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At least 217 records · Page 12Linked to original sources

USGS1979

Geohydrology and digital-simulation model of the Farrington aquifer in the northern coastal plain of New Jersey

A two-dimensional digital-computer flow model was developed to simulate the Farrington aquifer in the northern part of the Coastal Plain of New Jersey. The area of detailed study includes approximately 500 square miles in Middlesex and Monmouth Couties where the aquifer provides a large part of the municipal and industrial water supply. The area modeled is much larger, extending seaward as well as northeastward into Long Island. The aquifer consists chiefly of the Farrington Sand Member of the Raritan Formation and is composed of sand and some gravel. It thickens from a featheredge in outcrop to more than 170 feet, 11 miles to the southeast. The confining unit between the Farrington and the overlying Old Bridge Sand Member of the Magothy Formation consists primarily of the Woodbridge Clay Member of the Raritan Formation and has a maximum thickness of 244 feet. The model simulates both water-table and artesian conditions. The confining unit overlying the Farrington aquifer is simulated as having a variable thickness and vertical hydraulic conductivity. The effect of a declining water level in the overlying Old Bridge aquifer on the Farrington aquifer is also simulated by the model. Values used to describe the hydraulic properties of the Farrington aquifer are: a hydraulic conductivity of 105 feet per day, a storage coefficient of 1.6 x 10 -4 for artesian conditions, and a specific yield of 0.25 for water-table conditions. Values for the overlying confining unit are: a vertical hydraulic conductivity ranging from 4.2 x 10 -7 to 1.0 x 10 -10 feet per second and a specific storage of 4 x 10 -5 feet -1 . Aquifer simulation for the 15-year period, 1959-73, was used to calibrage the model. The model was calibrated by comparing the observed potentiometric surface of November 1973 with the simulated potentiometric surface. In addition, hydrographs for selected wells were compared with model results. Ground-water withdrawals for 1959 and 1973 were 12.1 and 28.5 milion gallons per day, respectively. Potentiometric surfaces for 1985 and 2000 were computed based on a linear projection of ground-water withdrawals (39.5 and 56.9 million gallons per day in 1985 and 2000, respectively) of the period 1959 through 1973. These surfaces are deeper than that of November, 1973, and the cone of depression is wider. The potentiometric head projected by the model in the vicinity of Sayreville will be more than 150 feet below mean sea level by 2000; the head in this area was 70 feet below sea level in 1973. The model calculated ground-water budgets for steady-state and transient conditions for the entire modeled area and for several rectangular subareas. Ground-water flow into the modeled Farrington aquifer under steady-state conditions before ground-water development was 16 cubic feet per second for the entire area. Recharge in the outcrop area and vertical leakage from the Old Bridge was 8 cubic feet per second each. Approximately 75 percent of the discharge occurred as seepage into surface-water bodies in and near the outcrop and as lateral flow southwestward into Burlington County near the outcrop area. The remaining 25 percent occurred southeast of the outcrop as vertical leakage into the overlying Old Bridge aquifer and as lateral flow to the south into Ocean and Burlington Counties. A transient water budget for 1973 was calculated for a subarea consisting mainly of Middlesex County. The model indicates that 48 percent (14.3 cubic feet per second) of the total inflow to the subareas was through its boundaries. Other sources of water include direct recharge within the subarea (5.4 cubic feet per second), vertical leakage (mainly from the Old Bridge) within the subarea (2.6 cubic feet per second), and water released from storage (3.4 cubic feet per second). Discharge from the subarea consisted mainly of withdrawals (26.5 cubic feet per second). It also included vertical leakage to the Old Bridge and discharge to surface-water bodies simulated by constant-head nodes (3.2 cubic feet per second).

New Jersey↗

USGS1986

Preliminary delineation and description of the regional aquifers of Tennessee– The Cretaceous aquifer system of west-Tennessee

The Cretaceous aquifer system in western Tennessee is composed of sand, gravel, and clay. The aquifer system is under confined conditions except in the outcrop area. Ground water is recharged by precipitation on the outcrop area and through some overlying permeable deposits. The hydraulic gradient in the confined aquifers is about 1 foot per mile generally toward the west. The Cretaceous aquifer system unconformably overlies the consolidated Paleozoic formations and is overlain and confined by the Porters Creek Clay. The Cretaceous aquifer system is used as a source of water supply primarily in the outcrop area. West of the outcrop of this aquifer system, ground water can be obtained at shallower depths and with better water quality. The water of the Cretaceous aquifers generally have very good quality in the outcrop area. The dissolved solids increase down gradient to more than 1,000 milligrams per liter in parts of Shelby County. High iron concentrations are present in some areas.

