SEARCH · Search USGS

Results for “Studies in Maine Geology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 955 records · Page 53Linked to original sources

USGS1999

40Ar/39Ar thermochronology of mesoproterozoic metamorphism in the Colorado Front Range

A low-pressure metamorphic episode in the Colorado Front Range has been identified by the presence of staurolite, andalusite, cordierite, and garnet porphyroblasts overprinting earlier assemblages. The overprinting assemblages and reaction textures are most consistent with porphyroblast growth on a prograde metamorphic path with peak temperatures exceeding ~525??C. Twenty-eight 40Ar/39Ar dates on hornblende, muscovite, biotite, and microcline were used to infer the age and thermal conditions of metamorphism. Muscovite and biotite 40Ar/39Ar ages fall mainly in the interval 1400-1340 Ma, consistent with cooling through the closure temperature interval of micas (~400??-300??C) after about 1400 Ma. In contrast, hornblende apparent ages (T(c)~500??-550??C) between 1600 and 1390 Ma reflect variable retention of radiogenic argon. Forward modeling of argon diffusion shows that the distribution of hornblende and mica ages is consistent with the partial resetting of argon systematics ca. 1400 Ma by a thermal pulse reaching maximum temperatures around 550??C and decaying within <20 m.yr. These temperatures match the conditions inferred from the overprinting assemblage; thus, muscovite and biotite ages are interpreted to date the cooling phase of this metamorphic event. This late metamorphism is broadly coeval with the intrusion of ca. 1400-Ma granitic plutons in the study area and throughout the southwestern United States. However, thermal effects are observed far from pluton margins, suggesting pervasive, regional crustal heating rather than restricted contact metamorphism. Our results suggest that ca. 1400-Ma metamorphism and plutonism are manifestations of a regional thermal episode that both partially melted the lower crust and pervasively metamorphosed middle crustal rocks.

Journal of Geology↗

USGS1995

Water-quality assessment of the upper Snake River Basin, Idaho and western Wyoming — Environmental setting, 1980-92

The 35,800-square-mile upper Snake River Basin is one of 20 areas studied as part of the National Water-Quality Assessment (NAWQA) Program of the U.S. Geological Survey. Objectives of NAWQA are to study ground- and surface-water quality, biology, and their relations to land-use activities. Major land and water uses that affect water quality in the basin are irrigated agriculture, grazing, aquaculture, food processing, and wastewater treatment. Data summarized in this report are used in companion reports to help define the relations among land use, water use, water quality, and biological conditions. The upper Snake River Basin is located in southeastern Idaho and northwestern Wyoming and includes small parts of Nevada and Utah. Total population in the basin was about 425,000 in 1990. Major urban areas are Idaho Falls, Pocatello, Rexburg, and Twin Falls, Idaho, which make up 10, 11,3, and 6 percent of the total population, respectively. Climate in the basin is mostly semiarid and mean annual precipitation ranges from 8 to more than 60 inches. The eastern Snake River Plain is the major geologic feature in the basin and is delineated mostly by Quaternary and Tertiary basalt flows. It is about 55 to 62 miles wide and 320 miles long and bisects the basin in a northeast-southwest direction. The Snake River is the dominant surface-water feature and flows about 453 miles from the southern border of Yellowstone National Park in Wyoming to King Hill, Idaho, where it leaves the basin. The Snake River flows through five reservoirs that provide a total storage capacity of more than 4 million acre-feet. Gravity-flow diversions are predominant in the upper part of the basin and totaled 8.8 million.acre-feet in 1980. Pumped diversions occur mainly in the lower part of the basin and totaled 408,500 acre-feet in 1980. The Snake River Plain aquifer is the predominant ground-water feature in the upper Snake River Basin and underlies the eastern Snake River Plain. The upper 500 feet of the aquifer may store 200 to 300 million acre-feet of water. Ground-water resources that supply agricultural lands are sustained by recharge from surface-water irrigation, precipitation, and tributary inflow. Major ground-water discharges are at springs and seeps or from ground-water pumpage for irrigation. Water use in the basin is dominated by irrigated agriculture, which is the largest consumptive water use in the basin. Major crops in the basin include potatoes, wheat, sugar beets, hay, and barley. Most irrigation needs are supplied from surface-water sources through a series of canals and laterals. In 1990, about 2.5 million acres were irrigated with more than 14.2 million acre-feet of surface and ground water. About 21 percent of the basin is agricultural land and 50 percent is rangeland. Idaho leads the Nation in trout production for commercial sale. Combined mean annual discharges from 12 aquacultural facilities in the basin (1985-90) were about 787,000 acre-feet. These facilities are clustered in a reach of the Snake River between Milner Dam and King Hill where ground-water discharge is from many seeps and springs that provide sufficient quantities of good-quality water. Other facilities that release effluent to the Snake River include 13 municipal wastewater treatment plants and 3 industrial facilities.

