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• rQP PINEY CREEK ALLUVIUM (UPPER HOLOCENE) —Dark gray, <br /> humic silt, sand and gravel. Cut by narrow gullies along many <br /> drainages. Caps terraces about 20 ft (6m) above North Fork South <br /> Platte River. Grades to colluvium at heads of valleys. <br /> Qc COLLUVIUM (UPPER HOLOCENE) —Poorly sorted sand and silt <br /> containing angular pebbles and cobbles. <br /> Qoa OLDER ALLUVIUM (PLEISTOCENE) — Gravel, sand, or silt on <br /> terrace 20 to 25 ft (6-8m) above Elk Creek north of Indian Springs <br /> Village and on terrace 35 to 40 ft (11-13m) above North Fork South <br /> Platte River, center sec. 29, T7S, R71 W. <br /> Ysp SILVER PLUME QUARTZ MONZONITE (PRECAMBRIAN Y)— <br /> Coarse-grained to fairly fine grained, muscovite-biotite quartz <br /> monzonite. Typical coarse-grained variety has tabular Carlsbad- <br /> twinned potassic feldspar phenocrysts to 0.5 to 1 cm long. Locally <br /> foliated. Contains numerous inclusions of migmatite. Forms large <br /> scabby outcrops and thin sandy soil. Rb-Sr age determinations show <br /> that the Silver Plume Quartz Monzonite is about 1,440 m.y. old <br /> (Hedge, 1969) <br /> Xm MIGMATITIC BIOTITE GNEISS (PRECAMBRIAN X) —Biotite <br /> gneiss and schist containing numerous layers and lenses of granitic <br /> gneiss and some layers of amphibolite, calc-silicate gneiss and <br /> quartzite. Locally deeply weathered on gentle slopes in northern part <br /> of quadrangle, but forms large outcrops on scarp adjacent to contact <br /> of Pikes Peak Granite (Ypp). <br /> Xma MIGMATITIC BIOTITE GNEISS AND AMPHIBOLITE <br /> (PRECAMBRIAN X) —Biotite gneiss and schist containing <br /> numerous layers and lenses of granitic gneiss. Amphibolite and <br /> biotite-plagioclase gneiss make up 10 to 20 percent of the unit. <br /> CONTACT— Generally inferred or approximately located. Dashed <br /> where indefinite; dotted where concealed. <br /> .-sF STRIKE AND DIP OF FOLIATION <br /> 15 STRIKE AND DIP OF COMPOSITIONAL LAYERING <br /> Generally parallel to foliation. <br /> ___= Indicates presence of numerous shears or fractures. <br /> JC 00785 <br /> PetersonlElk Creek <br /> — <br /> Notes: BRIERL.EY_ ELK CREEK QUARRY <br /> 1. From Reconnaissance Geologic Map of the Pine ASSOCIATES GEOLOGIC MAP <br /> (...Quadrangle; Map MF-598; by Bryant Bruce; 1974 4miteELubi+tyCompany EXPLANATION KEY <br /> JEFFERSON COUNTY, COLORADO <br /> ••cr+tmg So+u uneagrwna•• JULY 2004 <br />