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USGS2002

Geologic map of the Santa Ana Pueblo quadrangle, Sandoval County, New Mexico

The Santa Ana Pueblo quadrangle is located in the northern part of the Albuquerque basin, which is the largest basin or graben within the Rio Grande rift. The quadrangle is underlain by poorly consolidated sedimentary rocks of the Santa Fe Group and is dominated by Santa Ana Mesa, a volcanic tableland underlain by basalt flows of the San Felipe volcanic field. The San Felipe volcanic field is the largest area of basaltic lavas exposed in the Albuquerque basin. The structural fabric of the quadrangle is dominated by dozens of generally north striking, east- and west-dipping normal faults associated with the Neogene Rio Grande rift.

Miscellaneous Field Studies Map↗
USGS1950

Geology of the Limestone Hills, Broadwater County, Montana

The Limestone Hills, a natural topographic unit having an area of about 16 square miles, are situated a few miles west and southwest of Townsend, Broadwater County, Montana. They are composed of pre-Cambrian, Paleozoic, and Mesozoic sedimentary rocks i

Open-File Report↗
USGS1966

Ground-water resources and geology of northern and central Johnson County, Wyoming

Northern and central Johnson County, Wyo., is an area of about 2,600 square miles that lies principally in the western part of the Powder River structural basin but also includes the east flank of the Bighorn Mountains. Sedimentary rocks exposed range in age from Cambrian to Recent and have an average total thickness of about 16,000 feet. Igneous and metamorphic rocks of Precambrian age crop out in the Bighorn Mountains. Rocks of pre-Tertiary age, exposed on the flanks and in the foothills of the Bighorns, dip steeply eastward and lie at great depth in the Powder River basin. The rest of the project area is underlain by a thick sequence of interbedded sandstone, siltstone, and shale of Paleocene and Eocene age. Owing to the regional structure, most aquifers in Johnson County contain water under artesian pressure. The Madison Limestone had not been tapped for water in Johnson County at the time of the present investigation (1963), but several wells in eastern Big Horn and Washakie Counties, on the west flank of the Bighorn Mountains, reportedly have flows ranging from 1,100 to 2,800 gallons per minute. Comparable yields can probably be obtained from the Madison in Johnson County in those areas where the limestone is fractured or cavernous. The Tensleep Sandstone reportedly yields 600 gallons per minute to a pumped irrigation well near its outcrop in the southwestern part of the project area. Several flowing wells tap the formation on the west flank of the Bighorn Mountains. The Madison Limestone and the Tensleep Sandstone have limited potential as sources of water because they can be developed economically only in a narrow band paralleling the Bighorn Mountain front in the southwestern part of the project area. Overlying the Tensleep Sandstone is about 6,000 feet of shale, siltstone, and fine-grained sandstone that, with a few exceptions, normally yields only small quantities of water to wells. The Cloverly Formation and the Newcastle Sandstone may yield moderate quantities of water to wells; but, in some areas, properly constructed wells tapping both formations might yield large quantities of water. The Shannon Sandstone Member of the Cody Shale will probably yield only small quantities of water to Wells, but it is the best potential source of ground water in the stratigraphic interval between the Newcastle and Parkman Sandstones. The Parkman Sandstone and the Lance Formation yield water to relatively shallow wells principally in the southwestern part of the project area. The Fort Union Formation yields adequate supplies of water for stock and domestic use from relatively shallow wells near its outcrop almost everywhere in the county. A few deep wells tap the Fort Union along the Powder River valley in the northeastern part of Johnson County. Some of these wells flow, but their flows rarely exceed 10 gallons per minute; larger yields could be undoubtedly be obtained by pumping. The Wasatch Formation is the principal source of ground water in Johnson County. It yields adequate supplies to many relatively shallow stock and domestic wells, some of which flow, but much larger yields probably would require pumping lifts that are prohibitive for most purposes. The Kingsbury Conglomerate and Moncrief Members of the Wasatch Formation, though, may yield moderate quantities of water in some places. Alluvial deposits underlying the valleys of the Powder River and Crazy Woman, Clear, and Piney Creeks are potential sources of moderate to large supplies of water in the Powder River drainage basin. The permeability of these deposits decreases with distance from the Bighorn Mountain front, so that largest yields can probably be obtained along the upper reaches of these streams. Most ground water utilized in the project area is for domestic and stock supplies and is obtained from drilled wells and from springs. Water for irrigation is obtained almost entirely by diverting flows of perennial streams. The discharge of wel

