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A geologic map of an important deposit of rare earth metals studied recently by Geological Survey geologists near Mountain Pass, California has been completed Secretary of the Interior Oscar L. Chapman announced today. The discovery of this deposit was announced on January 16, and because of the great interest that has been shown in the deposit, the map is being made available for public inspection immediately, Secretary Chapman explained. The deposit covered by this map is in San Bernardino County, California near where prospectors made the original discovery on the Birthday claims in 1949. Subsequent studies by the Geological Survey have shown that an area roughly 6 miles long and 2 miles wide, extending southeast from the original discovery, contains a number of other rare carth-bearing deposits, including the large ore body covered by this map. This ore body is made up largely of a carbonate mineral and barite, but contains significant quantities of the rare earth mineral, bastnasite as well. It is exposed over an area 2,400 feet long and 400 feet wide.
The Green River Formation deposited in Eocene Lake Uinta in the Uinta and Piceance Basins, Utah and Colorado, contains the largest oil shale resource in the world with an estimated 1.53 trillion barrels of oil in-place in the Piceance Basin and 1.32 trillion barrels in the Uinta Basin. The Douglas Creek arch, a slowly subsiding hinge-line between the two basins, created separate deep depocenters with shallow water conditions near the crest of the arch. Lake Uinta was a saline lake throughout its history with a lower saline to hypersaline layer (monimolimnion) and an upper less saline layer (mixolimnion). Most of the organic matter in the Green River Formation was derived primarily from algae that lived in the photic zone of the lake and is very hydrogen-rich and oil-prone. In many modern large and deep lakes, rates of organic matter production are highly variable due to differences in nutrient supply. However, cyclonic circulation often leads to winnowing out organic and mineral matter in the mixolimnion leading to organic and fine-grained mineral matter being deposited in increasing amounts toward hydro-dynamically dead zones in the center of the circulation producing concentric bands of increasing organic matter content. Organic matter transport through the dense, hypersaline monimolimnion may have been facilitated by low density organic matter attaching to more dense clay mineral particles. Most of the oil shale intervals deposited in Lake Uinta display similar patterns in their organic matter distributions, increasing in very regular fashion toward the central areas of the lake’s two depocenters. This concentric feature is particularly prominent in the most laminated oil shale zones. Here, we propose that cyclonic circulation was present in Lake Uinta. Each basin appears to have had its own circulation currents, separated by shallow water conditions near the Douglas Creek arch, as well as one hydro-dynamically dead zone. Sediment gravity flow processes were also very active in some strata of Lake Uinta, leading to the reworking and redepositing of sediments. Two general types of sediment gravity flows are recognized: (1) organic-rich sediment gravity flows that reworked and may have concentrated organic-rich material closer to the two deep depocenters, and (2) sandstone and siltstone-rich organic-poor mass movement deposits that originated on marginal shelves. Mass movements could have been triggered by various natural processes and/or possibly by the movement of dense brines that evolved on marginal shelves and moved along the bottom of the water column toward the deep part of the lake. The uppermost, poorly consolidated sediment layer was incorporated in sediment gravity flows as they moved, and in many cases sediment gravity flows scoured down significantly into the more consolidated underlying sediment producing large rip-up clasts of laminated sediments. Truncation of more than 100 ft occurs at the base of a sequence of sediment gravity flows in one well, indicating a significant incised channel. Coarser-grained sediment gravity flows terminated before reaching the lake’s deepest areas, forming thick concentric buildups of organically-lean sediment near the base of the marginal slopes. Intervals dominated by organic-rich fine-grained sediment gravity flows have tightly concentric bands of increasing organic matter toward the deepest parts of the lake and can be organically richer than the richest laminated intervals. There is some evidence that the hydro-dynamically quiet zones did not always correspond closely to the deepest areas of the lake, extending in some cases into shallower areas.
