Triangulating from the cairns…
This study of the Pitkin area, which lies on the southwest slope of the Sawatch Range, makes available a geologic map of the area surrounding Pitkin, Colorado; a discussion of the structural features in the area; a detailed description of the metamorphic and igneous rocks and the stratigraphy of the Paleozoic rocks; a comparison of the stratigraphy of the Pitkin area with the stratigraphy of the surrounding areas; and an outline of the geologic history of the area. The pre-Cambrian rocks consist of mica schist, gneissic granite, and hornblende diorite. The Paleozoic section is comprised of the following units: the Upper Cambrian Sawatch quartzite, 25 to 132 feet of white, sugary quartzite; the Lower Ordovician Manitou dolomite, about 250 feet of massive, gray, crystalline dolomite with abundant lenses of chert; the Middle Ordovician Harding sandstone, 11 to 14 feet of sandstone; the Upper Ordovician Fremont dolomite, 38 to 107 feet of gray, crystalline dolomite; the Upper Devonian Chaffee formation, which is divided into the Parting quartzite member, 42 to 79 feet of quartzite, limestone, and dolomite overlying shale and shaly sand, and the Dyer dolomite member, 119 to 212 feet of gray to black dolomite and limestone; the Lower Mississippian Leadville limestone, gray to dark blue limestone and dolomite; and the Pennsylvanian Belden shale, interbedded sandstone, shale, and limestone. The Paleozoic sediments have been folded into a syncline which trends northwestward through the central part of the area. The south limb of the syncline is truncated by a steeply dipping fault which brings the Paleozoic sediments in contact with the pre-Cambrian gneissic granite. The throw of the fault cannot be determined because no sediments are found on the south side of the fault, but estimated throw is at least two thousand feet. The Tertiary (?) Napoleon quartz monzonite porphyry, which is found extensively in the Pitkin area, is roughly concordant with the bedding of the Mississippian and Pennsylvanian sediments.
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