Geologic map of the upper Arkansas River valley region, north-central Colorado
<p>This 1:50,000-scale U.S. Geological Survey geologic map represents a compilation of the most recent geologic studies of the upper Arkansas River valley…
Public-domain full text preserved in the Mountain Man Mining Library. Original source: pubs.usgs.gov.
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Ml Ml Ml Ml Ml Ml Ml Ml Of Of Oh Oh Oh Oh O m O ms O ms O ms Ofh Ofh Ofh Ofh Oh Oh O m Ml Oh Of Oh Ml Ml Ml Ml Ml Of Ofh Oh Ml Ml Ml Ofh Ofh O ms O ms O ms O ms O ms O ms Ofh Ofh Ofh Ofh Ofh Ofh Ml Ml Ml Ml Ml Ml Ml Ml Ml Ml Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nda Nda Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd Nd O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m O m Oh Oh O m O m O m Oh Oh b b b b b b bc bc bc b b b b b b b b b b b b b F A U LT S Y S T E M 106°30'00" 106°15' 39°22'30" 39°07'30" 106°15'00" 39°00'00" 38°30'00" 38°30'00" 39°07'30" 106°00'00" 38°52'30" 39°00'00" 38°52'30" 38°45'30" 38°45'30" 106°15'30" 106°07'30" 106°00'00" 38°37'30" 38°37'30" 39°15'30" 106°07'30" 39°15'30" 106°22'30" No. Symbol on map Sample number Rock type USGS 7½' quadrangle Age±2σ Reference A RGB12102 Dry Union Formation, ash layer Nd Salida West
Morgan and Cosca, 2017 B PP15147B Dry Union Formation, ash layer Nda? Salida East 15.6±0.32 Morgan and Cosca, 2017 Dry Union Formation, ash layer Nda Maysville 13.5±0.22,8 Hubbard and others, 2001 Dry Union Formation, ash layer Nda Maysville 14.4±1.42,8 Hubbard and others, 2001 Late felsite dike (Rasp. Gulch rhy) Mount Antero 22±1 Limbach, 1975 D GR11-711 Basaltic andesite porphyry flow Granite 24.12±0.12 Shroba and others, 2014 E GR11-756 Quartz porphyry stock Granite 24.3±0.6 (s?)2 Shroba and others, 2014 High-silica rhyolite dike 26.1±1.03 Limback, 19755 Leucogranite of Mount Antero Mount Antero? 29.97±0.13 McIntosh and Chapin, 2004 Rhyolite of Bald Mtn, upper flow Buena Vista East 29.25±0.12 McIntosh and Chapin, 2004 Rhyolite of Ruby Mtn Buena Vista East 29.25±0.21 McIntosh and Chapin, 2004 Rhyolite of Ruby Mtn Buena Vista East 30.47±0.08 McIntosh and Chapin, 2004 Rhyolite of Ruby Mtn lower flow Buena Vista East 30.74±0.08 McIntosh and Chapin, 2004 California bt-granite leucogranite Mount Antero 30.7±1.13 Coolbaugh, 19856 MP-27 Granite of North Fork 31.37±0.181 Zimmerer and McIntosh, 2012 Rhyodacite flow and tuff Poncha Pass 33.2±1.3 Van Alstine, 1974 Bonanza Tuff 33.31±0.08 McIntosh and Chapin, 2004 Bonanza Tuff 33.42±0.20 McIntosh and Chapin, 2004 Bonanza Tuff 33.12±0.03 Lipman and others, 2015 Badger Creek Tuff 34.83±0.221 Zimmerer and McIntosh, 2012 Mount Aetna ring dike 34.57±0.182,8 McIntosh and Chapin, 2004 Monzogranite of Mount Aetna 34.51±0.902,8 McIntosh and Chapin, 2004 Table 2. Isotopic ages for rocks in the upper Arkansas Valley region. [No., line number; --, for symbol on map, indicates location uncertain or unit was sampled outside of the map area; --, for sample number, indicates no number given;σ, sigma, standard