Samples of Bakken Formation core from the Fleckton 1-20 well in Ward County, North Dakota, were analyzed using the Strontium Residual Salt Analysis (SrRSA) method to assess pore-water communication among the upper, middle, and lower sections of the unit by analyzing 87 Sr/ 86 Sr in pore-water salts leached from the core. Major and trace element analyses were also conducted on bulk-rock samples and leachates (Elemental Residual Salt Analysis or ERSA). The middle part of the Bakken Formation, a calcareous and dolomitic siltstone to fine sandstone, is encased between two black shales—the upper and lower sections of the formation. These units are informal and herein named the upper, middle, and lower Bakken members. Strontium isotope measurements and concentration of some solutes in leachates indicate that pore water in the black shale of the upper Bakken member has remained isolated from pore water in the middle Bakken member except for within a few feet immediately near the contact where elemental profiles indicate diffusive mixing. The SrRSA 87 Sr/ 86 Sr values from the middle Bakken member are consistent with produced water collected from 28 wells in Montana and North Dakota. In contrast to the similarity in 87 Sr/ 86 Sr values, ratios of concentrations such as K/Rb, Ca/Sr, Ca/Mg, and Na/Cl are slightly different between the pore-water leachates and produced water values. The differences in K/Rb and Ca/Sr are probably due to selective adsorption of Rb leading to larger K/Rb ratios and minor dissolution of carbonate minerals leading to larger Ca/Sr ratios in the leachates.
The mineralogy of the Eocene Green River Formation in the Piceance Basin, Colorado, has been the subject of numerous studies since the 1920s. Most previous work has focused on the resource potential of these lacustrine mudrocks, which in addition to substantial oil shale potential (in-place resources of 353 billion barrels of synthetic crude oil for rocks yielding at least 25 gallons per ton, GPT), includes nahcolite, a currently utilized soda ash resource, and dawsonite, a potential alternative source of aluminum. Another reason to study the mineralogy in this system is that the geographic and stratigraphic distribution of various authigenic minerals may provide insights into the geochemistry and depositional environment of the long-lived Eocene Lake Uinta. In this study, legacy non-quantitative (presence/absence) X-ray diffraction (XRD) data recently published by the U.S. Geological Survey (USGS) for more than nine-thousand samples collected from thirty coreholes in the Green River Formation, Piceance Basin were examined. These data were used to better define the stratigraphic and paleogeographic extent of a set of indicator minerals (illite, analcime, albite, dawsonite, and nahcolite) within the Piceance Basin lacustrine strata. This set of minerals was selected based on observations from previous work and variability in their occurrence and co-occurrence within the Piceance Basin. The USGS database has been used to (1) construct maps showing geographic variations in mineral occurrences for 14 stratigraphically defined rich and lean oil shale zones; (2) assess co-occurrences of indicator minerals; and (3) compare occurrence results with quantitative XRD datasets collected on Piceance Basin oil shales. Occurrences of many authigenic minerals (analcime, dawsonite, and nahcolite) varied in the lacustrine strata near and around the depocenter, but others, like quartz, dolomite, and feldspar (potassium + undifferentiated), were widely and consistently present (>90% of samples) across the basin. Shifts in the distribution of indicator mineral occurrences generally coincide with changes identified in previous lake history descriptions and indicate that the water chemistry of Lake Uinta varied significantly going from near-shore to the depocenter and through time.
Late in its history, Eocene saline Lake Gosiute in the Greater Green River Basin, Wyoming and Colorado was progressively filled from north to south with coarse volcaniclastic sediments. During the infilling, Lake Gosiute began to drain southward across the Axial arch into saline Lake Uinta in the Piceance and Uinta Basins, Colorado and Utah (about 49 Ma) causing Lake Gosiute to freshen. Once Lake Gosiute was filled entirely (about 48 Ma), volcaniclastic sediments spilled over into Lake Uinta. The first coarse volcanic sediments entered the north part of Lake Uinta near the present-day mouth of Yellow Creek 15 miles south of the Axial arch during deposition of the Mahogany oil shale zone. There is evidence that a south-flowing river entered Lake Uinta from the Axial arch starting early in the history of the Lake and prior to substantial outflow from Lake Gosiute began. A petrographic study of sandstones from this period is consistent with an Axial arch source. It is likely that the outflow channel occupied this pre-existing drainage. Determining when outflow from Lake Gosiute began to move through this pre-existing channel is difficult as mainly mud-sized sediments would have entered Lake Uinta from Lake Gosiute prior to infilling. In addition, reliable dates for most of the strata deposited in Lake Uinta are lacking. A partial section of Lake Uinta strata is preserved at Deep Channel Creek about 10 mi south of the Axial arch. Here the R-6 oil shale zone, below the Mahogany zone, has graded into fluvial strata–the only place in the basin where this zone is not lacustrine. In addition, the underlying L-5 zone is atypically sandy. We propose that Lake Gosiute began to drain into Lake Uinta starting at about the beginning of deposition of the L-5 oil shale zone increasing the input of sediments into the northern part of Lake Uinta. Mud-sized sediments could have come from Lake Gosiute, but the coarser sediments likely came from the Axial arch. Volcaniclastic sediments produced a rapidly prograding deltaic complex that ultimately filled in much if not all of the eastern part of Lake Uinta. The first volcanic sediments to reach the deep depocenter were mainly fine-grained turbidites but ultimately the depocenter was largely filled by slumps off the over-steepened delta front. A petrographic study of the volcaniclastic sandstones indicates that the Absaroka volcanic field in northwest Wyoming is the likely source of the volcanic fraction.