Water Supply Paper↗
USGS2002

Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data

A high-resolution aeromagnetic survey of the Puget Lowland shows details of the Seattle fault zone, an active but largely concealed east-trending zone of reverse faulting at the southern margin of the Seattle basin. Three elongate, east-trending magnetic anomalies are associated with north-dipping Tertiary strata exposed in the hanging wall; the magnetic anomalies indicate where these strata continue beneath glacial deposits. The northernmost anomaly, a narrow, elongate magnetic high, precisely correlates with magnetic Miocene volcanic conglomerate. The middle anomaly, a broad magnetic low, correlates with thick, nonmagnetic Eocene and Oligocene marine and fluvial strata. The southern anomaly, a broad, complex magnetic high, correlates with Eocene volcanic and sedimentary rocks. This tripartite package of anomalies is especially clear over Bainbridge Island west of Seattle and over the region east of Lake Washington. Although attenuated in the intervening region, the pattern can be correlated with the mapped strike of beds following a northwest-striking anticline beneath Seattle. The aeromagnetic and geologic data define three main strands of the Seattle fault zone identified in marine seismic-reflection profiles to be subparallel to mapped bedrock trends over a distance of >50 km. The locus of faulting coincides with a diffuse zone of shallow crustal seismicity and the region of uplift produced by the M 7 Seattle earthquake of A.D. 900-930.

Washington↗
USGS2023

Thermal evolution of graptolite and solid bitumen properties at high maturity under natural and artificial conditions

To refine the use of graptolite and solid bitumen as thermal proxies at overmature conditions, we evaluated their evolution via Raman and infrared (IR) spectroscopies, reflectance, and geochemical screening using high-temperature pyrolysis experiments in comparison to naturally matured samples. Naturally matured samples included marine shales from the overmature Upper Ordovician Wufeng-Lower Silurian Longmaxi Formations (herein referred to as Wufeng-Longmaxi) of the Sichuan Basin, China. Immature samples for pyrolysis experiments included Mesoproterozoic (Ectasian) Xiamaling marine shale from Hebei, China (graptolite absent) and graptolite-bearing Ordovician (Tremadocian) Alum marine shale from Grönhögen, Sweden. Pyrolysis experiments at 360 °C for 10 days and 27 days (hydrous conditions), and 450 °C 3 days, 550 °C 3 days, and 550 °C 10 days (all anhydrous) created Xiamaling and Alum residues with solid bitumen and graptolite, respectively, of similar and higher maturity compared to the naturally matured Wufeng-Longmaxi samples. Compositional proxies from IR spectroscopy were inconclusive. Raman spectral properties including Raman band separation (RBS) and the full-width at half-maximum of the G-band (G-FWHM) exhibited robust positive and inverse relationships with increasing reflectance in pyrolysis residues, respectively. RBS values were systematically lower in artificially matured samples versus naturally matured samples with equivalent reflectance values, whereas G-FWHM values were systematically higher. This observation indicates that the limited duration or low internal reactor pressure of pyrolysis experiments is insufficient to allow alignment or ordering of aromatic carbon arrays in both organic matter types, relative to natural maturation occurring at geologic time scales. Reflectance of graptolite was typically higher than co-occurring solid bitumen in Wufeng-Longmaxi samples and the untreated Alum sample, suggesting inherently higher aromaticity. However, aromaticity in pyrolysis residues was systematically higher in solid bitumen compared to graptolite with equivalent reflectance values, indicating a higher kinetic barrier to molecular rearrangement in graptolite versus solid bitumen. These data further clarify differences in the molecular evolution of sedimentary organic matter in natural versus analogue laboratory environments and distinguish the properties of individual organic matter types in response to thermal stress.