deviation; rasp., raspberry; rhy, rhyolite; p'phy, porphyry.] MP-21 Monzogranite of Mount Aetna 34.36±0.591 Zimmerer and McIntosh, 2012 NM-2117 Basaltic lava, Tenderfoot Hill Salida East 34.31±0.162,8 Kellogg and others, 2017 NM-2118 basaltic lava, Tenderfoot Hill Salida East 34.34±0.142,8 Kellogg and others, 2017 NM-2116 basaltic lava, Tenderfoot Hill Salida East 35.74±1.172,8 Kellogg and others, 2017 Late white porphyry Climax 34.9±3.87 Bookstrom, 1989 Late white porphyry Pearson and others, 1962 Andesite of Triad Ridge Buena Vista East 36.61±0.102,8 McIntosh and Chapin, 2004 F MOS-4 Little Union Quartz Latite Leadville South 36.3±0.21 NM-2120 Capping andesite, Buffalo Peaks Marmot Peak 38.28±0.562,8 Kellogg and others, 2017 Tuff of Buffalo Peaks Marmot Peak 38.68±0.32 McIntosh and Chapin, 2004 G HL09-170-1 lower tuff of Buffalo Peaks Harvard Lakes 37.9±0.3 Kellogg and others, 2013 Upper tuff of Triad Ridge Buena Vista East 36.69±0.32 McIntosh and Chapin, 2004 Lower tuff of Triad Ridge Buena Vista East 37.96±0.22 McIntosh and Chapin, 2004 Tuff of Triad Ridge Buena Vista East 37.66±0.112,8 Wallace and Keller, 2003 Tuff of Triad Ridge Buena Vista East 38.45±0.302,8 Wallace and Keller, 2003 Wall Mountain Tuff 37.17±0.092,8 McIntosh and Chapin, 2004 Wall Mountain Tuff 37.25±0.104 Zimmerer and McIntosh, 2012 Mount Princeton batholith 34.75±0.212,8 McIntosh and Chapin, 2004 Mount Princeton batholith 36.6±0.45 McCalpin and Shannon, 2005 Mount Princeton batholith 35.80±0.101 Mills and Coleman, 2013 Mount Princeton batholith 35.37±0.101 Mills and Coleman, 2013 H MOS-20 Johnson Gulch Porphyry Mount Sherman 39.5±0.61 Kellogg and others, 2017 GR11-725 White felsite porphyry Granite 42.25±0.132 Shroba and others, 2014 TL Twin Lakes Granodiorite p'phy Mount Elbert 42.7±1.2 Obradovich and others, 1969 R8-28-84-8a Twin Lakes Granodiorite p'phy Mount Elbert 64.6±1.4 Fridrich and others, 1998 NM-2124 Granite porphyry of Tumble Hill Jones Hill 60.64±0.172,8 Kellogg and others, 2017 NM-2125 Granite porphyry of Tumble Hill Jones Hill 60.57±0.162,8 Kellogg and others, 2017 NM-2126 Granite porphyry of Tumble Hill Jones Hill 60.58±0.152,8 Kellogg and others, 2017 J MOS-5 correlated with Pando Porphyry Mount Sherman 64.1±0.91 Kellogg and others, 2017 correlated with Pando Porphyry Cunningham and others, 1994 Granite porphyry of Black Mtn. Jones Hill 60.97±0.152 Widmann and others, 2011 K HL09-44 Monzodiorite dike Harvard Lakes 65.3±0.5 Kellogg and others, 2013 HL09-89 Hornblende syenodiorite Harvard Lakes 65.4±0.5 Kellogg and others, 2013 M HL09-136 Hornblende-biotite diorite plug Harvard Lakes 68.1±0.9 Kellogg and others, 2013 N Rhyolite dike Granite 65.3±2.43 Marvin and others, 1989 Whitehorn Granodiorite Kwg Salida East? 69.4±2.1 McDowell, 1971 Whitehorn Granodiorite Kwg Salida East? 70.0±2.1 Wrucke, 1974 Whitehorn Granodiorite Kwg Salida East? 70.4±2.1 McDowell, 1971 9-13-84-1 Browns Pass Granite Ybp Mount Yale 1,439±111 Moscati and others, 2012 CO-38 Browns Pass Granite Ybp Mount Yale? 1,420±35 Wetherill and Bickford, 1965 O 8-3-83-1 Granodiorite of