U.S. Department of the Interior Scientific Investigations Map 3382 U.S. Geological Survey Sheet 2 of 2 Pamphlet accompanies map

CORRELATION OF MAP UNITS LIST OF MAP UNITS TERTIARY AND LATE CRETACEOUS INTRUSIVE ROCKS YXhd SURFICIAL DEPOSITS SURFICIAL DEPOSITS Hornblende diorite (Mesoproterozoic or Paleoproterozoic) ROCKS ASSOCIATED WITH ANTHROPOGENIC DEPOSITS Ygdh EARLY RIO GRANDE RIFTING Granodiorite of Mount Harvard (Mesoproterozoic) MASS- af Artificial-fill deposits (latest Holocene) Late rhyolite porphyry dikes and plugs of Mount Princeton region (late Ygl Langhoff Gulch Granite (Mesoproterozoic) EOLIAN MOVEMENT rp Oligocene) ALLUVIAL AND MASS- AND AND (OR) pt Placer-tailings deposits (latest Holocene) Yglf Strongly foliated facies l Olivine-augite lamprophyre dike (late Oligocene?) ANTHROPOGENIC GLACIAL MASS-MOVEMENT MOVEMENT ALLUVIAL GLACIAL WETLAND mw Mine-waste deposits (latest Holocene) Yge Elephant Rock Granite (Mesoproterozoic) DEPOSITS ALLUVIAL DEPOSITS DEPOSITS DEPOSITS DEPOSITS DEPOSITS DEPOSITS DEPOSITS dt Microtonalite (Oligocene?) ss Smelter-slag deposits (latest Holocene) Ygef Strongly foliated facies rc Hypabyssal rhyolite of Clear Creek (late Oligocene) Yhy afpt mw ss Qa ALLUVIAL DEPOSITS Hybrid mix of Langhoff Gulch Granite and Elephant Rock Granite Qtr Qw Qp Young stream-channel and overbank alluvium (Holocene) Leucogranite Suite of Mount Antero Qr Qa (Mesoproterozoic) ar Rhyolite dike (early? Oligocene) Ybp Browns Pass Granite of Fridrich and others (1998) (Mesoproterozoic) ? Qgp Outwash gravel of Pinedale glaciation (late Pleistocene) Ygrg Qpf Qf ap Border phase (early Oligocene) Granite of Granite (Mesoproterozoic) Qpf Younger flood gravel and channel deposits of Pinedale glaciation (late Qgp Qtp Pleistocene) ag Main phase (early Oligocene) Ygdm Granodiorite of Mount Elbert (Mesoproterozoic) Qpfo Qpfo Older flood gravel and channel deposits of Pinedale glaciation (late Qac Qc Qt Qes Leucogranite of the California Mine (early Oligocene) Yqd Quartz diorite (Mesoproterozoic) Pleistocene) cg Qgb Outwash gravel of Bull Lake glaciation, undivided (late and middle PRE-RIFT INTRUSIVE ROCKS Ygm Granite of Music Mountain (Mesoproterozoic) Pleistocene) Qgby Granite and granite dikes of North Fork (early Oligocene) Ygs St. Kevin Granite (Mesoproterozoic) Qls Qgby Younger outwash gravel of Bull Lake glaciation (late and middle? nf Qgb ? Qtb QUATERNARY Pleistocene) qmd Quartz monzodiorite (early Oligocene) Xgk Kroenke Granite (Paleoproterozoic) Qfo Qd Qgbo Qgbo Pleistocene Older outwash gravel of Bull Lake glaciation (late? and middle tm Porphyritic latite dike of Shannon (1988) (early Oligocene?) Xgy Granite of Mount Yale (Paleoproterozoic) Pleistocene) ? ? ? ? Outwash gravel of pre-Bull Lake age (middle and early Pleistocene) Rocks of The Mount Aetna Caldera Xdi Diorite (Paleoproterozoic) Qg4 (Early Oligocene or Late Eocene) Qapb Qg4 Outwash gravel of pre-Bull Lake age, level 4 (middle Pleistocene) Xgd Henry Mountain? Granite (Paleoproterozoic) Quartz latite porphyry ring dike Qg3 Qgpb Qpbf Qapb Gravelly stream alluvium of pre-Bull Lake age (middle Pleistocene) ma Xdk Denny Creek Granodiorite (Paleoproterozoic) Qtpb ib Intrusive breccia Qgpb Outwash gravel of pre-Bull Lake age, undivided (middle and early? Xgdm Granodiorite of Methodist