GEOLOGIC MAP OF THE PROTEROZOIC ROCKS OF THE CENTRAL … · nederland synform coal creek synform...
Transcript of GEOLOGIC MAP OF THE PROTEROZOIC ROCKS OF THE CENTRAL … · nederland synform coal creek synform...
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TKi
TKi
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TKi
TKi
Xgncs
TKi
TKi
XcbXcb
Xcb
Xgncs
Xgncs
Xgncs
Xgnca
Xgnca
Xgnca
Xgnca
Xqf
Xrsq
Xr
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Xgnq
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Xgng
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Xgng
Xgng
Xr
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Xgd
Xgd
Xgd
Xgd
Xgd
Xgd
Xgd
Xgd
Xhcs
Xgd
Xgd
Xgnc
Xgnc
Xgnc
Xgnc
Xgnc
Xgncs
Qa
Qa
Qa
Qa
Qa
Qa
Qa
Qa
Qa
QTg
QTg
QTg
QTg
Ypg
Ypg
Ypg
Xmb
Xmb
Xmb
Xmb
Xmb
Xmb
Xmb
Xmb
Xmb
Xma
Xma
Ypg
Ypg
Ypg
Ypg
Xgns
Xgns
Xgns
XgnsXgns
Xgns
Xgns
Xg
Xgns Xgns
Xgns
Xgns
Xgns
Xgns
Xgns
Xgnb
Xgnb
Xgnb
Xgg
Xgnb
Xhcs
Xhcs
Xhcs
Xhcs
Xgnh
Xgnh
Xgnh
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Xfh
Xfh
Xfh
Xfh
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xf
Xqs
Xq
Xq
Xq
Xq
Xam
Xam
Xam
Xam
Xqhd
Xgd
Xqhd
Xqhd
Xg
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Ysp
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Ysp
Ysp
Ysp
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Xgng
Xgng
PIKES
Xf
Xf
Xqhd
Xgns
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Qa
Xf Xf
Xf
Xf
Xgns Xgnh
TKiYsp
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Xgns
Xgns
Xgns
Ysp
Xgnh
XgncXgdXgd
XfXgns Xqm
Xghd
Xghd
Xqhd
XgnsXgns
Xam
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XgXgnh
Xgns
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XgnsXgnc
Xgd
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Xgnb
XgdQa
Xgnc
Ysp
Ysp
Ysp
Ysp
Xgnc
Qa
Xf
Xfh
Ysp
Xgnc
Xgnc
TKi
TKi
TKi
YspYsp
Ysp
Ysp
TKi
Xgns
Xqm
Ysp
Xqhd
XgnsXgnh
Ysp
Xqm
Ysp
Ysp
Xqm
Xgnc
XgnsXgnc
Xhcs
Xhcs
BOULDER CREEK BATHOLITH
Xqm
Xfh
Xgns
Xfh
Xf
Xqm
Xgnc
Xgnc
Xqhd
Xq
Qa
XqhdXqs
Xqs
Xq
Xgnb
Xqhd
Xgnh
Xhcs
Xhcs
Xhcs
Xhcs
QaQa
Qa
Xhcs
Xgng
Xgnh
TKi
Xfh
Xqhd
Xgd
Xgnh
Xqhd
Qa
TKi
Xam
Xgnh
Xgnh
Xgnh
Xam
Xgnh
XgnhXgns
Xgnb Xgns
XgnsXgng
Xgnh
Xgd
Xgd
Xgnc
Xgnc
Xgncs
Xf
TKi
TKi
TKi
XgnsTKi
Xam
Ysp
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XfXqhd
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Xgnc
Xgnc
Ysp
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Xgnca
Ysb
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Xf
MOUNT EVANS BATHOLITHQa
Xq
Xr
XgnsXf
Xcb
Xgnh
YspXhcs
XhcsXgd
Xqm
Xgd
Qa
QTg
Qa
Qa
Qa
QTg
Xgnca
Xf
Xfh
Xfh
Xf
XfhXfh
XgnhXhcs
Xf
Xfh
QaXgnca
Xgnb
Xgnca
Xf
Xgg
Xhcs
Xgns
Xhcs
Xghd
Xgns
Xgns
Xqm
Xgnh
Xqm
Xhcs
XhcsQa
XamXgns
Ysp
Ysp
Ypg
Ypg
Xmb
Xgnb
XgnhXgns
Xgns
Xgns
Xgns
Xam
QTg
Xgnh
Qa
Xgnh
Xfh
QTgXgd
Xgns
BATHOLITHPEAK
TKi
XfTKi
TKi
Xgnc
Xfh
P f
P f
P f
P f
Any use of trade names in this publication is fordescriptive purposes only and does not implyendorsement by the U.S. Geological Survey
For sale by U.S. Geological Survey Information ServicesBox 25286, Federal Center, Denver, CO 80225
Manuscript approved for publicationApril 24, 1997
This map is also available as a PDF file athttp://greenwood.cr.usgs.gov
CONVERSION FACTORS
Multiply By To obtain
centimeters (cm) 0.3937 inches (in.)meters (m) 3.281 feet (ft)kilometers (km) 0.6214 miles (mi)
GEOLOGIC MAP OF THE PROTEROZOIC ROCKS OF THE CENTRAL FRONT RANGE, COLORADO
Compiled byDolores J. Gable
2000
Base from U.S. Geological SurveyBailey, Denver West, 1983; Estes Park, 1984