Tennessee↗

USGS1983

Hydrology of the Wibaux-Beach lignite deposit area, eastern Montana and western North Dakota

The Paleocene Harmon lignite, the principal commercial bed of the Wihaux-Beach deposit, underlies at least 150 square miles along the Montana-North Dakota border. An estimated 1 billion tons of strippable reserves underlies about 50 square miles. The Harmon lignite bed also is the most consistently occurring shallow aquifer in the area. This study was conducted to determine possible impacts of surface mining on the area's water resources. Two aquifer systems, the lower Tongue River and the upper Ludlow, were identified within about 300 feet below the Harmon lignite aquifer, but none were identified within the overlying 350 feet. The aquifers (systems) are separated by varying thicknesses of interbedded clay and silt. The Harmon lignite aquifer extends uninterrupted for several miles eastward (down dip) from the outcrop. It is from 3 to 34 feet thick and from zero to 350 feet deep. The top of the lower Tongue River aquifer system is from 0 to 115 feet below the Harmon lignite and the system is 13 to 98 feet thick. The upper Ludlow aquifer system is 128 to 214 feet below the Harmon lignite and is 5 to 84 feet thick. Both the lower Tongue River and upper Ludlow aquifer systems consist of discontinuous, vertically stacked, sinuous sand bodies deposited as channel fill in meandering and braided streams. The probability of encountering a sand bed within the aquifer systems at any one location in the study area is about 60 percent for the lower Tongue River aquifer system and 80 percent for the upper Ludlow aquifer system. Water in each aquifer flows toward the northeast and occurs under confined conditions, except in the Harmon lignite aquifer near its outcrop. Recharge occurs directly by precipitation at the outcrops and by downward leakage elsewhere. The major discharge from each aquifer is by downward leakage, although the Harmon lignite aquifer discharges less than 0.20 cubic foot per second to surface drainages within the study area. Differences in chemical quality of water among the three aquifers are subtle, but significant. The mean dissolved-solids concentrations are: Harmon lignite aquifer, 1,930 milligrams per liter; lower Tongue River aquifer system, 1,810 milligrams per liter; and upper Ludlow aquifer system, 1,550 milligrams per liter. Alkalinity, calcium, and magnesium concentrations decrease with aquifer depth. The majority of the samples were a sodium sulfate-bicarbonate type. The median pH values, from the uppermost to the lowermost aquifer, were 8.1, 8.3, and 8.5. The chemical quality of water in the Harmon lignite aquifer near the outcrop is affected by reactions in the aerated soil zone and unsaturated parts of the aquifer. Where the outcrop is heavily clinkered, recharge waters reach the aquifer rapidly and have little opportunity for solute uptake in the unsaturated zone. In nonclinkered areas, recharge waters slowly percolate through chemically active soil and unsaturated parts of the aquifer. The resulting water commonly contains 2,500 to 5,000 milligrams per liter of dissolved solids, is a calcium-magnesium sulfate type, and has a pH of less than 7.0. The impacts of mining on streamflow and stream water quality should be manageable through the effective use of earth structures for routing and impoundment of runoff water. Mining-induced potentiometric declines in the Harmon lignite aquifer probably will be several feet up to 2 or 3 miles from the mine. Mining impacts on other aquifers will be minor.

