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USGS1990

Paleoecological interpretation of a middle Pennsylvanian coal bed in the central Appalachian basin, U.S.A.

At least 180 small spore species assignable to 62 miospore genera have been identified from the Middle Pennsylvanian Hernshaw coal bed in southern West Virginia, and its stratigraphic equivalent, the Fire Clay coal bed, in eastern Kentucky. The established natural affinities of a majority of these miospore taxa indicate that the Hernshaw-Fire Clay peat swamp supported a diverse flora consisting of arborescent and “herbaceous” lycopods, ferns (tree-like and small varities), calamities and cordaites. Four floral groupings are recognized in the Hernshaw-Fire Clay coal bed. The inferred paleoecology and vertical stratification of each of these four floral groupings is similar in structure to the “phasic” floral communities found in modern domed peat systems, suggesting that the ancient Hernshaw-Fire Clay peat swamp was a domed deposit. Compositional characteristics (petrographic make up, ash yield and sulfur content) associated with the four groupings are consistent with, and support this interpretation. Where uninterrupted by inorganic partings, the Hernshaw-Fire Clay coal bed commonly contains basal coal layers dominated by Lycospora -bearing arborescent lycopods, with successive increments showing a progression to a more fern- and “herbaceous”-lycopod-dominant flora in younger layers. These observations are corroborated by petrographic analyses, which show the bed to be compositionally stratified. Increments dominated by Lycospora have high vitrinite contents, in contrast to increments containing increased percentages of fern- and “herbaceous”-lycopod-affiliated taxa that are enriched in inertinite macerals. The volcanic ash fall, preserved as the flint-clay parting in the Hernshaw-Fire Clay coal bed, had a considerable effect on the development of the ancient Hernshaw-Fire Clay peat swamp. Besides interrupting peat formation, the presence of an inorganic substrate represent a major change in edaphic conditions within the swamp. This disruption is demonstrated by a change in palynflora and by the establishment and proliferation of some plant groups, notably cordaites and calamites, that may have been better adapted to growth on mineral soils.

International Journal of Coal Geology↗

USGS1979

Mineral resources of the Citico Creek Wilderness Study Area, Monroe County, Tennessee

The proposed Citico Creek Wilderness comprises about 5,670 hectares (56.7 km2) in the Cherokee National Forest south of the Little Tennessee River in easternmost Monroe County, Tennessee. Principal drainages are Citico Creek and Doublecamp Creek. Rocks of the study area include greenschist-facies arkosic metasandstone, metagraywacke, slate, and metaconglomerate of the Great Smoky Group of late Precambrian age. Minor deposits of unconsolidated Quaternary alluvium locally mantle the bedrock. Deformation is shown by asymmetric and overturned folds and by several major faults. More than 500 sample s of soil, rock, and stream sediment were collected and analyzed for 31 major, minor, and trace elements by semiquantitative spectrographic, atomic absorption, and fire assay methods No significant metal anomalies were detected. Concentrations of Cu, Co, As, Pb, and Zn slightly higher than background are found within sulfidic parts of a distinctive stratigraphic unit composed of graphitic slate and metagraywacke. Pyrite and pyrrhotite are the chief sulfide minerals, with traces o f accessory sphalerite, chalcopyrite, galena, and arsenopyrite occurring as microscopic intergrowths. A reconnaissance ground radiometric survey and subsequent neutron activation analyses of selected radioactive rock samples show that the sulfidic parts of the graphitic slate unit have a relatively high content of Th and U, but are not potentially economic. No metallic mineral resources appear to exist within the Citico Creek Wilderness Study Area. Resources of slate, silica, and stone are present, but they display no special qualities to differentiate them from other such material throughout the region. Ceramic evaluation tests on selected samples of slate indicate that the slate would have only marginal use for structural clay products such as brick and tile. Minor sand and gravel deposits occur along a few streams but are present in larger quantities and are more easily recovered in other areas.