Mount Harvard Ygdh Mount Harvard 1,414±201 Moscati and others, 2012 P 9-8-83-1 Granodiorite of Mount Elbert Ygdm Mount Elbert 1,415±151 Moscati and others, 2017 Q WRP-03-6B Granite of Granite Ygrg Granite 1,429±91 Moscati and others, 2017 R GR10-511 Granite of Granite Ygrg Granite 1,434±61 Moscati and others, 2017 S 8-31-84-3 Langhoff Gulch Granite Ygl Mount Sherman 1,435±261 Moscati and others, 2017 T 9-1-84-10 St. Kevin Granite Ygs Mount Massive 1,425±121 Moscati and others, 2017 U HL09-53 Langhoff Gulch Granite Ygl Harvard Lakes 1,441±541 Moscati and others, 2017 MP09-191 Langhoff Gulch Granite Ygl Marmot Peak 1,438±111 Moscati and others, 2017 W WRP03-7 Elephant Rock Granite Yge Buena Vista East 1,434±81 Moscati and others, 2017 HL09-121 Elephant Rock Granite Yge Harvard Lakes 1,436±81 Moscati and others, 2017 RB8-10-83-1 Granodiorite Winfield 1,436±111 Moscati and others, 2017 Y R8-17-83-2A Granite of Mount Yale Xgy Mount Yale 1,695±111 Moscati and others, 2017 Z 8-11-84-3 Denny Creek Granodiorite Xdk Mount Elbert 1,691±51 Moscati and others, 2017 R8-20-84-1 Denny Creek Granodiorite Xdk Mount Harvard 1,710±101 Moscati and others, 2017 AA Bickford Henry Mountain? Granite Xgd Cameron Mountain 1,672±51 Bickford and others, 1989 BB CM11-736 Henry Mountain? Granite Xgd Cameron Mountain 1,709±61 Moscati and others, 2017 WRP03-8 Metadacite of Salida Xvs Salida East 1,732±41 DD Z-3 Metadacite of Salida Xvs Salida East 1,728±61 Bickford and others, 1989 Kellogg and others, 2017 Kellogg and others, 2017 ar bf rc rp ag nr nr nr nr cg nf rd bt bt bt bc ma ma ma ab ab ab lw lw cn lu a tu tl tr tr tr tr wm wm mp mp mp mp gj wf tl tl gt gt gt Kw Kw gp Km Km Km Kw 1Mean 207Pb/206Pb zircon age or U-Pb zircon concordia age. 2 40Ar/39Ar date. Mineral dated: p, plagioclase; s, sanidine; b, biotite; m, muscovide; h, hornblende. 3K/Ar ages. Mineral dated: b, biotite; h, hornblende; w, whole rock; no letter, not specified. 4Weighted mean of five 40Ar/39Ar ages in sanadine. 5Average of twenty-one K-Ar and fission-track ages. 6Recalculated by Shannon, 1988. 7Apatite fission-track age. 8Recalculated using revised standards for Fish Canyon Tuff sanidine (Kuiper and others, 2008) 105°52'30" 106° 106°7'30" 106°15' 106°22'30" 106°30' 39°22'30" 39°15' 39°7'30" 39° 38°52'30" 38°45' 38°37'30" 38°30' MARMOT PEAK MOUNT ELBERT HOMESTAKE RESERVOIR LEADVILLE SOUTH FAIRPLAY WEST CASTLE ROCK GULCH WHITEPINE SAINT ELMO SOUTH PEAK JONES HILL GARFIELD MOUNT HARVARD MOUNT MASSIVE GRANITE CAMERON MOUNTAIN ANTERO RESERVOIR MAYSVILLE HARVARD LAKES SALIDA WEST WINFIELD MOUNT ANTERO LEADVILLE NORTH MOUNT SHERMAN CLIMAX ALMA FAIRPLAY EAST CUMBERLAND PASS MOUNT YALE NATHROP BUENA VISTA EAST SALIDA EAST TINCUP BUENA VISTA WEST GARO COMO USGS Ruleman, 2012 unpublished mapping CGS OF-08-17 (McCalpin and others, 2012b) USGS SIM 3271 (Bohannon and Ruleman, 2013) USGS Ruleman, 2012 unpublished mapping CGS OF-09-5 (McCalpin and others, 2012a) CGS OF-05-8 (McCalpin and Shannon, 2005) CGS OF-11-4 (Widmann and others, 2011) CGS OF-12-1 (Houck and others, 2012) CGS