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At least 991 records · Page 55Linked to original sources
USGS2014

A reconnaissance spatial and temporal assessment of methane and inorganic constituents in groundwater in bedrock aquifers, Pike County, Pennsylvania, 2012-13

Pike County in northeastern Pennsylvania is underlain by the Devonian-age Marcellus Shale and other shales, formations that have potential for natural gas development. During 2012–13, the U.S. Geological Survey in cooperation with the Pike County Conservation District conducted a reconnaissance study to assess baseline shallow groundwater quality in bedrock aquifers prior to possible shale-gas development in the county. For the spatial component of the assessment, 20 wells were sampled in summer 2012 to provide data on the occurrence of methane and other aspects of existing groundwater quality throughout the county, including concentrations of inorganic constituents commonly present at low levels in shallow, fresh groundwater but elevated in brines. For the temporal component of the assessment, 4 of the 20 wells sampled in summer 2012 were sampled monthly from July 2012 through June 2013 to provide data on seasonal variability in groundwater quality. All water samples were analyzed for major ions, nutrients, selected inorganic trace constituents (including metals and other elements), stable isotopes of water, radon-222, gross alpha- and gross beta-particle activity, dissolved gases (methane, ethane, and ethene), and, if possible, isotopic composition of methane. Additional analyses for boron and strontium isotopes, age-dating of water, and radium-226 were done on water samples collected from six wells in June 2013. Results of the summer 2012 sampling show that water from 16 (80 percent) of 20 wells had detectable concentrations of methane, but concentrations were less than 0.1 milligram per liter (mg/L) in most well-water samples; only two well-water samples had concentrations greater than 1 mg/L. The groundwater with elevated methane also had a chemical composition that differed in some respects (pH, selected major ions, and inorganic trace constituents) from groundwater with low methane concentrations. The two well-water samples with the highest methane concentrations (about 3.7 and 5.8 mg/L) also had the highest pH values (8.7 and 8.3, respectively) and the highest concentrations of sodium, lithium, boron, fluoride, and bromide. Elevated concentrations of some other constituents, such as barium, strontium, and chloride, were not limited to well-water samples with elevated methane, although the two samples with elevated methane also had among the highest concentrations of these constituents. One sample with elevated methane concentrations also had elevated arsenic concentrations, with the arsenic concentration of 30 micrograms per liter (μg/L) exceeding the drinking-water standard of 10 µg/L for arsenic. No other sample from the 20 wells sampled in summer 2012 had concentrations of constituents that exceeded any established primary drinking-water standards. However, radon-222 activities ranging up to 4,500 picocuries per liter (pCi/L) exceeded the proposed drinking-water standard of 300 pCi/L in 85 percent of the 20 well-water samples. The isotopic composition methane in the two high-methane samples (δC CH4 values of -64.55 and -64.41 per mil and δD CH4 values of -216.9 and -201.8 per mil, respectively) indicates a predominantly microbial source for the methane formed by a carbon dioxide reduction process. The stable isotopic composition of water (δD H20 and δ 18 O H20 ) in samples from all 20 wells falls on the local meteoric line, indicating water in the wells was of relatively recent meteoric origin (modern precipitation), including samples with elevated methane concentrations. Analytical results for 4 of the 20 wells sampled monthly for 1 year ending June 2013 in order to assess temporal variability in groundwater quality show that concentrations of major ions generally varied by less than 20 percent, with most differences less than 4 mg/L. Concentrations of methane varied by less than 1 μg/L (0.001 mg/L) in samples from three wells with low methane and by as much as 1 mg/L (1,000 μg/L) in samples from one well with relatively high methane. The isotopic composition of methane in the one well with relatively high methane varied slightly in the monthly samples, ranging from about -64.5 to -64.8 per mil for δ 13 C CH4 and from about -217 to -228 per mil for δD CH4 . The δ 13 C values for dissolved inorganic carbon (DIC) in water from this well were consistent with microbial methane formation by carbon dioxide reduction (drift-type methane) and varied little in the temporal samples, ranging from -10.5 to -10.1 per mil. Additional analyses of samples collected in late June 2013 from six wells with a range of methane and trace constituent concentrations provided baseline data on strontium and boron isotopic compositions ( 87 Sr/ 86 Sr ratios and δ 11 B, respectively) that potentially may be used to differentiate among sources of these constituents. The strontium and boron isotopic composition determined in the six shallow Pike County groundwater samples had 87 Sr/ 86 Sr ratios of 0.71426 to 0.71531 and δ 11 B values of 11.7 to 27.0 per mil, which differ from those reported for brines in Devonian-age formations in Pennsylvania. The June 2013 samples were also analyzed for radium-226 and age-dating dissolved gases. Activities of radium-226 ranged from 0.041 to 0.29 pCi/L in water samples from the six wells and were less than the drinking-water standard of 5 pCi/L for combined radium-226 and radium-228. Age-dating of groundwater using a method based on the presence of anthropogenic gases (chlorofluorocarbons and sulfur hexafluoride) released into the atmosphere yielded estimated recharge dates for water from these six wells that ranged from the 1940s to early 2000s. The oldest water was in samples from wells that had the highest methane concentrations and the youngest water was in samples from a continuously pumped 300-foot deep production well.

Pennsylvania↗
USGS1971

A geochemical hypothesis for dolomitization by ground water

Most modern disordered dolomite has been found in dynamic environments. However, solutions associated with modern dolomite formation do not have a common Mg/Ca ratio; the ratio ranges from about 3 to 100. Ground-water circulation may have a significant role in formation of regional dolomites; one of the primary requirements for regional dolomite formation is a large supply of magnesium ions. An X-ray study of well cuttings from the Tertiary limestone aquifer of central Florida indicates that it is composed primarily of calcite and dolomite with minor amounts of quartz and apatite. The magnesium content of the calcite is slightly lower (0-2 percent MgC03) in the recharge areas than in the deeper confined parts of the aquifer system (2-4 percent MgC03). Our data support other recent work and indicate an equilibrium constant for dolomite of 2 X 10-17. Inasmuch as this value is exactly the square of the calcite equilibrium constant (10~8-35), the Mg/Ca ratio must be unity for the three-phase equilibrium, calcite-dolomite-water. The Mg/Ca ratio in water from the aquifer is as low as 0.05 in the recharge area where the water is also undersaturated with respect to both calcite and dolomite. With time and length of travel path in the system, the water increases systematically in Mg/Ca ratio, which approaches unity; saturation with respect to the two carbonates also increases downgradient until the solution apparently becomes over-saturated with respect to both carbonates. In Tertiary limestones of the Yucatan Peninsula, the Mg/Ca range in water is similar to that for Florida. The small amount of magnesium available from the solution of magnesium calcites and dolomite in the potable zone of active circulation is insufficient to provide the amount required for extensive dolomitization unless enormous quantities of rock are available for dissolution. However, dolomite may be forming in the zones of brackish water that underlie the Florida and Yucatan Peninsulas. The required magnesium may be derived from the readily available ocean water or reflux brines as the hydrologic regimen is changed because of relative fluctuations of sea level.

Florida↗
USGS1989

Studies of geology and hydrology in the Basin and Range Province, Southwestern United States, for isolation of high-level radioactive waste - Basis of characterization and evaluation

The geologic and hydrologic factors in selected regions of the Basin and Range province were examined to identify prospective areas for further study that may provide isolation of high-level radioactive waste from the accessible environment. The six regions selected for study were characterized with respect to the following guidelines: (1) Potential repository media; (2) Quaternary tectonic conditions; (3) climatic change and geomorphic processes; (4) ground-water conditions; (5) ground-water quality; and (6) mineral and energy resources. The repository medium will function as the first natural barrier to radionuclide travel by virtue of associated slow ground-water velocity. The principal rock types considered as host media include granitic, intermediate, and mafic intrusive rocks; argillaceous rocks; salt and anhydrite; volcanic mudflow (laharic) breccias; some intrusive rhyolitic plugs and stocks; partially zeolitized tuff; and metamorphic rocks. In the unsaturated zone, the permeability and hydrologic properties of the rocks and the hydrologic setting are more important than the rock type. Media ideally should be permeable to provide drainage and should have a minimal water flux The ground-water flow path from a repository to the accessible environment needs to present major barriers to the transport of radionuclides. Factors considered in evaluating the ground-water conditions include ground-water traveltimes and quality, confining beds, and earth materials favorable for retardation of radionuclides. Ground-water velocities in the regions were calculated from estimated hydraulic properties of the rocks and gradients. Because site-specific data on hydraulic properties are not available, data from the literature were assembled and synthesized to obtain values for use in estimating ground-water velocities. Hydraulic conductivities for many rock types having granular and fracture permeability follow a log-normal distribution. Porosity for granular and very weathered crystalline rock tends to be normally distributed; porosity of fractured crystalline rock probably follows a log-normal distribution. The tectonic setting needs to prevent an increase in radionuclides to the accessible environment. Data on historic seismicity and heat flow, Quaternary faults, volcanism, and uplift were used to assess the tectonic conditions. Long-term late Cenozoic rates of vertical crustal movement in the Basin and Range province range from less than 2 meters per 104 years to greater than 20 meters per 104 years. Shortterm rates of vertical movement may be more than an order of magnitude greater, based on geodetic leveling. Changes in tectonic and climatic processes may potentially cause changes in hydrologic conditions and geomorphology that could affect the integrity of a deep, mined repository either adversely or beneficially. The transition from a full-glacial climate to the current interglacial condition has occurred within the past 15,000 years. Reconstructions of the last full-glacial climate indicate that, at that time, there was greater water availability for runoff and vegetation growth than there is now. Based on the increased water availability and depending on seasonal distribution of precipitation, on soil characteristics, on topography, and on other characteristics, ground-water recharge during the full-glacial climate is estimated to have been possibly 2 to 10 or more times the modern rate. During the full-glacial climate, more than 100 lakes occupied closed basins in the province. Any increase in ground-water recharge and refilling of Pleistocene lakes will tend to decrease the distance of ground-water flow and its time of travel. The unsaturated zone this zone is considered a potential host medium where the thickness is greater than 150 m will be decreased by these changes. In contrast, incision of streams and other geomorphic, tectonic, or climatically induced changes that lower the ground-water discharge level will tend to increase the thickness of the unsaturated zone. Aggradation in basinal troughs may either decrease or increase the thickness of the unsaturated zone. Aggradation in basins that causes the ground-water discharge level to rise will tend to decrease the thickness of unsaturated zone in the adjacent uplands; aggradation in basins where the ground-water discharge level remains the same or is lowered will increase the unsaturated thickness of basin fill. Records show that, throughout late Cenozoic time in the Basin and Range province, continued vertical crustal movements have tended to maintain mountain ranges and closed basins, whereas aggradation of the basins and erosion of the mountain ranges have tended to decrease the topographic relief. Maximum rates of denudation for small basins in areas climatically similar to the Basin and Range province are about 2 meters per 104 years. For sites unaffected by stream incision and scarp retreat, a conservative estimate of erosion affecting long-term changes in depth of burial would appear to be 2 meters per 104 years, or, equal to the long-term rate of vertical crustal movement where greater than 2 meters per 104 years. The response of the ground-water conditions to climatic and geomorphically induced boundary conditions is significant from the points of: (1) The potential maximum change in the ground-water flow system; (2) the time of response of the ground-water system; and (3) the present state of the ground-water system as a result of past changes. Effects of longterm climatic and tectonic changes on hydrologic and geomorphic conditions differ from area to area, and rates of change of geomorphic and hydrologic conditions may vary significantly. Therefore, sitespecific studies need to be made to assess the long-term integrity of deep, mined repositories.