Mountain (Paleoproterozoic) Qg2 Pleistocene) m Monzonite and latite dikes (early Oligocene or late Eocene) ? Xgg Foliated granodioritic augen gneiss and granitic gneiss (Paleoproterozoic) ? BASIN-FILL Qg3 Outwash gravel of pre-Bull Lake age, level 3 (middle Pleistocene) lw Late white porphyry (late Eocene) Qg1 ? DEPOSITS Xlg Leucogranite gneiss (Paleoproterozoic) Qpbf Flood gravel of pre-Bull Lake age (middle Pleistocene) QNg lu Little Union Quartz Latite (late Eocene) ? Xgb Gabbro (Paleoproterozoic) Qg2 Outwash gravel of pre-Bull Lake age, level 2 (middle or early Pleistocene) Nda Rocks of the Mount Princeton Batholith Nd Pliocene Qg1 PALEOPROTEROZOIC ROCKS OF THE Outwash gravel of pre-Bull Lake age, level 1 (early Pleistocene) mp Ndc and Neogene Granitic rock of Mount Princeton batholith, undivided (late Eocene) GUNNISON-SALIDA VOLCANO-PLUTONIC BELT QNg Very old alluvial gravel of Arkansas River (early Pleistocene? or Nds Miocene bqm Boulder Mountain monzogranite porphyry of Shannon (1988) (early Metagabbro of the Gunnison-Salida volcano-plutonic belt TERTIARY AND LATE Pliocene) Xgs Oligocene or late Eocene) CRETACEOUS INTRUSIVE ROCKS Nb Xba Metabasalt GLACIAL DEPOSITS mpf Finer-grained facies OLIGOCENE AND EOCENE VOLCANIC Qr Rock-glacier deposits (early Holocene and latest Pleistocene?) Xvs Metavolcanic rocks, metasedimentary rocks, and metagabbro sills, ROCKS ASSOCIATED mpk Alkali-feldspar monzogranite AND MIXED VOLCANIC, VOLCANICLASTIC, undivided WITH EARLY RIO GRANDE RIFTING Till (late to early Pleistocene) AND SEDIMENTARY ROCKS mpm Equigranular biotite-hornblende monzogranite interior facies Xms Aluminous gneiss and schist, calc-silicate gneiss, and quartzite ? ? Qtp Till of Pinedale glaciation (late Pleistocene) l dt bf rp rc mpp Augite-bearing granodiorite porphyry Xmc Muscovite-cordierite schist ? VOLCANIC ROCKS ? Qtb Till of Bull Lake glaciation (late and middle Pleistocene) Oligocene mpb METASEDIMENTARY ASSOCIATED WITH EARLY nr Leucogranite Suite of Mount Antero Border phase PRE-RIFT Qtpb ar ap ag Till of pre-Bull Lake age (middle and early Pleistocene) Eocene and Paleocene AND METAIGNEOUS ROCKS RIO GRANDE RIFTING cg nt ? INTRUSIVE ROCKS Intrusive Intermediate and Felsic Rocks ALLUVIAL AND MASS-MOVEMENT DEPOSITS YXm Intermixed metasedimentary and metaigneous rocks (Mesoproterozoic Qf Fan deposits (Holocene and late Pleistocene) and Paleoproterozoic) qmd ai Intrusive andesite (late Eocene?) bt Rocks of the Mount Aetna Caldera nf Xb Biotite gneiss tm Qac Alluvium and colluvium, undivided (Holocene to middle? Pleistocene) gp Gray porphyry group, undivided (Eocene or Paleocene) bc rd ? ? Xhc Hornblende gneiss, amphibolite, and calc-silicate gneiss Qfo Old fan deposits (late and middle Pleistocene ) ib gj Johnson Gulch Porphyry (Eocene) ? ma tc ab MASS-MOVEMENT DEPOSITS Xhg Hornblende gneiss and amphibolite m lw TERTIARY gs Sacramento Porphyry (Eocene) ? Qc Colluvium (Holocene to middle? Pleistocene) PRE-RIFT VOLCANIC, rs lu er Eagle River Porphyry (Eocene?) ? Rocks of the ? Qt Talus deposits (Holocene to middle? Pleistocene) VOLCANICLASTIC, AND Mount Princeton Batholith cn Paleogene gl Lincoln Porphyry (Eocene or Paleocene) SEDIMENTARY ROCKS Qls Landslide deposits (Holocene to early? Pleistocene) di Diorite of Buckskin Gulch (Eocene? or Paleocene?) wm