Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

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North Fork. Deposits typically composed of both matrix-supported beds (debris flow facies) and clast-supported beds (streamflow facies), often interbedded. Clasts are mostly angular to subround with varied lithologies dependant upon local source rock. Sediments Figure 12. View of younger alluvial fan deposits (Qfy) on south side of South Arkansas River. are deposited by debris flows, hyperconcentrated flows, streams, and sheetwash. Deposit overlies and thus post-dates Pinedale outwash and till deposits. Maximum thickness may exceed 16 ft. Extreme precipitation events are likely to trigger future deposition on these young alluvial-fan deposits. Fan deposits may be prone to collapse when wetted or loaded. Qfo Alluvial-fan deposits, older (middle to late Pleistocene) – Moderately sorted, sand- to boulder-size gravel in dissected, fan-shaped deposits derived from tributary streams. Deposits typically composed of both matrix-supported beds (debris flow facies) and clast-supported beds (streamflow facies), often interbedded. Clasts are mostly 58
angular to subangular. Deposits generally predate the Pinedale glaciation and lie 66 ft or more above modern streams. Maximum thickness is at least 16 ft. Qfol Mixed landslide and alluvial-fan deposits, older (middle to late Pleistocene) – Poorly sorted, sand- to boulder-size gravel in a fan-shaped deposit downslope from landslide deposits between the two branches of Squaw Creek. Deposit is poorly exposed but is thought to contain multiple generations of flow-type landslide deposits (earthflows and debris flows), lateral spreads, and landslide deposits reworked by running water. Deposit probably represents the distal facies of landslide and flowslide deposits from landslide failure of saturated till on the steep terminal moraine fronts overlying active traces of the Shavano fault zone. Maximum thickness is unknown but is inferred to be at least 16 ft. Qfvo Alluvial-fan deposits, very old (early to middle Pleistocene) – Moderately sorted, sand- to boulder-size gravel in small erosional remnants of very old alluvial fans. Mapped on the south side of the South Arkansas River, where small terrace-like remnants lie 350-400 ft above the river between Green Creek and Pass Creek. Also mapped on the drainage divide west of lower Willow Creek. Deposits are poorly exposed and may include components of both alluvial fans shed from Dry Union Formation terrane and of mainstream gravels of the ancestral South Arkansas River. Deposits possibly correlative with Nebraskan alluvium (Qna2) of the range-front piedmont, based on height above streams. Maximum thickness is at least 16 ft. TERTIARY ROCKS AND DEPOSITS Tertiary sedimentary and igneous rocks cover a large part (approximately 31.1 percent) of the Maysville quadrangle. Igneous rocks are only a small percentage of this (about 3.1 percent). Tertiary sedimentary rocks are represented by the Dry Union Formation (Td and Td2), which covers the largest surface area (estimated about 28 percent) of any single lithologic unit in the Maysville quadrangle. The Dry Union 59
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OPEN-FILE REPORT 06-10 Geologic Map
Page 3 and 4:
TABLE OF CONTENTS Introduction…
Page 5 and 6:
mylonitic, augen textures………
Page 7 and 8: INTRODUCTION LOCATION AND ACCESS Th
Page 9 and 10: SAWATCH RANGE RIFT-SHOULDER UPLIFT
Page 11 and 12: of the South Arkansas River (subseq
Page 13 and 14: EXPLANATION Rio Grande Rift Neogene
Page 15 and 16: in descriptions of the geologic uni
Page 17 and 18: During the Early and Middle Paleozo
Page 19 and 20: Mountains, and White River uplifts
Page 21 and 22: field are the largest remnants of t
Page 23 and 24: Figure 5. Detailed geologic-structu
Page 25 and 26: with the Colorado mineral belt (Boo
Page 27 and 28: Shannon, 2005). Widmann and others
Page 29 and 30: the Upper Arkansas graben (fig. 5)
Page 31 and 32: 15-minute quadrangle, which is adja
Page 33 and 34: etween the northern and southern se
Page 35 and 36: on U.S. Forest Service color aerial
Page 37 and 38: We use fractional map units on the
Page 39 and 40: Qpt Pinedale till, undivided (late
Page 41 and 42: weathered, but Mount Princeton quar
Page 43 and 44: stratified, matrix-supported, bould
Page 45 and 46: as rockfalls, rock avalanches, rock
Page 47 and 48: stream-channel deposits of all pere
Page 49 and 50: Figure 10. View west up South Arkan
Page 51 and 52: Figure 11. View west up South Arkan
Page 53 and 54: valley near the eastern map boundar
Page 55 and 56: lithologies are variable and depend
Page 57: Arkansas River in parts of Redman C
Page 61 and 62: elations, age constraints from foss
Page 63 and 64: elated to the inferred Squaw Creek
Page 65 and 66: Figure 14. Crude bedding in coarse
Page 67 and 68: microcline, and muscovite. The latt
Page 69 and 70: Volcanic Ash Figure 17. View of eas
Page 71 and 72: Figure 18. Close-up view of intense
Page 73 and 74: The western zone of brecciated Pale
Page 75 and 76: Tr Rhyolite dikes (early to late Ol
Page 77 and 78: as the overall N47°E trend of the
Page 79 and 80: One age determination on the rhyoli
Page 81 and 82: northwest-trending fault. Thus, fie