Tennessee↗

USGS1971

Selected fluvial monazite deposits in the southeastern United States

Farther southwest in Georgia, around Griffin and Zebullon, along streams tributary to the Flint River in the monazite belt the flood plains are generally small and discontinuous, and only about 1 percent of the sediment is gravel. The area between Griffin, Zebullon, and the Flint River is underlain by biotite schist and biotite gneiss into which biotite granite has been intruded. Only along one stream, Flat Creek, which drains monazite-bearing granite near Zetella, Ga., are the tenors in monazite even moderately high, but a combination of thick, clayey overburden and discontinuous flood plains make the stream unsuitable for placer mining. Elsewhere in the Flint River area the heavy-mineral concentrates contain less than 1 percent monazite. The southwesternmost area in which reconnaissance of the monazite belt was conducted includes a groups of southwest-flowing tributaries to the Chattahoochee River north of Pine Mountain and near La Grange, Ga. A combination of three characteristics of the alluvium make the area unfavorable for mining: (1) the upper half of the sedimentary sequence is clay and silt, (2) there is scant gravel, and (3) much of the sand is fine grained. Monazite is associated with the Snelson Granite, schists, and gneisses north of the Towaliga fault, but even in this area the tenor of most riffle sediments is only 0.1 to 0.5 pound of monazite per cubic yard, and the average tenor of the alluvium is about 0.2 pound per cubic Yard. Rocks south of the Towaliga fault contain scant monazite. The monazite-bearing area in the drainage basin of the Chattahoochee River has no monazite placers. Evidence from the areas on the Flint and Chattahoochee Rivers shows that streams in western Georgia are a much poorer source of monazite than streams farther to the northeast in Georgia, South Carolina, and North Carolina. Also, the northeastern part of the belt in the drainage basins of the Yadkin and Dan Rivers is a poorer source for monazite than the area between the Savannah and Catawba Rivers, S.C.-N.C. Monazite-bearing crystalline rocks in the western belt contain about 0.06 pound of monazite per cubic yard. Residual soil derived from the crystalline rocks contains about 0.3 to 0.4 pound of monazite per cubic yard, and colluvial sediments formed by sheet-wash from saprolite, residual soil, and, rarely, old stream deposits, have an average of 3.1 pounds of monazite to the cubic yard. The data on the tenors of residual and colluvial deposits are far less comprehensive than those an the quantity of monazite in the crystalline rocks, but the tenors are probably of the correct order of magnitude. Neither the crystalline rocks nor the residual soils are ores of monazite. Because the colluvial deposits are thin and have patch distribution they could not be mined independently, but some colluvium could be stripped from the adjoining hills in conjunction with the mining of alluvial deposits in the valleys. It is most unlikely that alluvial monazite placers have formed in the trunk streams leading southeastward out of the monazite belt. Churn drilling on the Broad and North Tyger Rivers, South Carolina, at the east edge of the belt has shown that the bulk of the alluvium is fine-grained sediment that contains 0.2 to 0.4 pound of monazite per cubic yard--tenors that represent no considerable enrichment over those in the crystalline rocks and residual soils. The probable persistence of predominantly fine-grained alluvium downstream to the Coastal Plain and the certain dilution of monazite-bearing concentrates by the inflow of monazite-free suites of heavy minerals between the belt and the fall line suggest that the trunk streams east of the belt are the least favorable sources for alluvial monazite in the Piedmont?

Open-File Report↗

USGS2023

Stratigraphic architecture and fluvial interpretations of the Upper Cretaceous (Turonian?) Middendorf Formation, Chesterfield County, South Carolina, U.S.A.

The Upper Cretaceous (Turonian?) Middendorf Formation is a sand-rich stratigraphic unit of fluvial origin that forms a large aquifer in the U.S. Atlantic Coastal Plain. In Chesterfield County (South Carolina), which is the site of the type locality, the formation ranges in thickness from 66.5 to > 119.7 meters. The base of the formation is an unconformity above Paleozoic metasiltstone, and the upper contact is an unconformity above which lies sand of the Quaternary Pinehurst Formation. Outcrops display the following five facies assemblages: 1) sandstone to conglomeratic sandstone (fluvial bar and channel deposits), 2) beds of alternating laminae of sandstone and mudstone (fluvial overbank or floodplain deposits), 3) ≥ 1 m-thick beds of clay (swamp deposits, floodplain deposits, and/or sediment that accumulated in abandoned fluvial channels), 4) 0.2–0.5 m-thick planar to slightly undulatory beds of framework-supported sandstone with a mud matrix (traction-dominated current deposits at the top of fluvial bars, upper-flow-regime bedform deposits in subsidiary fluvial channels, or coarse-grained overbank deposits), and 5) sandstone to conglomeratic sandstone cemented by iron (interpreted as fluvial bar and channel deposits, with the iron cement being a diagenetic “groundwater ferricrete” that formed via the circulation of shallow groundwater and the oxidation of iron-bearing minerals). Kaolinite in various forms is pervasive throughout the formation and is interpreted as an early diagenetic phenomenon that formed by prolonged postdepositional weathering and flushing by meteoric water under a warm and humid paleoclimate. The fluvial system that formed the Middendorf Formation prograded into the area from the west or northwest from uplifted margins of Mesozoic rift basins and/or the Appalachian Mountains. This progradation was a response to a base-level fall and the sediment accumulated during base-level lowstand and subsequent early transgression. In Chesterfield County, the Middendorf Formation can be subdivided into three fining-upward sequences. Each sequence consists predominantly of medium to coarse sand with a greater abundance of gravel in the lower part of the sequence and a greater abundance of clay and silt beds in the upper part. Each sequence is interpreted as either a response to autogenic processes or a response to allogenic sea-level changes, specifically a higher-order (higher-frequency) progression from relative lowstand conditions to early transgression whereby coarse sand and gravel (e.g., fluvial bar and channel deposits) were preserved during initial lowstand conditions and a greater proportion of mud and finer-grained sand (floodplain deposits) were preserved during subsequent early transgression. The Middendorf Formation is correlative with several other kaolinite-rich fluvial sandstones in North America including the Raritan Formation in New Jersey, the Tuscaloosa Formation of the eastern Gulf of Mexico (Alabama, Mississippi, Louisiana), the Woodbine Formation of the central Gulf of Mexico (Texas), and the Frontier Formation of Wyoming. The accumulation and preservation of these formations occurred in response to a Turonian eustatic sea-level fall and subsequent transgression, and the early diagenetic kaolinite in these formations is attributed to similar warm and humid paleoclimate conditions.