UPPER EOCENE bqm mpf mpk mpm mpp Eocene and EOLIAN AND ALLUVIAL DEPOSITS VOLCANIC ROCKS OF mp Paleocene Intrusive Qes Eolian sediments and alluvium, undivided (Holocene to middle? Felsic plutons and dikes of Fridrich and others (1998) (Eocene) ? mpb wf tr Intermediate and Felsic Rocks Eocene Pleistocene) sb BUFFALO PEAKS CENTER md Monzodiorite porphyry (Eocene?) ? ? ? an MASS-MOVEMENT AND (OR) GLACIAL DEPOSITS ra cr ql va vb ? ? ? tu Qtr Talus and rock-glacier deposits, undivided (Holocene and late Regional Paleogene and la a ai Pleistocene) Late Cretaceous Intrusive Rocks Qd tl Diamicton (Pleistocene) gt bal a Granite porphyry of Tumble Hill (Paleocene) ? gj gs er WETLAND DEPOSITS tlg Regional ? Qw Wetland deposits (Holocene and late Pleistocene) Twin Lakes Granodiorite (Paleocene) md Paleogene And wf di Late Cretaceous Rocks ? Qp Peat deposits (Holocene and late Pleistocene) Kw Early white porphyry group (Paleocene or Late Cretaceous) gl gp BASIN-FILL DEPOSITS Kdi Diorite sill (Paleocene or Late Cretaceous) ? gt Nd Dry Union Formation (lower Pliocene? and Miocene) ? ? ? Paleocene Kd Rhyodacite and dacite plugs and dikes (Paleocene or Late Cretaceous) tlg Nda Volcanic-ash beds (late Pliocene? and Miocene) Km Hornblende monzonite, monzodiorite, and gabbro (Paleocene or Late Km Cretaceous) Kdi Ndc Clay subfacies (Miocene) View to the north of Buffalo Peaks, which are composed mostly of andesite Late Kwg Whitehorn Granodiorite (Late Cretaceous) Kw Kd Kwg CRETACEOUS flows, andesite breccias, lahars, and welded tuff deposited on Mesoprotero- Cretaceous Nds Slide-block subfacies (Miocene) zoic granite. The peak on the left is West Buffalo Peak (4,062 m; 13,326 ft) PALEOZOIC SEDIMENTARY ROCKS Kad Kad Andesite dike (Late Cretaceous?) Nb and the peak on the right is East Buffalo Peak (4,054 m; 13,330 ft). Figure 10 Unconformity ? ? ? ? Browns Canyon Formation (Miocene or upper Oligocene) in pamphlet. Photograph by Karl Kellogg, 2011. OLIGOCENE AND EOCENE VOLCANIC PALEOZOIC SEDIMENTARY ROCKS Lower Permian PERMIAN AND MIXED VOLCANIC, VOLCANICLASTIC, Pm Maroon Formation (Lower Permian to Middle Pennsylvanian) Pm AND SEDIMENTARY ROCKS Upper Pennsylvanian m Minturn Formation (Middle Pennsylvanian) VOLCANIC ROCKS ASSOCIATED me WITH EARLY RIO GRANDE RIFTING Evaporite facies EXPLANATION m Vesicular basaltic-andesite flow (upper Oligocene) mc bf Coffman Member Contact—Dashed where approximately located, short dash where inferred. Queried Middle where identity or existance is questionable me Pennsylvanian PENNSYLVANIAN nr Topaz rhyolite flow of Nathrop Volcanics, including basal vitrophyre u Middle and Lower Pennsylvanian, Mississippian, Devonian, Ordovician, (lower Oligocene) and Cambrian rocks, undivided Fault—Dashed where approximately located. Dotted where concealed. Tick shows 65 mc nt Tuff and tuffaceous breccia of Nathrop Volcanics (lower Oligocene) b Belden Formation (Middle and Lower Pennsylvanian) dip value and direction b PRE-RIFT VOLCANIC, VOLCANICLASTIC, bc Quartz-pebble conglomerate and sandstone member Normal fault—Dashed where approximately located, short dash where inferred, bc k Lower AND SEDIMENTARY ROCKS dotted where concealed. Bar and ball on downthrown side. Traces of inferred Pennsylvanian k Disconformity bt Bonanza Tuff (lower Oligocene) Kerber