Universal Transverse Mercator projection1927 North American datum
Geology compiled 1976–84Additions in 1995, with assistanceof William D. Johnson, Jr. Map digitizedby Springfield and Springfield. Digitalcartography by Denny Welp and GayleDumonceaux. Edited by F.C. Brunstein.
0
01
1
CONTOUR INTERVAL 50 METERSNATIONAL GEODETIC VERTICAL DATUM OF 1929
1
1 5 KILOMETERS
5 MILES2
2
SCALE 1:100 0003 4
43
TRU
E N
OR
TH
MA
GN
ETIC
NO
RTH
APPROXIMATE MEANDECLINATION, 1999
12 °
39°37'30"
30'
39°22'30"
105°30'
105°
22'30" 15'
40°
40°00'
52'30"
45'
7'30"
7'30"
U.S. DEPARTMENT OF THE INTERIORU.S. GEOLOGICAL SURVEY
105°52'30" 45' 37'30"
40°7'30"
40°00'
52'30"
45'
39°30'
GEOLOGIC INVESTIGATIONS SERIESI–2605
37'30"
39°22'30"
105°30' 22'30" 15' 105°7'30"
Printed on recycled paper
45° 37°30'
CORRELATION OF MAP UNITS
Qa
QTg
INTRUSIVE ROCKS
SEDIMENTARY ROCKS
UnconformityINTRUSIVE ROCKS
TKi
P f
Ypg
Ysp Yspm Yspb
Xqm Xgg Xgd Xg Xqhd
Xq Xqs
Xf Xfh
Xgnb Xma Xmb
Xgng Xgnq
Xgnca Xgnc
Xgns
Xgncs
Xr Xrsq Xqf
METAMORPHIC ROCKS
METASEDIMENTARY ANDMETAVOLCANIC ROCKS
Xam
Xgnh Xhcs
Xcb
Xgmc
Interlayeredlithologic units;no stratigraphicorder implied
Early Tertiaryand
Late Cretaceous
Holocene andlate Pleistocene QUATERNARY
QUATERNARYAND TERTIARY
TERTIARY ANDCRETACEOUS
MIDDLEPROTEROZOIC
EARLYPROTEROZOIC
PERMIAN ANDPENNSYLVANIAN
TKi
Xgnb
Xgns
Xqm
Ypg
Ysp
Yspm
Xgg
Xma
Xcb
Xqf
Xrsq
Xr
Xgmc
Xgncs
Xgnc
Xgnca
Xgnq
Xgng
Xmb
Xgd
Xg
Xqhd
Xam
Xq
Xqs
Xf
Xfh
Xgnh
Xhcs
Yspb
QTg
Qa
P f
DESCRIPTION OF MAP UNITS
SURFICIAL DEPOSITSAlluvium, colluvium, and glacial deposits (Holo-
cene and late Pleistocene)—In northwest part of area (Strawberry Lake quadrangle), locally in-cludes Troublesome Formation (Miocene and Oligocene) adjacent to Proterozoic rock units
Gravels (Quaternary and Tertiary)—Rounded to subangular pebbles, and boulders derived from metamorphic and igneous rocks mostly to the west of the map area. Patterned area consists of debris derived almost entirely from Precam-brian rocks and found on higher slopes above modern drainage channels
EARLY TERTIARY AND LATE CRETACEOUSINTRUSIVE ROCKS
Monzonite, granodiorite, and syenite—May in-clude minor amounts of mafic rocks, such as pyroxenite
SEDIMENTARY ROCKSFountain Formation (Permian and Pennsylvani-
an)—Map unit locally includes Lykins Forma-tion (Triassic and Permian) and Lyons Sand-stone (Permian). Fountain Formation, predomi-nantly arkosic conglomerate and moderately coarse grained sandstone; Lykins Formation, red and light-green calcareous sandstone; Lyons Sandstone, red and pink fine-grained to very fine grained sandstone
PROTEROZOIC INTRUSIVE ROCKSPikes Peak Granite (Middle Proterozoic)—Biotite
granite and biotite-hornblende granite, minor quartz syenite, fayalite granite, riebeckite gran-ite, and locally granodiorite and quartz monzon-ite. Rb-Sr age about 1,040 m.y. (Hedge, 1970)
Silver Plume Granite (or Quartz Monzonite) of the Berthoud Plutonic Suite (Middle Proter-ozoic)
Quartz monzonite and monzogranite—Mostly massive, gray to buff, fine- to medium-grained quartz monzonite or monzogranite displaying aligned tabular feldspar crystals and aligned bio-tite laths, especially along borders of plutons. U-Pb zircon age 1,400 m.y. (Aleinikoff and others, 1990)
Monzodiorite to granodiorite facies—Medium- to coarse-grained, grayish-white and black, foli-ated monzodiorite to granodiorite. Exists locally in Mount Evans batholith. Contains 6–8 per-cent magnetite. U-Pb zircon age of 1,443 m.y. (Aleinikoff and others, 1990)
