(200) .RESOURCE COMPIlATiON SECTION T67~p·v ~tcr: 707 G E 0 L 0 G Y 0 F T H E U R A V A N Q U A D' R A N G L E, MONTROSE COUNTY, COLORADO By Fred W. Cater, Jr., A. Po Butler, Jr., and E. J. McKay, with a section on "The mines" by Robert L. Boardman Trace Elements Memorandum Report 707 GEOLOGICAL SURVEY UNXTED STATES DEPARTMENT OF THE INTERIOR TEPCO RECEIVED GEOLOGICAL SURVEY Denver IN REPLY REFER TO: (::< 60) TC7~~\. UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY WASHINGTON 25, D. C. JUN 18 ~954 D:t.'o Ph:lllip Lo Merritt, Assistant Director Di~ision of Raw Materials ITo So Atomic Energy Commission Po Oo Box 30, Ansonia Station N~r~ York 2:J ~ New York De a:~ Ph:ll ~ Transmitted herewith is one copy of TEM--707, "Geology of the UJ:Jiaii'al?. quadrangle t> Montrose County, Colorado," by Fred Wo Cater, Jr o 9 We are asking ~. Hosted to approve OUI" plan to publish this. repo~t in the Surveyus Quadrangle Map Serieso fo-r" Wo He Bradley Chief Geologist Geology and Mineralogy This document consists of 25 pageso plus 1 figure. Series A UNITED STATES DEPARTMENT OF THE XNTIERXOR G -EOLOGXC AL SURVEY GlEOLOGY OF THE URAVAN QUADRAN<;iLEo MONTROSE COUNTY o COLORADO"' By Fred W. Catero Jro o .A. P. Butler. Jro. and E. J. McKayo with a section on "The mines" by Robert L. Boardman March 1954 Trace Elements Memorandum Report 707 This preliminary report is distributed without editorial and technical review for conformity with official standards and nomenclatureo H is not for public inspection or quotation. *This report concerns WOJ['k done partly on behalf of the Division of Raw Materials of the U. s. Atomic Energy Commission, 2 USGS - TEM-707 GEOLOGY AND MENERALOGY Dlisttli.butli.on (Series A) Noo of copies .Division of Raw Matedalso Washington ., o o 0 0 o 0 o o o o 1 Division of Raw Materialso New York o o 0 o o • o 0 1 1Cxpl<>~ration Division0 Grand Junction Operations Office 0 ., • 1 Grand Junction Operations Offi~ ., • o 0 1 'fechnli.cal linfoll'matlloJrn Senli.ceo Oak Ridge 1 U., S., Geological Survey~ Geochemistry and Petrology Brancho Washington 1- Geophysics Branch0 _ Washington o o o o 1 Mineral Deposits Branc~ Washington 1 R, Po Fbchero Grand Jumctlon 1 Wo A., !Fischero W ashli.ngton 1 TlEPCOo Dernver 0 • o o ., 0 0 0 0 1 TlEPCOo RPSo Washington 2 ~lineludling master) 13 3 CONTENtS Page Abstl'act 4 ITntroduetion o • 4 . Regional geology 5 Stll'atigraphy 6 Chinle fo!l'mation • 6 Glen Canyon group 7 Winga1te sandstone 7 Kayenta formation 8 Navajo sandstone 8 San Rafael group • • o • 9 Carmel formation and Entrada sandstone 9 Summerville forrnation 10 Mo1rdson formation • • o • 11 Salt Wash sandstone member 0 11 Brushy Basin shale member 12 ·!Blll.lill'tr.o Cal))Wn.full'mation 13 Dakota sandstone 14 QIUatemary deposits o 14 8 tlructu.rure o o o o o • • o • o 0 0 0 9 15 Regional setting 15 Structme in Uiravan quadrangle 15 Structural history 16 MfLnell'al deposits 0 ... 18 Mineralogy 18 Ore bodies 19 Origin of olt'e 20 Suggestions foll' pll'ospecting ooOaoooooooo 21 The mines a o • o o o • o 22 Long lfllark No. 6 mine 23 Black Dinah mine 23 Bitter Creek mines 0 fl 23 Other deposits ''24 Lherature cited 25 iLLUSTRATION Preliminary geologic map andl section of the Uravan Quadrangle, Colorado ••• En envelope 4 GEOLOGY OF THE URAVAN QUADRANGLE. MONTROSIE COUNTY. COLOR4DO By Fred W. Cater. Jrci o A. P. Butler. Jr •• and E. J. McKay with a section of "The mines·~ by Robert L~ Boardman ABSTRACT The Uuvan quad~,angle is one of eighteen 7 1/2-minute quadrangle~ covering the principal carnotite- producing area of southwestern Colorado. The geology of these quadrangles was mapped by· the u. s. Geological Smvey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteen quadrangles consist· of crystalline rocks of pre -Cambrian age mdi:iseldimentary rocks that range in age from late Paleozoic to Quaternary., Over much of the area the sedimentary rocks are flat lying. btu1t in places the rocks are disrupted by high-angle faults. and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the camotite deposits are confined to the Salt Wash sandstone member of the Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as the "Uravan mineral belt". individual deposits range in size from irregular masses containing only a few tons of ore to large. tabular masses containing many thousands of tons. The ore consists largely of sand~tone selectively impregnated and in pan replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition. ENTRODUCTION The U. s. Geological