Idaho, Wyoming↗

USGS1958

Titaniferous sedimentary rocks in the Cuyuna district, central Minnesot

The ore-yielding main iron-formation of the Cuyuna district is strati-graphically overlain by approximately 300 feet of titaniferous sedimentary rocks, and a field test for titahia has been an effective supplement to customary stratigraphic studies. The titanium is in leucoxene. The sedimentary rocks of the district are highly folded, and the main iron-formation serves as the reference for relative stratigraphic position. The strata older than the main iron-formation are light-gray argillite and siltstone with local lenses of quartzite near the upper contact; the older strata contain about 0.5 percent titania. The main iron-formation is a persistent layer of chemically precipitated ferruginous sediments that contain about 0.2 percent titania. The strata younger than the main iron-formation are gray or black argillite, partly carbonaceous, partly ferruginous, and are transitional into lenses of lean upper iron-formation. At the base of the younger strata, 250-350 feet of argillite and slate contain 1-3.7 percent titania and average 2.0 percent. This titaniferous argillite is similar to argillite higher in the younger sequence which contains less than 1.5 percent titania and averages about 1 percent. There are weathered rocks interpreted as tuffs and basalt flows locally interlayered near the bottom of the titaniferous zone. The basalt contains 1-2 percent titania. The high titania content of the 250-350-foot zone suggests a volcanic origin; the argillite probably is reworked basaltic pyroclastics. A few titaniferous bodies have been found in rocks below, within, and above the main iron-formation and thin titaniferous argillaceous layers occur within the main iron-formation.

Minnesota↗

USGS2023

Assessment of riparian vegetation patterns and change downstream from Glen Canyon Dam from 2014 to 2019

Changes in riparian vegetation cover and composition occur in relation to flow regime, geomorphic template, and climate, and can have cascading effects on aquatic and terrestrial ecosystems. Tracking such changes over time is therefore an important part of monitoring the condition and trajectory of riparian ecosystems. Maintaining diverse, self-sustaining riparian vegetation comprised of mostly native species is identified in the Glen Canyon Dam Long-Term Experimental and Management Plan as a key resource objective for the section of the Colorado River between Glen Canyon Dam and Lake Mead. The U.S. Geological Survey Grand Canyon Monitoring and Research Center implemented an annual monitoring program in 2014 to assess the status and trends of riparian vegetation along this section of river, particularly as they relate to flow regime. In this report, we summarize plant species composition and cover data collected under the annual monitoring program from 2014 to 2019, with special consideration given to the hydrologic position, associated geomorphic feature class, local climate patterns, native and nonnative species, and floristic region for key vegetation metrics and species. We divided the study area into four river segments (referred to as Glen Canyon, Marble Canyon, eastern Grand Canyon, and western Grand Canyon) on the basis of geography and floristic composition and calculated each recorded plant species’ relative frequency and foliar cover by river segment. These data were then used to evaluate species composition relationships among river segments, hydrologic zones, geomorphic features, and sampling years through ordination analysis. Temporal trends in our focal resource objectives—species richness, total foliar cover, proportion of native to nonnative species richness, proportion of native to nonnative species cover, Tamarix cover, Pluchea sericea cover, and Baccharis species cover—were assessed using mixed-effects models. Four patterns related to species composition emerged: (1) species composition of fixed-site sandbars differed from that of randomly selected sites (including randomly selected sandbars), (2) species composition of Glen Canyon sites differed from that of other previously identified floristic regions, (3) species composition differed across hydrologic zones related to dam operations, and (4) species composition within river segments did not change across years. For temporal patterns, four main findings emerged: (1) trends differed between fixed-sites and randomly selected sites; (2) although few directional changes were observed from 2014 to 2019, Baccharis species cover increased at randomly selected sites in areas influenced by daily water fluctuations; (3) native species cover and richness were greater than nonnative species cover and richness across all hydrologic zones; and (4) the temporal trend metrics used here can be used across floristic groups, enabling assessment of the Colorado River ecosystem as a whole. In addition to these findings, lists of recorded plant species are included as appendixes. The variations and patterns in vegetation status and trends presented in this report can be used as a baseline against which future monitoring can be compared.

Arizona↗

USGS1984

Relation of urban land-use and dry-weather, storm, and snowmelt flow characteristics to stream-water quality, Shunganunga Creek basin, Topeka, Kansas

Overland runoff from urban areas can cause concentrations of some water-quality constituents in local receiving streams to increase. The U.S. Geological Survey in cooperation with the Kansas Department of Health and Environment investigated the water-quality characteristics of streams draining Topeka, Kansas, and adjacent parts of the Shunganunga Creek basin from October 1979 through November 1981. The purpose of this investigation was to provide the data and interpretation necessary to determine the effects of runoff from urban areas on the water-quality characteristics of receiving streams. Water-quality characteristics for three streamflow conditions were determined: (1) dry-weather streamflow--a combination of base flow and point-source contributions, (2) storm streamflow--mainly provided by overland runoff from storms, and (3) snowmelt streamflow- mainly provided by overland runoff from snowmelt. Median concentrations of trace metals and nutrients were larger in storm streamflow than in dry-weather streamflow. Median concentrations of total lead and zinc were largest in storm streamflow from the more urban basins. Regression equations were developed to estimate median concentrations of total lead and zinc in storm streamflow from the percentage of drainage area in residential plus commercial land-use areas (correlation coefficients were 0.98 for total lead and 0.88 for total zinc); and from street density in lane miles per square mile (correlation coefficients were 0.89 for total lead and 0.84 for total zinc). Median concentrations of dissolved nitrite plus nitrate nitrogen and total phosphorus averaged, respectively, 76-percent and 70-percent larger during storm streamflow than during dry-weather streamflow and were largest in storm streamflow from the more agricultural basins. Median concentrations of dissolved sodium, chloride, and solids in snowmelt streamflow at all study sites averaged 218-percent larger for dissolved sodium, 296-percent larger for dissolved chloride, and 71-percent larger for dissolved solids relative to median concentrations in dry-weather streamflow. Regression equations also were developed to estimate median concentrations of dissolved sodium, chloride, and solids in snowmelt streamflow from the summation of percentages of the drainage area in residential, commercial, and industrial land-use areas (correlation coefficients were 0.97 for each of the three relationships) and from street density in lane miles per square mile (correlation coefficients were 0.93 for dissolved sodium and 0.94 for both dissolved chloride and dissolved solids). Multiple-correlation and regression analysis relating storm-runoff volumes and average constituent concentrations to land-use and storm characteristics produced significant relations (0.05 level of significance) for storm-runoff volume (0.81 coefficient of determination), total lead (0.71 coefficient of determination), total zinc (0.50 coefficient of determination), and suspended sediment (0.58 coefficient of determination).