Inclusions—Profuse inclusions mostly of biotite gneiss in Silver Plume Granite
Quartz Monzonite (Early Proterozoic)—Light gray to light tan, leucocratic, and fine to medium grained. Includes Twin Spruce Quartz Monzon-ite of the Eldorado Springs area. Field evidence suggests Twin Spruce is both younger and the same age as the Boulder Creek Granodiorite. Patterned where unit contains numerous biotite gneiss inclusions
Granodiorite (Early Proterozoic)—Gray to pink-ish-gray, medium- to coarse-grained gneissic granodiorite; weathers darker pinkish gray. Ex-ists locally at Mt. Morrison and in Clear Creek and Turkey Creek canyons. Isotopically fits the 1,700 m.y. isochron of the Boulder Creek Granodiorite (C.E. Hedge, oral commun., 1976)
Boulder Creek Granodiorite and associated rocks of the Routt Plutonic Suite (Early Pro-terozoic)—Mottled grayish-white and black, medium- to very coarse grained, locally por-phyritic, predominantly granodiorite but in-cludes lenses and layers of gabbro, hornblende diorite, hornblendite, and quartz diorite. Rb-Sr determinations suggest the Boulder Creek is about 1,700 m.y. old (Peterman and others, 1968; Reed and others, 1987)
Gabbro and related rocks (Early Proterozoic)— Dark-gray to pinkish-gray, black and white, massive, coarse-grained to very coarse grained rock ranging in composition from metagabbro to quartz diorite; contains intermediate plagio-clase and orthopyroxene and clinopyroxene
Hornblende diorite, quartz-bearing hornblende diorite, quartz diorite, and hornblendite (Ear-ly Proterozoic)—Gray to black, medium- to fine-grained, gray to black hornblende-bearing rocks. Exists in small plutons, lenses, pods, and dikes
EARLY PROTEROZOIC METAMORPHIC ROCKS [The mineralogy and modal, chemical, and quantitative analyses of the metamorphic rocks are given in Gable
(1996).]Amphibolite—Dark-greenish-gray to black, fine- to
medium-grained, nonlayered to poorly layered, weakly to strongly foliated rock, composed mostly of hornblende and plagioclase
EARLY PROTEROZOIC METASEDIMENTARY AND METAVOLCANIC ROCKS
Quartzite and quartz gneiss—Quartzite is white, gray, and pinkish or purplish gray, medium to coarse grained, and locally conglomeratic. In-terlayered with quartz-mica schist and some calc-silicate gneiss lenses. Quartzite along Coal Creek and in Eldorado Springs area is interlay-ered with conglomeratic quartzite. At some lo-calities, foliated quartz gneiss is conspicuously layered and contains variable amounts of gar-net, magnetite-ilmenite, and epidote
Quartz-biotite-muscovite schist—Silver-gray to dark-gray, fine- to medium-grained, micaceous schist; locally contains porphyroblasts of anda-lusite, cordierite, and garnet and small amounts of staurolite and sillimanite. Mapped along mountain front in Ralston Buttes area
Feldspar-rich gneiss—Light-gray, leucocratic, fine- to medium-grained, microcline-plagioclase-quartz-biotite gneiss. Conspicuously foliated; granitic in appearance. Locally garnetiferous and ubiquitously interlayered with conformable thin to thick layers and lenses of hornblende gneiss, amphibolite, biotite gneiss, and locally calc-silicate rock
Interlayered feldspar-rich gneiss and hornblende gneiss—Feldspar-rich gneiss may contain horn-blende and is generally darker than the feld-spar-rich gneiss unit (Xf). Interlayered horn-blende gneiss is black, white, and dark gray or greenish gray and similar in composition to the hornblende gneiss in hornblende gneiss unit (Xgh). Layers and lenses of biotite gneiss, am-phibolite, calc-silicate rock, and biotite-quartz-plagioclase gneiss make up 10–30 percent of unit