Greater than 33 trillion cubic feet of gas, 68 million barrels of natural gas liquids (NGL), and 192 million barrels of water have been produced from the Middle Devonian Marcellus Shale of the Hamilton Group in the Appalachian Basin. These volumes are from more than 11,700 non-commingled wells. Areas of greatest production and future potential for gas and NGL from the Marcellus Shale are within and near the northeast-trending Rome trough in northern West Virginia and Pennsylvania. Southernmost New York, eastern Ohio, western Virginia, and Maryland also contain petroleum potential and (or) reserves. A confluence of factors enhances gas and NGL reserves and resources in the Marcellus Shale. These include (1) brittleness based on lithofacies composition; (2) thickness and distribution of brittle and organic-rich shale; (3) measured thermal maturity of 1% vitrinite reflectance and greater; (4) at least 2 weight percent total organic carbon; (5) dense and complex fracturing and faulting; (6) presence of evaporite beds in the underlying Silurian Salina Group; (7) potential overpressure; (8) current depths of 1,370 m (4,500 ft) and greater; and (9) predominately horizontal wells with laterals that are oriented to the northwest or southeast, or roughly perpendicular to the direction of maximum horizontal stress, and that cross major fault and fracture sets.
Nine 1D burial history models were built across the Appalachian Basin to reconstruct the burial, erosional, and thermal maturation histories of contained petroleum source rocks. Models were calibrated to measured downhole temperature and to vitrinite reflectance (% R o ) data from Devonian through Pennsylvanian petroleum source rocks. The highest levels of thermal maturity in Devonian and Mississippian source rocks are within and proximal to the Rome trough in the deep basin, which is also within the confluence of increased structural complexity and associated faulting, overpressured Devonian shales, and thick intervals of salt in the underlying Silurian Salina Group. Models incorporate minor erosion from 260 to 140 million years ago (Ma) that allows for extended burial and heating of underlying strata and generally results in less eroded thickness, compared to previously published models. Two modeled times of increased erosion, from 140 to 90 Ma and 23 to 5.3 Ma, are followed by less erosion from 5.3 Ma to Present. Absent strata are mainly Permian shales and sandstone; thickness of these removed layers increased from about 6,200 ft (1,890 m) west of the Rome trough to as much as 9,650 ft (2,940 m) within the trough. The onset of oil generation is based on 0.6% R o for Pennsylvanian coal samples; time of onset for the Ordovician Utica Shale ranges from 387 to 306 Ma, and 359 to 282 Ma for Middle Devonian to basal Mississippian shales. The ∼1.2% R o onset of wet gas generation ranges from 360 to 281 Ma in the Utica Shale, and 298 to 150 Ma for Middle Devonian to lowermost Mississippian shales.