Kansas↗

USGS2021

Reconnaissance study of the major and trace element content of bauxite deposits in the Arkansas bauxite region, Saline and Pulaski Counties, central Arkansas

The Arkansas bauxite district, which comprises about 275 square miles (710 square kilometers) of central Arkansas, produced an order of magnitude more bauxite and alumina than the other bauxite districts in the United States combined. Bauxite was mined in the region continuously from 1898 to 1982. These bauxites are laterite deposits, formed from intensive in-place weathering of the exposed surface of the Granite Mountain pluton, a Late Cretaceous batholith composed mainly of nepheline syenite and lesser amounts of syenite. Nepheline syenite was the aluminum source for the bauxite and clay deposits that blanket the pluton. The early Eocene continental sedimentary rocks that contain and overlie the bauxite deposits indicate that central Arkansas had a warm tropical environment during bauxite formation. Bauxite ores are the principal sources of aluminum. Some of the global bauxite deposits have been found to contain co-occurring metals that have essential applications in modern technologies. For example, bauxite is the largest global source of gallium (Ga), used in semiconductors, which is recovered as a byproduct of processing bauxite to recover alumina. Other critical metal commodities within some bauxites that reportedly have potential for byproduct recovery include niobium (Nb), scandium (Sc), and rare earth elements (REEs). Currently (2021), the United States is wholly dependent on imports for its supplies of bauxite for processing to produce alumina. The United States is also dependent on foreign sources of gallium, niobium, and scandium, as well for most of its domestic requirements of REEs. For these reasons, samples were collected from Arkansas bauxite deposits, associated clays, mill residue wastes (respectively referred to as red muds and black sands), and the parent nepheline syenite to determine their elemental content, with a particular focus on gallium, niobium, scandium, and REEs. Each sample was analyzed for 60 elements; these data and the methods used are published as a U.S. Geological Survey data release. The results indicate that, of the critical metals in bauxites, gallium is a potential byproduct from the central Arkansas bauxite deposits. The highest gallium concentrations occur in the raw bauxite ore, with an average concentration of 76 parts per million (ppm). Gallium partitions with alumina (the product) rather than into mine waste residues. Results indicate an average niobium content of 662 ppm in the Arkansas bauxite ores. Niobium progressively increases in concentration from parent syenite (247 ppm) to clays (315 ppm) and further from bauxite (662 ppm) to processed residues (1,075 ppm). Low concentrations of scandium were found in all samples, averaging 10 ppm or less in the parent rock (syenite), bauxite, clays, and processing residues. Modest concentrations of the light and heavy REEs were found in samples of bauxite ores, bauxitic clays and interbedded clays, syenite, and the residues of ore. The highest REE values were found in processed residues, with average concentrations of 613 ppm total light REEs and 130 ppm total heavy REEs. These concentrations suggest that additional processing to recover REEs is unlikely to be economic in the foreseeable future.

Arkansas↗

USGS2011

Trace and minor element variations and sulfur isotopes in crystalline and colloform ZnS: Incorporation mechanisms and implications for their genesis

Various models have been proposed to explain the formation mechanism of colloform sphalerite, but the origin is still under debate. In order to decipher influences on trace element incorporation and sulfur isotope composition, crystalline and colloform sphalerite from the carbonate-hosted Mississippi-Valley Type (MVT) deposit near Wiesloch, SW Germany, were investigated and compared to sphalerite samples from 52 hydrothermal vein-type deposits in the Schwarzwald ore district, SW Germany to study the influence of different host rocks, formation mechanisms and fluid origin on trace element incorporation. Trace and minor element incorporation in sphalerite shows some correlation to their host rock and/or origin of fluid, gangue, paragenetic minerals and precipitation mechanisms (e.g., diagenetic processes, fluid cooling or fluid mixing). Furthermore, crystalline sphalerite is generally enriched in elements like Cd, Cu, Sb and Ag compared to colloform sphalerite that mainly incorporates elements like As, Pb and Tl. In addition, sulfur isotopes are characterized by positive values for crystalline and strongly negative values for colloform sphalerite. The combination of trace element contents, typical minerals associated with colloform sphalerite from Wiesloch, sulfur isotopes and thermodynamic considerations helped to evaluate the involvement of sulfate-reducing bacteria in water-filled karst cavities. Sulfate-reducing bacteria cause a sulfide-rich environment that leads in case of a metal-rich fluid supply to a sudden oversaturation of the fluid with respect to galena, sphalerite and pyrite. This, however, exactly coincides with the observed crystallization sequence of samples involving colloform sphalerite from the Wiesloch MVT deposit.