OF-05-8 (McCalpin and Shannon, 2005) OF-98-4 CGS (Wallace and Lawson, 1998) CGS OF-03-1 (Wallace and Keller, 2003) CGC OF-97-6 (Wallace and others, 1997) CGS OF-04-3 (Widman and others, 2004) CGS OF-06-10 (McCalpin and Shannon, 2006) Colo.School of Mines T-1593 Ph.D. dissertation Knepper, 1974) CGS OF-04-4 (Keller and others, 2004) USGS SIM 3294 (Shroba and others, 2014) USGS SIM 3267 (Kellogg and others, 2014) USGS I-952 (Brock and Barker, 1972) USGS PP 289 (Dings and Robinson, 1957) USGS PP 829 (Van Alstine, 1974) USGS PP 626 (Van Alstine and Cox, 1969) USGS Kellogg, 2012 unpublished mapping USGS Kellogg, 2009 unpublished mapping USGS Kellogg, 2012 E. DeWitt, 1995 unpublished mapping GUNNISON COUNTY CHAFFEE COUNTY PARK COUNTY LAKE COUNTY 5 KILOMETERS 5 MILES Base modified from U.S. Geological Survey digital data, 2,000,000 Universal Transverse Mercator projection, zone 13N North American Datum of 1927 (NAD27) Extent of lidar coverage and sources of geologic mapping. For U.S. Geological Survey (USGS) publications, the publication number, and year of publication are shown. For non-USGS publications, the State agency or institution, the and year of publication are shown. CGS, Colorado Geological Survey; SIM, Scientific Investigations Map; PP, Professional Paper. Behre (1953) Boardman (1976) Hedlund (1985) Ruleman (2012) Tweto (1974a) Tweto and Reed (1973) Fridrich and others (1998) Shannon (1988) Lidar coverage Boundary of map area EXPLANATION Sources of geologic data Twin Lakes Taylor Park Reservoir Antero Reservoir Clear Creek Reservoir Turquoise Lake Homestake Reservoir Robinson Tailings Pond 105°52'30" 106° 106°7'30" 106°15' 106°22'30" 106°30' 106°37'30" 39°30' 39°22'30" 39°15' 39°7'30" 38°52'30" 38°45' 38°37'30" 38°30' 38°22'30" 39° BROWNS CANYON NATIONAL MONUMENT FCW LNFH CHAFFEE COUNTY FREMONT COUNTY PARK COUNTY GUNNISON COUNTY SAGUACHE COUNTY PITKIN COUNTY EAGLE COUNTY LAKE COUNTY SUMMIT COUNTY Fairplay Granite Breckenridge Buena Vista Salida Leadville Poncha Springs Alma SDCW SAN ISABEL NATIONAL FOREST SAN ISABEL NATIONAL FOREST SAN ISABEL NATIONAL FOREST SAN ISABEL NATIONAL FOREST RGNF RGNF RGNF PIKE NATIONAL FOREST PIKE NATIONAL FOREST WHITE RIVER NATIONAL FOREST WRNF WHITE RIVER NATIONAL FOREST WHITE RIVER NATIONAL FOREST GUNNISON NATIONAL FOREST BUFFALO PEAKS WILDERNESS MOUNT MASSIVE WILDERNESS HUNTERFRYINGPAN WILDERNESS HOLY CROSS WILDERNESS COLLEGIATE PEAKS WILDERNESS COLLEGIATE PEAKS WILDERNESS WRNF 10 MILES 10 KILOMETERS MAP LOCATION COLORADO DENVER Map area Seleced boundaries. Generalized selected Federal boundaries in the map area. FCW, Fossil Creek Wilderness; LNFH, Leadville National Fish Hatchery; RGNF, Rio Grande National Forest; SDCW, Sangre de Cristo Wilderness; WRNF, White River National Forest. Federal lands information was obtained from the U.S. Geological Survey The National Map, May 2017 at ://nationalmap.gov/small_scale/atlasftp.?openChapters=chpbound#chpbound and the Bureau of Land Management, May 2017 at ://navigator.blm.gov/data. There may be private inholdings within