Water-Resources Investigations Report↗

USGS1988

Hydrogeology and predevelopment flow in the Texas Gulf Coast aquifer systems

A multilayered ground-water flow system exists in the Coastal Plain sediments of Texas. The Tertiary and Quaternary clastic deposits have an area! extent of 128,000 square miles onshore and in the Gulf of Mexico. Two distinct aquifer systems are recognized for the sediments, which range in thickness from a few feet to more than 12,000 feet. The older system the Texas coastal uplands aquifer system consists of four aquifers and two confining units in the Wilcox and Claiborne Groups. It is bounded from below by the practically impermeable Midway confining unit or by the top of the geopressured zone. It is bounded from above by the poorly permeable Vicksburg-Jackson confining unit, which separates it from the younger coastal lowlands aquifer system. The coastal lowlands aquifer system consists of five permeable zones and two confining units that range in age from Oligocene to Holocene. The hydrogeologic units of both systems are exposed in bands that parallel the coastline. The units dip and thicken toward the Gulf. Quality of water in the aquifer systems varies greatly, with dissolved solids ranging from a few hundred to more than 200,000 milligrams per liter. A three-dimensional, variable-density digital model was developed to simulate predevelopment flow in the aquifer systems, for which steady-state conditions were assumed. Horizontal hydraulic conductivities of the aquifers and permeable zones in the calibrated model range from 15 feet per day for the middle Wilcox aquifer, to 170 feet per day for the Holocene-upper Pleistocene aquifer. Vertical hydraulic conductivities range from 1 x 10 -5 foot per day for the Vicksburg-Jackson confining unit, to 1 x 10 -2 foot per day for four of the aquifers and permeable zones. The simulated values of transmissivity and leakance are functions of the percent of sand that is present in each model grid block. There is a large range in precipitation across the study area, from about 21 inches per year in the west to about 56 inches per year in the east. Eastward from a line through Corpus Christi and San Antonio, average annual precipitation ranges from about 30 to about 56 inches. A few inches per year reaches the saturated zone in topographically high areas and is discharged in low areas as evapotranspiration, seepage, springflow, and stream base flow. A smaller amount of water flows through the aquifers and permeable zones downdip from the outcrop areas. This flow results in upward or downward leakage into adjacent hydrogeologic units, but is generally upward into overlying units. Westward from the line through Corpus Christi and San Antonio, average annual precipitation ranges from about 30 to about 21 inches. The general pattern of flow in the aquifers and permeable zones is similar to that in the east, but rates of flow are somewhat smaller. In contrast to the east, ground-water discharge in the west is generally not visible. Evapotranspiration is the main mechanism for ground-water discharge, with most ground water being discharged through evapotranspiration by phreatophytes. Simulated discharge and recharge rates in the combined outcrop areas of all units do not exceed 6 inches per year. The large rates occur in small, local topographically low and high areas. The average discharge rate simulated in the outcrops of the units is 0.45 inch per year. The recharge area is considerably smaller than the discharge area, and the average recharge rate over this smaller area is 0.74 inch per year. Total simulated recharge in the outcrop areas is 269 million cubic feet per day, which is offset by an equal amount of discharge in the outcrop areas. The smallest rates of leakage are across the Vicksburg-Jackson confining unit, with downward and upward rates of less than one million cubic feet per day. The greatest rate of leakage is 47 million cubic feet per day upward into the Holocene-upper Pleistocene permeable zone.

Texas↗

USGS1998

Streamflow characteristics for the Black Hills of South Dakota, through water year 1993

This report summarizes streamflow records and describes streamflow characteristics for streams draining the Black Hills of western South Dakota. Monthly and annual streamflow records are tabulated for all available years of record, through water year 1993, for 129 continuous-record gaging stations, including 111 stations for which records of daily flow are available and 18 stations for which only monthly records are available. Various summary statistics and graphics are presented for stations with sufficient periods of record. In addition to streamflow summaries, records of monthend contents are presented for five reservoirs operated by the Bureau of Reclamation in the Black Hills area. Streamflow characteristics are described for four categories of hydrogeologic settings, including interior sedimentary basins, interior crystalline basins, interior basins downstream of loss zones (loss-zone basins), and exterior basins. All of the interior basins are located predominantly within the outermost extent of the outcrop of the Inyan Kara Group and the exterior basins are located predominantly beyond this outcrop. Distinct differences in variability of annual and monthly streamflow are described for the four categories of hydrogeologic settings. The interior sedimentary basins, which are dominated by springflow from headwater areas, have the smallest variability in both annual and monthly flow, as a group. The exterior basins, as a group, have the largest variability in both annual and monthly flow. Streamflow variability for the interior crystalline basins, which are composed primarily of Precambrian and Tertiary igneous and metamorphic rocks, generally falls midway between the interior sedimentary and exterior basins. Loss-zone stations, which are located downstream of loss zones that occur where streams cross outcrops of the Madison Limestone and other overlying sedimentary units, exhibit the widest range in streamflow variability of any of the categories. Most of the loss-zone basins have springs located upstream of the gaging stations, but downstream of the loss zones. Flow at several of the loss-zone stations is dominated by large and consistent springflow; however, flow at other loss-zone stations is dominated by streamflow losses or by tributary inflows between the loss zones and the gaging stations, which results in extremely variable streamflow characteristics. It is demonstrated that springflow in Battle, Spring, Elk, and Bear Butte Creeks is much more variable than in Cascade Springs, Fall River, Beaver Creek, and Redwater River. Interior crystalline basins and exterior basins are shown to be much more responsive to climatic conditions than the springflow-dominated basins. Zero-flow months have been recorded for all of the exterior basins and most of the interior crystalline basins; however, zero-flow months have not been recorded for any of the interior sedimentary basins. Zero-flow months have not been recorded for the loss-zone stations with large, consistent springflow; however, zero-flow months are common for loss-zone stations with smaller, less consistent springs. Direct surface runoff is demonstrated to be uncommon for outcrops of the Madison Limestone and Minnelusa Formation. Examination of streamflow records for two basins with large outcrops of these formations indicates that direct surface runoff seldom occurs. Annual streamflow is shown to increase from south to north, which is consistent with climatic patterns for the area. Annual yield generally is larger for all of the interior categories than for the exterior basins; however, this is consistent with larger precipitation and smaller evapotranspiration rates at higher elevations. Annual yields generally are largest for the interior sedimentary basins; however, all of these basins are located in the northern Black Hills. Interior crystalline basins located in the northern Black Hills have annual yields that are comparable with interior sedimentary basins.

