. Deep synclinal folds with adjacent anticlines over-turned toward each other, minor slump features, the St. Regis Breccia resembling a "quickstone breccia" and abundant evidence of past hydrothermal activity all seem to support the theory of an ancient rift graben.

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