the boundaries of National or State reservations shown on this map. Map area Major roads County boundary National Forests Wilderness Areas and Browns Canyon National Monument Leadville National Fish Hatchery Other lands EXPLANATION EXPLANATION Surficial deposits (Quaternary) Dry Union Formation and Santa Fe Group (Pliocene and Miocene) Predominantly sedimentary deposits (Oligocene and Eocene) Volcanic rocks (Oligocene and Eocene) Ignimbrites of San Juan and Thirtynine Mile volcanic fields (early Oligocene to middle Eocene) Felsic, mostly porphyritic intrusive rocks (Oligocene to Late Cretaceous) Leucogranite suite of Mount Antero (early Oligocene) Monzogranite of Mount Aetna (late Eocene) Rocks of Mount Princeton batholith (late Eocene) South Park Formation (Paleocene and Upper Cretaceous) Upper Cretaceous to Triassic sedimentary rocks Paleozoic sedimentary rocks Mesoproterozoic granite and granodiorite Intrusive rocks of either Mesoproterozoic or Paleoproterozoic age— Mostly granitic rock Intrusive rocks of Paleoproterozoic age Metasedimentary rocks (Paleoproterozoic) Metavolcanic and metasedimentary rocks of the Gunnison-Salida metamorphic belt Paleoproterozoic) Contact Normal fault—Bar and ball on downthrown side Reverse fault—Rectangles on upthrown block (hanging wall) Fault—Type undetermined. Dashed where location is concealed Mount Aetna cauldron ring-dike Qu Nd s t Kg cs u u Yg Xg Xm Xvs YXg lg ma mp Kg Kg Kg Kg Kg Kg Kg Kg Kg Kg s t t t t t t Kg Kg mp t t ma t t t t t t t lg s lg lg mp mp t t s s Kg Kg cs u u u u u u u u u u u u u u u u u u u u u u u u u Qu Qu Qu Qu Qu Qu Qu Qu Qu Nd Nd Qu Qu Kg Kg Kg YXg YXg YXg YXg YXg YXg Xg Xg Xg Xg Xg Xvs Xvs Xvs Xvs Xvs Xvs Xvs bv Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Yg Xm Xm Xm Xm Xm Xm Xm Yg Yg Nd Nd Nd Xg Xg Xg Xg Xg Xg Xm YXg Xm Xm Xm Nd Nd Nd Nd Xm Xm Xm Xm u Poncha Pass Antero Reservoir Twin Lakes Homestake Reservoir Turquoise Reservoir LONDON FAULT FAULT MOSQUITO Clear Creek Reservoir SAWATCH RANGE FAULT ZONE ST. KEVINS GRANITE TWIN LAKES PORPHYRY Independence Pass Browns Canyon horst MOUNT PRINCETON BATHOLITH MOUNT AETNA CALDERA SOUTH PARK S A W AT C H R A N G E M O S Q U I T O R A N G E BUFFALO PEAKS PALEOVALLEY TROUT CREEK PALEOVALLEY WAUGH MOUNTAIN PALEOVALLEY Map outline The Upper Arkansas River Valley Arkansas River MAYSVILLE-SALIDA FAULT WESTON PASS FAULT SYSTEM 106°15' 106° 106°30' 39°30' 39° 38°45' 38°30' 39°15' 106°30' 106°15' 106° Fairplay Granite Breckenridge Buena Vista Salida Leadville Poncha Springs Alma 20 KILOMETERS 20 MILES Base modified from U.S. Geological Survey digital data Universal Transverse Mercator projection, zone 13N North American Datum of 1927 (NAD27) Regional structure map of the mapped area. Figure 1A in text. MAP LOCATION COLORADO DENVER Map area View to the north of Buffalo Peaks, which are composed mostly of andesite flows, andesite breccias, lahars, and welded tuff deposited on Mesoproterozoic granite. The peak on the left is West Buffalo Peak (4,062 meters [m]; 13,326 feet [ft]) and the peak on the