South Dakota↗

USGS2013

Hydrocarbon-bearing sandstone in the Upper Jurassic Naknek Formation on the south shore of Kamishak Bay

The presence of an active petroleum system in Kamishak Bay is demonstrated by an outcrop of hydrocarbon-bearing sandstone in the Upper Jurassic Naknek Formation near the south shore of the bay (fig. 1). The outcrop is about 140 km southwest of Homer on a small, unnamed island near the mouth of the Douglas River (fig. 17). The existence of this outcrop was kindly reported to us by Les Magoon (U.S. Geological Survey, emeritus), who also provided a topographic map showing its exact position. The outcrop was mentioned very briefly in publications by Magoon and others (1975, p. 19) and by Lyle and Morehouse (1977, p. E-1), but to our knowledge there are no detailed descriptions of this outcrop or its hydrocarbons in the published scientific literature.

Alaska↗

USGS1993

Cleat development in coals of the Upper Cretaceous Mesaverde Formation, Pilot Butte area, Wind River Reservation, Wyoming

The cleat system developed in low-rank (mean viltrinite reflectance of 0.43 to 0.5 percent) coal beds in the Upper Cretaceous Mesaverde Formation was studied in outcrop and in coreholes drilled for coalbed methane evaluation near Pilot Butte in the central part of the Wind River Reservation. Cleats are the principal permeability pathway for fluids in coal beds. As a result, coalbed gas cannot be economically produced without significant cleat development. Two drillholes about 800 ft (244 m) apart encountered Mesaverde coal beds at depths ranging from 307 to 818 ft (93.6 to 249.3 m). One of the coal beds penetrated while drilling, the lowest coal in the Mesaverde coaly interval, is well exposed about a mile south of the two drillholes and the cleat development in this coal bed on outcrop was compared with that of the same coal in the drillholes. The 3 in (7.62 cm) diameter core is less than ideal for this study because cleat spacing in low-rank coals such as these typically averages greater than 7.62 cm. Nonetheless, face cleats at spacing of from 0.25 to 2.5 cm was observed in many of the coal beds. Cleats were less well-developed in other coal beds and no cleats were observed in a few beds. As expected, butt cleats were somewhat less well-developed than the face cleats. Attempts to relate cleat spacing to gas content, bed thickness, and ash content were not successful. A 3.0 m by 1.8 m area of the upper surface of the coal bed exposed a mile south of the drillsites was cleaned off and studied in detail. Cleat development in this limited study area varied from well-developed face and butt cleats in some places to few or no cleats in others. Face cleats trended roughly perpendicular to the fold axis of the nearby Pilot Butte anticline. Cleats did not penetrate a 2.5 cm thick carbonaceous shale bed about 20 cm above the base of the coal bed indicating that thin carbonaceous shale beds will act a permeability barriers. Two types of face cleats were observed on outcrop: 1) major face cleats that could be traced for as much as a meter along outcrop and averaged as little as 1.6 cm apart; and 2) microfractures or microcleats which paralleled the face cleats but averaged from 0.10 to 0.17 cm apart. The microcleats were more visible on outcrop than in core because of surface weathering which dried out the coal causing the microcleats to open up. This surface weathering also increased the aperture widths on many of the major cleats, and no attempt was made to systematically study aperture widths. These microcleats may contribute significantly to the permeability of the coals in the subsurface. Dewatering of the coal during the early stages of coalbed methane production may help open these microcleats thereby increasing permeability, and hence coalbed gas production, with time.

Conference Paper↗

USGS2015

Flushing of distal hillslopes as an alternative source of stream dissolved organic carbon in a headwater catchment

We investigated potential source areas of dissolved organic carbon (DOC) in headwater streams by examining DOC concentrations in lysimeter, shallow well, and stream water samples from a reference catchment at the Hubbard Brook Experimental Forest. These observations were then compared to high-frequency temporal variations in fluorescent dissolved organic matter (FDOM) at the catchment outlet and the predicted spatial extent of shallow groundwater in soils throughout the catchment. While near-stream soils are generally considered a DOC source in forested catchments, DOC concentrations in near-stream groundwater were low (mean = 2.4 mg/L, standard error = 0.6 mg/L), less than hillslope groundwater farther from the channel (mean = 5.7 mg/L, standard error = 0.4 mg/L). Furthermore, water tables in near-stream soils did not rise into the carbon-rich upper B or O horizons even during events. In contrast, soils below bedrock outcrops near channel heads where lateral soil formation processes dominate had much higher DOC concentrations. Soils immediately downslope of bedrock areas had thick eluvial horizons indicative of leaching of organic materials, Fe, and Al and had similarly high DOC concentrations in groundwater (mean = 14.5 mg/L, standard error = 0.8 mg/L). Flow from bedrock outcrops partially covered by organic soil horizons produced the highest groundwater DOC concentrations (mean = 20.0 mg/L, standard error = 4.6 mg/L) measured in the catchment. Correspondingly, stream water in channel heads sourced in part by shallow soils and bedrock outcrops had the highest stream DOC concentrations measured in the catchment. Variation in FDOM concentrations at the catchment outlet followed water table fluctuations in shallow to bedrock soils near channel heads. We show that shallow hillslope soils receiving runoff from organic matter-covered bedrock outcrops may be a major source of DOC in headwater catchments in forested mountainous regions where catchments have exposed or shallow bedrock near channel heads.