Arizona, California, Idaho, Nevada, New Mexico, Te↗
USGS2003

Sediment-starved sand ridges on a mixed carbonate/siliciclastic inner shelf off west-central Florida

High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed that the mixed carbonate/siliciclastic, inner shelf of west-central Florida supports a highly complex field of active sand ridges mantled by a hierarchy of bedforms. The sand ridges, mostly oriented obliquely to the shoreline trend, extend from 2 km to over 25 km offshore. They show many similarities to their well-known counterparts situated along the US Atlantic margin in that both increase in relief with increasing water depth, both are oriented obliquely to the coast, and both respond to modern shelf dynamics. There are significant differences in that the sand ridges on the west-central Florida shelf are smaller in all dimensions, have a relatively high carbonate content, and are separated by exposed rock surfaces. They are also shoreface-detached and are sediment-starved, thus stunting their development. Morphological details are highly distinctive and apparent in side-scan imagery due to the high acoustic contrast. The seafloor is active and not a relict system as indicated by: (1) relatively young AMS 14C dates (< 1600 yr BP) from forams in the shallow subsurface (1.6 meters below seafloor), (2) apparent shifts in sharply distinctive grayscale boundaries seen in time-series side-scan mosaics, (3) maintenance of these sharp acoustic boundaries and development of small bedforms in an area of constant and extensive bioturbation, (4) sediment textural asymmetry indicative of selective transport across bedform topography, (5) morphological asymmetry of sand ridges and 2D dunes, and (6) current-meter data indicating that the critical threshold velocity for sediment transport is frequently exceeded. Although larger sand ridges are found along other portions of the west-central Florida inner shelf, these smaller sand ridges are best developed seaward of a major coastal headland, suggesting some genetic relationship. The headland may focus and accelerate the N-S reversing currents. An elevated rock terrace extending from the headland supports these ridges in a shallower water environment than the surrounding shelf, allowing them to be more easily influenced by currents and surface gravity waves. Tidal currents, storm-generated flows, and seasonally developed flows are shore-parallel and oriented obliquely to the NW-SE trending ridges, indicating that they have developed as described by the Huthnance model. Although inner shelf sand ridges have been extensively examined elsewhere, this study is the first to describe them in a low-energy, sediment-starved, dominantly mixed siliciclastic/carbonate sedimentary environment situated on a former limestone platform. ?? 2003 Elsevier B.V. All rights reserved.

Florida↗
USGS1993

The analysis of forms of sulfur in ancient sediments and sedimentary rocks: comments and cautions

Assumptions commonly made during analysis of the amount of monosulfides [acid-volatile sulfides (AVS)] and disulfides in modern sediments, may not be valid for ancient sedimentary rocks. It is known that ferric iron can oxidize H2S during AVS analysis unless a reducing agent such as stannous chloride is added to the treatment. In addition, some monosulfides such as greigite and pyrrhotite require heat during the AVS analysis in order to dissolve completely. However, the use of heat and/or stannous chloride in the AVS treatment may partially dissolve disulfides and it is generally recommended that stannous chloride not be used in the AVS treatment for modern sediments. Most of the monosulfides are assumed to be recovered as AVS without the addition of stannous chloride. This study investigates the recovery of monosulfides during sulfur speciation analysis with application to ancient sedimentary rocks. Sulfur in samples containing naturally occurring greigite and mackinawite or pyrite was measured using variations of a common sulfur-speciation scheme. The sulfur-speciation scheme analyzes for monosulfide sulfur, disulfide sulfur, elemental sulfur, inorganic sulfate and organically bound sulfur. The effects of heat, stannous chloride and ferric iron on the amounts of acid-volatile sulfide and disulfide recovered during treatment for AVS were investigated. Isotopic compositions of the recovered sulfur species along with yields from an extended sulfur-speciation scheme were used to quantify the effects. Hot 6 N HCl AVS treatment recovers > 60% of the monosulfides as AVS in samples containing pure greigite and mackinawite. The remaining monosulfide sulfur is recovered in a subsequent elemental sulfur extraction. Hot 6 N HCl plus stannous chloride recovers 100% of the monosulfides as AVS. The addition of ferric iron to pure greigite and mackinawite samples during AVS treatment without stannous chloride decreased the amount of monosulfides recovered as AVS and, if present in great enough concentration, oxidized some of the AVS to a form not recovered in later treatments. The hot stannous chloride AVS treatments dissolve <5% of well-crystallized pyrite in this study. The amount of pyrite dissolved depends on grain size and crystallinity. Greigite in ancient sedimentary rocks was quantitatively recovered as AVS only with hot 6 N HCl plus stannous chloride. Hot 6 N HCl AVS treatment of these rocks did not detect any monosulfides in most samples. A subsequent elemental sulfur extraction did not completely recover the oxidized monosulfides. Therefore, the use of stannous chloride plus heat is recommended in the AVS treatment of ancient sedimentary rocks if monosulfides are present and of interest. All assumptions about the amount of monosulfides and disulfides recovered with the sulfur-speciation scheme used should be verified by extended sulfur-speciation and/or isotopic analysis of the species recovered. ?? 1993.

Chemical Geology↗
USGS2014

Hydrogeology and hydrology of the Punta Cabullones wetland area, Ponce, southern Puerto Rico, 2007-08

The U.S. Geological Survey, in cooperation with the Municipio Autónomo de Ponce and the Puerto Rico Department of Natural and Environmental Resources, conducted a study of the hydrogeology and hydrology of the Punta Cabullones area in Ponce, southern Puerto Rico. (Punta Cabullones is also referred to as Punta Cabullón.) The Punta Cabullones area is about 9 square miles and is an ecological system made up of a wetland, tidal flats, saltflats, mangrove forests, and a small fringing reef located a short distance offshore. The swales or depressions between successive beach ridges became development avenues for saline to hypersaline wetlands. The Punta Cabullones area was designated by the U.S. Fish and Wildlife Service as a coastal barrier in the 1980s because of its capacity to act as a buffer zone to ameliorate the impacts of natural phenomenon such as storm surges. Since 2003, Punta Cabullones has been set aside for preservation as part of the mitigation effort mandated by Federal and State laws to compensate for the potential environmental effects that might be caused by the construction of the Las Américas Transshipment Port. Total rainfall measured during 2008 within the Punta Cabullones area was 36 inches, which is slightly greater than the long-term annual average of 32 inches for the coastal plain near Ponce. Two evapotranspiration estimates, 29 and 37 inches, were obtained for the subarea of the Punta Cabullones area that is underlain by fan-delta and alluvial deposits by using two variants of the Penman semi-empirical equation. The long-term water stage and chemical character of the wetland in Punta Cabullones are highly dependent on the seasonal and annual variations of both rainfall and sea-wave activity. Also, unseasonal short-term above-normal rainfall and sea-wave events resulting from passing storms may induce substantial changes in the water stage and the chemical character of the wetland. In general, tidal fluctuations exert a minor role in modifying the water quality and stage of the wetland in Punta Cabullones. The role of the tidal fluctuations becomes important during those times when the outlets/inlets to the sea are not blocked by a sand bar and is allowed to freely flow into the wetland interior. The salinity of the wetland varies from brackish to hypersaline. The hypersaline conditions, including the occurrence of saltflats, within the Punta Cabullones wetland area result from a high evapotranspiration rate. The hypersaline conditions are further enhanced by a sand bar that blocks the inlet/outlet of the wetland’s easternmost channel, particularly during the dry season. Groundwater in Punta Cabullones mostly is present within beds of silisiclastic sand and gravel. During the study period, the depth to groundwater did not exceed 4 feet below land surface. The movement and direction of the groundwater flow in Punta Cabullones are driven by density variations that in turn result from the wide range of salinities in the groundwater. The salinity of the groundwater decreases within the first 60 to 100 feet of depth and decreases outward from a mound of hypersaline groundwater centered on piezometer nest PN2. The main groundwater types within the Punta Cabullones area vary from calcium-bicarbonate type in the northernmost part of the study area to a predominantly sodium-potassium-chloride groundwater type southward. According to stable-isotope data, groundwater within the study area is both modern meteoric water and seawater highly affected by evaporation. The chemical and stable-isotopic character of local groundwater is highly influenced by evapotranspiration because of its shallow depth. Equivalent freshwater heads indicate groundwater moves away from a mound centered on piezometer nest PN2, in a pattern similar to the spatial distribution of groundwater salinity. Vertical groundwater flow occurs in Punta Cabullones due to local differences in density. In the wetland subarea of Punta Cabullones, groundwater and surface water are hydraulically coupled. Locally, surface-hypersaline water sinks into the aquifer, providing recharge and serving as a mechanism to redistribute salt throughout the study area. The evapotranspiration in the wetland subarea is estimated at about 11 million gallons per day (Mgal/d) that is equivalent to about 12,586 acre-feet per year. The balance of evapotranspiration, in excess of the about 0.5 Mgal/d of groundwater flow within the wetland, is supplied by saline to hypersaline surface water that may include seawater and meteoric water highly affected by evaporation with dissolved salts. In one of the extreme scenarios in which no groundwater is intercepted by pumpage at the Restaurada well field, the amount of saline to hypersaline water in the wetland consumed by evapotranspiration is about 10.5 Mgal/d. In the opposite extreme in which the entire regional groundwater flow is intercepted by pumpage in the Restaurada well field, the entire evapotranpiration requirement is met by saline to hypersaline water. Hydrologic, isotopic, and chemical data indicate that all of, or a large portion of, the historical groundwater flow to Punta Cabullones is being captured by the Puerto Rico Aqueducts and Sewer Authority pumpage at the Restaurada well field at a rate of about 2 Mgal/d. As a consequence, seawater intrusion into the aquifer at the Punta Cabullones area seems to be occurring, while the current pumpage at the Restaurada well field is sustained by storage depletion of the aquifer.