Hornblende gneiss and amphibolite—Black, black and white, and dark gray or greenish gray, fine to medium grained, and layered; has weak to strong foliation. Consists of hornblende-plagioclase- quartz gneiss or hornblende-clinopyroxene- quartz-feldspar gneiss; in places interlayered with amphibolite, calc-silicate gneiss, biotite-quartz-plagioclase gneiss, and minor quartzite
Interlayered hornblende gneiss, calc-silicate gneiss, and amphibolite—Black and white, light gray, greenish gray, and yellowish green, fine to medium grained, layered; has moder-ate to good compositional layering and mod-erate to weak foliation. More leucocratic than hornblende gneiss (Xgnh) because individual gneiss layers are thicker and contain more fel-sic, calcic, and quartz-bearing layers. Contains minor cordierite-biotite gneiss and biotite-quartz-plagioclase gneiss
Biotite gneiss—Dark-gray, fine- to medium-grained, foliated, biotite-quartz-plagioclase gneiss; locally garnetiferous and microcline-bearing, and interlayered with hornblende gneiss, calc-silicate gneiss, and sillimanite-bio-tite-quartz gneiss. Patterned areas contain pro-fuse lenses and layers of granite gneiss
Biotite gneiss and amphibolite—Gray, fine- to medium-grained biotite-quartz-plagioclase gneiss interlayered and intergraded; includes profuse thin lenses and layers of amphibo-lite. Locally contains lenses and layers of hornblende-biotite-plagioclase gneiss, calc-silicate gneiss, quartzite, and profuse lenses and layers of granite gneiss and pegmatite
Biotite-plagioclase gneiss—Interlayered and in-tergraded biotite-quartz-plagioclase gneiss and sillimanite-biotite-quartz-plagioclase gneiss; has profuse lenses and layers of granitic gneiss and pegmatite, and at some localities contains small lenses and layers of calc-silicate gneiss, amphibolite, and quartzite. Contains much less amphibole than the biotite gneiss and amphib-olite unit (Xma)
Garnet-biotite gneiss—Exists as individual layers that grade into and are interlayered with minor units of biotite-quartz-plagioclase gneiss, garnet-sillimanite-biotite gneiss, and cordierite-garnet-sillimanite-biotite gneiss
Quartz-plagioclase gneiss—Leucocratic, poorly fo-liated, and contains thin layers of biotite gneiss, feldspar-rich gneiss, quartzite, hornblende gneiss, and amphibolite. Only mapped along mountain front south of Morrison
Cordierite-garnet-gedrite-biotite gneiss—Dark gray to black, medium to very coarse grained, foliated to massive. Interlayered with thinner layers of cordierite-biotite gneiss, garnet-bio-tite gneiss, and cordierite-garnet-sillimanite-bi-otite gneiss. K-feldspar is not present or is rare in these rocks
Cordierite-garnet-sillimanite-biotite gneiss ± K-feldspar ± plagioclase—Generally gray to very dark gray, fine to medium grained, and foliated. Foliation or layering disrupted by pegmatite, gar-net, fibrolitic sillimanite, and clusters of cordierite and biotite. May be finely interlayered with one or more of the following types of gneiss: garnet- sillimanite-biotite, cordierite-biotite, garnet-biotite, cordierite-garnet-biotite, cordierite-sillimanite-biotite, magnetite-sillimanite-biotite, and cordierite-magnet-ite-sillimanite-biotite