New Hampshire↗

USGS2001

Quantifying contributions to storm runoff through end-member mixing analysis and hydrologic measurements at the Panola Mountain research watershed (Georgia, USA)

The geographic sources and hydrologic flow paths of stormflow in small catchments are not well understood because of limitations in sampling methods and insufficient resolution of potential end members. To address these limitations, an extensive hydrologic dataset was collected at a 10 ha catchment at Panola Mountain research watershed near Atlanta, GA, to quantify the contribution of three geographic sources of stormflow. Samples of stream water, runoff from an outcrop, and hillslope subsurface stormflow were collected during two rainstorms in the winter of 1996, and an end-member mixing analysis model that included five solutes was developed. Runoff from the outcrop, which occupies about one-third of the catchment area, contributed 50-55% of the peak streamflow during the 2 February rainstorm, and 80-85% of the peak streamflow during the 6-7 March rainstorm; it also contributed about 50% to total streamflow during the dry winter conditions that preceded the 6-7 March storm. Riparian groundwater runoff was the largest component of stream runoff (80-100%) early during rising streamflow and throughout stream recession, and contributed about 50% to total stream runoff during the 2 February storm, which was preceded by wet winter conditions. Hillslope runoff contributed 25-30% to peak stream runoff and 15-18% to total stream runoff during both storms. The temporal response of the three runoff components showed general agreement with hydrologic measurements from the catchment during each storm. Estimates of recharge from the outcrop to the riparian aquifer that were independent of model calculations indicated that storage in the riparian aquifer could account for the volume of rain that fell on the outcrop but did not contribute to stream runoff. The results of this study generally indicate that improvements in the ability of mixing models to describe the hydrologic response accurately in forested catchments may depend on better identification, and detailed spatial and temporal characterization of the mobile waters from the principal hydrologic source areas that contribute to stream runoff. Copyright ?? 2001 John Wiley & Sons, Ltd.

Hydrological Processes↗

USGS1993

Rock-eval pyrolysis and vitrinite reflectance trends in the Cleveland Shale Member of the Ohio Shale, eastern Kentucky

Within eastern Kentucky, organic petrographic and geochemical data indicate a southeastwards increase in maturation of the Cleveland Shale Member of the Ohio Shale (Devonian-Mississippian). Reflectance levels of dispersed organic material in the Cleveland Shale increase from 0.5% in the outcrop belt in central Kentucky, to slightly over 1.0% in Pike County, eastern Kentucky. A decrease in fluorescence intensity of liptinitic components, such as Tasmanites , accompanies this reflectance increase, as does a shift in fluorescence color of the alginite towards the red. In the highest rank areas, fluorescence is almost absent. Groundmass fluorescence is observed also, and follows trends similar to those shown by the alginite. Kerogen in the Cleveland Shale is primarily Type II, as indicated by petrographic observations and Rock-Eval data. Total organic carbon contents of this shale decrease from over 12% in the outcrop belt, to less than 2% in the eastern-most part of the study area. Source rock potential ranges from good to very good, with the highest potentials occurring in the outcrop belt. T max values for this unit increase from under 430°C in the outcrop belt to over 450°C in the southeast, confirming the increase in maturation trends indicated by vitrinite reflectance data. Both petrographic and geochemical maturation parameters place the Cleveland Shale of eastern Kentucky within the oil window. Comparison with maturation data for Pennsylvanian-age coals upsection suggests that maturation indices are retarded, or suppressed, in the Devonian shales. The level of maturation indicated for the Cleveland may be problematical considering that the Ohio Shale is a major gas-producer in this area.