South Carolina↗

USGS1979

Geology and industrial mineral resources of the Macon-Gordon kaolin district, Georgia

The Macon-Gordon kaolin district is about 80 miles (130 km) southeast of Atlanta, Georgia. It extends across the boundary between, and includes parts of, the Piedmont and Atlantic Coastal Plain physiographic provinces. The rocks in the Piedmont are mainly intensely folded sericite schist and granite gneiss containing irregular masses of amphibolite and feldspathic biotite gneiss and scattered igneous intrusive rocks. Most of the crystalline rocks are thought to be of Paleozoic age, but some of the intrusive rocks may be younger. The crystalline rocks are cut by a major unconformity and are overlain by sedimentary formations ranging in age from Cretaceous to Miocene. The valuable kaolin deposits occur in the Cretaceous beds, undivided, and in the Huber Formation which is of Paleocene to middle Eocene age. The resources of kaolin in the district are estimated in millions of metric tons as follows: reserves, 100; subeconomic resources, 700 to 900; undiscovered resources, probably 700 to 1,000. In addition to kaolin, the leading mineral commodity mined in the district, crushed stone and sand are now being produced, and fuller's earth and a minor amount of limestone were formerly produced. The crushed stone is quarried from igneous rocks in the Piedmont province. The sand is washed from the Cretaceous beds, undivided. The fuller's earth was mined from the Twiggs Clay Member of the Barnwell Formation, and limestone was dug from the Tivola Limestone.

Georgia↗

USGS2004

Summary of the hydrogeology of the Valley and Ridge, Blue Ridge, and Piedmont Physiographic Provinces in the eastern United States

The Appalachian Valley and Piedmont Regional Aquifer-System Analysis study (1988-1993) analyzed rock types in the 142,000-square-mile study area, identified hydrogeologic terranes, determined transmissivity distributions, determined the contribution of ground water to streamflow, modeled ground-water flow, described water quality, and identified areas suitable for the potential development of municipal and industrial ground-water supplies. Ground-water use in the Valley and Ridge, the Blue Ridge, and the Piedmont Physiographic Provinces exceeds 1.7 billion gallons per day. Thirty-three rock types in the study area were analyzed, and the rock types with similar water-yielding characteristics were combined and mapped as 10 hydrogeologic terranes. Based on well records, the interquartile ranges of estimated transmissivities are between 180 to 17,000 feet squared per day (ft 2 /d) for five hydrologic terranes in the Valley and Ridge; between 9 to 350 ft 2 /d for two terranes in the Blue Ridge; and between 9 to 1,400 ft 2 /d for three terranes in the Piedmont Physiographic Province. Based on streamflow records, the interquartile ranges of estimated transmissivities for all three physiographic provinces are between 290 and 2,900 ft 2 /d. The mean ground-water contribution to streams from 157 drainage basins ranges from 32 to 94 percent of mean streamflow with a median of 67 percent. In three small areas in two of the physiographic provinces, more than 54 percent of ground-water flow was modeled as shallow and local. Although ground-water chemical composition in the three physiographic provinces is distinctly different, the water generally is not highly mineralized, with a median dissolved-solids concentration of 164 milligrams per liter, and is mostly calcium, magnesium, and bicarbonate. Based on aquifer properties and current pumpage, areas favorable for the development of municipal and industrial ground-water supplies are underlain by alluvium of glacial origin near the northeastern part of the study area, by clay-free carbonate rocks primarily in the Valley and Ridge Physiographic Province, and by siliciclastic rocks in the three northernmost Mesozoic basins.

Alabama, Delaware, Georgia, Maryland, New Jersey, ↗

USGS1974

Geology and mineralogy of phosphate rock in the Bambui group near Cedro do Abaete and vicinity, Minas Gerais, Brazil

Discontinuous lenticular masses of phosphate rock are present near or at the contact between the green mudstone and the underlying red and yellow clay-stone units of the Serra da Saudade Member of the Rio Paraopeba Formation of the Bambui Group of late Precambrian to early Paleozoic age. The lenses are as much as 8 meters thick and 400 meters long. The phosphate rock is folded and faulted and is overlain by flat-lying rocks of Cretaceous age. The phosphate mineral is a carbonate fluorapatite, but only a small amount of C0 2 substitutes for PO 4 . Crystalline apatite in veinlets is clearly younger than the groundmass apatite, and contains almost no C0 2 . Surficial parts of the phosphate lenses have been altered to a rock characterized by aluminum phosphate. Samples of the green mudstone contain muscovite-illite, quartz, and what is believed to be glauconite. Samples collected adjacent to the phosphate lenses also contain veinlets of apatite or wavellite. Chemical analyses of the phosphate rock show that it contains from 16 to 35 percent P 2 0 5 , and all samples are deficient in Ca0 relative to P 2 0 5 , indicating that some of the phosphate in all samples is combined with alumina. The samples contain as much as 8 percent K 2 0 in the minerals muscovite-illite or glauconite. All the samples collected are extremely fine grained. The rocks are laminated and show the effects of slight deformation; for example, crumpled bedding, offset veinlets, and slight development of muscovite along bedding planes. The phosphate probably is not economically important on the world market, but possibly could be used locally for direct application depending on agricultural lands.