Page 83 and 84: on the North Fork leucogranite intr
Page 85 and 86: A small 400 by 400 foot body of Nor
Page 87 and 88: N12°E, 62°NW (about 6,000 ft sout
Page 89 and 90: The age of the quartz latite porphy
Page 91 and 92: Tma Mount Aetna quartz monzonite po
Page 93 and 94: of the Maysville quadrangle and the
Page 95 and 96: Mount Aetna ring dikes (Tma), one i
Page 97 and 98: the margins of the pluton, includin
Page 99 and 100: Shannon (1988). The average of seve
Page 101 and 102: indicating a granite b composition
Page 103 and 104: analysis by Crawford (1913), two an
Page 105 and 106: locally tanish to pinkish gray. It
Page 107 and 108: quadrangle (tables 1 and 3) were fr
Page 109 and 110:
slices of Paleozoic sedimentary roc
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south-southwest of Maysville is a 9
Page 113 and 114:
There is one additional Paleozoic s
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near the southwest margin of the qu
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eastern contact of the diorite intr
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endoskarn zones. The two widely sep
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Xhig) along the southeastern contac
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Xgd Granodiorite (Early Proterozoic
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Hybrid granodiorite is locally deve
Page 127 and 128:
Xcs Calc-silicate gneiss (Early Pro
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Many of the calc-silicate gneiss zo
Page 131 and 132:
typically expressed by intermittent
Page 133 and 134:
The field relations and characteris
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the north side of all three segment
Page 137 and 138:
eplaced by muscovite. The western m
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sillimanite-quartz-muscovite that a
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sillimanite gneiss (Xmsg) and the m
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Figure 35. Outcrop of Proterozoic h
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samples) indicates they are compose
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Xal Lineated amphibolite (Early Pro
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of the Proterozoic metamorphic rock
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that the present structural configu
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elated to rotation of domain blocks
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sometimes terminate at a cross stru
Page 157 and 158:
limestone that is exposed in a wind
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quadrangle are intimately associate
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of the quadrangle. The north-northw
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quartz monzonite ring dikes (Tma).
Page 165 and 166:
that truncates the Upper Arkansas g
Page 167 and 168:
as at the mouth of Squaw Creek. How
Page 169 and 170:
adjacent to the southwestern edge o
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graben and the Upper Arkansas Valle
Page 173 and 174:
GEOLOGIC HAZARDS Potential geologic
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In addition, older landslides may h
Page 177 and 178:
sparse vegetation. One such area is
Page 179 and 180:
Table 7. Historical (pre-instrument
Page 181 and 182:
4262272N. ECONOMIC GEOLOGY Currentl
Page 183 and 184:
A number of the larger pegmatite bo
Page 185 and 186:
River placers near Buena Vista (Van
Page 187 and 188:
The small mines and prospects along
Page 189 and 190:
elatively recent (post-1970) explor
Page 191 and 192:
contact of two Quaternary gravels (
Page 193 and 194:
quadrangle. The first area is a clu
Page 195 and 196:
y Sharp (1976) to be a fault slice
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quadrant of the Maysville quadrangl
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the large Paleozoic rock outlier) i
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WATER RESOURCES Water resources on
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water near Maysville is being produ
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to Rudy C. Epis: Colorado School of
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University, M.Sc. thesis, 50 p. Din
Page 209 and 210:
Hutchinson, R.M., and Hedge, C.E.,
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Litsey, L.R., 1958, Stratigraphy an
Page 213 and 214:
County, Colorado, in Berg, R.R., an
Page 215 and 216:
Stark, J.T., and Barnes, F.F., 1935
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Tweto, O., 1987, Rock units of the
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quadrangle, Colorado: U.S. Geologic
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94A 391996 4263422 Prospect YXp;Xbf
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336A 396189 4274961 Prospect Xgdf B
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854 391849 4268852 42 Adit; Geochem
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Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

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