Kentucky↗

USGS2009

Thermal maturity and organic composition of Pennsylvanian coals and carbonaceous shales, north-central Texas: Implications for coalbed gas potential

Thermal maturity was determined for about 120 core, cuttings, and outcrop samples to investigate the potential for coalbed gas resources in Pennsylvanian strata of north-central Texas. Shallow (< 600??m; 2000??ft) coal and carbonaceous shale cuttings samples from the Middle-Upper Pennsylvanian Strawn, Canyon, and Cisco Groups in Archer and Young Counties on the Eastern Shelf of the Midland basin (northwest and downdip from the outcrop) yielded mean random vitrinite reflectance (Ro) values between about 0.4 and 0.8%. This range of Ro values indicates rank from subbituminous C to high volatile A bituminous in the shallow subsurface, which may be sufficient for early thermogenic gas generation. Near-surface (< 100??m; 300??ft) core and outcrop samples of coal from areas of historical underground coal mining in the region yielded similar Ro values of 0.5 to 0.8%. Carbonaceous shale core samples of Lower Pennsylvanian strata (lower Atoka Group) from two deeper wells (samples from ~ 1650??m; 5400??ft) in Jack and western Wise Counties in the western part of the Fort Worth basin yielded higher Ro values of about 1.0%. Pyrolysis and petrographic data for the lower Atoka samples indicate mixed Type II/Type III organic matter, suggesting generated hydrocarbons may be both gas- and oil-prone. In all other samples, organic material is dominated by Type III organic matter (vitrinite), indicating that generated hydrocarbons should be gas-prone. Individual coal beds are thin at outcrop (< 1??m; 3.3??ft), laterally discontinuous, and moderately high in ash yield and sulfur content. A possible analog for coalbed gas potential in the Pennsylvanian section of north-central Texas occurs on the northeast Oklahoma shelf and in the Cherokee basin of southeastern Kansas, where contemporaneous gas-producing coal beds are similar in thickness, quality, and rank.

International Journal of Coal Geology↗

USGS2015

Hydrothermal alteration and diagenesis of terrestrial lacustrine pillow basalts: Coordination of hyperspectral imaging with laboratory measurements

We investigate an outcrop of &sim;187 Ma lacustrine pillow basalts of the Talcott Formation exposed in Meriden, Connecticut, USA, focusing on coordinated analyses of one pillow lava to characterize the aqueous history of these basalts in the Hartford Basin. This work uses a suite of multidisciplinary measurements, including hyperspectral imaging, other spectroscopic techniques, and chemical and mineralogical analyses, from the microscopic scale up to the scale of an outcrop. The phases identified in the sample are albite, large iron oxides, and titanite throughout; calcite in vesicles; calcic clinopyroxene, aegirine, and Fe/Mg-bearing clay in the rind; and fine-grained hematite and pyroxenes in the interior. Using imaging spectroscopy, the chemistry and mineralogy results extend to the hand sample and larger outcrop. From all of the analyses, we suggest that the pillow basalts were altered initially after emplacement, either by heated lake water or magmatic fluids, at temperatures of at least 400-600°C, and the calcic clinopyroxenes and aegirine identified in the rind are a preserved record of that alteration. As the hydrothermal system cooled to slightly lower temperatures, clays formed in the rind, and, during this alteration, the sample oxidized to form hematite in the matrix of the interior and Fe 3+ in the pyroxenes in the rind. During the waning stages of the hydrothermal system, calcite precipitated in vesicles within the rind. Later, diagenetic processes albitized the sample, with albite replacing plagioclase, lining vesicles, and accreting onto the exterior of the sample. This albitization or Na-metasomatism occurred when the lake within the Hartford Basin evaporated during a drier past climatic era, resulting in Na-rich brines. As Ca-rich plagioclase altered to albite, Ca was released into solution, eventually precipitating as calcite in previously-unfilled vesicles, dominantly in the interior of the pillow. Coordinated analyses of this sample permit identification of the alteration phases and help synthesize the aqueous history of pillow lavas of the Talcott formation. These results are also relevant to Mars, where volcanically-resurfaced open basin lakes have been found, and this Hartford Basin outcrop may be a valuable analog for any potential volcano-lacustrine interactions. The results can also help to inform the utility and optimization of potentially complementary, synergistic, and uniquely-suited techniques for characterization of hydrothermally-altered terrains.

Connecticut↗

USGS2002

Seafloor geology of the Monterey Bay area continental shelf

Acoustic swath-mapping of the greater Monterey Bay area continental shelf from Point An??o Nuevo to Point Sur reveals complex patterns of rock outcrops on the shelf, and coarse-sand bodies that occur in distinct depressions on the inner and mid-shelves. Most of the rock outcrops are erosional cuestas of dipping Tertiary rocks that make up the bedrock of the surrounding lands. A mid-shelf mud belt of Holocene sediment buries the Tertiary rocks in a continuous, 6-km-wide zone on the northern Monterey Bay shelf. Rock exposures occur on the inner shelf, near tectonically uplifting highlands, and on the outer shelf, beyond the reach of the mud depositing on the mid-shelf since the Holocene sea-level rise. The sediment-starved shelf off the Monterey Peninsula and south to Point Sur has a very thin cover of Holocene sediment, and bedrock outcrops occur across the whole shelf, with Salinian granite outcrops surrounding the Monterey Peninsula. Coarse-sand deposits occur both bounded within low-relief rippled scour depressions, and in broad sheets in areas like the Sur Platform where fine sediment sources are limited. The greatest concentrations of coarse-sand deposits occur on the southern Monterey Bay shelf and the Sur shelf. ?? 2002 Elsevier Science B.V. All rights reserved.