Minas Gerais↗

USGS2006

A 16-year record of eolian dust in Southern Nevada and California, USA: Controls on dust generation and accumulation

An ongoing project monitors modern dust accumulation in the arid southwestern United States to (1) determine the rate and composition of dust inputs to soils and (2) relate dust accumulation to weather patterns to help predict the effects of climate change on dust production and accumulation. The 16-year records of 35 dust-trap sites in the eastern Mojave Desert and southern Great Basin reveal how generation and accumulation of dust, including the silt-clay, carbonate, and soluble-salt fractions, is affected by the amount and seasonal distribution of rainfall and the behavior of different source types (alluvium, dry playas, and wet playas). Accumulation rates (fluxes) of the silt-clay fraction of dust, including carbonates, range from about 2-20 g/m2/yr. Average rates are higher in the southern part of the study area (south of latitude 36.5??N) and annually fluctuate over a larger range than rates in the northern part of the area. Sites throughout the study area show peaks in dust flux in the 1984-1985 sampling period and again in 1997-1999; northern sites also show increased flux in 1987-1988 and southern sites in 1989-1991. These peaks of dust flux correspond with both La Nina (dry) conditions and with strong El Nino (wet) periods. The accumulation rates of different components of mineral dusts fluctuate differently. For example, soluble-salt flux increases in 1987-1988, coincident with a moderate El Nino event, and increases very strongly in 1997-1999, overlapping with a strong El Nino event. Both of these high-rainfall winters were preceded and accompanied by strong summer rains. In contrast, little or no change in soluble-salt flux occurred during other periods of high winter rainfall but little summer rain, e.g. 1992-1995. The differences between northern vs. southern sites and between sites with playa dust sources vs. alluvial dust sources indicate that regional differences in the response of precipitation and vegetation growth to ENSO influence and differences in the response of source types control dust production and accumulation. A major factor is the hydrologic condition of surface sediments. The silt-clay and soluble-salt fluxes increased during the El Nino events of 1987-1988 and 1997-1998 at sites close to "wet" playas with shallow depths to groundwater (<10 m), consistent with the concept that active evaporative concentration of salts disrupts surface crusts and increases the susceptibility of surface sediment to deflation. The silt-clay flux also increased during drought periods (1989-1991, 1995-1997) at sites downwind of alluvial sources and "dry" playas with deeper groundwater (<10 m). These increases are probably related to the die-off of drought-stressed vegetation on alluvial sediments, and in some cases to local runoff events that deliver fresh sediment to playa margins and distal portions of alluvial fans. ?? 2006 Elsevier Ltd. All rights reserved.

Journal of Arid Environments↗

USGS2008

Hydrated silicate minerals on Mars observed by the Mars Reconnaissance Orbiter CRISM instrument

Phyllosilicates, a class of hydrous mineral first definitively identified on Mars by the OMEGA (Observatoire pour la Mineralogie, L’Eau, les Glaces et l’Activitié) instrument 1 , 2 , preserve a record of the interaction of water with rocks on Mars. Global mapping showed that phyllosilicates are widespread but are apparently restricted to ancient terrains and a relatively narrow range of mineralogy (Fe/Mg and Al smectite clays). This was interpreted to indicate that phyllosilicate formation occurred during the Noachian (the earliest geological era of Mars), and that the conditions necessary for phyllosilicate formation (moderate to high pH and high water activity 3 ) were specific to surface environments during the earliest era of Mars’s history 4 . Here we report results from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) 4 of phyllosilicate-rich regions. We expand the diversity of phyllosilicate mineralogy with the identification of kaolinite, chlorite and illite or muscovite, and a new class of hydrated silicate (hydrated silica). We observe diverse Fe/Mg-OH phyllosilicates and find that smectites such as nontronite and saponite are the most common, but chlorites are also present in some locations. Stratigraphic relationships in the Nili Fossae region show olivine-rich materials overlying phyllosilicate-bearing units, indicating the cessation of aqueous alteration before emplacement of the olivine-bearing unit. Hundreds of detections of Fe/Mg phyllosilicate in rims, ejecta and central peaks of craters in the southern highland Noachian cratered terrain indicate excavation of altered crust from depth. We also find phyllosilicate in sedimentary deposits clearly laid by water. These results point to a rich diversity of Noachian environments conducive to habitability.