Puerto Rico↗
USGS2018

Status and understanding of groundwater quality in the Monterey-Salinas Shallow Aquifer Study Unit, 2012–13: California GAMA Priority Basin Project

Groundwater quality in the approximately 7,820-square-kilometer (km 2 ) Monterey-Salinas Shallow Aquifer (MS-SA) study unit was investigated from October 2012 to May 2013 as part of the second phase of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is in the central coast region of California in the counties of Santa Cruz, Monterey, and San Luis Obispo. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in cooperation with the U.S. Geological Survey and the Lawrence Livermore National Laboratory. The MS-SA study was designed to provide a statistically robust assessment of untreated-groundwater quality in the shallow aquifer systems. The assessment was based on water-quality samples collected by the U.S. Geological Survey from 100 groundwater sites and 70 household tap sites, along with ancillary data such as land use and well-construction information. The shallow aquifer systems were defined by the depth interval of wells associated with domestic supply. The MS-SA study unit consisted of four study areas—Santa Cruz (210 km 2 ), Pajaro Valley (360 km 2 ), Salinas Valley (2,000 km 2 ), and Highlands (5,250 km 2 ). This study had two primary components: the status assessment and the understanding assessment . The first primary component of this study—the status assessment —assessed the quality of the groundwater resource indicated by data from samples analyzed for volatile organic compounds (VOCs), pesticides, and naturally present inorganic constituents, such as major ions and trace elements. The status assessment is intended to characterize the quality of groundwater resources in the shallow aquifer system of the MS-SA study unit, not the treated drinking water delivered to consumers by water purveyors. As opposed to the public wells, however, water from private wells, which often tap the shallow aquifer, is usually consumed without any treatment. The second component of this study—the understanding assessment —identified the natural and human factors that potentially affect groundwater quality by evaluating land-use characteristics, measures of location, geologic factors, groundwater age, and geochemical conditions of the shallow aquifer. An additional component of this study was a comparison of MS-SA water-quality results to those of the GAMA Monterey Bay and Salinas Valley Groundwater Basins study unit. This study unit covered much of the same areal extent as the MS-SA, but assessed the deeper, public drinking-water aquifer system. Relative concentrations (sample concentration divided by the benchmark concentration) were used to evaluate concentrations of constituents in groundwater samples relative to water-quality benchmarks for those constituents that have Federal or California benchmarks, such as maximum contaminant levels. For organic and special-interest constituents, relative concentrations were classified as high, greater than 1.0; moderate, greater than 0.1 and less than or equal to 1.0; or low, less than or equal to 0.1. For inorganic constituents, relative concentrations were classified as high, greater than 1.0; moderate, greater than 0.5 and less than or equal to 1.0; or low, less than or equal to 0.5. A relative concentration greater than 1.0 indicates that the concentration was greater than a benchmark. Aquifer-scale proportions were used to quantify regional-scale groundwater quality. The aquifer-scale proportions are the areal percentages of the shallow aquifer system where relative concentrations for a given constituent or class of constituents were high, moderate, or low. Inorganic constituents were measured at high and moderate relative concentrations more frequently than organic constituents. In the MS-SA study unit, inorganic constituents with benchmarks were detected at high relative concentrations in 51 percent of the study unit. The greatest proportions of high relative concentrations of trace elements and radioactive constituents were in the Highlands and Santa Cruz study areas, whereas high relative concentrations of nutrients were most often detected in the Salinas Valley and Pajaro Valley study areas and salinity indicators were most often detected in the Highlands and Salinas Valley study areas. The trace elements detected at high relative concentrations were arsenic, boron, iron, manganese, molybdenum, selenium, and strontium. The radioactive constituents detected at high relative concentrations were adjusted gross alpha radioactivity and uranium. The nutrient detected at high relative concentrations was nitrate plus nitrite. The salinity indicators detected at high relative concentrations were chloride, sulfate, and total dissolved solids. Organic constituents (VOCs and pesticides) were not detected at high relative concentrations in any of the study areas. The fumigant 1,2-dichloropropane was detected at moderate relative concentrations. The VOC chloroform and the pesticide simazine were the only organic constituents detected in more than 10 percent of samples. The constituents of special interest NDMA ( N -nitrosodimethylamine) and perchlorate were detected at high relative concentrations in the MS-SA study unit. Selected constituents were evaluated with explanatory factors to identify potential sources or processes that could explain their presence and distribution. Trace elements and radioactive constituents came from natural sources and were not elevated by anthropogenic sources or processes, except for selenium and the radioactive constituent uranium. Arsenic, manganese, iron, selenium, and uranium concentrations were all influenced by oxidation-reduction conditions. Unlike other trace elements and radioactive constituents, uranium and selenium can be affected by agricultural practices. Uranium and selenium can be released from aquifer sediments as a result of irrigation recharge water interacting with bicarbonate systems. Nitrate can be strongly affected by anthropogenic sources. Nitrate concentrations were significantly higher in modern groundwater, indicating recent inputs of nitrate to the shallow aquifer system. Nitrate was positively correlated with agricultural land use, indicating that irrigation-return water could be leaching nitrogen fertilizer and naturally present nitrate to elevate nitrate concentrations in shallow groundwater. The salinity indicators total dissolved solids, chloride, and sulfate all had natural sources in the MS-SA study unit, primarily marine sediments. Concentrations of the constituents were elevated as a result of evaporative concentration of irrigation water or precipitation. Sulfate concentrations were significantly correlated to agricultural land use, indicating that agricultural land-use practices are a contributing source of sulfate to groundwater. The samples with most of the detections of VOCs were from sites in the Pajaro Valley and northern part of the Salinas Valley. Most of the samples with pesticide detections were from sites in the Salinas Valley study area. The herbicide simazine was positively correlated to the percentage of agricultural land use, and its concentrations were higher in modern groundwater than in pre-modern groundwater. Perchlorate, similar to nitrate, has natural and anthropogenic sources. Correlations of perchlorate to dissolved oxygen, nitrate, and percentage of agricultural land use indicated that the irrigation-return water could be leaching naturally present perchlorate, as well as perchlorate from historical applications of Chilean nitrate fertilizer, to increase perchlorate concentrations in groundwater. The quality of the water in the shallow aquifer system from this study was compared with the quality of water in the public drinking-water aquifer in a previous GAMA (MS-PA) study in the same area. The shallow system was more oxic and had more sites with modern groundwater than the public drinking-water aquifer, which was more anoxic and had sites with more pre-modern groundwater. Arsenic and selenium were found at high relative concentrations in a greater proportion of the shallow system. Manganese and iron were found at high relative concentrations in a greater proportion of the public drinking-water aquifer. Uranium was found at higher relative concentrations in a greater proportion of the shallow system. Concentrations of arsenic, iron, manganese, and molybdenum are not likely to change much as groundwater percolates from the shallow system to the public drinking-water aquifer because there are no anthropogenic sources affecting these constituents. Uranium and selenium concentrations in the public drinking-water aquifer could be affected by the higher concentrations in the shallow system because of irrigation-return water, however. Nitrate and salinity indicators had concentrations that were much higher in the shallow system than the deeper public drinking-water aquifer. High concentrations of these constituents in the shallow system could lead to increased concentrations in the public drinking-water aquifer in parts of the study units because of land-use practices, such as irrigated agriculture. Organic constituents were detected more frequently in the public drinking-water aquifer than in the shallow system, possibly because more of the sites sampled in the public drinking-water aquifer were in urban areas compared to the sites sampled for the shallow system or because sources of contamination have decreased as a result of changes in use at the land surface.