Marine Geology↗

USGS2006

The rocks of Gusev Crater as viewed by the Mini-TES instrument

The Miniature Thermal Emission Spectrometer (Mini-TES) on board the Mars Exploration Rover Spirit is part of a payload designed to investigate whether a lake once existed in Gusev Crater. Mini-TES has observed hundreds of rocks along the rover's traverse into the Columbia Hills, yielding information on their distribution, bulk mineralogy, and the potential role of water at the site. Although dust in various forms produces contributions to the spectra, we have established techniques for dealing with it. All of the rocks encountered on the plains traverse from the lander to the base of the Columbia Hills share common spectral features consistent with an olivine-rich basaltic rock known as Adirondack Class. Beginning at the base of the West Spur of the Columbia Hills and across its length, the rocks are spectrally distinct from the plains but can be grouped into a common type called Clovis Class. These rocks, some of which appear as in-place outcrop, are dominated by a component whose spectral character is consistent with unaltered basaltic glass despite evidence from other rover instruments for significant alteration. The northwest flank of Husband Hill is covered in float rocks known as Wishstone Class with spectral features that can be attributed uniquely to plagioclase feldspar, a phase that represents more than half of the bulk mineralogy. Rare exceptions are three classes of basaltic "exotics" found scattered across Husband Hill that may represent impact ejecta and/or float derived from local intrusions within the hills. The rare outcrops observed on Husband Hill display distinctive spectral characteristics. The outcrop called Peace shows a feature attributable to molecular bound water, and the outcrop that hosts the rock called Watchtower displays a dominant basaltic glass component. Despite evidence from the rover's payload for significant alteration of some of the rocks, no unambiguous detection of crystalline phyllosilicates or other secondary silicates has been observed by Mini-TES. The mineralogical results supplied by Mini-TES provide no clear evidence that a lake once existed in Gusev Crater. Copyright 2006 by the American Geophysical Union.

Journal of Geophysical Research E: Planets↗

USGS2011

Field Reconnaissance Geologic Mapping of the Columbia Hills, Mars: Results from MER Spirit and MRO HiRISE Observations

Chemical, mineralogic, and lithologic ground truth was acquired for the first time on Mars in terrain units mapped using orbital Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment (MRO HiRISE) image data. Examination of several dozen outcrops shows that Mars is geologically complex at meter length scales, the record of its geologic history is well exposed, stratigraphic units may be identified and correlated across significant areas on the ground, and outcrops and geologic relationships between materials may be analyzed with techniques commonly employed in terrestrial field geology. Despite their burial during the course of Martian geologic time by widespread epiclastic materials, mobile fines, and fall deposits, the selective exhumation of deep and well-preserved geologic units has exposed undisturbed outcrops, stratigraphic sections, and structural information much as they are preserved and exposed on Earth. A rich geologic record awaits skilled future field investigators on Mars. The correlation of ground observations and orbital images enables construction of a corresponding geologic reconnaissance map. Most of the outcrops visited are interpreted to be pyroclastic, impactite, and epiclastic deposits overlying an unexposed substrate, probably related to a modified Gusev crater central peak. Fluids have altered chemistry and mineralogy of these protoliths in degrees that vary substantially within the same map unit. Examination of the rocks exposed above and below the major unconformity between the plains lavas and the Columbia Hills directly confirms the general conclusion from remote sensing in previous studies over past years that the early history of Mars was a time of more intense deposition and modification of the surface. Although the availability of fluids and the chemical and mineral activity declined from this early period, significant later volcanism and fluid convection enabled additional, if localized, chemical activity.

Journal of Geophysical Research E: Planets↗

USGS2006

Distribution of volatile organic compounds in a New Jersey coastal plain aquifer system