Nature↗

USGS2022

Development and description of a composite hydrogeologic framework for inclusion in a geoenvironmental assessment of undiscovered uranium resources in Pliocene- to Pleistocene-age geologic units of the Texas Coastal Plain

A previously completed mineral resources assessment of the Texas Coastal Plain indicated the potential for the future discovery of uranium resources. Geoenvironmental assessments that include the hydrogeologic framework can be used as a tool to understand the potential effects of mining operations. The hydrogeologic framework for this study focused on the composite hydrogeologic unit of the tract permissive for the occurrence of uranium consisting of the upper part of the Miocene-age Fleming Formation/Lagarto Clay, Pliocene-age Goliad and Pleistocene-age Willis Sands, Pleistocene-age Lissie and Beaumont Formations, and Holocene-age alluvial sediments (fluvial alluvium and eolian sand deposits). This composite hydrogeologic unit, which contains the Chicot and Evangeline aquifers of the Gulf Coast aquifer system, is intended for inclusion in a regional-scale geoenvironmental assessment of as yet undiscovered uranium resources. This article provides (1) a brief literature review describing the geologic and hydrogeologic settings, (2) the methodology used to develop a composite hydrogeologic framework, and (3) descriptions and maps of the land-surface altitude, composite hydrogeologic unit base and midpoint depth, water-level altitude, depth of water, unsaturated and saturated zone thickness, and transmissivity and hydraulic conductivity. A composite hydrogeologic unit, created by combining geologic and hydrogeologic data and maps for individual geologic and hydrogeologic units, is intended for use as a tool in a geoenvironmental assessment to evaluate potential contaminant migration through various avenues. Potential applications include using the hydrogeologic framework as an input into a geoenvironmental assessment to help estimate the potential for (1) runoff of contaminants into surface water, (2) infiltration of contaminants into the groundwater (aquifers), or (3) movement of contaminants from the mining area through wind, groundwater-flow, or streamflow in a given permissive tract. The procedures outlined in this paper also provide a method for developing hydrogeologic frameworks that can be applied in other areas where mining may occur.

Texas↗

USGS1984

Geologic and hydrologic characterization and evaluation of the Basin and Range Province relative to the disposal of high-level radioactive waste: Part I, Introduction and guidelines

The U.S. Geological Survey's program for geologic and hydrologic evaluation of physiographic provinces to identify areas potentially suitable for locating repository sites for disposal of high-level nuclear wastes was announced to the Governors of the eight States in the Basin and Range Province on May 5, 1981. Representatives of Arizona, California, Idaho, New Mexico, Nevada, Oregon, Texas, and Utah, were invited to cooperate with the Federal Government in the evaluation process. Each Governor was requested to nominate an Earth scientist to represent the State in a province working group composed of State and U.S. Geological Survey representatives. This report, Part I of a three-part report, provides the background, introduction and scope of the study. This part also includes a discussion of geologic and hydrologic guidelines that will be used in the evaluation process and illustrates geohydrologic environments and the effect of individual factors in providing multiple natural barriers to radionuclide migration. Part II is a reconnaissance characterization of the geologic and hydrologic factors to be used in the initial screening of the Basin and Range Province. Part III will be the initial evaluation of the Province and will identify regions that appear suitable for further study. The plan for study of the Province includes a stepwise screening process by which successively smaller land units are considered in increasing detail. Each step involves characterization of the geology and hydrology and selection of subunits for more intensive characterization. Selection of subunits for further study is by evaluation of geologic and hydrologic conditions following a set of guidelines. By representation on the Province Working Group, the States participate in a consultation and review role in: (1) Establishing geologic and hydrologic guidelines, and (2) characterizing and evaluating the Province. The States also participate in compilation of geologic and hydrologic data used in characterizing the Province. The current (1983) needs for a high-level radioactive waste repository include: (1) Disposal in a mined repository; (2) retrievability of the waste for as much as 50 years; and (3) confidence of isolation of the waste from the accessible environment. Isolation of the waste needs to be assured using geologic and hydrologic conditions that: (1) Minimize risk of inadvertent future intrusions by man; (2) minimize the possibility of disturbance by processes that would expose the waste or increase its mobility; and (3) provide a system of natural barriers to the migration of waste by ground water. The guidelines adopted by the Province Working Group are designed to provide a standard with which these conditions can be compared. The guidelines can be grouped into four principal categories: (1) Potential host media, (2) ground-water conditions, (3) tectonic conditions, and. (4) occurrence of natural resources. Ideally the host medium constitutes the first natural barrier to migration of radionculides. The host medium ideally should be a rock type that prevents or retards dissolution and transport of radionuclides. Rocks in both the saturated and unsaturated zones may have desirable characteristics for host media. Rocks-other than the host-in the ground-water flow path from the repository ideally should be major barriers to radionuclide migration. Confining beds of low permeability might be present to retard the rate of flow between more permeable beds. Additionally, sorption of radionuclides by materials such as clays and zeolites in the flow path can further retard the flow of radionuclides by several orders of magnitude. Tectonic conditions in an area should not present a probable cause for exhumation or increased mobility of radioactive waste. Natural resources are a factor for consideration because of the problem of future human intrusion and exposure to radioactivity in the quest for minerals, oil, gas, water, and geothermal resources. The ultimate evaluation of the suitability of a geohydrologic environment for developing a mined repository needs to assess all geologic and hydrologic characteristics and their interaction in providing confidence that a geohydrologic environment will effectively isolate radionuclides from human access. Several hypothetical settings with typical geohydrologic conditions in the Basin and Range Province are used to illustrate the effect of multiple barriers in the isolation of radionuclides.