Formation (Lower Pennsylvanian) faults were identified on lidar imagery Mls Middle and MI Leadville Limestone (Lower Mississippian)—Queried where the Ml Lower MISSISSIPPIAN bc Badger Creek Tuff (lower Oligocene or upper Eocene) Reverse fault—Dashed where approximately located, dotted where concealed. Disconformity Mississippian identification is not certain Rectangles on upthrown block rd Rhyodacite flow and tuff (lower Oligocene or upper Eocene) Mls Quartzite of Sheep Mountain Dd Tallahassee Creek Conglomerate (lower Oligocene and upper Eocene?) Lineament—As observed on lidar imagery Dc Upper Devonian DEVONIAN tc Mu Mississippian?, Devonian, Ordovician, and Cambrian rocks, undivided Dp Anticline—Trace of axial plane ab Basalt, andesite, and latite flows, and associated plugs (upper Eocene) (Mississippian? to Cambrian) Disconformity Dc Chaffee Group, undivided (Lower Mississippian? and Upper Devonian) Syncline—Trace of axial plane; dotted where concealed rs Rhyodacite lava of Salida East (upper Eocene?) u Of Upper Ordovician Dd Dyer Dolomite (Lower Mississippian? and Upper Devonian) Quartzite layer—A Paleoproterozoic quartzite layer (qz) in units Xhg, Xvs, and cn Capping andesite porphyry of Triad Ridge of Thirtynine Mile Andesite Ofh Disconformity Xms Dp Parting Sandstone (Upper Devonian) that is interpreted as being a metachert. Consists of light- to dark-gray, very Or Middle Ordovician (upper Eocene) fine- to fine-grained quartz-magnetite-hematite rock. Quartzite beds are as thick Mu Oh ORDOVICIAN wm Wall Mountain Tuff (upper Eocene) Or as 8 m and hundreds of meters long Disconformity Ordovician rocks, undivided tr Tuff of Triad Ridge (upper Eocene) Om Om Lower Ordovician Ofh Fremont Dolomite and Harding Sandstone, undivided (Upper and Middle Breccia zone—Marked by sheared to granulated deformation fabric in bedrock Disconformity sb Trout Creek slide block (Eocene?) Ordovician) 25 Inclined bedding—Showing strike and dip Oms Of Fremont Dolomite (Upper Ordovician) ra Rhyodacite porphyry flow, ash, and mud-flow deposit of Van Alstine and Upper Cambrian CAMBRIAN 20 Overturned bedding—Showing strike and dip ds Cox (1969) (upper or middle Eocene) Oh Harding Sandstone (Middle Ordovician) 40 cr Calico rhyodacite lava of Shannon (1988) (upper? Eocene) Inclined foliation—Showing strike and dip Om Unconformity Manitou Dolomite, upper part (Lower Ordovician) ql Quartz-latite porphyry flow (upper? Eocene) Vertical foliation—Showing strike Om Manitou Dolomite, including Upper Cambrian Taylor Pass Member of PROTEROZOIC ROCKS va Volcaniclastic conglomerate and ash (upper? Eocene) Myrow and others (2003) (Lower Ordovician and Upper Cambrian) A Sample or site location—Letter correlates with field number (see table 1 in pamphlet) Oms Manitou Dolomite (Lower Ordovician and Upper Cambrian) and Lava Creek B ash bed INTRUSIVE ROCKS UPPER EOCENE VOLCANIC ROCKS SL–MM06–91 METASEDIMENTARY OF BUFFALO PEAKS CENTER Sawatch Quartzite (Upper Cambrian), undivided Location of Lava Creek B ash bed—Identified at two localities by Scott (1975): (1) AND METAIGNEOUS ROCKS on the east side of the Arkansas River, about 8 km northwest of Buena Vista, ? an Andesite ds Dotsero Formation and Sawatch Quartzite, undivided (Upper Cambrian) Yla where the ash overlies bouldery flood gravel of unit