Wiesloch↗

USGS2009

The performance of nearshore dredge disposal at Ocean Beach, San Francisco, California, 2005-2007

Ocean Beach, California, contains an erosion hot spot in the shadow of the San Francisco ebb tidal delta that threatens valuable public infrastructure as well as the safe recreational use of the beach. In an effort to reduce the erosion at this location a new plan for the management of sediment dredged annually from the main shipping channel at the mouth of San Francisco Bay was implemented in May 2005 by the United States Army Corps of Engineers, San Francisco District (USACE). The USACE designated a temporary nearshore dredge disposal site for the annual disposal of about 230,000 m3 (300,000 yd3) of sand about 750 m offshore and slightly south of the erosion hot spot, in depths between approximately 9 and 14 m. The site has now been used three times for a total sediment disposal of about 690,000 m3 (about 900,000 yds3). The disposal site was chosen because it is in a location where strong tidal currents and open-ocean waves can potentially feed sediment toward the littoral zone in the reach of the beach that is experiencing critical erosion, as well as prevent further scour on an exposed outfall pipe. The onshore migration of sediment from the target disposal location might feed the primary longshore bar or the nearshore zone, and provide a buffer to erosion that peaks during winter months when large waves impact the region. The United States Geological Survey (USGS) has been monitoring and modeling the bathymetric evolution of the test dredge disposal site and the adjacent coastal region since inception in May 2005. This paper reports on the first 2.5 years of this monitoring program effort (May 2005 to December 2007) and assesses the short-term coastal response. Here are the key findings of this report: *Approximately half of the sediment that has been placed in the nearshore dredge-disposal site during the 2.5 years of this study remains within the dredge focus area. *In the winter of 2006-7, large waves transported the dredge-mound material onshore. *High rates of seasonal cross-shore sediment transport mask any potential profile change in the Coastal Profiling System data due to dredge placement. *Pockets of accretion have been recorded by topographic surveying adjacent to the dredge site, but it is unclear if the accretion is linked to the nourishment. *Cross-shore profile modeling suggests that dredge material must be placed in water depths no greater than 5 m to drive a positive shoreline response. *Area modeling demonstrates that the new dredge site increases wave dissipation and modifies local sediment-transport patterns, although the effect on the nearshore morphology is largely negligible. *Any increase in beach width or wave energy-dissipation related to the nourishment is likely to be realized only in the vicinity directly onshore of the nourishment site, which is several hundred meters south of the area of critical erosion. *Larger waves from the northwest and smaller waves from the west or southwest contribute most to the sediment transport from the dredge mound onshore.

California↗

USGS1968

A lead isotope study of galenas and selected feldspars from mining Districts in Utah

The leads in feldspars from the main Tertiary intrusive bodies in each of three mining regions in Utah are isotopically similar to the lead deposits immediately associated with them. These deposits are the largest and also the least radiogenic in each region, whereas the smaller deposits are more radiogenic. Throughout each region the 'ore leads appear to be mixtures in various proportions of lead derived from the intrusive magma and a radiogenic lead component derived from the upper crustal rocks through which the mineralizing fluids passed. Linear relationships are exhibited between the lead isotope ratios within each mining region, and these enable the ages of the upper crustal basement rocks to be determined. A simple tvo-stage model theory for the development of the lead ores yields the folloving data: Oquirrh Mountains region, t 1,650 4-150 m.y., p-Cottonwood-Park City region, t = 2,415 4-30 m.y., p- = 8.87. Tintlc region, t 2,075 4-30 m.y., Milford region, t 1 765 4-70 m.y., p-T ( Us ) = , = 8.83. An alternative "mixing" model is also proposed which requires only 1,650-m.y. and 2,400-m.y. events in these regions. In either case these ages confirm and supplement our present geochronological knowledge of the basement rocks of Utah .

Utah↗

USGS1987

Relationship between peat geochemistry and depositional environments, Cranberry Island, Maine

The Heath, Great Cranberry Island, Maine, offers a unique locality for studying lateral and vertical relationships between radically different peat types within 1 km 2 . The majority of The Heath is a Sphagnum moss-dominated raised bog. Surrounding the raised bog is a swamp/marsh complex containing grass, sedge, Sphagnum moss, alder, tamarack, and skunk cabbage. Swamp/ marsh-deposited peat occurs both around the margins of The Heath and under Sphagnum -dominated peat, which was deposited within the raised bog. A third peat type, dominated by herbaceous aquatics, is present underlying the swamp/marsh-dominated peat but is not present as a dominant botanical community of The Heath. The three peat types have major differences in petrographic characteristics, ash contents, and associated minerals. Sulfur contents range from a low of 0.19 wt.% (dry) within the raised bog to a high of 4.44 wt% (dry) near the west end of The Heath, where swamp/marsh peat occurring directly behind a storm beach berm has been influenced by marine waters. The presence of major geochemical variations within a 1-km 2 peat deposit suggests the need for in-depth characterization of potential peat resources prior to use.

International Journal of Coal Geology↗

USGS2001

The geology of a part of Acadia and the nature of the Acadian orogeny across Central and Eastern Maine