Samples for analysis of volatile organic compounds were collected from 315 wells in the Potomac-Raritan-Magothy aquifer system in southwestern New Jersey and a small adjacent area in Pennsylvania during 1980–82. Volatile organic compounds were detected in all three aquifer units of the Potomac-Raritan-Magothy aquifer system in the study area. Most of the contamination appears to be confined to the outcrop area at present. Low levels of contamination, however, were found downdip of the outcrop area in the upper and middle aquifers. Trichloroethylene, tetrachloroethylene, and benzene were the most frequently detected compounds. Differences in the areal distributions of light chlorinated hydrocarbons, such as trichloroethylene, and aromatic hydrocarbons, such as benzene, were noted and are probably due to differences in the uses of the compounds and the distribution patterns of potential contamination sources. The distribution patterns of volatile organic compounds differed greatly among the three aquifer units. The upper aquifer, which crops out mostly in less-developed areas, had the lowest percentage of wells with volatile organic compounds detected (10 percent of wells sampled). The concentrations in most wells in the upper aquifer which had detectable levels were less than 10 /μg/1. In the middle aquifer, which crops out beneath much of the urban and industrial area adjacent to the Delaware River, detectable levels of volatile organic compounds were found in 22 percent of wells sampled, and several wells contained concentrations above 100 μ/1. The lower aquifer, which is confined beneath much of the outcrop area of the aquifer system, had the highest percentage of wells (28 percent) with detectable levels. This is probably due to (1) vertical leakage of contamination from the middle aquifer, and (2) the high percentage of wells tapping the lower aquifer in the most heavily developed areas of the outcrop.

Groundwater↗

USGS2024

Field geology under the sea with a remotely operated vehicle: Mona Rift, Puerto Rico

We implemented concepts of field geology at great ocean depths by constructing virtual outcrops from a string of overlapping video frames collected by remotely operated vehicles (ROVs). This lower-cost alternative to drilling boreholes allows stratigraphic extension into the offshore and regional interpretation of marine seismic profiles. The imagery was collected along a dive transect on the western wall of Mona Rift, a deep and narrow rift northwest of Puerto Rico, between water depths of 1560 m and 3927 m. The northern coast of Puerto Rico and its large offshore area are underlain by a mid-Eocene and younger forearc basin topped by a thick carbonate platform. There are no drill holes offshore, and tying seismic lines across the shoreline there is problematic. We describe our virtual outcrop and constrain its age and stratigraphy using seven rock samples collected by ROV and compare the outcrop's stratigraphy to deep boreholes and outcrops on land. Our formation descriptions and ages agree, for the most part, with those on land, but we identified a 100-m-thick section that is represented on land by an unconformity. Our stratigraphic interpretation indicates lateral variations in formation thicknesses and establishes a cross-section for additional sampling of the Eocene–Pliocene geology. It also suggests that Mona Rift has formed since the mid-Pliocene. The presence or absence of ferromanganese (Fe-Mn) crust on rocks along the transect may be correlated with the smoothness of the rock surface.

Mona Rift, Puerto Rico↗

USGS1919

The oil fields of Allen County, Kentucky, with notes on the oil geology of adjoining counties

This report is based on a reconnaissance investigation of the oil field of Allen County, Ky., which was part of a broader study of the oil and gas fields of Kentucky, Tennessee, and Alabama, on which a general report is planned. Most of the field work was done by Mr. Mather, who spent three and a half weeks in and around the county. Mr. Shaw visited Scottsville, the county seat of Allen County, a few years ago and spent a few days in that vicinity at the beginning of the recent field work, which extended from the middle of April to the middle of May, 1917 He prepared also the first draft of the report and reviewed the literature, including reports in oil and gas journals. The purpose of the field work was to investigate the geology of the county, particularly the structure or lay of the oil-bearing strata and the results of drilling to date. Structural conditions in the producing fields were determined by running level lines to the wells and correlating the data recorded in the well logs generously furnished by the operators. Traverses were made of outcrops, and observations of the dip and strike were made in different parts of the county. Lack of a topographic base map and of time and funds for making an accurate topographic survey render the results of the work somewhat incomplete, but it is hoped they will form a valuable contribution to the knowledge of the geology of this relatively little known region, for little detailed geologic work has been done heretofore within 50 miles of Scottsville. The dips are generally too low to be read by the clinometer, but in some localities unmistakable dips can be observed in extensive outcrops along creek banks and can be measured with a level or hand transit. Few of the beds of this region can be followed any considerable distance, though by means of fossils the stratigraphic position of beds outcropping many miles apart can be determined within a few feet. The black shale is the best horizon marker, but it outcrops in only a few places and is reached in only a few wells outside the oil fields. The field work thus consisted largely in observations on out- , cropping beds in different localities and in estimating the altitude of those identified, in collecting fossils for use in future detailed work, and in obtaining from oil operators data concerning the wells and their output. It included the determination of the general lay of the rocks in the county and surrounding territory and details of structure in certain areas. The rocks lie so nearly flat that without topographic data only the general dip could be made out for a large part of the area examined. A complete set of logs of wildcat wells in the region would have thrown much light on the structure and oil possibilities, but little is known of many of the earlier wells drilled in the region, especially of those altogether unsuccessful. An unsuccessful test is soon forgotten, though the data thus obtained concerning the depth at which different beds were found and the yield of porous strata, whether water, oil, or gas, is of great value to the geologist and oil prospector.

Kentucky↗