Arizona, California, Idaho, Nevada, New Mexico, Or↗

USGS2009

The Eocene-Oligocene sedimentary record in the Chesapeake Bay impact structure: Implications for climate and sea-level changes on the western Atlantic margin

A multidisciplinary investigation of the Eocene-Oligocene transition in the International Continental Scientific Drilling Program (ICDP)-U.S. Geological Survey (USGS) Eyreville core from the Chesapeake Bay impact basin was conducted in order to document environmental changes and sequence stratigraphic setting. Planktonic foraminifera and calcareous nannofossil biostratigraphy indicate that the Eyreville core includes an expanded upper Eocene (Biozones E15 to E16 and NP19/20 to NP21, respectively) and a condensed Oligocene-Miocene (NP24-NN1) sedimentary sequence. The Eocene-Oligocene contact corresponds to a =3-Ma-long hiatus. Eocene- Oligocene sedimentation is dominated by great diversity and varying amounts of detrital and authigenic minerals. Four sedimentary intervals are identified by lithology and mineral content: (1) A 30-m-thick, smectite- and illite-rich interval directly overlies the Exmore Formation, suggesting long-term reworking of impact debris within the Chesapeake Bay impact structure. (2) Subsequently, an increase in kaolinite content suggests erosion from soils developed during late Eocene warm and humid climate in agreement with data derived from other Atlantic sites. However, the kaolinite increase may also be explained by change to a predominant sediment input from outside the Chesapeake Bay impact structure caused by progradation of more proximal facies belts during the highstand systems tract of the late Eocene sequence E10.Spectral analysis based on gamma-ray and magnetic susceptibility logs suggests infl uence of 1.2 Ma low-amplitude oscillation of the obliquity period during the late Eocene. (3) During the latest Eocene (Biozones NP21 and E16), several lithological contacts (clay to clayey silt) occur concomitant with a prominent change in the mineralogical composition with illite as a major component: This lithological change starts close to the Biozone NP19/20-NP21 boundary and may correspond to sequence boundary E10-E11 as observed in other northwest Atlantic margin sections. It could result from a shift to more distal depositional environments and condensed sedimentation during maximum fl ooding, rather than refl ecting a climatic change in the hinterland. The distinct 1% increase of the oxygen isotopes may correspond to the short-term latest Eocene "precursor isotope event." (4) The abrupt increase of sediment grainsize, carbonate content, and abundance of authigenic minerals (glauconite) across the major unconformity that separates Eocene from Oligocene sediments in the Eyreville core refl ects deposition in shallower settings associated with erosion, winnowing, and reworking. Sediments within the central crater were affected by the rapid eustatic sea-level changes associated with the greenhouse-icehouse transition, as well as by an abrupt major uplift event and possibly enhanced current activity on the northwestern Atlantic margin. ?? 2009 The Geological Society of America.

Chesapeake Bay↗

USGS1996

MUDMASTER: A Program for Calculating Crystalline Size Distributions and Strain from the Shapes of X-Ray Diffraction Peaks

Particle size may strongly influence the physical and chemical properties of a substance (e.g. its rheology, surface area, cation exchange capacity, solubility, etc.), and its measurement in rocks may yield geological information about ancient environments (sediment provenance, degree of metamorphism, degree of weathering, current directions, distance to shore, etc.). Therefore mineralogists, geologists, chemists, soil scientists, and others who deal with clay-size material would like to have a convenient method for measuring particle size distributions. Nano-size crystals generally are too fine to be measured by light microscopy. Laser scattering methods give only average particle sizes; therefore particle size can not be measured in a particular crystallographic direction. Also, the particles measured by laser techniques may be composed of several different minerals, and may be agglomerations of individual crystals. Measurement by electron and atomic force microscopy is tedious, expensive, and time consuming. It is difficult to measure more than a few hundred particles per sample by these methods. This many measurements, often taking several days of intensive effort, may yield an accurate mean size for a sample, but may be too few to determine an accurate distribution of sizes. Measurement of size distributions by X-ray diffraction (XRD) solves these shortcomings. An X-ray scan of a sample occurs automatically, taking a few minutes to a few hours. The resulting XRD peaks average diffraction effects from billions of individual nano-size crystals. The size that is measured by XRD may be related to the size of the individual crystals of the mineral in the sample, rather than to the size of particles formed from the agglomeration of these crystals. Therefore one can determine the size of a particular mineral in a mixture of minerals, and the sizes in a particular crystallographic direction of that mineral.