Qpbf, and (2) at one locality MESOPROTEROZOIC vb Volcanic breccia PROTEROZOIC ROCKS by Scott and others (1975) on the west side of the Arkansas River about 4 km Ygdh Ygl Yglf Yge Ygef Yhy Ybp Ygrg Ygdm Yqd Ygm Ygs southwest of Nathrop where the ash overlies deposits of unit Qg3. Ash has a tu Upper tuff INTRUSIVE ROCKS 40 39 Bishop ash bed Ar/ Ar mean age of 639±2 ka (Lanphere and others, 2002) YXp YXhm YXhd SL–MM06–91 Xgk a Air-fall and ash-flow tuff Yla Lamprophyre and andesite dikes (Mesoproterozoic?) Location of Bishop ash bed—Identified at one locality by Scott and others (1975) YXgr on the west side of the Arkansas River, about 7 km southwest of Nathrop, where la Lahar deposit YXp Pegmatite (Mesoproterozoic and Paleoproterozoic) Xgy Xdi Xgd Xdk Xgdm the ash overlies deposits of unit Qg2. Ash has a 40Ar/39Ar age of 759±2 ka YXm tl Lower tuff Granitic rock, undivided (Mesoproterozoic or Paleoproterozoic) (Sarna-Wojcicki and others, 2000) Xgg Xlg Xgb PALEOPROTEROZOIC ROCKS PALEOPROTEROZOIC YXgr OF THE GUNNISON-SALIDA bal Basal andesite YXhm Hornblende monzodiorite (Mesoproterozoic or Paleoproterozoic) Water body VOLCANO-PLUTONIC BELT

XbaXvs Xms Xmc Xgs Xb Xhc Xhg Divisions of Quaternary, Neogene, and Paleogene time used in this report1

Period or Epoch Age For more information concerning this publication, contact: subperiod Center Director, USGS Geosciences and Environmental Change Science Center Holocene 0–11.5 ka Box 25046, Mail Stop 980 Denver, CO 80225 Quaternary late 11.5–132 ka (303) 236-5344 middle 132–788 ka Pleistocene Geologic Map of the Upper Arkansas River Valley Region, North-Central Colorado Or visit the Geosciences and Environmental Change Science Center Web site at: early 788 ka–2.588 Ma COLORADO http://gec.cr.usgs.gov/ Pliocene 2.588–5.332 Ma Digital files available at https://doi.org/10.3133/sim3382 or Neogene Miocene 5.332–23.03 Ma DENVER By To learn about the USGS and its information products visit http://pubs.usgs.gov/sim/3382 Oligocene 23.03–33.9 Ma http://www.usgs.gov/ GIS files are available for this report as a data release from ScienceBase at Paleogene Eocene 33.9–55.8 Ma 1 1 1 1 2 1-888-ASK-USGS https://doi.org/10.5066/F75B00XQ Paleocene 55.8–65.5 Ma Karl S. Kellogg, Ralph R. Shroba, Chester A. Ruleman, Robert G. Bohannon, William C. McIntosh, For product and ordering information visit: Suggested citation: Kellogg, K.S., Shroba, R.R., Ruleman, C.A., Bohannon, McIntosh, 1 http://store.usgs.gov/ Ages of time boundaries are those of the U.S. Geological Survey Geologic Names 1 1 1 1 W.C., R.G., Premo, W.R., Cosca, M.A., Moscati, R.J., and Brandt, T.R., 2017, Geologic Committee (2010) except those for the late-middle Pleistocene boundary and middle- Wayne R. Premo, Michael A. Cosca, Richard J. Moscati, and Theodore R. Brandt map of the upper Arkansas River valley region, north-central Colorado: U.S. early Pleistocene boundary, which are those of Richmond and Fullerton (1986). Ages ISSN 2329-132X (online) are expressed in ka for kilo-annum (thousand years) and Ma for mega-annum 1U.S. Geological Survey Geological Survey Scientific Investigations Map 3382, pamphet 70 p., scale (million years). MAP LOCATION 2017 2 New Mexico Institute of Mining and Technology https://doi.org/10.3133/sim3382 1:50,000, https://doi.org/10.3133/sim3382.