California↗
USGS2017

Fluorine

Fluorine compounds are essential in numerous chemical and manufacturing processes. Fluorspar is the commercial name for fluorite (isometric CaF 2 ), which is the only fluorine mineral that is mined on a large scale. Fluorspar is used directly as a fluxing material and as an additive in different manufacturing processes. It is the source of fluorine in the production of hydrogen fluoride or hydrofluoric acid, which is used as the feedstock for numerous organic and inorganic chemical compounds. The United States was the world’s leading producer of fluorspar until the mid-1950s. In the mid-1970s, the U.S. fluorspar mining industry began to decline because of foreign competition. By 1982, there was essentially only a single U.S. producer left, and that company ceased mining in 1996. Consumption of fluorspar in the United States peaked in the early 1970s, which was also the peak period of U.S. steel production. Since then, U.S. fluorspar consumption has decreased substantially; the United States has nonetheless increased its imports of downstream fluorine compounds, such as, in order of tonnage imported, hydrofluoric acid, aluminum fluoride, and cryolite. This combination of no U.S. production (until recently) and high levels of consumption has made the United States the world’s leading fluorspar-importing country, in all its various forms. The number of fluorspar-exporting countries has decreased substantially in recent decades, and, as a result, the United States has become dependent on just a few countries to supply its needs. In 2013, the United States imported the majority of its fluorspar from three countries, which were, in descending order of the amount imported, Mexico, China, and South Africa. Geologically, in igneous systems, fluorine is one of a number of elements that are “incompatible.” These incompatible elements become concentrated in the residual magma while the common silicates crystallize upon magma ascent and cooling, leading to relatively high fluorine concentrations in the more evolved or differentiated igneous rocks and in hydrothermal deposits associated with those evolved igneous rocks. In sedimentary rocks, fluorine’s highest concentrations are found in phosphorites because fluorine substitutes for hydroxyl ions in apatite, which leads to fluorine concentrations of, typically, from 2 to 4 weight percent in phosphorites. Because of the presence of fluorine, phosphate fertilizer manufacturers can produce a fluorosilicic acid byproduct. Most deposits mined for fluorine are hydrothermal, however, and consist of fluorine minerals that precipitated from hot water. Magmatic brines and brines from deep within sedimentary basins that have high concentrations of dissolved fluoride are the mineralizing fluids for various types of hydrothermal fluorspar deposits. Relatively dilute hydrothermal fluids that formed in some volcanic rocks can also transport sufficient fluoride to form a high-grade fluorspar deposit. Fluorite has low solubility in a common range of hydrothermal temperatures, particularly from about 160 degrees Celsius (°C) down to 60 °C. The increasing fluorite solubility below 60 °C partly explains why some water with exceptionally high levels of dissolved fluorine are found even at ambient temperatures in evaporitic lake basins in some East African Rift valleys in Kenya and Tanzania. The geologic conditions that led to the high concentrations there are known to exist in a number of other places in the world as well, including, perhaps, places in the Basin and Range province of the United States. Eight minerals or mineral groups have sufficient fluorine in their structures to be considered as possible ores of the element; they are bastnaesite (also spelled bastnäsite; and other fluorocarbonates), cryolite, sellaite, villiaumite, fluorite, fluorapatite (in phosphorites), various phyllosilicates, and topaz. Fluorite is currently the only mineral that is mined for fluorine, and nomineral except fluorite is likely to become a source of commercially produced fluorine as a primary product as long as supplies from relatively thick and high-grade fluorite deposits continue to be available. At least seven classes (which include one subclass) of hydrothermal fluorite deposits are recognized; they are classified according to their tectonic and (or) magmatic settings, as follows: (1) carbonatite-related fluorspar deposits; (2) alkaline-intrusion-related fluorspar deposits; (3) alkaline-volcanic-related epithermal fluorspar deposits; (4) Mississippi Valley-type fluorspar deposits (and a subclass of salt-related carbonate-hosted fluorspar deposits); (5) fluorspar deposits related to strongly differentiated granites; (6) subalkaline-volcanic-related epithermal fluospar deposits; and (7) fluorspar deposits that appear to be conformable within tuffaceous limy lacustrine sediments. An eighth class (not hydrothermal) is that of fluorspar deposits concentrated in soils and weathered zones; that is, residual fluorspar deposits. Generally, fluorspar deposits related to strongly differentiated granites have larger tonnages and lower grades than carbonatite-related fluorspar deposits, which, in turn, have larger tonnages and lower grades than fluorspar vein deposits from various other classes. The United States has a few identified resources of fluorspar, most notably the Klondike II property in the Illinois- Kentucky fluorspar district located about 8 kilometers southwest of Salem, Kentucky, which has a large vein that contains at least 1.6 million metric tons at a grade of 60 percent CaF 2 (Feytis, 2009). Additional fluorspar resources of lower grade but larger tonnage have been identified at Hicks Dome in the Illinois-Kentucky fluorspar district and at Lost River near the western tip of the Seward Peninsula in Alaska, along with a couple of dozen smaller, higher grade resources. Internationally, new mines that either opened before the beginning of 2013 or were scheduled to open soon after that time include the Nui Phao tungsten-fluorspar-bismuth-copper-gold deposit in northern Vietnam; the St. Lawrence project in Newfoundland, Canada, which is located in a well-known fluorspar district; the Bamianshan deposit, which is related to a strongly differentiated granite in northwestern Zhejiang Province, China, near some of that Province’s large, subalkaline-volcanic-related epithermal veins; and the Nokeng project in South Africa, which is also related to a strongly differentiated granite. Other deposits in northwestern Australia, Nevada (United States), Norway, South Africa, and Sweden have been identified and could be put into production within just a few years. Among undiscovered resources, an interesting possibility might be to produce a fluorine product from evaporitic, high-fluorine, high-pH sodium-carbonate brines like Lake Magadi (Kenya) and Lake Natron (Tanzania) in Africa’s Eastern Rift Valley. In addition, apparently conformable fluorspar deposits in tuffaceous limy lacustrine sediments, such as those in Italy, are likely to occur in similar young alkalic volcanic settings elsewhere in the world. Modern geophysical and geochemical exploration techniques have typically not been brought to bear in exploration for new fluorspar deposits, although such techniques are likely to be used in future exploration. The tendency for fluorine to dissolve in significant concentrations in water at low temperature allows both surface water and groundwater to be used as sampling media in geochemical exploration. Evolved granite-related fluorspar deposits may be particularly susceptible to geophysical exploration methods because crystalline rocks that form a basement to sedimentary sections can be approximately defined with gravity and magnetic methods, and magnetite-bearing skarns can be directly detected with magnetic surveys. Environmental considerations of fluorine mining focus especially on drinking water, where high fluorine concentrations can lead to tooth decay; dental and skeletal fluorosis; and bone and cartilage conditions, including genu valgum, which is the crippling bone deformity more commonly known as knock knee. Trace amounts of other elements in fluorspar ores are a concern at some deposits; for example, high beryllium concentrations in alkaline-volcanic-related epithermal deposits or high cadmium concentrations associated with Mississippi Valley-type and salt-related carbonate-hosted fluorspar deposits. Future research might include testing whether fluorine can be extracted economically from high-pH, sodium-carbonate brines and exploring for new occurrences of apparently conformable fluorspar deposits in tuffaceous limy lacustrine sediments outside of the Latium Region of Italy. Other promising new areas of research could be studies of fluorspar deposit fluid inclusion compositions by quadrupole mass spectrometry, by noble gas mass spectrometry on irradiated fluid inclusions, or by chlorine isotopes, while also measuring the chemistry of the same fluid inclusions either by bulk crush-and-leach methods or by laser ablation-inductively coupled plasma mass spectrometry. Advanced studies of fluid inclusion chemistry could be applied beneficially to some of the enigmatic large epithermal fluorspar veins at various places in the world, where they might determine those deposits’ possible relationships to igneous intrusions, or to dissolved salt, or to heated meteoric water in volcanic sections, or perhaps to all three. This knowledge could help focus new exploration.

Professional Paper↗
USGS1998

Palynology of latest Neogene (Middle Miocene to late Pliocene) strata in the Delmarva Peninsula of Maryland and Virginia

Palynology of Miocene and Pliocene formations in the Delmarva Peninsula of Maryland and Virginia reveals a significant representation of exotic pollen interspersed in pollen assemblages that are otherwise comparable to those from the modern vegetation of the Mid-Alantic coastal plain region. The late Tertiary arboreal pollen (AP) assemblages are dominated by oak, hickory, pine, birch and alder with minor amounts of mid- and southern coastal tree taxa, as well as minor spruce and hemlock and a trace of fir. Nonarboreal pollen (NAP) include grass, sedge, composite and aquatic taxa. Exotic pollen in these assemblages represent plants now foreign to this region. They may be placed in three categories. First, there are extinct forms, such as Labrapollis, Plicatopollis, and Multiporopollenites, that can be traced from the Cretaceous or Early Tertiary into the Late Tertiary. The second group includes forms, such as Podocarpus, Engelhardtia, Pterocarya, Ephedra, Eucommia, Ulmus-Zelkova, Glyptostrobus, Palmae, and Cyathea, that are not found in this region today and not found in early Pleistocene sediments in the eastern United States. Many of these taxa are subtropical or greatly restricted in geographic range. A third group of exotics, mainly Cyrilla, Planera, Gordonia, Jussiaea, and Sapotacaea, including Minusops, are generally found south of the study area or have their northern limit here at this time. The lack of the extinct or distant exotics in early to mid-Pleistocene sediments in the mid-Atlantic coastal plain and the last appearance of Pterocarya, as the last exotic taxon in the early Pleistocene of western Europe, support the stratigraphic assignment of the Pliocene units. The number of exotic taxa diminish markedly between the Miocene pollen assemblages and those of the Late Pliocene. Climatic fluctuations characterize the Late Tertiary environments. The Miocene, for example, incorporates a warming trend between the upper, middle Miocene and the Manokin beds and the late Miocene of the Pokomoke beds. The late Miocene was probably somewhat warner than the present climate in the Delmarva region. This trend is based on the presence of colder climate indicators, mainly spruce and hemlock, in the Manokin pollen record. The two distinct pollen assemblages constitute two pollen zones. Similarly, the Pliocene pollen record also shows a warming trend. The pollen zone of the Yorktown Formation of the early Pliocene age contains the colder climate indicators spruce and hemlock. The Beaverdam and Walston formation of late Pliocene age contain pollen assemblages that reflect climatic conditions warmer than the present time.

