Description: Summary and conclusion: More than 4000 feet of Lower Miocene lake sediments were deposited upon a gneissic basement rock, at least locally. The sediments have been gently folded into broad anticlines and synclines and have been cut by high-angle faults with displacements on the order of 100 feet. Both basaltic (?) and acid andesitic lavas have intruded the sediments. A Pleistocene (?) conglomerate unconformably overlies all older exposed rocks. The lake sediments were considered to overlie the adjacent thick series of andesite flows (l). This was not established by a cursory examination. The sediments appeared to be in fault contact with the lavas although the relationship was always obscured by the younger conglomerate or alluvial cover. Since a dike of this acid andesitic composition was observed cutting the sediments, there is a possibility that the lake sediments are older than or contemporaneous with the thick extrusive andesite series.
Date: January 1958
Creator: Reyner, Millard L. & Ashwill, Walter R.
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