Open-File Report↗

USGS2017

Rare-earth elements

The rare-earth elements (REEs) are 15 elements that range in atomic number from 57 (lanthanum) to 71 (lutetium); they are commonly referred to as the “lanthanides.” Yttrium (atomic number 39) is also commonly regarded as an REE because it shares chemical and physical similarities and has affinities with the lanthanides. Although REEs are not rare in terms of average crustal abundance, the concentrated deposits of REEs are limited in number. Because of their unusual physical and chemical properties, the REEs have diverse defense, energy, industrial, and military technology applications. The glass industry is the leading consumer of REE raw materials, which are used for glass polishing and as additives that provide color and special optical properties to the glass. Lanthanum-based catalysts are used in petroleum refining, and cerium-based catalysts are used in automotive catalytic converters. The use of REEs in magnets is a rapidly increasing application. Neodymium-iron-boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys. China, which has led the world production of REEs for decades, accounted for more than 90 percent of global production and supply, on average, during the past decade. Citing a need to retain its limited REE resources to meet domestic requirements as well as concerns about the environmental effects of mining, China began placing restrictions on the supply of REEs in 2010 through the imposition of quotas, licenses, and taxes. As a result, the global rare-earth industry has increased its stockpiling of REEs; explored for deposits outside of China; and promoted new efforts to conserve, recycle, and substitute for REEs. New mine production began at Mount Weld in Western Australia, and numerous other exploration and development projects noted in this chapter are ongoing throughout the world. The REE-bearing minerals are diverse and often complex in composition. At least 245 individual REE-bearing minerals are recognized; they are mainly carbonates, fluorocarbonates, and hydroxylcarbonates (n = 42); oxides (n = 59); silicates (n = 85); and phosphates (n = 26). Many of the world’s significant REE deposits occur in carbonatites, which are carbonate igneous rocks. The REEs also have a strong genetic association with alkaline magmatism. The systematic geologic and chemical processes that explain these observations are not well understood. Economic or potentially economic REE deposits have been found in (a) carbonatites, (b) peralkaline igneous systems, (c) magmatic magnetite-hematite bodies, (d) iron oxide-copper-gold (IOCG) deposits, (e) xenotime-monazite accumulations in mafic gneiss, (f) ion-absorption clay deposits, and (g) monazite-xenotime-bearing placer deposits. Carbonatites have been the world’s main source for the light REEs since the 1960s. Ion-adsorption clay deposits in southern China are the world’s primary source of the heavy REEs. Monazite-bearing placer deposits were important sources of REEs before the mid-1960s and may be again in the future. In recent years, REEs have been produced from large carbonatite bodies mined at the Mountain Pass deposit in California and, in China, at the Bayan Obo deposit in Nei Mongol Autonomous Region, the Maoniuping deposit in Sichuan Province, the Daluxiang deposit in Sichuan Province, and the Weishan deposit in Anhui Province. Alkaline igneous complexes have recently been targeted for exploration because of their enrichments in the heavy REEs. Information relevant to the environmental aspects of REE mining is limited. Little is known about the aquatic toxicity of REEs. The United States lacks drinking water standards for REEs. The concentrations of REEs in environmental media are influenced by their low abundances in crustal rocks and their limited solubility in most groundwaters and surface waters. The scarcity of sulfide minerals, including pyrite, minimizes or eliminates concerns about acid-mine drainage for carbonatite-hosted deposits and alkaline-intrusion-related REE deposits. For now, insights into environmental responses of REE mine wastes must rely on predictive models.

Professional Paper↗

USGS2006

Origin and significance of clay-coated fractures in mudrock fragments of the SAFOD borehole (Parkfield, California)

The clay mineralogy and texture of rock fragments from the SAFOD borehole at 3067 m and 3436 m measured depth (MD) was investigated by electron microscopy (SEM, TEM) and X-ray-diffraction (XRD). The washed and ultrasonically cleaned samples show slickenfiber striations and thin films of Ca-K bearing smectite that are formed on polished fault surfaces, along freshly opened fractures and within adjacent mineralized veins. The cation composition and hydration behavior of these films differ from the Namontmorillonite of the fresh bentonite drilling mud, although there is more similarity with circulated mud recovered from 3479 m MD. We propose that these thin film smectite precipitates formed by natural nucleation and crystal growth during fault creep, probably associated with the shallow circulation of low temperature aqueous fluids along this shallow portion of the San Andreas Fault. Copyright 2006 by the American Geophysical Union.

Geophysical Research Letters↗

USGS2010

Mineralogy and stratigraphy of phyllosilicate-bearing and dark mantling units in the greater Mawrth Vallis/west Arabia Terra area: Constraints on geological origin

Analyses of MRO/CRISM images of the greater Mawrth Vallis region of Mars affirm the presence of two primary phyllosilicate assemblages throughout a region ∼1000 × 1000 km. These two units consist of an Fe/Mg-phyllosilicate assemblage overlain by an Al-phyllosilicate and hydrated silica assemblage. The lower unit contains Fe/Mg-smectites, sometimes combined with one or more of these other Fe/Mg-phyllosilicates: serpentine, chlorite, biotite, and/or vermiculite. It is more than 100 m thick and finely layered at meter scales. The upper unit includes Al-smectite, kaolin group minerals, and hydrated silica. It is tens of meters thick and finely layered as well. A common phyllosilicate stratigraphy and morphology is observed throughout the greater region wherever erosional windows are present. This suggests that the geologic processes forming these units must have occurred on at least a regional scale. Sinuous ridges (interpreted to be inverted channels) and narrow channels cut into the upper clay-bearing unit suggesting that aqueous processes were prevalent after, and possibly during, the deposition of the layered units. We propose that layered units may have been deposited at Mawrth Vallis and then subsequently altered to form the hydrated units. The Fe/Mg-phyllosilicate assemblage is consistent with hydrothermal alteration or pedogenesis of mafic to ultramafic rocks. The Al-phyllosilicate/hydrated silica unit may have formed through alteration of felsic material or via leaching of basaltic material through pedogenic alteration or a mildly acidic environment. These phyllosilicate-bearing units are overlain by a darker, relatively unaltered, and indurated material that has probably experienced a complex geological history.

