Abstract

The Anderson Ridge quadrangle was mapped on a reconnaissance scale while 10 sq mi in the western part of the quadrangle were mapped in detail. In the detailed area, Palmer Draw, a peraluminous granite stock and related pegmatites have been emplaced in pelitic and quartzo-feldspathic metasediments. The metasediments are mainly quartz-biotite-plagioclase and quartz-biotite-plagioclase-paragonite porphyroblastic "peanut" schists with a contact zone surrounding the granite stock. The metasediments of the Palmer Draw area have been complexly folded and faulted and their field relations and geometry indicated 3 episodes of deformation. The area was divided into 2 fields of approximate structural homogeneity for analysis. The fabric of field 1 indicates flexural folding of S, a well-defined foliation parallel to the original bedding around a nearly horizontal fold axis B s1 . This is thought to represent the first episode of deformation. In field 2 the fabric of S and L 2 lineations, minor fold axes, indicate flexural folding of S around a nearly vertical fold axis B s2 . This episode of folding affected primarily the steep limbs of the previous B s1 folds. Field relations and the projection pattern of the L 3 lineations, biotite traces, suggest a penetrative surface S'. S' is planar through the B s2 minor folds which they transect at various angles. This and other evidence indicates that S' is later than the B s2 folds and is superimposed on the B s2 folds. The last episode of deformation then involve faulting and passive folding by movements on S'. It is thought that the granitic emplacements preceded the B s2 folding. This is consistent with evidence of a thermal metamorphism preceding a regional metamorphism. The B s1 and B s2 folds are thought to be Precambrian in age. S' may be Laramide in age and related to the overthrusting of the western slope of the Wind River Range.

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