Northeastern Geology and Environmental Sciences↗
USGS2015

Shift in Global Tantalum Mine Production, 2000–2014

Introduction Tantalum has a unique set of properties that make it useful in a number of diverse applications. The ability of the metal to store and release electrical energy makes it ideally suited for use in certain types of capacitors that are widely used in modern electronics. Approximately 60 percent of global tantalum consumption is in the electronics industry. The ductility and corrosion resistance of the metal lends itself to application in the chemical processing industry, and its high melting point and high strength retention at elevated temperatures make it an important component of super alloys used in aircraft engines. As a major industrialized nation, the United States is a leading consumer of tantalum and tantalum-containing products. Domestic deposits typically are of low grade, and no tantalum has been recovered from mining activities in the United States since 1959. Consequently, the United States is nearly completely reliant on imports to meet its domestic consumption of tantalum for economic and national security needs. The recovery of tantalum from mine production is economically viable in only a few countries. Although developed countries dominated tantalum mine production in the early 2000s, production today is dominated by countries in the Great Lakes Region of Africa. There is concern that the sales of minerals, including columbite-tantalite or &ldquo;coltan,&rdquo; a mineral from which tantalum is derived, have helped finance rebel groups accused of violating human rights as part of the continuing armed conflict in the Democratic Republic of the Congo (DRC) and neighboring countries. These accusations have prompted the passage of legislation in the United States to curb the procurement of these mineral commodities, referred to as &ldquo;conflict minerals,&rdquo; from the DRC. Specifically, section 1502 of the 2010 Dodd-Frank Wall Street Reform and Consumer Protection Act (Public Law 111&ndash;203, 124 Stat. 2213&ndash;2218) requires companies that source tantalum, tin, tungsten, and gold (3TG) to perform due diligence on their supply chains to determine if the materials they use originate from the DRC or adjoining countries (defined as sharing a border with the DRC). The DRC, Rwanda, and surrounding countries are not globally significant sources of tin, tungsten, or gold, accounting for only about 2 percent of the mined world supply for each of these elements. The region has, however, evolved to become the world&rsquo;s largest producer of mined tantalum. A further complication of the production of tantalum stems from the opacity of the tantalum market. Unlike most base and precious metals, tantalum concentrates are not publicly traded through commodities exchanges but are bought and sold through networks of dealers and on contract between producers and consumers, some of whom may not provide accurate statistical data concerning the amounts, origins, and destination of the concentrates. Some price data can be found in trade journals or in other publications; however, there are no recognized official set exchange prices for either concentrate or tantalum metal. Because price is determined by negotiation between buyer and seller, published prices for concentrate are probably not representative of global prices paid for concentrate. The development of a mine-to-market supply-chain analysis is complicated and difficult because many of the industry participants that produce, trade, and consume tantalum do not publish statistical information, contracts are long term between miners and buyers, and much of the industry is vertically integrated. As a result of these and other considerations, tantalum is considered by many to be a &ldquo;critical&rdquo; commodity. This fact sheet identifies and addresses the major geographic shifts in the source of mine production of tantalum which have occurred over the past 15 years, some of the factors that drove this shift, and some of the related consequences. One of the activities of the U.S. Geological Survey National Minerals Information Center (USGS-NMIC) is to analyze global supply chains and characterize major components of mineral and material flows from ore extraction through processing to first tier products. These analyses support the core mission of the USGS-NMIC as the Federal entity responsible for the collection, analysis, and dissemination of objective, unbiased, factual information on minerals essential to the U.S. economy and national security.

Fact Sheet↗
USGS2007

Evaluation of ground-water and boron sources by use of boron stable-isotope ratios, tritium, and selected water-chemistry constituents near Beverly Shores, northwestern Indiana, 2004

Concentrations of boron greater than the U.S. Environmental Protection Agency (USEPA) 900 μg/L removal action level (RAL) standard were detected in water sampled by the USEPA in 2004 from three domestic wells near Beverly Shores, Indiana. The RAL regulates only human-affected concentrations of a constituent. A lack of well logs and screened depth information precluded identification of whether water from sampled wells, and their boron sources, were from human-affected or natural sources in the surficial aquifer, or associated with a previously defined natural, confined aquifer source of boron from the subtill or basal sand aquifers. A geochemically-based classification of the source of boron in ground water could potentially determine the similarity of boron to known sources or mixtures between known sources, or classify whether the relative age of the ground water predated the potential sources of contamination. The U.S. Geological Survey (USGS), in cooperation with the USEPA, investigated the use of a geochemical method that applied boron stable isotopes, and concentrations of boron, tritium, and other constituents to distinguish between natural and human-affected sources of boron in ground water and thereby determine if the RAL was applicable to the situation. Boron stable-isotope ratios and concentrations of boron in 17 ground-water samples and tritium concentrations in 9 ground-water samples collected in 2004 were used to identify geochemical differences between potential sources of boron in ground water near Beverly Shores, Indiana. Boron and δ 11 B analyses for this investigation were made on unacidified samples to assure consistency of the result with unacidified analyses of δ 11 B values from other investigations. Potential sources of boron included surficial-aquifer water affected by coal-combustion products (CCP) or domestic-wastewater, upward discharge of ground water from confined aquifers, and unaffected water from the surficial aquifer that was distant from human-affected boron sources. Boron concentrations in potential ground-water sources of boron were largest (15,700 to 24,400 μg/L) in samples of CCP-affected surficial aquifer water from four wells at a CCP landfill and smallest (27 to 63 μg/L) in three wells in the surficial aquifer that were distant from human-affected boron sources. Boron concentrations in water from the basal sand aquifer ranged from 656 μg/L to 1,800 μg/L. Boron concentrations in water from three domestic-wastewater-affected surficial aquifer wells ranged from 84 to 387 μg/L. Among the representative ground-water samples, boron concentrations from all four samples of CCP-affected surficial aquifer water and four of five samples of water from the basal sand aquifer had concentrations greater than the RAL. A comparison of boron concentrations in acid-preserved and unacidified samples indicated that boron concentrations reported for this investigation may be from about 11 to 16 percent less than would be reported in a standard analysis of an acidified sample. The stable isotope boron-11 was most enriched in comparison to boron-10 in ground water from a confined aquifer, the basal sand aquifer (δ 11 B, 24.6 to 34.0 per mil, five samples); it was most depleted in CCP-affected water from the surficial aquifer (δ 11 B, 0.1 to 6.6 per mil, four samples). Domestic-wastewater-affected water from the surficial aquifer (δ 11 B, 8.7 to 11.7 per mil, four samples) was enriched in boron-11, in comparison to individual samples of a borax detergent additive and a detergent with perborate bleach; it was intermediate in composition between basal sand aquifer water and CCP-affected water from the surficial aquifer. The similarity between a ground-water sample from the surficial aquifer and a hypothetical mixture of unaffected surficial aquifer and basal sand aquifer waters indicates the potential for long-term upward discharge of ground water into the surficial aquifer from one or more confined aquifers. Estimated δ 11 B values for acidified samples were depleted by 1.9 to 2.8 per mil in comparison to unacidified samples from the four wells sampled; those differences were small in comparison to the differences between δ 11 B values of representative sources of boron in ground water. Tritium concentrations ranged from 7.0 to 10.3 tritium units in six samples from the surficial aquifer and were less than 0.8 tritium units in three samples from the basal sand aquifer. Water from wells in the surficial aquifer represents predominantly modern, post-1972 recharge and sources of boron and other constituents. Water from the basal sand aquifer is associated with pre-1952 recharge from sources not affected by local boron inputs. Ground water from six wells (five domestic wells and one public-supply well) where the ground-water source was unknown had boron concentrations, boron isotope ratios, and tritium concentrations similar to water from the basal sand aquifer. Boron concentrations greater than the RAL were found in water from four of these six wells. The boron isotope and tritium data from these four wells indicate a natural source of boron in ground water; therefore, the RAL does not apply to boron concentrations in water from these wells. Water samples from two domestic wells where the ground-water source was unknown had boron concentrations less than the RAL and boron isotope ratios and tritium concentrations that were similar to domestic-wastewater-affected water from the surficial aquifer. The boron isotope ratio for a sample from one domestic well was similar to that of CCP-affected water from the surficial aquifer and detergent compositions; the boron concentration of that sample was less than the RAL. The classifications of differences among representative sources of boron in ground water and water samples from wells where the ground-water source was unknown generally agreed with distinctions based on strontium-87/strontium-86 ratios and concentrations of strontium, chloride, nitrate, and ammonia. This application of boron concentrations, boron isotope ratios, and tritium concentrations to classify differences in relation to potential sources of boron in ground water was able to distinguish between boron from natural sources and from human-affected sources that are subject to regulation.