International Journal of Coal Geology↗
USGS1972

Reconnaissance geology of the Sabkhat Muraysis quadrangle, Kingdom of Saudi Arabia

The Sabkhat Muraysis quadrangle .covers an area of 2843 sq km in the central part of the Kingdom of Saudi Arabia. In the northwestern quarter of the area Precambrian rocks are exposed. They are overlain toward the .south and east by sedimentary formations of Permian and younger age. Four main units of Precambrian .rocks were identified in this area. From oldest to youngest they are: hornblende-biotite granite gneiss; amphibolite and rhyolite of the Halaban Group; graywacke and chlorite-sericite schist of the Bi'r Khountina Group; and biotite-hornblende granite, The hornblende-biotite granite gneiss unit and the biotite-hornblende granite .unit are both poorly exposed and largely covered by veneers of sand, Owing to these factors the boundaries between the granitic, rocks are obscure, Much of what is shown as hornblende-biotite granite gneiss may actually be biotite-hornblende granite. The Halaban Group is represented by an older amphibolite unit called the Umm Mushraha Formation and by a younger rhyolite unit., called the Wadi al Jifr Formation. Layered and msslve components in the Umm Mushraha Formation represent metamorphosed .andesite and graywacke, ,and metamorphosed diorite., gabbro, and pyroxenite. The Wadi al Jifr Formation consists of virtually unmetamorphosed to strongly sheared and metamorphosed rhyolite, rhyolite porphyry, and rhyolite tuff which at many places has been metamorphosed to quartz-sericite schist and biotite-muscovite schist. These schists retain porphyroclasts of blue quartz which also form conspicuous phenocrysts in the unsheared rhyolite. Locally, the sheared rhyolite ha s been hydrothermally altered resulting in the formation of quartz-chlorite-ankerite veins and a sparse impregnation of pyrite. The Bi'r Khountina Group consists of a unit of graywacke and argillite with interbedded andesite that is metamorphosed to chlorite-sericite schist near the contacts of intrusive biottte-hornblende granite. This .unit is-called the Abu Sawarir Formation. It is Intruded by masslve gabbro and pyroxenite. No ancient mines or old prospects were found in the Precambrian part of the quadrangle. Three alteration zones in rhyolite near the northwestern corner of the quadrangle tend to have threshold amounts of molybdenum and tungsten, but they have only background amounts of the base metals and silver. Pyrite is more common in the altered rhyolite than in adjacent rocks. Geological mapping plus and electromagnetic surveys of this area are recommended to explore for sulfide minerals.

Open-File Report↗
USGS2011

Characterization of hydrology and salinity in the Dolores project area, McElmo Creek region, southwest Colorado, water years 1978-2006