Sections of the Upper Cretaceous (Coniacian to Campanian) Niobrara Formation in two cores from Kansas and Colorado, the Amoco Rebecca Bounds and USGS Portland 1, respectively, were examined by hyperspectral core imaging and analysis. A spectral imaging system combining high-resolution photography (50 μm), 3D laser profiling (20 μm), and near-visible + short-wave infrared reflectance spectroscopy (wavelengths from 450 to 2500 nm, 500 μm pixel size) was applied to these cores to provide spectral and textural data facilitating creation of continuous mineral and lithology class maps. In addition, compositing of pixel-based results to group pixels to create mineralogical and lithological logs (0.5 ft resolution) was performed to facilitate comparisons to other geochemical datasets. The results show general correspondence in trends identified by previous geochemistry studies, with some exceptions due to instrumental limitations related to low reflectance of some rock intervals and the limited range of infrared wavelengths examined. This study provides a cursory overview of an extensive dataset meant to demonstrate the utility of hyperspectral core scanning to studies of mudrocks in petroleum systems as well as the kinds of information this technique can provide for detailed examination of stratigraphic features in sedimentary systems more generally.
The U.S. Geological Survey (USGS) determined the physical and chemical properties of more than 260 feed coal and coal combustion byproducts from two coal-fired power plants. These plants utilized a low-sulfur (0.23-0.47 wt. % S) and low ash (4.9-6.3 wt. % ash) subbituminous coal from the Wyodak-Anderson coal zone in the Tongue River Member of the Paleocene Fort Union Formation, Powder River Basin, Wyoming. Fifty-three samples of bituminous coal were collected and analyzed from a Kentucky power plant, which used several sources of bituminous coals from the Appalachian and Illinois Basins. Based on scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses of feed coal samples collected and analyzed from 1996 through the late 2000s, two mineral suites were identified: (1) a primary or detrital suite consisting of quartz (including beta-form grains), biotite, feldspar, and minor zircon; and (2) a secondary authigenic mineral suite containing alumino-phosphates (crandallite and gorceixite), kaolinite, carbonates (calcite and dolomite), quartz, anatase, barite, and pyrite. The detrital mineral suite is interpreted, in part, to be of volcanic origin, whereas the authigenic mineral suite is interpreted, in part, to be the result of the alteration of the volcanic minerals. The mineral suites have contributed to the higher amounts of barium, calcium, magnesium, phosphorus, sodium, strontium, and titanium in the Powder River Basin feed coals in comparison to eastern US coals. XRD analysis indicates that (1) fly ash is mostly aluminate glass, perovskite, lime, gehlenite, quartz, and phosphates with minor amounts of periclase, anhydrite, hematite, and spinel group minerals; and (2) bottom ash is predominantly quartz, plagioclase (albite and anorthite), pyroxene (augite and fassaite), rhodonite, and akermanite, and spinel group minerals. Microprobe and SEM analyses of fly ash samples revealed quartz, zircon, and monazite, euhedral laths of corundum with merrillite, hematite, dendritic spinels/ferrites, wollastonite, and periclase. The abundant calcium and magnesium mineral phases in the fly ash are attributed to the alteration of carbonate, clay, and phosphate minerals in the feed coal during combustion. The calcium- and magnesium-rich and alumino-phosphate mineral phases in the coal combustion byproducts can be attributed to volcanic minerals deposited in peat-forming mires. Dissolution and alteration of these detrital volcanic minerals occurred either in the peat-forming stage or during coalification and diagenesis, resulting in the authigenic mineral suite. The presence of free lime (CaO) in fly ash produced from Wyodak-Anderson coal acts as a self-contained “scrubber” for SO 3 , where CaO + SO 3 form anhydrite either during combustion or in the upper parts of the boiler. Considering the high lime content in the fly ash and the resulting hydration reactions after its contact with water, there is little evidence that major amounts of leachable metals are mobilized in the disposal or utilization of this fly ash.