Indiana↗
USGS1990

Studies of angiospermous woods in Australian brown coal by nuclear magnetic resonance and analytical pyrolysis: new insight into early coalification

Many Tertiary coals contain abundant fossilized remains of angiosperms, which commonly dominated the ancient peat-swamp environments; modern analogs of such swamps can be found in tropical and subtropical regions of the world. Comparisons of angiospermous wood from Australian brown coal with similar wood buried in modern peat swamps of Indonesia have provided some new insights into coalification reactions. These comparisons were made by using solid-state 13 C nuclear magnetic resonance (NMR) techniques and pyrolsis-gas chromatography-mass spectrometry (py-gc-ms). These two modern techniques are especially suited for detailed structural evaluation of the complex macromolecules in coal. The earliest transformation (peatification) of organic matter in angiospermous wood is the degradation and removal of cellulosic components and the concomitant selective preservation of lignin-derived components. The angiospermous lignin that becomes enriched in wood as a result of cellulose degradation also is modified by coalification reactions; this modification, however, does not involve degradation and removal of the lignin. Rather, the early coalification process transforms the lignin phenols (guiacyl and syringyl) to eventually yield the aromatic structures typically found in brown coal. One such transformation, which is determined from NMR data, involves the cleavage of aryl-ether bonds that link guaiacyl and syringyl units in lignin, and this transformation leads to the formation of free lignin phenols. Another transformation, which is also determined from the NMR data, involves the loss of methoxyl groups, probably via demethylation, to produce catechol-like structures. Coincident with ether-cleavage and demethylation, the aromatic rings derived from lignin phenols become more carbon-substituted and cross linked, as determined by dipolar-dephasing NMR studies. This cross linking is probably responsible for preventing the lignin phenols, which are freed from the lignin macromolecule by ether cleavage, from being removed from the coal by dissolution. Pyrolysis data suggest that the syringyl units are altered more readily than are guaiacyl units, and this difference in resistance leads to an enrichment of the guaiacyl units in fossil angiospermous woods. Many of the coalification reactions noted above occur to some degree in all angiospermous fossil wood examined; however, some significant differences are observed in the degree of coalification of the fossil wood samples from the same burial depth in the brown coal. These differences indicate that the depth and duration of burial are probably not entirely responsible for the variations in degree of coalification. Different rates of degradation in peat may have contributed to the variations in the apparent degree of coalification; some woods may have been altered more rapidly at the peat stage than others. Although preliminary, this systematic study of botanically related wood in peat and coal results in a more detailed differentiation of coalification reactions than have previous investigations. The combined use of solid-state 13 C NMR and py-gc-ms has facilitated this detailed insight into the coalification of angiospermous wood.

International Journal of Coal Geology↗
USGS1988

Late Wisconsinan-Holocene paleogeography of Delaware Bay; a large coastal plain estuary

Analyses of an extensive grid of seismic reflection profiles along with previously published core data and modern sedimentary environment information from surrounding coastal areas permit an outline of the paleogeography of the large Delaware Bay estuary during the last transgression of sea level. During late Wisconsinan times, the Delaware River system eroded a dendritic drainage pattern into the gravelly and muddy sands of Tertiary and younger age beneath the southern half of the lower bay area. This system included the trunk valley of the ancestral river and a large tributary valley formed by the convergence of secondary streams along the Delaware coast. The evolution of the estuary from this drainage system proceeded as follows: (1) When local relative sea level was at -50 m, the head of the tide reached the present bay-mouth area. (2) At -40 m (possibly 15,000-12,000 yrs ago), the trunk valley of the drainage system was a tidal river that extended more than 30 km up the bay, and a small contiguous inlet existed at the bay mouth. (3) At -30 m (approximately 11,000-10,000 yrs ago), the estuary comprised two narrow passages formed by the drowning of the main and tributary river valleys, and the bay-mouth inlet was 5-6 km wide. (4) At -20 m (between 8000 and 7000 yrs ago), the two passages of the estuary were joined, except for a series of small islands on top of a low intervening ridge, and the inlet channel was 11 km wide. (5) At -10 m (between 6000 and 5000 yrs ago), the estuary was nearly continuous and encompassed about 60% of the present lower bay area. Thin, coarse-grained fluvial deposits accumulated initially within the main channels of the former drainage system as base level was elevated by rising sea level. During the subsequent development of the estuary, clayey silts were deposited rapidly beneath the nontidal estuarine depocenter (turbidity maximum) as it migrated through the bay area, and organic muds accumulated in tidal wetlands that occupied the mouths of tributaries and small marginal embayments. As the fetch and tidal prism of the estuary increased, narrow barrier and headland beaches, composed of fine to coarse sands, were formed locally along the bay shorelines. In the later stages of development, sediment scour, reworking and transport became the dominant processes within the open estuary. Data from this study demonstrate the great temporal and spatial variability of sedimentary deposits within large drowned river-valley estuaries and outline a model that can be used to interpret ancient estuarine strata. ?? 1988.

Delaware, New Jersey↗
USGS2019

Summary of hydrologic testing, wellbore-flow data, and expanded water-level and water-quality data, 2011–15, Fort Irwin National Training Center, San Bernardino County, California

In view of the U.S. Army’s historical reliance and plans to increase demands on groundwater to supply its operations at Fort Irwin National Training Center (NTC), California, coupled with the continuing water-level declines in some developed groundwater basins as a result of pumping, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army, evaluated the water resources, including water quality and potential groundwater supply, of undeveloped basins in the NTC. Previous work in the three developed groundwater basins—Langford, Bicycle, and Irwin—provided information to support water-resources management of those basins. During 2009–12, the USGS installed 41 wells at the NTC; 34 wells were at 14 single- or multiple-well monitoring sites, and 7 wells were long-screen test wells. The majority of the wells were installed in previously undeveloped or minimally developed groundwater basins (Cronise, Red Pass, the Central Corridor area, Superior, Goldstone, and Nelson Basins). During 2012–15, the USGS tested hydrologic properties at 32 wells in 8 basins to help characterize the aquifer system. This report presents data and analyses from core samples; slug tests and single-well aquifer tests; coupled measurements of wellbore flow, water levels, and water-quality constituents; and results from two-dimensional numerical modeling. This information provides a basis for developing and constraining basin-scale hydrogeologic framework and groundwater-flow models to further evaluate water resources in each groundwater basin. Core samples were tested for vertical saturated hydraulic conductivity, physical properties, and particle-size distribution. Vertical saturated hydraulic conductivities of the cores ranged from less than 0.00001 to 18.13 feet per day, and porosities ranged from 0.15 to 0.56. These physical properties and particle-size analyses indicate the high degree of heterogeneity of the hydrogeologic deposits penetrated by the boreholes. Horizontal hydraulic conductivities estimated from slug tests in 22 monitoring wells in 6 basins (Cronise, Central Corridor area, Goldstone, Langford, Bicycle, and Nelson Basins) ranged from less than 0.1 to 40 feet per day. Results of the aquifer tests at six test wells in the Goldstone, Nelson, and Superior Basins indicate hydraulic conductivities ranged from 0.37 to 66 feet per day; associated transmissivity values ranged from 130 to 28,000 feet squared per day. Wellbore-flow data, collected from the six test wells under unpumped and pumped conditions, generally showed downward movement of water. Flow data collected under unpumped conditions indicate groundwater entered the well through the upper part of the screened interval and exited to aquifer zones in the lower part of the screened interval at rates ranging from 1 to 3 gallons per minute. Flow data collected under pumping conditions show increased flow downward in the test wells, indicating higher yields from deeper aquifers. Water levels, measured periodically between 2011 and 2015, remained stable during this period in the majority of the wells measured since 2011, except at two monitoring sites in developed basins (Bicycle and Langford). Vertical hydraulic gradients were generally low throughout the NTC, but ranged from –0.0003 to 0.27 during the summer of 2015. Multiple-well monitoring sites in Bicycle, Central Corridor area, Cronise, Goldstone, Nelson, and Superior Basins, had downward vertical gradients. Groundwater in wells in Nelson and Superior Basins, and wells BLA5, CCT1, and GOLD2 #2, was characterized as sodium-bicarbonate water, whereas groundwater from the remaining wells in Goldstone Basin was characterized as sodium-chloride water and Cronise Basin, and well LL04 was characterized by sodium-sulfate water. Total dissolved solids (TDS) ranged from 285 to 13,400 milligrams per liter (mg/L) TDS and chloride concentrations ranged from 19 to 1,030 mg/L chloride, with lowest concentrations of each in groundwater from Superior and Nelson Basins and highest concentrations in Cronise Basin. Nitrate plus nitrite as nitrogen ranged from less than 0.040 mg/L in groundwater from Cronise and Goldstone Basins to about 20 mg/L in Nelson Basin. Groundwater from wells in Nelson Basin was isotopically light, whereas groundwater samples from wells CRTH1, CRTH2, and LL04 were isotopically heavier and plotted along an evaporative trend line. No measurable tritium was detected in groundwater from 13 wells sampled in 2015, indicating that groundwater was recharged prior to 1952. Measured carbon-14 ( 14 C) activities in groundwater from four wells sampled in 2015 ranged from about 7.9 to 23.5 percent modern carbon and had apparent (uncorrected) ages of 11,970–20,980 years. Arsenic concentrations were above the maximum contaminant level of 10 micrograms per liter in groundwater from all wells, except those in Goldstone Basin and the two deepest wells in Langford Basin (LL04); likewise, fluoride concentrations were above the California maximum contaminant level of 2 mg/L in groundwater from most wells, except those in Goldstone and Superior Basins, the middle well in Langford Basin, middle and deep wells in two locations in Cronise Basin, and two wells in Nelson Basin. Wellbore flow was simulated for each well by using an integrated-flow analysis tool, AnalyzeHOLE, to evaluate aquifer properties and heterogeneity. Horizontal layers in the model (hydrogeologic units) were defined by lithostratigraphic‐geophysical units, interpreted from lithologic and geophysical logs for each well, and were adjusted during calibration. The saturated hydraulic conductivities derived from the calibrated simulations ranged from less than 0.01 to 60 feet per day in Nelson, Goldstone, and Superior Basins.