Increasing salinity loading in the Colorado River has become a major concern for agricultural and municipal water supplies. The Colorado Salinity Control Act was implemented in 1974 to protect and enhance the quality of water in the Colorado River Basin. The U.S. Geological Survey, in cooperation with the Bureau of Reclamation and the Colorado River Salinity Control Forum, summarized salinity reductions in the McElmo Creek basin in southwest Colorado as a result of salinity-control modifications and flow-regime changes that result from the Dolores Project, which consists of the construction of McPhee reservoir on the Dolores River and salinity control modifications along the irrigation water delivery system. Flow-adjusted salinity trends using S-LOADEST estimations for a streamgage on McElmo Creek (site 1), that represents outflow from the basin, indicates a decrease in salinity load by 39,800 tons from water year 1978 through water year 2006, which is an average decrease of 1,370 tons per year for the 29-year period. Annual-load calculations for a streamgage on Mud Creek (site 6), that represents outflow from a tributary basin, indicate a decrease of 7,300 tons from water year 1982 through water year 2006, which is an average decrease of 292 tons per year for the 25-year period. The streamgage Dolores River at Dolores, CO (site 17) was chosen to represent a background site that is not affected by the Dolores Project. Annual load calculations for site 17 estimated a decrease of about 8,600 tons from water year 1978 through water year 2006, which is an average decrease of 297 tons per year for the 29-year period. The trend in salinity load at site 17 was considered to be representative of a natural trend in the region. Typically, salinity concentrations at outflow sites decreased from the pre-Dolores Project period (water years 1978—1984) to the post-Dolores Project period (water years 2000—2006). The median salinity concentration for site 1 (main basin outflow) decreased from 2,210 milligrams per liter per day in the preperiod to 2,110 milligrams per liter per day in the postperiod. The median salinity concentration for site 6 (tributary outflow) increased from 3,370 milligrams per liter per day in the preperiod to 3,710 milligrams per liter per day in the postperiod. Salinity concentrations typically increased at inflow sites from the preperiod to the postperiod. Salinity concentrations increased from 178 milligrams per liter per day during the preperiod at Main Canal #1 (site 16) to 227 milligrams per liter per day during the postperiod at the Dolores Tunnel Outlet near Dolores, CO (site 15). Calculation of the historical flow regime in McElmo Creek was done using a water-budget analysis of the basin. During water years 2000—2006, an estimated 845,000 acre-feet of water was consumed by crops and did not return to the creek as streamflow. The remaining 76,000 acre-feet, or 10,900 acre-feet per year for the 7-year postperiod, was assumed to represent a historical flow condition. The historical flow of 10,900 acre-feet per year is equivalent to 15.1 cubic feet per second. Average total dissolved solids concentrations for water in each type of sedimentary rock were used to estimate natural salinity loads. Most surface-water sites used to fit the criteria needed to achieve a natural TDS concentration were springs. An average spring TDS value for sandstones geology in the basin was 350 milligrams per liter, and the average value for Mancos Shale geology was 4,000 milligrams per liter. The natural salinity loads in McElmo Creek were estimated to be 29,100 tons per year, which is 43 percent of the salinity load that was calculated for the postperiod.

Colorado↗
USGS2018

Maturity of nearby faults influences seismic hazard from hydraulic fracturing

Understanding the causes of human-induced earthquakes is paramount to reducing societal risk. We investigated five cases of seismicity associated with hydraulic fracturing (HF) in Ohio since 2013 that, because of their isolation from other injection activities, provide an ideal setting for studying the relations between high-pressure injection and earthquakes. Our analysis revealed two distinct groups: ( i ) deeper earthquakes in the Precambrian basement, with larger magnitudes (M > 2), b-values < 1, and many post–shut-in earthquakes, versus ( ii ) shallower earthquakes in Paleozoic rocks ∼400 m below HF, with smaller magnitudes (M < 1), b-values > 1.5, and few post–shut-in earthquakes. Based on geologic history, laboratory experiments, and fault modeling, we interpret the deep seismicity as slip on more mature faults in older crystalline rocks and the shallow seismicity as slip on immature faults in younger sedimentary rocks. This suggests that HF inducing deeper seismicity may pose higher seismic hazards. Wells inducing deeper seismicity produced more water than wells with shallow seismicity, indicating more extensive hydrologic connections outside the target formation, consistent with pore pressure diffusion influencing seismicity. However, for both groups, the 2 to 3 h between onset of HF and seismicity is too short for typical fluid pressure diffusion rates across distances of ∼1 km and argues for poroelastic stress transfer also having a primary influence on seismicity.

