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<br />anticline is complexly faulted with cross folds, horsts, grabens and thrust faults, and the <br />Precambrian body is bordered by the eastern foothills belt of faulted, tilted, and locally <br />folded sedimentary formations (Boos+Boos, 1957). <br />Quarry Geology <br />The Deer Creek Quarry site can be found on the Geologic Map of the Indian Hills <br />Quadrangle. In this area, the mainly metamorphic Precambrian rocks were originally <br />layered sedimentary and volcanic rock most likely deposited in an island-arc environment <br />several hundred million years before they were complexly deformed twice and highly <br />metamorphosed to about 1,700 million years ago. Pegmatites and numerous lenses of <br />granodiorite were emplaced in the biotite gneiss near swell-developed migmatite. Rock <br />composition mapped in the area and observed in the quarry included foliated schists and <br />gneiss'; quartz-, mica-, and feldspar-rich metamorphic rocks containing some garnet and <br />sillimanite (Bryant et al, 1973). <br />There are numerous folds and faults mapped in the quadrangle. The most significant <br />areal faults are the Floyd Hill Fault, about 2 miles west of the quarry, and an unnamed <br />a.:.... ..,•.~M1., ~: ~-'e'ra <br />fault just to the northwest- c]~+`~',BsjditiYe~an~f`one small <br />(.. ~' FiY}'?: y1~La'.d`3_vA.Ra.,.~.w.s ..~.. }..-;r.ea... <br />faujt'was,nlapgof'tfie•jb~iitsh~ve`a'nortittvesistri~Cet~ei~id refate~'to'the regioriaF~'" <br />r ~ = -.b.-,.. <br />fracfiirep8tteri-,shawr~bp~tti~ijq~tweatuendiEig;Because none of the faults in the <br />Indian Hills Quadrangle is known to have had measurable displacement during historic <br />time in the last 120 years and the faults are in the bedrock units, the likelihood of ground <br />movement along the faults in the future is slight (Bryant et a1,.1973). <br />Watef:ef~e~~#i~Cf~ft~st>~tCfiit~IhitteAl~tte~haFic~SmaliS`~ir'~~"cartcentratectialoru~- •' <br />ttie~:nortF'i``~i~fl~e~lcavatigr_1:~~Total flow at the time of the field examination was <br />estimated at only 20 gallons per minute, a relatively small amount considering this spring's <br />heavy precipitation. Average annual precipitation in the area is 17-20 inches. <br />2 <br />