California↗
USGS2014

Status and understanding of groundwater quality in the Sierra Nevada Regional study unit, 2008: California GAMA Priority Basin Project

Groundwater quality in the Sierra Nevada Regional (SNR) study unit was investigated as part of the California State Water Resources Control Board&rsquo;s Groundwater Ambient Monitoring and Assessment Program Priority Basin Project. The study was designed to provide statistically unbiased assessments of the quality of untreated groundwater within the primary aquifer system of the Sierra Nevada. The primary aquifer system for the SNR study unit was delineated by the depth intervals over which wells in the State of California&rsquo;s database of public drinking-water supply wells are open or screened. Two types of assessments were made: (1) a status assessment that described the current quality of the groundwater resource, and (2) an evaluation of relations between groundwater quality and potential explanatory factors that represent characteristics of the primary aquifer system. The assessments characterize untreated groundwater quality, rather than the quality of treated drinking water delivered to consumers by water distributors. The status assessment was based on water-quality data collected by the U.S. Geological Survey from 83 wells in the SNR study unit in 2008 and from 117 wells in 3 small study units within the SNR study unit in 2006&ndash;07 and on water-quality data compiled in the State&rsquo;s database for 1,066 wells sampled in 2006&ndash;08. To provide some context for the results, water-quality data were converted to relative-concentrations (RCs), which are the sample concentrations divided by the concentrations of Federal or California regulatory and non-regulatory benchmarks for drinking-water quality. RCs for inorganic constituents (major ions, trace elements, nutrients, and radioactive constituents) were classified as &ldquo;high&rdquo; (RC > 1.0, indicating that concentration is above the benchmark), &ldquo;moderate&rdquo; (1.0 &ge; RC > 0.5), or &ldquo;low&rdquo; (RC &le; 0.5). For organic constituents (volatile organic compounds and pesticides) and special-interest constituents (perchlorate and N -nitrosodimethylamine [NDMA]), the boundary between moderate and low RCs was set at 0.1. All benchmarks used for organic constituents were health-based, whereas health-based and aesthetic-based benchmarks were used for inorganic constituents. The primary metric used for quantifying regional-scale groundwater quality was &ldquo;aquifer-scale proportion.&rdquo; Aquifer-scale proportions were calculated as the areal percentages of the primary aquifer system having high, moderate, and low RCs for a given constituent or class of constituents. The SNR study unit area was classified into four aquifer lithologic types&mdash;granitic rocks, metamorphic rocks, sedimentary deposits, and volcanic rocks&mdash;and aquifer-scale proportions were calculated on an area-weighted basis for each of the four aquifer lithologies and for the study unit as a whole (aggregated system). The results of the status assessment indicated that inorganic constituents were present at high and moderate RCs in greater proportions in the SNR study unit aggregated primary aquifer system than were organic constituents and that there were significant differences (p < 0.05) between the four aquifer lithologies. One or more inorganic constituents with health-based benchmarks were present at high RCs in 16 percent of the aggregated primary aquifer system and at moderate RCs in 21 percent. Arsenic (9.7 percent), uranium (2.9 percent), boron (2.0 percent), fluoride (1.8 percent), and nitrate (1.4 percent) were the constituents most commonly present at high RCs. For inorganic constituents with aesthetic-based benchmarks, 18 percent of the aggregated primary aquifer system had high RCs of one or more constituent, and 6.8 percent had moderate RCs. Iron (15.8 percent), manganese (15.1 percent), and total dissolved solids (1.3 percent) were the constituents most commonly present at high RCs. Organic constituents were not detected in 72 percent of the primary aquifer system. One or more organic constituents had high RCs in 0.1 percent of the primary aquifer system, moderate RCs in 3.0 percent, and low RCs in 25 percent. Proportions of the four lithologic primary aquifer systems with high or moderate concentrations of organic constituents were not significantly different. Three organic constituents had area-weighted detection frequencies greater than 10 percent in the primary aquifer system as a whole or at least one of the four lithologic primary aquifer systems: the gasoline oxygenate methyl tert -butyl ether, the trihalomethane chloroform, and the herbicide simazine. The special-interest constituent perchlorate was detected at high RCs in 0.01 percent of the primary aquifer system and at moderate RCs in 1.0 percent, and detection frequencies could be accounted for by the distribution of perchlorate under natural conditions. Statistical tests were used to evaluate relations between constituent concentrations and potential explanatory factors descriptive of land use, geography, depth, geochemical conditions, and groundwater age. Higher concentrations of trace elements, radioactive constituents, and constituents with aesthetic-based benchmarks generally were associated with anoxic conditions, higher pH, and location within a particular compositional band in the Sierra Nevada batholith corresponding to the southwestern part of the study unit. High concentrations of organic constituents generally were associated with greater proportions of urban land use. No significant relations were observed between the concentrations of organic constituents and measures of well depth or groundwater age, perhaps because of the high proportions of springs and modern groundwater in the dataset.

California↗
USGS2013

National assessment of shoreline change: historical shoreline change along the Pacific Northwest coast

Beach erosion is a chronic problem along most open ocean shores of the United States. As coastal populations continue to increase and infrastructure is threatened by erosion, there is increased demand for accurate information regarding past and present trends and rates of shoreline movement. There is also a need for a comprehensive analysis of shoreline movement that is consistent from one coastal region to another. To meet these national needs, the U.S. Geological Survey (USGS) is conducting an analysis of historical shoreline changes along the open-ocean sandy shores of the conterminous United States and parts of Hawaii, Alaska, and the Great Lakes. One purpose of this work is to develop standard, repeatable methods for mapping and analyzing shoreline movement so that periodic, systematic, and internally consistent updates regarding coastal erosion and land loss can be made nationally. In the case of the analysis of shoreline change in the Pacific Northwest (PNW), the shoreline is the interpreted boundary between the ocean water surface and the sandy beach. This report on the PNW coasts of Oregon and Washington is the seventh in a series of regionally focused reports on historical shoreline change. Previous investigations include analyses and descriptive reports of the U.S. Gulf of Mexico (Morton and others, 2004), the southeastern Atlantic (Morton and Miller, 2005), the sandy shorelines (Hapke and others, 2006) and coastal cliffs (Hapke and Reid, 2007) of California, the New England and mid-Atlantic coasts (Hapke and others, 2011), and parts of the Hawaii coast (Fletcher and others, 2012). Like the earlier reports in this series, this report summarizes the methods of analysis, interprets the results of the analysis, provides explanations regarding long- and short-term trends and rates of shoreline change, and describes how different coastal communities are responding to coastal erosion. This report differs from the early USGS reports in the series in that those shoreline change analyses incorporated only four total shorelines to represent specific time periods. This assessment of the PNW incorporates all available shorelines that meet minimum quality standards for resolution and positional accuracy. Shoreline change evaluations are based on a comparison of historical shoreline positions digitized from maps or aerial photographic data sources with recent shorelines, at least one of which is derived from lidar surveys. The historical shorelines cover a variety of time periods ranging from the 1800s through the 1980s, whereas the lidar shoreline is from 2002. Long-term rates of change are calculated using all available shoreline data and short-term rates of change are calculated using the lidar shoreline and the historical shoreline that will produce an assessment for a 15- to 35-year period. The rates of change presented in this report represent conditions up to the date of only the most recent shoreline data and therefore are not intended for predicting future shoreline positions or rates of change. The PNW coast was subdivided into eight analysis regions for the purpose of graphically reporting regional trends in shoreline change rates. The average rate of long-term shoreline change for the entire PNW coast was 0.9 meter per year (m/yr) of progradation with an uncertainty of 0.07 m/yr. This rate is based on 8,823 individual transects, of which 36 percent was determined to be eroding. Long-term shoreline change was generally more progradational in Washington than in Oregon. This is primarily due to the influence of the Columbia River and human perturbations to the natural system, particularly the construction of jetties at both the mouth of the Columbia River and at Grays Harbor, Washington. The majority of the beaches in southwestern Washington have responded to these large-scale engineered structures by experiencing dramatic beach progradation during the past century. Although these beaches are still responding to the human effects, in several locations beaches that had been rapidly prograding are now either prograding at a slower rate or eroding. The average rate of short-term shoreline change in the PNW was also progradational at a rate of 0.9 m/yr with an uncertainty of 0.03 m/yr. This rate is based on 9,087 individual transects, of which 44 percent was determined to be eroding. Similar to the results of the long-term shoreline change analysis, the shorelines in Washington were typically more progradational than those in Oregon in the short term. However, many stretches of coast in Oregon are either less accretional, changed from accretional to erosional, or more erosional when comparing the long- and short-term rate calculations. In the long and short term, there are significantly different historical shoreline change trends for beaches deriving their modern sediments from the Columbia River in southwestern Washington and northwestern Oregon, and beaches elsewhere in the PNW. The majority of shorelines in Oregon and in Washington’s Olympic Peninsula are not influenced by the human effects to the Columbia River littoral cell and typically have not experienced the human-induced century-scale trends apparent in southwestern Washington and northwestern Oregon. An increase in erosion hazards in much of Oregon may be related to the effects of sea-level rise and increasing storm wave heights. Of importance, particularly in the short term, is the alongshore variability in land uplift rates due to tectonics, which results in an alongshore varying rate of relative sea level rise that appears to at least partially control the regional variability in short-term shoreline change rates. Other climate related processes, such as the occurrence of major El Niño events, also significantly affect the shoreline changes in the region. Major El Niño events elevate monthly mean sea levels by tens of centimeters throughout the winter and produce a shift in the storm tracks, resulting in alongshore redistributions in sand volumes on the beaches, leading to hotspot beach erosion and property losses north of headlands and tidal inlets to bays and estuaries. There are limited modern-day sources of sand to Oregon’s beaches, with much of the sand being relict in having arrived thousands of years ago at a time of lowered sea levels when headlands did not prevent the alongshore movement of the beach sediments, the result being that many beaches today are deficient in sand volumes and therefore do not provide sufficient buffer protection to backshore properties during winter storms.