The eastern Snake River Plain (ESRP) is a northeast-trending topographic basin interpreted to be the result of the time-transgressive track of the North American plate above the Yellowstone hotspot. The track is defined by the age progression of silicic volcanic rocks exposed along the margins of the ESRP. However, the bulk of these silicic rocks are buried under 1 to 3 kilometers of younger basalts. Here, silicic volcanic rocks recovered from boreholes that penetrate below the basalts, including INEL-1, WO-2 and new deep borehole USGS-142, are correlated with one another and to surface exposures to assess various models for ESRP subsidence. These correlations are established on U/Pb zircon and 40Ar/39Ar sanidine age determinations, phenocryst assemblages, major and trace element geochemistry, δ18O isotopic data from selected phenocrysts, and initial εHf values of zircon. These data suggest a correlation of: (1) the newly documented 8.1 ± 0.2 Ma rhyolite of Butte Quarry (sample 17KS03), exposed near Arco, Idaho to the upper-most Picabo volcanic field rhyolites found in borehole INEL-1; (2) the 6.73 ± 0.02 Ma East Arco Hills rhyolite (sample 16KS02) to the Blacktail Creek Tuff, which was also encountered at the bottom of borehole WO-2; and (3) the 6.42 ± 0.07 Ma rhyolite of borehole USGS-142 to the Walcott Tuff B encountered in deep borehole WO-2. These results show that rhyolites found along the western margin of the ESRP dip ~20º south-southeast toward the basin axis, and then gradually tilt less steeply in the subsurface as the axis is approached. This subsurface pattern of tilting is consistent with a previously proposed crustal flexural model of subsidence based only on surface exposures, but is inconsistent with subsidence models that require accommodation of ESRP subsidence on either a major normal fault or strike-slip fault.
We formally assign, describe and interpret a principal reference section for the middle Turonian Codell Sandstone Member of the Carlile Shale near Codell, Kansas. This section, at the informally named Pumpjack Road, provides the thickest surface expression (9 m, ∼30 ft) of the unit in Ellis County. The outcrop exposes features that typify the Codell throughout the southern Denver Basin and vicinity. At this reference section, the Codell conformably overlies the Blue Hill Shale Member of the Carlile Shale and is unconformably overlain by the Fort Hays Limestone Member of the Niobrara Formation or locally by a thin (<0.9 m, <3 ft) discontinuous mudstone known as the Antonino facies. The top contact of the Codell is slightly undulatory with possible compaction features or narrow (<30.5 m, <100 ft), low-relief (0.3-0.6 m, 1-2 ft) scours, all of which hint that the Codell is a depositional remnant, even at the type section. At Pumpjack Road, the Codell coarsens upward from a recessive-weathering argillaceous medium-grained siltstone with interbedded mudstone at its base to a more indurated cliff-forming muddy, highly bioturbated, very fine-grained sandstone at its top. The unit contains three informal gradational packages: a lower Codell of medium to coarse siltstone and mudstone, a middle Codell of muddy coarse siltstone, and an upper muddy Codell dominated by well-sorted very fine-grained sandstone. The largest grain fractions, all <120 mm in size, are mostly quartz (40-80%), potassium feldspar (7-12%), and albite (1-2%), with some chert (<15%), zircon, and other constituents such as abraded phosphatic skeletal debris. Rare fossil fish teeth and bones also occur. Detrital and authigenic clays make up 9 to 42% of the Codell at the reference section. Detrital illite and mixed layer illite/smectite are common, along with omnipresent kaolinite as grain coatings or cement. As is typical for the Codell, the sandstone at the type section has been pervasively bioturbated. Most primary structures and bedding are obscured, particularly toward the top of the unit where burrows are larger, deeper and more diverse than at its base. This bioturbation has created a textural inversion in which the larger silt and sand grains are very well sorted but are mixed with mud. Detrital zircons from the upper Codell are unusual in that they are mostly prismatic to acicular, euhedral, colorless, unpitted, and unabraded, and have a near-unimodal age peak centered at ∼94 Ma. These characteristics suggest they were reworked mainly from Cenomanian bentonites; their ultimate source was likely from the Cordilleran orogenic belt to the west and northwest.