The zone of Acadian collision between the Medial New England and Composite Avalon terranes is well preserved in Maine. A transect from northwest (Rome) to southeast (Camden) crosses the eastern part of Medial New England comprising the Central Maine basin, Liberty-Orrington thrust sheet, and Fredericton trough, and the western part of Composite Avalon, including the Graham Lake, Clarry Hill, and Clam Cove thrust sheets. U-Pb geochronology of events before, during, and after the Acadian orogeny helps elucidate the nature and distribution of tectonostratigraphic belts in this zone and the timing of some Acadian events in the Northern Appalachians. The Central Maine basin consists of sedimentary and volcanic rocks of Middle Ordovician (∼470 to ∼460 Ma) age overlain with probable conformity by latest Ordovician(?) through earliest Devonian marine rift and flysch sedimentary rocks; these are intruded by weakly to undeformed plutonic rocks of Early and Middle Devonian age (∼399–378 Ma). The Fredericton trough consists of Early Silurian gray pelite and sandstone to earliest Late Silurian calcareous turbidite, deformed and variably metamorphosed prior to the emplacement of Late Silurian (∼422 Ma) and Early to Late Devonian (∼418 to ∼368 Ma) plutons. The Liberty-Orrington thrust sheet consists of Cambrian(?)-Ordovician (>∼474 to ∼469 Ma and younger) clastic sedimentary and volcanic rocks intruded by highly deformed Late Silurian (∼424 to ∼422 Ma) and Devonian (∼418 to ∼389 Ma) plutons, possibly metamorphosed in Late Silurian time (prior to ∼417 Ma), and metamorphosed to amphibolite facies in Early to Middle Devonian time (∼400 to ∼381 Ma). The Graham Lake thrust sheet contains possible Precambrian rocks, Cambrian sedimentary rocks with a volcanic unit dated at ∼503 Ma, and Ordovician rocks with possible Caradocian Old World fossils, metamorphosed and deformed in Silurian time and intruded by mildly to undeformed Late Silurian (∼421 Ma) and Late Devonian (∼371 to ∼368 Ma) plutons. The Clarry Hill thrust sheet consists of poorly studied, highly metamorphosed Cambrian (?) rocks. The Clam Cove thrust sheet contains highly deformed Precambrian limestone, shale, sandstone, and conglomerate, metamorphosed to epidote amphibolite facies and intruded by a mildly deformed pluton dated at ∼421 Ma. Metamorphism, deformation, and voluminous intrusive igneous activity of Silurian age are common to both the most southeastern parts of Medial New England and the thrust sheets of Composite Avalon. In contrast to Medial New England, the thrust sheets of Composite Avalon show only modest effects of Devonian deformation and metamorphism. Regional stratigraphic relations, paleontologic findings, and U-Pb geochronology suggest that the Graham Lake, Clarry Hill, and Clam Cove thrust sheets are far-traveled allochthons that were widely separated from Medial New England in the Silurian. One hundred nine (109) new U-Pb analyses of zircon, monazite, and sphene from 25 samples of metamorphosed, stratified, and intrusive igneous rocks are used to decipher the history of events along the transect. In our view, many of the structures within Medial New England were formed during the closing of the back-arc ocean during the waning stages of the Taconian orogeny. These features include the precursors to the upright folds found in Silurian sedimentary rocks, the west-facing Liberty-Orrington thrust sheet, and the Silurian plutons of Medial New England. Acadian tectonic features, including flysch sedimentation, igneous activity, deformation with nappe emplacement, and metamorphism record the progressive loading of Medial New England by a stack of thrust nappes emplaced in latest Silurian to Middle Devonian time. The Acadian orogeny is a prolonged event, lasting from earliest Late Silurian to the Late Devonian, whose evolution involved: (1) convergence between Medial New England and Composite Avalon along an east-dipping subduction zone from earliest Late Silurian to Early Devonian time; (2) collision and concurrent delamination of lithospheric mantle beneath Medial New England in Early Devonian time resulting in deformation, high-grade metamorphism, and intrusive igneous activity in the most eastern part of Medial New England and the western parts of Composite Avalon; (3) Early to Middle Devonian northwest-migrating penetrative deformations of the Acadian Main stage, including northwest-directed thrusting and recumbent folding followed by tightening of folds possibly produced in the waning stages of the Taconian orogeny and forming folded wave trains of isoclinal folds (∼419 to ∼404 Ma), (4) asymmetrical folds produced by east-west shortening (∼399 to ∼380 Ma); and (5) final westward emplacement of Composite Avalon thrust sheets onto Medial New England in Late Devonian time (∼380 to ∼371 Ma). The present boundary between rocks of Medial New England and Composite Avalon at the surface is the Sennebec Pond fault, a high-angle fault that cuts the Graham Lake and Clarry Hill thrusts, and is intruded by the Mt. Waldo pluton (∼371), one of several Late Devonian plutons (∼371 to ∼367 Ma) that mark the end of the Acadian orogeny in coastal Maine. The thrust sheets of Composite Avalon carried rocks of peri-Gondwanan affinity and with possible Old World fauna many kilometers to the west over Medial New England, thus potentially hiding the original suture at depth under the Gulf of Maine.

Maine↗

USGS2023

Groundwater discharge by evapotranspiration from the Amargosa Wild and Scenic River and contributing areas, Inyo and San Bernardino Counties, California