right is East Buffalo Peak (4,054 m; 13,330 ft). Figure 10 in text. View north of ash bed (white layer ~30 centimeters [cm] thick), about 1 meter (m) below the top of an exposed section of Dry Union Formation, just below the Qg2 outwash gravel deposit, on which the person is standing. Note the few clasts of unit Qg2 in colluvial mantle in the lower left of the photo. The ash bed in the photo is correlated with dated ash exposed at location B, about 0.9 kilometers (km) southwest of photo. The ash bed at location B has a U-Pb zircon age of 10.233±0.032 Ma (table 2). Figure 9 in text. Bighorn sheep on a large outcrop of Langhoff Gulch Granite, about 5 km north of the town of Granite, Colo. Photograph by K.S. Kellogg, July 2013. SCALE 1:50 000 1/ 2 4 MILES 21000 FEET 5 KILOMETERS COLORADO MAP LOCATION DENVER Kellogg compiled and revised the geology of the map area and wrote the map-units descriptions and other text during 2009-2014. Shroba mapped many of the Quaternary and Neogene deposits with the aid of lidar (light detection and ranging) imagery during 2014-2016. He revised the map-units descriptions and other text describing Quaternary and Neogene deposits. Ruleman and Shroba remapped Quaternary faults and lineaments in Quaternary deposits with the aid of the lidar imagery. Bohannon mapped the bedrock geology and structure in the USGS Mount Sherman 7.5' quadrangle during 2010-2012. McIntosh, Premo, Cosca, and Moscati determined isotopic ages of Proterozoic and Tertiary bedrock units in the map area. Brandt assisted in interpretation of Quaternary features from lidar data, generated slope and shaded-relief scenes from lidar data used for geologic and shoreline-feature interpretation, and prepared the digital compilation of the geologic map. GIS database and digital cartography by T.R. Brandt Publishing support provided by Denver Publishing Service Center Edit and digital layout by L.J. Binder Manuscript approved for publication May 23, 2017 Topographic base from U.S. Geological Survey 1:100,000-scale Bailey, 1983; Leadville, 1983; Gunnison, 1984; and Pikes Peak, 1983 Shaded relief base from U.S. Geological Survey National Elevation Dataset (NED), accessed on March 15, 2016 at ://lta.cr.usgs.gov/NED North American Datum of 1927 (NAD 27) Universal Transverse Mercator, zone 13 Boundary of Browns Canyon National Monument from the Bureau of Land Management, April 26, 2017 There may be private inholdings within the boundaries of the National and State reservations shown on this map. This map is not a legal document. Public lands are subject to change and leasing, and may have access restrictions; check with appropriate offices. Obtain permission before entering private lands. CONTOUR INTERVAL 50 METERS NORTH AMERICAN VERTICAL DATUM 1929 APPROXIMATE MEAN DECLINATION, 2016 TRUE NORTH MAGNETIC NORTH 9° Suggested citation: Kellogg, K.S., Shroba, R.R., Ruleman, C.A., Bohannon, R.G., McIntosh, W.C., Premo, W.R., Cosca, M.A., Moscati, R.J., and Brandt, T.R., 2017, Geologic map of the upper Arkansas River valley