Survey mapped the geology of the Uravan quadrangle, Colo•• as part of a comprehensive study of carnotite deposits. The study. covering the principal carnotite-producing area in southwestem Coloradoo included detailed examination of mines and geologic mapping of eighteen 7 1/2- minute quadrangles. of which the Uravan quadrangle is one. Parts of the texts accompanying these maps have been standardized: these parts comprise some descriptions of geologic formations and general descdptions of regional structural setting. geologic history. and ore deposits. A comprehensive report 5 presenting in greater detail the geologic featmes of the entire area and interpretations of these features is in preparationo Work was started in the area in 1939 as a cooperative project with the State of Colorado Geological Survey Board and the Colorado Metal Mining fund and was continued through 1945 as a wartime strategic m!nerals project. Since 1947 the Geological Survey has been continuing this geologic study on behalf of the Division of Raw Materials of the Atomic Energy Commission. The Uravan quadrangle was mapped in 194lt and 1948 0 The Uravan quadrangle covers about 59 square miles in Montrose County, Colo., and lies in the Canyon Lands division. of the Colorado Plateau physiographic province. The quadrangle is largely a rugged au·ea·of mesas and cany~ns, but considerable areas on the larger mesas and in Paradox Valley are relatively flat and feat~ll'elesso Total relief. within the quadrangle is about 10 900 feet: altitudes range from about 4 0 940 feet in the canyon of the San Miguel River to 6, 849 feet on the northeast rim of.P aradox Valley. The San Miguel River and its tributaries drain all the area except Paradox Valley which is draJned by East Paradox Creek. No accurate informatlon on rainfall !s available, but tqe_ annual precipitation is probably between 10 and 15 inches; the area is semi-add·' and supports a moderate growth of juniper and pinon on rocky tenain and abundant s.1gebrush where soils are thicko Cacti and sparse grass are widely distributed. Most of the quadungle is accessible over Colorado Highway 141 and a system of dry-weather roads. REGEONAL GEOLOGY Rocks exposed in the 18 quadrangles mapped consist of crystalline pre-Cambrian rocks and sedimentary rocks that range in age from late Paleozoic to Quaternary. Crystalline rocks crop out only in the north- eastern part of the area along the flanks of the Uncompahgre Plateau; the rest of the area is undell'lain by sedimentary rockso The latest Paleozoic and earliest M~sozoic beds wedge out northeastward against the crystalline pre-Cambrian rocks, but later Mesoz<?ic units were deposited on top of the pre-Cambrian rocks. \ Over most of'"the n:egion the sedimentary beds are flat lying, but in places they are disrupted by high-angle faults, or folded into north~st-trending monocl:inc.s, shallow synclines, and strongly developed anticlines. 6 The la~rgest of the folds is the Uncompahgre Plateau uplif~ a fold nearly 100 miles long that traverses the no!ftheastern part of the aliea. Well-developed anticlines having intrusive cores of salt and gypsum underlie Sll.nbad Valley9 Pa!I'adox ValleyD ~nd Gypsum Valley in the centtal part of the area:. the Dolores anticline in the soa.nthwestem part of the are~ p!iOb~bly has a salt~gypsum core, althougll $tis not exposed. The quadrangle U.es in the e!llst-centtal pa:rt of the 18:-'quadrangle area9 about eight miles southwest of the Uncompahgre Plateau; the southwest comer of the quadrangle is traversed by the edge of Paradox Valley. STR~TIGRAPHY The oldest ~rocks exposed in the Uravan quadr~ngle are Upper Triassic beds that crop out along the sides and on ~e flooli of Paradox Valley'1 Rocks of Pennsylvami.an and Permian age, although not exposed within the quadrangle0 crop out extensively in adjacent quadrangles. .Jrurassic rocks crop out along the sides of Paradox Valley and in the canyon walls and on the benches and slopes below the mesas. Cretaceous rocks cap the mesas. Recem deposits of wind ... blowllll material and sheet wash are widely distdbuted on top of the mesas 9 alollllg the benches, and on the valley floors. Teuace gravels occur along the San Miguel River at various altitudes as much as 700 feet above the present river .level. The str41tigraphic sequence is similar to that studied by Baker ( 1933) and Dane ( 1935) in nearby alieas in Utah; most of the formAtions can be oraced continuously from the Uravan quadrangle into Utah.