Sillimanite-biotite gneiss—Banded light gray, very dark gray, or black; at some localities interlay-ered with biotite-quartz-plagioclase gneiss and layers and lenses of amphibolite, biotite gneiss, calc-silicate gneiss, and garnet-biotite gneiss. South of the Idaho Springs-Ralston shear zone, primary muscovite and trace amounts of cor-dierite present in unit. Pattern shows area that contains profuse pods and lenses of Silver Plume Granite (Ysp)
Cordierite-magnetite-sillimanite-biotite gneiss and minor magnetite-sillimanite-biotite gneiss—Light gray to nearly black, fine to me-dium grained, compositionally layered. In pla-ces layers discontinuous due to stringers and clots of pegmatite and knots of cordierite, silli-manite, biotite, and magnetite. Both rock types gradational into cordierite-garnet-sillimanite-bio-tite gneiss (Xgnc) and sillimanite-biotite gneiss (Xgns)
Cordierite-sillimanite-biotite gneiss—Light-gray, medium-grained, foliated biotite gneiss. Map-ped only in Evergreen-Squaw Pass area
Calc-silicate gneiss—Variable gray, green, white, or black and fine to coarse grained. Color de-pends on the type and quantity of minerals present, such as hornblende, diopside, biotite, calcic-plagioclase, scapolite, and quartz. Folia-tion poor but compositional layering good
Rutile-bearing, sillimanite-quartz gneiss and bio-tite-quartz gneiss—Light gray, fine to medium grained, and commonly interlayered with bio-tite-quartz gneiss and sillimanite-quartz gneiss. Exists as thin lenses in the Evergreen-Squaw Pass area
Sillimanite-quartz gneiss containing accessory rutile lenses—Light gray to gray, fine to medium grained, and foliated. Exists only as thin lenses 15 cm to 30 m wide in the Evergreen and Squaw Pass quadrangles; most are of limited extent but one is 6 km long
Augen gneiss—Fine-grained, sheared gneiss contain-ing small, pink feldspar augen in a well-foliated bi-otitic matrix. Mapped only in Ralston Buttes area
Contact—Approximately located, dotted where concealed; queried where inferred
Fault or fracture zone—Dashed where approxi-mately located; dotted where concealed; quer-ied where uncertain. Arrows show apparent di-rection of relative movement. Pattern indicates broad zone of brecciation
Fault zone—Shown where map unit is fractured and not identifiable
Zone of closely spaced shears
Boundary of Idaho Springs-Ralston shear zone
Folds—Showing approximate trace of axial plane and direction of plunge. Dotted where con-cealed; queried where inferred
Antiform
Overturned antiform
Synform
Overturned synform
Small-scale linear and planar features
Bearing and plunge of axis of minor folds— Symbols show plan view of minor folds
Strike and dip of foliationInclined
Vertical
Bearing and plunge of lineation—Lineations de-fined by aligned minerals, mineral streaks, and fold axes or intersection of planar elements. Symbol may be combined with foliation symbol
IDAHO S
PRINGS
EVER
GREEN
MORRIS
ON
CONIFER
INDIA
N HILL
S
BAILEY
PINE
PLATT
E CANYO
N
KASSLER
SQUAW PA
SS
ISOLA
TION
PEAK
ALLEN
SPA
RK
STRAW
BERRY
LAKE
MONARCH
LAKE
WARD
GOLD H
ILL
BOULDER
EAST P
ORTAL
NEDER
LAND
TUNGSTE
N
ELDORADO
SPRINGS
EMPIR
E
CENTR
AL CIT
Y
BLACK H
AWK
RALSTO
NBUTT
ES
GOLDEN
SHADOWM
OUNTAIN
40°15'
7'30"
40°00'
105°00'
7'30"
15'22'30"
30'37'30"45'105°52'30"
52'30"
45'
37'30"
30'
39°22'30"
1 2 3
45678
9 10 11 12
1314151617
18 19 20 21
2223
24 25 2627
1. Pearson (1980) 2. Pearson (1980) 3. Pearson (1980) 4. Wrucke and Wilson (1967) 5. Gable (1980) 6. Gable and Madole (1976) 7. Pearson (1980) 8. Schroeder (1995) 9. Young (1991)10. Gable (1969)11. Gable (1972)12. Wells (1967)13. Van Horn (1972)14. Sheridan and others (1967)15. Taylor (1976)16. Sims and Gable (1967)
