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1.3 Geology <br /> 1.3.1 Regional Geology <br /> The area of the Front Range of the Rocky Mountains near Morrison was formed during the <br /> Laramide Orogeny in the late Cretaceous and Tertiary Periods. The gneissic bedrock within <br /> the quarry is believed to have undergone two or three episodes of deformation during the <br /> Precambrian Period. During the deformations, the existing bedrock was intruded by several <br /> distinct igneous mafic dikes and granitic pegmatites. The intrusions in the area near Morrison <br /> are generally continuous over long distances. Regional geologic mapping is shown in <br /> Figure 2. <br /> 1.3.2 Site Geology <br /> The bedrock at Morrison Quarry is consistent with regional geology and generally consists of <br /> Precambrian aged granitic and biotitic gneisses. The gneissic foliations are mapped as <br /> striking generally northeast-southwest orientation and generally dipping shallowly to the <br /> southwest. <br /> The regional mafic dikes and granitic pegmatites are observed in the exposed highwalls <br /> within the South Quarry and are evident in rock cores obtained during geotechnical drilling. <br /> The mafic dikes are generally linear features, near vertical, about 1 to 2 feet in width, and <br /> compose of fine-grained materials. The dikes are generally softer and more weathered than <br /> the adjacent gneisses. The granitic pegmatites tend to be randomly oriented features and have <br /> more variable widths than the mafic dikes, ranging from 1-inch to 3-feet wide. <br /> A fault has been mapped near the Morrison Quarry and through the footprint of the South <br /> Quarry (Scott, 1972). Fault traces have been observed in previous geological field mapping <br /> and in samples collected during previous geotechnical field investigations. The fault is <br /> observable in the highwalls on benches around El. 6700 and El. 6760, and generally consists <br /> of shear zones with weak granitic and biotitic gneiss as well as highly fractured, fibrous, <br /> sillimanitic gneiss. Where exposed the fault dips at approximately 70' to the south and the <br /> associated zone of weak rock and sillimanitic gneiss extends approximately 150 feet on <br /> either side. The sillimanitic gneiss appears to be related to source rock (pre-metamorphic <br /> episode) depositional environment(minerology) rather than a result of/associated with the <br /> fault. This is evidenced by sillimanitic gneiss present at depth (out of potential fault impact) <br /> and observed at various depths and thicknesses interbedded with granitic and biotitic gneiss. <br /> Aggregate Industries Morrison Quarry GEI Consultants, Inc. <br /> South Quarry Highwall Design Technical Revision 4 August 2017 <br />