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' of the strike and dip of existing discontinuities were possible at this distance; however, due <br /> to this constraint, detailed observations of the planarity, roughness, infilling characteristics <br /> 1 and asperity descriptions of structural features were not included in this analysis. <br /> GEOLOGIC SETTING <br /> Regional Geology <br /> The ancestral Colorado Front Range is the result of the complex physical history of the <br /> ' area involving the deposition of a great thickness of sedimentary rocks of variable <br /> resistance, the intrusion of dikes and small stocks, the out-pouring of lava flows, and the <br /> development of a great anticlinal uplift during the Laramide Orogeny. There were <br /> repeated erosion cycles following renewed uplifts (LeRoy, 1946). <br /> In Late Cretaceous and Early Tertiary time, during the Laramide Orogeny, a large anticlinal <br /> arch developed at the same time as the downwarping of the Denver Basin to the east. <br /> 1 This anticline rose 15,000 to 25,000 feet during the Orogeny, followed by deep truncation <br /> which exposed a core of crystalline rocks, mostly Precambrian in age. The core is a long <br /> block of hard igneous and metamorphic rock, granite, gneiss, and schist, 1,000 to 1,750 <br /> million years old (Van Tuyl, 1955). <br /> Intense folding and faulting of the metamorphic formations accompanied the Laramide <br /> ' Orogeny. The resulting dominant tectonic pattern has a northwest trend. The anticline is <br /> complexly faulted with cross-folds, horsts, grabens and thrust faults, and the Precambrian <br /> body is bordered by the eastern foothills belt of faulted, tilted, and locally folded <br /> sedimentary formations (Boos & Boos, 1957). <br /> Quarry Geology <br /> The Spec-Agg quarry lies just west of the North-South trending Golden Fault in the <br /> Precambrian bedrock. The quarry is a major source of crushed aggregate and decorative <br /> 4 <br />