The Amargosa Wild and Scenic River, located in the southwestern Mojave Desert in Inyo and San Bernardino Counties, California, is a Federally protected waterway that supports the biodiversity of the region. Water in the river primarily comes from interbasin groundwater flow that originates as precipitation in the Spring Mountains. The precipitation enters the regional groundwater system and flows westerly beneath Pahrump, Chicago, and California Valleys before discharging into the Amargosa Wild and Scenic River system. In Pahrump Valley, groundwater discharge occurs as evapotranspiration (ET), spring discharge, and groundwater pumping, and in Chicago and California Valleys, groundwater discharge occurs as ET and spring discharge. Remaining groundwater flows into the Amargosa Wild and Scenic River and its main tributary, the China Ranch Wash, or is discharged from regional springs downgradient from Chicago and California Valleys. The Amargosa Wild and Scenic River and the China Ranch Wash sustain areas of deep-rooted vegetation (phreatophytes) that consume regional groundwater. Discharge from regional springs in the area only flows on the land surface for short distances before seeping back into the ground where the water generally is consumed by evaporation from moist soil or by transpiration of plants. Intermittent Amargosa River flow out of the study area is the only other form of discharge. In arid regions such as the Mojave Desert, groundwater discharge by evapotranspiration (ET g ) often is the only significant form of discharge in a regional water budget, and therefore, an estimate of annual ET g is a good approximation of the total annual groundwater discharge. In this study area, however, total annual discharge is annual ET g plus the annual surface-water discharge of the Amargosa River that exits the study area. Therefore, the annual ET g from Chicago and California Valleys and along the Amargosa Wild and Scenic River and the China Ranch Wash, plus the discharge of the Amargosa River, is a good approximation of the total annual groundwater discharge required to sustain the riparian habitats and surface-water flow in the Amargosa Wild and Scenic River. The Amargosa Conservancy and Inyo County, Calif., are interested in quantifying the total annual groundwater discharge required to sustain the riparian habitats and surface-water flow in the Amargosa Wild and Scenic River and entered into a cooperative agreement with the U.S. Geological Survey to estimate ET g from the Amargosa Wild and Scenic River study area. The study area consists of open-water bodies, areas with perennially moist soil, and areas with phreatophytes, all of which are discharging regional groundwater in Chicago and California Valleys, along the Amargosa Wild and Scenic River, and in the China Ranch Wash. Annual ET g for the Amargosa Wild and Scenic River study area is estimated to be 10,139,000 cubic meters. The estimate was determined by delineating boundaries of open water, perennially moist soil, and phreatophytes, multiplying the areas by appropriate site-scale ET g to derive annual ET g for each ET unit, and then adding the annual ET g for all ET units in the GDAs and study area. Boundaries of discharge areas were visually delineated using high-resolution aerial imagery and refined by field verification. Open water and moist soil ET g were estimated in previous investigations, and phreatophyte ETg was estimated from a quadratic relation between site-scale ET g and a vegetation index of the study area. The quadratic relation was derived from four points. Two points were based on the site-scale ET g estimated for this study and two points corresponded to theoretical minimum and maximum points. Site-scale ET g was measured at two ET-monitoring sites using the eddy-covariance method. At one site, located in sparse shrubs, ET g was 0.121 meters per year, and at the other site, located in dense wetland vegetation, ET g was 1.056 meters per year. A scaled normalized difference vegetation index (NDVI) that encompasses the study area was created from 0.6-meter resolution multispectral (4-band) aerial imagery from 2020 and was used as an indicator of plant density or cover.

California↗

USGS2018

Punctuated sediment discharge during early Pliocene birth of the Colorado River: Evidence from regional stratigraphy, sedimentology, and paleontology

The Colorado River in the southwestern U.S. provides an excellent natural laboratory for studying the origins of a continent-scale river system, because deposits that formed prior to and during river initiation are well exposed in the lower river valley and nearby basinal sink. This paper presents a synthesis of regional stratigraphy, sedimentology, and micropaleontology from the southern Bouse Formation and similar-age deposits in the western Salton Trough, which we use to interpret processes that controlled the birth and early evolution of the Colorado River. The southern Bouse Formation is divided into three laterally persistent members: basal carbonate, siliciclastic, and upper bioclastic members. Basal carbonate accumulated in a tide-dominated marine embayment during a rise of relative sea level between ~ 6.3 and 5.4 Ma, prior to arrival of the Colorado River. The transition to green claystone records initial rapid influx of river water and its distal clay wash load into the subtidal marine embayment at ~ 5.4–5.3 Ma. This was followed by rapid southward progradation of the Colorado River delta, establishment of the earliest through-flowing river, and deposition of river-derived turbidites in the western Salton Trough (Wind Caves paleocanyon) between ~ 5.3 and 5.1 Ma. Early delta progradation was followed by regional shut-down of river sand output between ~ 5.1 and 4.8 Ma that resulted in deposition of marine clay in the Salton Trough, retreat of the delta, and re-flooding of the lower river valley by shallow marine water that deposited the Bouse upper bioclastic member. Resumption of sediment discharge at ~ 4.8 Ma drove massive progradation of fluvial-deltaic deposits back down the river valley into the northern Gulf and Salton Trough. These results provide evidence for a discontinuous, start-stop-start history of sand output during initiation of the Colorado River that is not predicted by existing models for this system. The underlying controls on punctuated sediment discharge are assessed by comparing the depositional chronology to the record of global sea-level change. The lower Colorado River Valley and Salton Trough experienced marine transgression during a gradual fall in global sea level between ~ 6.3 and 5.5 Ma, implicating tectonic subsidence as the main driver of latest Miocene relative sea-level rise. A major fall of global sea level at 5.3 Ma outpaced subsidence and drove regional delta progradation, earliest flushing of Colorado River sand into the northern Gulf of California, and erosion of Bouse basal carbonate and siliciclastic members. The lower Colorado River valley was re-flooded by shallow marine waters during smaller changes in global sea level ~ 5.1–4.8 Ma, after the river first ran through it, which requires a mechanism to stop delivery of sand to the lower river valley. We propose that tectonically controlled subsidence along the lower Colorado River, upstream of the southern Bouse study area, temporarily trapped sediment and stopped delivery of sand to the lower river valley and northern Gulf of California for ~ 200–300 kyr. Massive progradation of the fluvial-deltaic system back down the river valley into the Salton Trough starting ~ 4.8–4.5 Ma apparently was driven by a huge increase in sediment discharge that overwhelmed the sediment-storage capacity of sub-basins along the lower river corridor and established the fully integrated river channel network.