Oregon;Washington↗
USGS2010

Status and understanding of groundwater quality in the North San Francisco Bay groundwater basins, 2004: California GAMA Priority Basin Project

Groundwater quality in the approximately 1,000-square-mile (2,590-square-kilometer) North San Francisco Bay study unit was investigated as part of the Priority Basin Project of the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The study unit is located in northern California in Marin, Napa, and Sonoma Counties. The GAMA Priority Basin Project is being conducted by the California State Water Resources Control Board in collaboration with the U.S. Geological Survey (USGS) and the Lawrence Livermore National Laboratory. The GAMA North San Francisco Bay study was designed to provide a spatially unbiased assessment of untreated groundwater quality in the primary aquifer systems. The assessment is based on water-quality and ancillary data collected by the USGS from 89 wells in 2004 and water-quality data from the California Department of Public Health (CDPH) database. The primary aquifer systems (hereinafter referred to as primary aquifers) were defined by the depth interval of the wells listed in the CDPH database for the North San Francisco Bay study unit. The quality of groundwater in shallower or deeper water-bearing zones may differ from that in the primary aquifers; shallower groundwater may be more vulnerable to surficial contamination. The first component of this study, the status of the current quality of the groundwater resource, was assessed by using data from samples analyzed for volatile organic compounds (VOC), pesticides, and naturally occurring inorganic constituents, such as major ions and trace elements. This status assessment is intended to characterize the quality of groundwater resources within the primary aquifers of the North San Francisco Bay study unit, not the treated drinking water delivered to consumers by water purveyors. Relative-concentrations (sample concentration divided by the health- or aesthetic-based benchmark concentration) were used for evaluating groundwater quality for those constituents that have Federal and (or) California benchmarks. A relative-concentration greater than (>) 1.0 indicates a concentration above a benchmark, and less than or equal to (≤) 1.0 indicates a concentration equal to or below a benchmark. Relative-concentrations of organic and special interest constituents were classified as “high” (relative-concentration > 1.0), “moderate” (0.1 < relative-concentration ≤ 1.0), or “low” (relative-concentration ≤ 0.1). Inorganic constituent relative-concentrations were classified as “high” (relative-concentration > 1.0), “moderate” (0.5 < relative-concentration ≤ 1.0), or “low” (relative-concentration ≤ 0.5). Aquifer-scale proportion was used as a metric for evaluating regional-scale groundwater quality. High aquifer-scale proportion is defined as the percentage of the primary aquifers that have a relative-concentration greater than 1.0; proportion is calculated on an areal rather than a volumetric basis. Moderate and low aquifer-scale proportions were defined as the percentage of the primary aquifers that have moderate and low relative-concentrations, respectively. Two statistical approaches—grid-based and spatially-weighted—were used to evaluate aquifer-scale proportion for individual constituents and classes of constituents. Grid-based and spatially-weighted estimates were comparable in the North San Francisco Bay study unit (90-percent confidence intervals). For inorganic constituents with human-health benchmarks, relative-concentrations were high in 14.0 percent of the primary aquifers, moderate in 35.8 percent, and low in 50.2 percent. The high aquifer-scale proportion of inorganic constituents primarily reflected high aquifer-scale proportions of arsenic (10.0 percent), boron (4.1 percent), and lead (1.6 percent). In contrast, relative-concentrations of organic constituents (one or more) were high in 1.4 percent, moderate in 4.9 percent, and low in 93.7 percent (not detected in 64.8 percent) of the primary aquifers. The high aquifer-scale proportion of organic constituents primarily reflected high aquifer-scale proportions of PCE (1.3 percent), TCE (0.1 percent), and 1,1-dichloroethene (0.1 percent). The inorganic constituents with secondary maximum contaminant levels (SMCL), manganese and iron, had relative-concentrations that were high in 40.8 percent and 24.4 percent of the primary aquifers, respectively. Of the 255 organic and special-interest constituents analyzed for, 26 constituents were detected. Two organic constituents were frequently detected (in 10 percent or more of samples), the trihalomethane chloroform and the herbicide simazine, but both were detected at low relative-concentrations. The second component of this study, the understanding assessment, identified the natural and human factors that affect groundwater quality by evaluating land use, physical characteristics of the wells, geochemical conditions of the aquifer, and water temperature. Results from these evaluations were used to explain the occurrence and distribution of constituents in the study unit. The understanding assessment indicated that a majority of the wells that contained nitrate also had an urban or agricultural land-use classification, had a modern or mixed age classification, and had depths to their top perforations <100 ft (30 m). Geochemical data are consistent with partial denitrification of nitrate in some reducing groundwaters in the terminal and deeper parts of the flow system. High and moderate relative-concentrations of arsenic may be attributed to reductive dissolution of manganese or iron oxides, or to desorption or inhibition of arsenic sorption under alkaline conditions. Arsenic concentrations increased with increasing depth and groundwater age in the North San Francisco Bay study unit. High to moderate relative-concentrations of boron were primarily associated with hydrothermal activity or high-salinity waters in the Napa Sonoma lowlands. Simazine was detected in groundwater classified as modern and mixed age more often than in groundwater classified as pre-modern age, while chloroform was detected most often in groundwater classified as mixed age. Simazine and chloroform also were observed in wells that had surrounding land use classified as agricultural or land use classified as urban, and top of perforation depths less than 100 ft (30 m). Together, the occurrence of chloroform and simazine in shallow wells with modern or mixed groundwater located in urban or agricultural areas suggests that these constituents result from anthropogenic activities during the last 50 years. Tritium, helium-isotope, and carbon-14 data were used to classify the predominant age of groundwater samples into three categories: modern (water that has entered the aquifer in the last 50 years), pre-modern (water that entered the aquifer more than 50 years to tens of thousands of years ago), and mixed (mixtures of modern- and pre-modern-age waters). Arsenic, iron, and total dissolved solids (TDS) concentrations were significantly greater in groundwater having pre-modern-age classification than modern, suggesting that these constituents accumulate with groundwater residence time.

California↗
USGS1982

Recommended procedures and techniques for the petrographic description of bituminous coals

Modern coal petrology requires rapid and precise description of great numbers of coal core or bench samples in order to acquire the information required to understand and predict vertical and lateral variation of coal quality for correlation with coal-bed thickness, depositional environment, suitability for technological uses, etc. Procedures for coal description vary in accordance with the objectives of the description. To achieve our aim of acquiring the maximum amount of quantitative information within the shortest period of time, we have adopted a combined megascopic-microscopic procedure. Megascopic analysis is used to identify the distinctive lithologies present, and microscopic analysis is required only to describe representative examples of the mixed lithologies observed. This procedure greatly decreases the number of microscopic analyses needed for adequate description of a sample. For quantitative megascopic description of coal microlithotypes, microlithotype assemblages, and lithotypes, we use (V) for vitrite or vitrain, (E) for liptite, (I) for inertite or fusain, (M) for mineral layers or lenses other than iron sulfide, (S) for iron sulfide, and (X 1 ), (X 2 ), etc. for mixed lithologies. Microscopic description is expressed in terms of V representing the vitrinite maceral group, E the exinite group, I the inertinite group, and M mineral components. volume percentages are expressed as subscripts. Thus (V) 20 (V 80 E 10 I 5 M 5 ) 80 indicates a lithotype or assemblage of microlithotypes consisting of 20 vol. % vitrite and 80% of a mixed lithology having a modal maceral composition V 80 E 10 I 5 M 5 . This bulk composition can alternatively be recalculated and described as V 84 E 8 I 4 M 4 . To generate these quantitative data rapidly and accurately, we utilize an automated image analysis system (AIAS). Plots of VEIM data on easily constructed ternary diagrams provide readily comprehended illustrations of the range of modal composition of the lithologic units making up a given coal bed. The use of bulk-specific-gravity determinations is alo recommended for identification and characterization of the distinctive lithologic units. The availability of an AIAS also enhances the capability to acquire textural information. Ranges of size of maceral and mineral grains can be quickly and precisely determined by use of an AIAS. We assume that shape characteristics of coal particles can also be readily evaluated by automated image analysis, although this evaluation has not yet been attempted in our laboratory. Definitive data on the particulate mineral content of coal constitute another important segment of petrographic description. Characterization of mineral content may be accomplished by optical identification, electron microprobe analysis, X-ray diffraction, and scanning and transmission electron microscopy. Individual mineral grains in place in polished blocks or polished this sections, or separated from the coal matrix by sink-float methods are studied by analytical techniques appropriate to the conditions of sampling.

International Journal of Coal Geology↗