17. Braddock (1969)18. Moench and others (1962) Moench (1964) Hawley and Moore (1967)19. Sheridan and Marsh
(1976)20. Sheridan and others
(1972)21. Gable (1968)22. Bryant and others (1973)23. Bryant (1974a)24. Bryant (1976)25. Bryant (1974b)26. Peterson (1964)27. Scott (1963)
SOURCES OF GEOLOGIC DATA
COLORADO
MAP LOCATION
Map area
Mountain
Front
REFERENCES CITED
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Braddock, W.A., 1969, Geology of the Empire quadrangle, Grand, Gilpin, and Clear Creek Counties, Colorado: U.S. Geological Survey Professional Paper 616, 56 p.
Bryant, B.H., 1974a, Reconnaissance geologic map of the Conifer quadrangle, Jefferson County, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF–597, scale 1:24,000.
———1974b, Reconnaissance geologic map of the Pine quadrangle, Jefferson County, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF–598, scale 1:24,000.
———1976, Reconnaissance geologic map of the Bailey quadrangle, Jefferson and Park Counties, Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF–816, scale 1:24,000.
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———1972, Geologic map of the Tungsten quadrangle, Boulder, Gilpin, and Jefferson Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ–978, scale 1:24,000.
———1980, Geologic map of the Gold Hill quadrangle, Boulder County, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ–1525, scale 1:24,000.
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Moench, R.H., 1964, Geology of Precambrian rocks, Idaho Springs district, Colorado: U.S. Geological Survey Bulletin 1182–A, 70 p.
Moench, R.H., Harrison, J.E., and Sims, P.K., 1962, Precambrian folding in the Idaho Springs-Central City area, Front Range, Colorado: Geological Society of America Bulletin, v. 73, p. 35–58.
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Peterson, W.L., 1964, Geology of the Platte Canyon quadrangle, Colorado: U.S. Geological Survey Bulletin 1181–C, 23 p.
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Schroeder, D.A., 1995, Geologic map of the Strawberry Lake quadrangle, Grand County, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ–1764, scale 1:24,000.
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Sheridan, D.M., and Marsh, S.P., 1976, Geologic map of the Squaw Pass quadrangle, Clear Creek, Jefferson, and Gilpin Counties, Colorado: U.S. Geological Survey Geologic Quadrangle Map GQ–1337, scale 1:24,000.
Sheridan, D.M., Maxwell, C.H., and Albee, A.L., 1967, Geology and uranium deposits of the Ralston Buttes district, Jefferson County, Colorado, with a section on Paleozoic and younger sedimentary rocks, by Richard Van Horn: U.S. Geological Survey Professional Paper 520, 121 p.
Sheridan, D.M., Reed, J.C., Jr., and Bryant, B.H., 1972 [1973], Geologic map of the Evergreen quadrangle, Jefferson County, Colorado: U.S. Geological Survey Miscellaneous Geologic Investigations Series Map I–786–A, scale 1:24,000.
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Van Horn, Richard, 1972, Surficial and bedrock geologic map of the Golden quadrangle, Jefferson County, Colorado: U.S. Geological Survey Folio of the Golden quadrangle, Colorado, Map I–761–A, scale 1:24,000.
Wells, J.D., 1967, Geology of the Eldorado Springs quadrangle, Boulder and Jefferson Counties, Colorado: U.S. Geological Survey Bulletin 1221–D, 85 p.
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