Ohio↗
USGS2017

Reconnaissance sedimentology of selected tertiary exposures in the upland region bordering the Yukon Flats basin, east-central Alaska

This report summarizes reconnaissance sedimentologic and stratigraphic observations made during six days of helicopter-supported fieldwork in 2002 on Tertiary sedimentary rocks exposed in the upland region around the flanks of the Yukon Flats basin in east-central Alaska (fig. 1). This project was a cooperative effort between the Alaska Division of Geological & Geophysical Surveys (DGGS) and the U.S. Geological Survey (USGS) to investigate the geology of the basin in preparation for an assessment of the undiscovered, technically recoverable hydrocarbon resources (Stanley and others, 2004). Field observations and interpretations summarized in this report are reconnaissance level. At most, no more than a few hours were spent on the ground at any location. Measured sections included in this report are sketch sec- tions and thicknesses shown are approximate. Relatively detailed observations were made by the authors at only three locations, including The Mudbank (Hodzana River), Rampart (east bank of the Yukon River), and Bryant Creek (along the Tintina fault near the Canada border). These three locations are described first in relative detail, then followed by general descriptions of other locations.

Alaska↗
USGS1968

Uranium deposits in the Jackpile Sandstone, New Mexico

Ultimate sources of uranium are believed to be either fluids from Morrison volcanoes (not demonstrable) or labile constituents in the Jackpile Sandstone. Petrographic studies indicate considerable pre-Dakota diagenesis, which would have made uranium in feldspars, heavy minerals, and volcanic debris available. Deposition of uranium occurred while host sandstone was near the surface during the pre-Dakota hiatus. Sedimentary permeability was the principal factor in distribution of ore and of the organic decomposition products that precipitated it.

New Mexico↗
USGS1979

Geologic map of the Arcadia Quadrangle of Mars

The Arcadia quadrangle of Mars contains three distinct geological provinces: (1) the 1000-km-diameter shield field volcano of Alba Patera, which occupies the southwestern quadrant ; (2) the complex T empe province, which comprises a number of younger volcanic and sedimentary blanket deposits over an ancient, highly cratered crust forming a plateau in the southwestern quadrant ; and (3) a plains province, consisting of northern wind-swept , c ratered plains and some younger subpolar deposits in the northeast corner of the quadrangle, plus less cratered plains surrounding much of the T empe and Alba regions. The plateau, informally named the Tempe Plateau and part of the proposed forma l term Tempe Terra, is separated from the main regions of cratered martian highlands to the south by Kasei Vallis , appearing at the extreme southeast corner of the map, which slopes northeastward onto Chryse Planitia.

IMAP↗
USGS2012

Calculation of hydrocarbon-in-place in gas and gas-condensate reservoirs - Carbon dioxide sequestration

The Energy Independence and Security Act of 2007 (Public Law 110-140) authorized the U.S. Geological Survey (USGS) to conduct a national assessment of geologic storage resources for carbon dioxide (CO 2 ), requiring estimation of hydrocarbon-in-place volumes and formation volume factors for all the oil, gas, and gas-condensate reservoirs within the U.S. sedimentary basins. The procedures to calculate in-place volumes for oil and gas reservoirs have already been presented by Verma and Bird (2005) to help with the USGS assessment of the undiscovered resources in the National Petroleum Reserve, Alaska, but there is no straightforward procedure available for calculating in-place volumes for gas-condensate reservoirs for the carbon sequestration project. The objective of the present study is to propose a simple procedure for calculating the hydrocarbon-in-place volume of a condensate reservoir to help estimate the hydrocarbon pore volume for potential CO 2 sequestration.