Journal of Geophysical Research↗

USGS2014

Mineralogical, chemical and K-Ar isotopic changes in Kreyenhagen Shale whole rocks and <2 µm clay fractions during natural burial and hydrous-pyrolysis experimental maturation

Progressive maturation of the Eocene Kreyenhagen Shale from the San Joaquin Basin of California was studied by combining mineralogical and chemical analyses with K–Ar dating of whole rocks and <2 μm clay fractions from naturally buried samples and laboratory induced maturation by hydrous pyrolysis of an immature outcrop sample. The K–Ar age decreases from 89.9 ± 3.9 and 72.4 ± 4.2 Ma for the outcrop whole rock and its <2 μm fraction, respectively, to 29.7 ± 1.5 and 21.0 ± 0.7 Ma for the equivalent materials buried to 5167 m. The natural maturation does not produce K–Ar ages in the historical sense, but rather K/Ar ratios of relative K and radiogenic 40 Ar amounts resulting from a combined crystallization of authigenic and alteration of initial detrital K-bearing minerals of the rocks. The Al/K ratio of the naturally matured rocks is essentially constant for the entire depth sequence, indicating that there is no detectable variation in the crystallo-chemical organization of the K-bearing alumino-silicates with depth. No supply of K from outside of the rock volumes occurred, which indicates a closed-system behavior for it. Conversely, the content of the total organic carbon (TOC) content decreases significantly with burial, based on the progressive increasing Al/TOC ratio of the whole rocks. The initial varied mineralogy and chemistry of the rocks and their <2 μm fractions resulting from differences in detrital sources and depositional settings give scattered results that homogenize progressively during burial due to increased authigenesis, and concomitant increased alteration of the detrital material. Hydrous pyrolysis was intended to alleviate the problem of mineral and chemical variations in initially deposited rocks of naturally matured sequences. However, experiments on aliquots from thermally immature Kreyenhagen Shale outcrop sample did not mimic the results from naturally buried samples. Experiments conducted for 72 h at temperatures from 270 to 365 °C did not induce significant changes at temperatures above 310 °C in the mineralogical composition and K–Ar ages of the rock and <2 μm fraction. The K–Ar ages of the <2 μm fraction range from 72.4 ± 4.2 Ma in the outcrop sample to 62.4 ± 3.4 Ma in the sample heated the most at 365 °C for 216 h. This slight decrease in age outlines some loss of radiogenic 40 Ar, together with losses of organic matter as oil, gas, and aqueous organic species. Large amounts of smectite layers in the illite–smectite mixed layers of the pyrolyzed outcrop <2 μm fraction remain during thermal experiments, especially above 310 °C. With no illitization detected above 310 °C, smectite appears to have inhibited rather than promoted generation of expelled oil from decomposition of bitumen. This hindrance is interpreted to result from bitumen impregnating the smectite interlayer sites and rock matrix. Bitumen remains in the <2 μm fraction despite leaching with H 2 O 2 . Its presence in the smectite interlayers is apparent by the inability of the clay fraction to fully expand or collapse once bitumen generation from the thermal decomposition of the kerogen is completed, and by almost invariable K–Ar ages confirming for the lack of any K supply and/or radiogenic 40 Ar removal. This suggests that once bitumen impregnates the porosity of a progressively maturing source rock, the pore system is no longer wetted by water and smectite to illite conversion ceases. Experimental attempts to evaluate the smectite conversion to illite should preferentially use low-TOC rocks to avoid inhibition of the reaction by bitumen impregnation.

California↗

USGS2020

Lead speciation, bioaccessibility and source attribution in Missouri's Big River watershed

The Southeast Missouri Lead District is among the most productive lead deposits exploited in modern times. Intensive mining conducted prior to regulations resulted in a legacy of lead contaminated soil, large piles of mine tailings and elevated childhood blood lead levels. This study seeks to identify the source of the lead contamination in the Big River and inform risk to the public. Isotopic analysis indicated the mine tailing piles at the head of the Big River are the primary source of the lead contamination. The isotopic signature of the lead in these mine tailings matched the lead over 100 km downstream. All of the other potential lead sources investigated had different isotopic signatures. Lead concentrations in soils and sediments decrease with distance downstream of the mine tailings piles. Additionally, the speciation of the lead changes from predominantly mineralized forms, such as galena, to adsorbed lead. This is reflected in the in-vitro bioaccessibility assay (IVBA) analysis which shows higher bioaccessibility further downstream, demonstrating the importance of speciation in risk evaluation.

Missouri↗