Colorado River↗

USGS1996

Habitat characteristics of benchmark streams in agricultural areas of eastern Wisconsin

Stream habitat characteristics were measured at twenty sites in agricultural areas of eastern Wisconsin by the U.S. Geological Survey in May and June, 1993 as part of the National Water-Quality Assessment Program Western Lake Michigan Drainages study unit. These "benchmark" stream sites were selected for study to represent standards of reference for comparison to other streams in similar physical settings that appear to be more detrimentally affected by agriculture. The agricultural benchmark streams were selected from four physical settings, or relatively homogeneous units (RHU's), that differ in bedrock type and texture of surficial deposits. Habitat characteristics at streams in these four physical settings are described and compared to each other, and a habitat classification scheme was used to rank the quality of habitat in these streams. Additional aquatic information was collected along with the habitat data: water-quality data and population surveys of fish, invertebrates, and algae. Habitat data were collected at three levels: drainage basin, stream segment between major tributaries (length from 1 to 14 km), and stream reach (approximately 150m). Results of statistical analyses show that, in general, most correlations are among basin-level habitat characteristics. Few correlations were observed among reach- and basin-level characteristics. Principal components analysis (PCA) on basin-level data resulted in principal components that reflect RHU, land use or latitude, and basin size. Groupings of habitat characteristics at the reach level are less clearly attributed to some outside environmental factor. Streams that have undergone habitat restoration for fisheries group closely together on PCA ordination plots. Less than half of the habitat characteristics were found to be significantly different between one RHU and the other three. Characteristics that differed between RHU's were mainly at the basin level but also included some reach-level characteristics. Stream-habitat characteristics were classified according to the Michigan Department of Environmental Quality, Great Lakes Environmental Assessment Section (GLEAS) Procedure 51. No relation was found between GLEAS scores and RHU or the percentage of agricultural land in the drainage basins above the benchmark-stream sites. GLEAS scores were varied in each RHU. Streams with high GLEAS scores (rated good or excellent) can be considered benchmark or reference streams as far as habitat is concerned. Of the 20 streams sampled, 16 met this criterion.

Wisconsin↗

USGS1989

Marine origin of pyritic sulfur in the Lower Bakerstown coal bed, Castleman coal field, Maryland (U.S.A.)

The amount, kind, distribution, and genesis of pyrite in the Lower Bakerstown coal bed in a 150 × 15 m area of the Bettinger mine, Castleman coal field, Maryland, were studied by various analytical techniques. The mined coal, which had a nonmarine roof rock, contained 1.4–2.8 wt.% total sulfur, generally much lower than the high-sulfur coal (> 3.0 wt.% total S) to the north, which is associated with marine roof rocks. Small-scale systematic and nonsystematic variations in total sulfur and pyrite distribution were found in the mined area. In the column sample, most of the pyrite was found in the upper 9 cm of the 69-cm-thick mined coal and occurred mainly as a pyrite lens containing cell fillings in seed-fern tissue (coal ball). As-bearing pyrite was detected by laser microprobe techniques in the cell walls of this tissue but not elsewhere in the column sample. This may indicate that the As was derived from decomposition of organic matter in the cell walls. The sulfur isotopic composition and distribution of pyrite in the coal are consistent with introduction of marine sulfate shortly after peat deposition, followed by bacterial reduction and pyrite precipitation. Epigenetic cleat pyrite in the coal is isotopically heavy, implying that later aqueous sulfate was 34 S-enriched.