Open-File Report↗
USGS1972

Geology and mineral deposits of the Hekimhan-Hasancelebi iron district, Turkey

An area of 210 sq km was investigated in the Hekimhan-Hasancelebi district. of central Turkey as part of the Maden Tetkik ve Arama Institusu(MTA)-U. S. Geological Survey(USGS) mineral exploration and training project to explore for iron deposits and to provide on-.the-job training for MTA geologists. The rocks of the area are Cretaceous and Tertiary sedimentary and volcanic rocks intruded by syenite and a serpentinized mafic and ultramafic complex and overlain unconformably by late .Tertiary basalt. The base of the section is a thick mafic volcanic-sedimentary sequence with diverse rocks that include conglomerate, sandstone, shale, tuff, limestone, and basalt. The upper part of the sequence is metasomatized near syenite contacts. The sequence is conformably overlain by trachyte and unconformably overlain by massive limestone. Overlying the limestone is a Tertiary sedimentary sequence which is dominantly conglomerate and sandstone with local limestone and volcanic rocks. This series is in turn overlain by olivine basalt. Mineral deposits are associated with the two types of intrusive rocks. Hematite-magnetite in the Karakuz mine area and in the Bahcedami-Hasancelebi area is related to the syenite, and siderite in the Deveci mine area is possibly related to the mafic-ultramafic rocks. Significant iron resources are found, only in the Karakuz and Deveci areas. In the Karakuz area disseminations, veins, and replacements consisting of hematite and magnetite are present. Most of the material is low grade. In the Deveci mine area a large deposit of siderite apparently is a replacement of carbonate beds adjacent to serpentinized igneous rock. The upper part of the siderite deposit is weathered and enriched to a mixture of iron and manganese oxides of direct shipping ore grade. Additional investigation of both the Karakuz and .Deveci mine areas is recommended including: 1. A detailed gravity and magnetic survey of part of the Karakuz area. 2. Diamond drilling at both the Karakuz and Deveci areas.

Open-File Report↗
USGS1953

Geology of the Anderson Mesa quadrangle, Colorado

The Anderson Mesa quadrangle is one of the eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of the southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite deposits. The rocks exposed in the eighteenth quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quarternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by high-angle faults, and northwest-tending folds. Conspicuous among the folds are large anticlines having cores of intrusive slat and gypsum. Most of the carnotite 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 many thousands of tons. The ore consists of largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Colorado↗
USGS1953

Geology of the Atkinson Creek quadrangle, Montrose county, Colorado

The Atkinson Creek quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of the quadrangles was mapped by the U.S. Geological Survey 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 and sedimentary rocks that rangein age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but 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 carnotite deposits are confines 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 Bath". 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 sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstone of favorable composition.

Colorado↗
USGS1953

Geology of Bull Canyon quadrangle, Montrose and San Miguel counties, Colorado

The Bull Canyon quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey for the Atomic Energy Commission as part of a comprehensive study of carnotite depots. The rocks exposed in the eighteen quadrangles consist of crystalline rocks of pre-Cambrian age and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but 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 carnotite 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 tones. The ore consists largely of sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Colorado↗
USGS1953

Geology of the Calamity Mesa quadrangle, Mesa county, Colorado

The Calamity Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey 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 and sedimentary rocks the range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but 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 carnotite 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 sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Colorado↗
USGS1953

Geology of the Davis Mesa quadrangle, Colorado

The Davis Mesa quadrangle is one of eighteen 7 1/2-minute quadrangles covering the principal carnotite-producing area of southwestern Colorado. The geology of these quadrangles was mapped by the U.S. Geological Survey 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 and sedimentary rocks that range in age from late Paleozoic to Quaternary. Over much of the area the sedimentary rocks are flat lying, but in places the rocks are disrupted by hih-angle faults, and northwest-trending folds. Conspicuous among the folds are large anticlines having cores of intrusive salt and gypsum. Most of the carnotite deposits are confined to the Salt Wash sandstone member of Jurassic Morrison formation. Within this sandstone, most of the deposits are spottily distributed through an arcuate zone known as "Uruvan 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 sandstone selectively impregnated and in part replaced by uranium and vanadium minerals. Most of the deposits appear to be related to certain sedimentary structures in sandstones of favorable composition.

Colorado↗