Geological studies in the Cretaceous Western Interior Seaway (KWIS) in North America reveal highly variable sedimentological conditions on its western shore caused by rapidly changing sea level and detrital input during the seaway’s closure. Here we examine a 601-foot (183 meters) continuous core through the lower part of the Maastrichtian Lewis Shale in the eastern Washakie Basin, Wyoming, through integrating stratigraphic and geochemical analyses to better understand organic matter deposition and preservation during the final marine transgression within the seaway. The core penetrates eight organic-rich flooding intervals (F1-F8) and a regional condensed section, informally known as the Asquith marker. The lower portions of the core record sediment input from a southern source, likely the Sierra Madre/Park Ranges, while the upper part records sediment input from a northern source, likely the Granite Mountains. This provenance transition is supported by regional stratigraphic analysis and changes in bulk mineral and trace metal composition. The Asquith marker and early flooding surfaces are enriched in oil-prone, marine organic matter deposited under dysoxic to euxinic conditions, whereas younger flooding surfaces show increased terrigenous input and poorer preservation conditions. The Asquith marker is identified as a prime oil-prone source rock. Although younger flooding surfaces also exhibit favorable source-rock properties, their generative potential is reduced due to increased clastic and terrigenous organic matter deposition caused by regression. These results emphasize the importance of sediment source variability, organic matter preservation, and changing redox conditions to provide insight into the sediment provenance and petroleum potential of the Lewis Shale in the context of the final transgression within the KWIS.
In the Cretaceous section of the thrust belt, fossils are especially useful for dating and correlating repetitive facies of different ages in structurally complex terrain. The biostratigraphic zonation for the region is based on megafossils (chiefly ammonites) , which permit accurate dating and correlation of outcrop sections, and which have been calibrated with the radiometric time scale for the Western Interior. Molluscan and vertebrate zone fossils are difficult to obtain from the subsurface, however, and ammonites are restricted to rocks of marine origin. Palynomorphs (plant microfossils) have proven to be the most valuable fossils in the subsurface because they can be recovered from drill cuttings. Palynomorphs also are found in both marine and nonmarine rocks and can be used for correlation between facies. Stratigraphic ranges of selected Cretaceous marine and nonmarine palynomorphs in previously designated reference sections in Fossil Basin, Wyoming are correlated with the occurrence of ammonites and other zone fossils in the same sections. These correlations can be related to known isotopic ages, and they contribute to the calibration of palynomorph ranges in the Cretaceous of the Western Interior. -from Authors
The basal part, or the Chalk Creek Member, of the non-marine lower Frontier Formation (Upper Cretaceous) includes a thin coal bed that grades S into a carbonaceous shale. The latter plus associated sandstones and shales pinch out S of Cumberland Gap and lie stratigraphically below the top of the Aspen Shale. The beds in the upper part of the Aspen, in turn, pinch out within the Frontier Formation. The coal bed and equivalent carbonaceous shale represent in-place accumulation of peat. The interfingering suggests that in SW Wyoming the Lower/Upper Cretaceous boundary is within the Chalk Creek Member. -from Author
Detailed facies analyses of closely spaced measured surface sections in the Trinidad and adjacent areas of Colorado reflect deposition in the river-influenced delta. That this deltaic system was accompanied by abandonment of subdeltas is indicated by a destructional-deltaic facies of heavily bioturbated, carbonaceous sandstones, siltstones, and shales best recorded in the delta front deposits of the Trinidad Sandstone. Coal accumulation of the Vermejo deposits nevertheless remained primarily controlled by persistent organic sedimentation in interdistributary backswamps. These backswamps, which accumulated thick, lenticular coals, were formed during the normal constructional phase of the delta plain. -from Authors
This Sandstone represents a regressive littoral marine unit deposited during the final retreat of the Cretaceous epeiric sea. Differences in rock type, internal and penecontemporaneous deformation structures, textural sequences, mineral composition and trace fossil content permit recognition of laterally contemporaneous delta-front and barrier lithofacies. The delta-front lithofacies consists of distal bar, distributary mouth bar, and distributary channel deposits. The barrier lithofacies consists of shoreface, beach, washover channel, tidal inlet, tidal channel, and ebb-tidal delta deposits; these lithofacies are coarsening-upward sequences of shale, siltstone and sandstone, locally scoured in the upper part by fining-upward channel deposits.-from Authors
Tectonism in SW Wyoming and adjoining areas, and fluctuations of sea level in the central USA during the mid-Cretaceous are represented by the regional stratigraphy of the Frontier Formation. The Frontier consists mainly of clastic rocks that were deposited in marine and nonmarine environments during latest Albian, Cenomanian, Turonian, and Coniacian time. -from Author