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1100318 R0T0 0811 JRW1 19
<br />5 Investigation of Landslide Cause
<br />5.1 Geologic Setting
<br />Pikeview Quarry is located within the Rampart Range fault zone. The fault zone marks the
<br />tectonic boundary between the Rocky Mountain Front Range uplift and the sedimentary strata of
<br />the Colorado Piedmont to the east. Fault movements, subsequent erosion, and topographic
<br />lowering of the Piedmont have folded and structurally isolated lower Paleozoic rocks. Pikeview
<br />Quarry is developed from this formation in a fault bounded block of Manitou Formation
<br />limestone (Om). Prior investigators have mapped several faults near and within the Pikeview
<br />Quarry as seen in Figure 17.47
<br />The bedrock on the west side of the Pikeview Quarry Manitou Limestone block and west of the
<br />western fault is Pikes Peak Granite (Ypp). The bedrock on the east side of the limestone block
<br />and east of the eastern fault is Pierre Shale (Kp). The rock unit within and below the Pikeview
<br />Quarry Manitou Formation is the Sawatch Formation, (s).
<br />The Paleozoic strata exposed in and around the Pikeview Quarry represent a period of time
<br />ranging from the Late Cambrian through the Early Ordovician Periods.48 The exposed strata
<br />preserve a nearly continuous record of marine sedimentation over this time interval. The
<br />sediments reflect the occurrence of a classical marine transgression. Specifically, the earliest
<br />sediments (lower Sawatch Formation, deposited directly on granitic basement rocks), are
<br />consistent with a sandy beach/nearshore marine environment. Subsequent strata reflect a
<br />change to deeper marine sedimentation (upper Sawatch Formation), followed by transition
<br />(basal Manitou Formation) to a carbonate bank environment (roughly analogous to the seafloor
<br />around the Bahama Islands today) that must have been far from the nearest continental shoreline
<br />
<br />47 Morgan, M.L., Siddoway, C.S., Rowley, P.D., Temple, J., Keller, J.W., Archuleta, B.H., and Himmelreich, Jr.,
<br />J.W., 2003, Geologic Map of the Cascade Quadrangle, El Paso County, Colorado, Colorado Geological Survey
<br />Open-File Report 03-18, Denver, CO, 1:24,000-scale (Appendix 37)
<br />48 Morgan, M.L., Siddoway, C.S., Rowley, P.D., Temple, J., Keller, J.W., Archuleta, B.H., and Himmelreich, Jr.,
<br />J.W., 2003, Geologic Map of the Cascade Quadrangle, El Paso County, Colorado, Colorado Geological Survey
<br />Open-File Report 03-18, Denver, CO, 1:24,000-scale (Appendix 37)
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