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Showing 1 to 3 of 3 for “"Needle Mountains"”.
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A sedimentological and structural analysis of the Proterozoic Uncompahgre Group, Needle Mountains, Colorado
… Phase 1 structures (localized to the West Needle Mountains) include bedding-parallel deformation zones, F₁ folds and an S₁ cleavage. Phase 2 coaxial deformation resulted in the development of upright, macroscopic F₂ folds and an axial-planar crenulation cleavage, S₂. In addition …
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Structural studies in a Proterozoic gneiss complex and adjacent cover rocks, west Needle Mountains, Colorado
Proterozoic rocks in the Needle Mountains include ca. 1750 Ma amphibolite-grade, metavolcanic and metaplutonic gneisses and ca. 1690 Ma granitoids that comprise the basement to the siliciclastic Uncompahgre Group. The mafic and felsic gneisses underwent synkinematic metamorphism and two phases of …
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New stratigraphy, polyphase deformational history and basement-involved thrust belt model for the Proterozoic Uncompahgre Group and Vallecito Conglomerate, Needle Mountains, Colorado
… Group and the Vallecito Conglomerate in the Needle Mountains, southwestern Colorado, provide insight into the depositional and deformational history of one of the best exposed of these Paleoproterozoic cover successions. This study documents a gradational contact between the basal Vallecito …