International Journal of Coal Geology↗

USGS2007

Abstracts of the Annual Meeting of Planetary Geologic Mappers, Tucson, AZ 2007

Introduction Report of the Annual Mappers Meeting Planetary Science Institute Tucson, Arizona June 28 and 29, 2007 Approximately 22 people attended this year's mappers meeting, and many more submitted abstracts and maps in absentia. The 2007 meeting was convened by Tracy Gregg, Les Bleamaster, Steve Saunders, and Ken Tanaka and was hosted by David Crown and Les Bleamaster of the Planetary Science Institute (PSI) in Tucson, Arizona. Oral presentations and poster discussions took place on Thursday, June 28 and Friday, June 29. This year's meeting also included a unique opportunity to visit the operations centers of two active Mars missions; field trips to the University of Arizona took place on Thursday and Friday afternoons. Outgoing Geologic Mapping Subcommittee (GEMS) chairperson, Tracy Gregg, commenced the meeting with an introduction and David Crown followed with a discussion of logistics and the PSI facility; Steve Saunders (Planetary Geology and Geophysics Discipline Scientist) then provided a brief program update. Science presentations kicked off with Venus mapper Vicki Hansen and graduate students Eric Tharalson and Bhairavi Shankar of the University of Minnesota, Duluth, showing a 3-D animation of the global distribution of tesserae and discussing the implications, a progress report for V-45 quadrangle mapping, and a brief discussion of circular lows. Les Bleamaster (PSI) followed with a progress report on mapping of the V-50 quadrangle and the 1:10M Helen Planitia quadrangle. David Crown (PSI) concluded the Venus presentations with a discussion of progress made on the V-30 quadrangle. The remainder of Thursday's presentations jumped around the Solar System including Mars, Io, and Earth. Ken Tanaka of the U.S. Geological Survey (USGS) began the afternoon with a general discussion of the status of the planetary mapping program at USGS. Buck Janes (University of Arizona) provided background information about the Mars Odyssey Gamma Ray Spectrometer (GRS) and presented some new element maps, which may be useful for geologic mapping. Dave Williams of Arizona State University reported on the progress of his global Io map and James Dohm (University of Arizona) discussed results of terrestrial remote mapping studies. Thursday afternoon, the mappers were given a tour of the High Resolution Imaging Science Experiment (HiRISE) operations facility and were given some basic information about how the images are obtained, processed, and publicly released. With official GEMS transition completed at lunch on Thursday, incoming GEMS chair Leslie Bleamaster took the reigns of Friday's meeting. Science presentations began with Ken Tanaka discussing 1:20M-scale global and 1:2M-scale polar mapping of Mars. Jim Zimbelman (Smithsonian Institution) described his 1:1M Medusae Fossae map (MC-8 SE), which is nearing completion, and new mapping (MC-16 NW and MC-23 NW) to further evaluate the Medusae Fossae. Brent Garry, also of the Smithsonian Institution, presented work on Ascraeus Mons. Peter Mouginis-Mark (University of Hawai`i) reported progress on his 1:200K and larger maps of Tooting crater and of the Olympus Mons summit caldera. Laszlo Keszthelyi (USGS) presented mapping of Athabasca Valles, with much of the credit going to Windy Jaeger. Jim Skinner (USGS) introduced a new mapping project including nine MTM quadrangles in the Utopia Planitia region. Tracy Gregg finished off the day's science presentations with discussion of Hesperia Planum. After discussion was complete, the group once again traveled to the University of Arizona - this time for a tour of the Mars Phoenix operations center. Principal Investigator Peter Smith beamed as he led mappers through the multi-million dollar facility. A main topic of discussion throughout the entire meeting was that of nomenclature, specifically how to classify the individual depressions at the tops of volcanoes. Paterae, as has been used for Mars, Venus, and Io, was suggested, but i

Open-File Report↗

USGS1996

Circulation and effluent dilution modeling in Massachusetts Bay : model implementation, verification and results

A three-dimensional hydrodynamic model was developed as part of a cooperative U.S. Geological Survey/Massachusetts Water Resources Authority program to study contaminated sediment accumulation and transport in Massachusetts Bay. This report details the development of the model and assesses how well the model represents observed currents and water properties in the bay. It also summarizes circulation and comparative effluent dilution simulations from existing and future Boston sewage outfalls over a three-year period from October 1, 1989 to December 31, 1992. The ECOM-si model, a semi-implicit version of the Blumberg and Mellor (1987) Estuarine, Coastal and Ocean Model, is shown to reproduce many of the important hydrodynamical features of Massachusetts Bay: the seasonal evolution of the pycnocline, the mean flow pattern, and the strength of sub-tidal current fluctuations. Throughout the simulation period, during both vertically well-mixed and stratified conditions, the seasonal statistics of observed currents are well-represented by the model. The model is therefore appropriate for studying the average dilution of sewage effluent and other continuously discharged substances over seasonal time scales. The ability of the model to reproduce individual flow events varies with season and location within the bay. Flow events during unstratified conditions in western Massachusetts Bay are particularly well-represented, indicating that the model is appropriate for studying processes such as the transport of suspended material from the future outfall site due to winter storms. Individual flow events during stratified conditions and in the offshore Stellwagen Bank region, however, are less well-represented due to small length scales (caused by upwelling and river discharge events) coupled with insufficient data to specify open boundary forcing from the Gulf of Maine. Thus while the model might be used to answer issues such as the frequency with which Gulf of Maine river plumes visit the new outfall site, attempting to predict whether a particular plume would visit the outfall site could be problematic. Comparative simulations of effluent discharged from the existing and future Boston outfalls show that the region of relatively high effluent concentrations (1 part effluent to 200 parts sea water) is significantly smaller with the future outfall and is limited to Western Massachusetts Bay during both unstratified and stratified seasons. The region of even higher concentration (1 part effluent to 50 parts sea water) that covers much of Boston Harbor with the existing outfall is non-existent in the future outfall simulation. Additional simulations of chlorination plant failure predict that the offshore location of the future outfall will lead to dramatically lower levels of pathogens at area beaches.

Open-File Report↗

USGS1976

Mineral deposits and occurrences in the McCarthy Quadrangle, Alaska

The McCarthy quadrangle contains numerous and diverse mineral deposits in various geologic settings. Copper is the dominant mineral commodity, both historically and in terms of potential future production. Gold and silver are the only other metals that have been produced. The metalliferous deposits are concentrated in a northwest-trending belt along the southern flank of the Wrangell Mountains, and, to a lesser extent, in a similar belt along the northeast flank of the range. Both belts have upper Paleozoic (Skolai Group) basements, abundant Mesozoic rocks, and some Tertiary intrusive rocks. They are marked by numerous faults, mainly northwest-striking. Mineral deposits are uncommon elsewhere in the quadrangle, especially in large tracks underlain by Wrangell Lava and in smaller areas underlain by the Kaskawulsh Group of Kindle (1953). Both the Wrangell Lava and the Kaskawulsh underlie rugged mountainous regions with extensive snow and ice cover, and could conceivably contain undetected concealed deposits. The metallic, nonmetallic, and energy resources of the quadrangle are described sequentially. Copper, gold, and silver, because of their importance, are described early in the section on metal commodities; descriptions of the other metals follows in alphabetic sequence. Locations of the deposits and relative supplementary data for individual deposits are given in the accompanying map and table.

Alaska↗