region, north-central Colorado: U.S. Geological Survey Scientific Investigations Map 3382, pamphlet 70 p., scale 1:50,000, ://doi.org/10.3133/sim3382. For more information concerning this publication, contact: Center Director, USGS Geosciences and Environmental Change Science Center Box 25046, Mail Stop 980 Denver, CO 80225 (303) 236-5344 Or visit the Geosciences and Environmental Change Science Center Web site at: ://gec.cr.usgs.gov/ ScienceBase GIS data release files available at ://doi.org/10.5066/F75B00XQ Report digital files available at ://doi.org/10.3133/sim3382 or ://pubs.usgs.gov/sim/3382 To learn about the USGS and its information products visit ://www.usgs.gov/ 1-888-ASK-USGS For product and ordering information visit: ://store.usgs.gov/ ISSN 2329-132X (online) ://doi.org/10.3133/sim3382 Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. This database, identified as SIM 3382, has been approved for release and publication by the U.S. Geological Survey (USGS). Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, it is released on condition that neither the USGS nor the U.S. Government may be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. This map or plate is offered as an online-only, digital publication. Users should be aware that, because of differences in rendering processes and pixel resolution, some slight distortion of scale or color may occur when viewing it on a computer screen or when printing it on an electronic plotter, even when it is viewed or printed at its intended publication scale. Conversion Factors Multiply By To obtain Length centimeter (cm) inch (in) millimeter (mm) inch (in) meter (m) foot (ft) kilometer (km) mile (mi) Area square kilometer (km2) square mile (mi2) Altitude, as used in this report, refers to distance above sea level. Flow rate cubic meter per second (m3/s) cubic foot per second (ft3/s) Mass metric ton (t) ton, short [2,000 lb] International System of Units to Inch/Pound Multiply By To obtain Mass ton, short (2,000 lb) metric ton (t) ounce, avoirdupois (oz) gram (g) U.S. customary units to International System of Units Geologic Map of the Upper Arkansas River Valley Region, North-Central Colorado By Karl S. Kellogg,1 Ralph R. Shroba,1 Chester A. Ruleman,1 Robert G. Bohannon,1 William C. McIntosh,2 Wayne R. Premo,1 Michael A. Cosca,1 Richard J. Moscati,1 and Theodore R. Brandt1 1U.S. Geological Survey 2New Mexico Institute of Mining and Technology Lava Creek B ash bed 74-SM-1 639±2 Ka Lava Creek B ash bed 74-SM-2 639±2 Ka Lava Creek B ash bed V-774 639±2 Ka Bishop ash bed V-767 759±2 Ka ai Breccia zone Breccia zone Breccia zone Breccia zone PINE CREEK SCHOOL LANDSLIDE L O N D O N M O S Q U I T O F A U LT F A U LT F A U LT F A U LT W E S T O N W E S T O N P A S S P A S S F A U LT S Y S T E M M AY S V I L L E F A U LT S Y S T E M - S A L I D A L O N D O N B R O W N S C A N Y O N H O R S T S A W AT C H S A W AT C H F A U LT S Y S T E M U.S. Department of the Interior U.S. Geological Survey Scientific Investigations Map 3382 Sheet 1 of 2 Pamphlet accompanies map