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At least 397 records · Page 22Linked to original sources
USGS1971

Data file, Continental Margin Program, Atlantic Coast of the United States: vol. 2 sample collection and analytical data

The purpose of the data file presented below is twofold: the first purpose is to make available in printed form the basic data relating to the samples collected as part of the joint U.S. Geological Survey - Woods Hole Oceanographic Institution program of study of the Atlantic continental margin of the United States; the second purpose is to maintain these data in a form that is easily retrievable by modern computer methods. With the data in such form, repeate manual transcription for statistical or similar mathematical treatment becomes unnecessary. Manual plotting of information or derivatives from the information may also be eliminated. Not only is handling of data by the computer considerably faster than manual techniques, but a fruitful source of errors, transcription mistakes, is eliminated.

Report↗
USGS2002

Historical and modern distributions of benthic foraminifers on the continental shelf of Monterey Bay, California

Historical (early 1930s) and modern samples provide a detailed account of the spatial distribution of benthic foraminifers on the continental shelf of Monterey Bay, California. Ten species among a total of 110 present dominated the 110 samples investigated in the historical study. A cluster analysis of the foraminiferal abundances in the historical study identified five assemblages: Inner Shelf, Middle Shelf, Outer Shelf, Southeastern Shelf and Southwestern Shelf. Specimens with calcareous tests were most prevalent in all the assemblages. A cluster analysis of the modern foraminiferal frequencies from 95 samples also defined five assemblages: Inner Shelf, Middle Shelf, Middle/Outer Shelf Arenaceous, Outer Shelf, and Southern Shelf. Although arenaceous taxa dominate much of the modern fauna, the spatial distribution of the modern assemblages is similar to that of the historical record when presumably unrecognized taxa are eliminated from the data. Both the historical and, to a greater degree, the modern foraminiferal assemblages exhibit a strong correlation with the sediment grain size distribution. ?? 2002 Elsevier Science B.V. All rights reserved.

Marine Geology↗
USGS1978

A reexamination of the Pennsylvanian trace fossil Olivellites

The original interpretation of Olivellites plummeri Fenton and Fenton as the trace of an infaunal gastropod, is reconsidered and rejected. The original slab bearing several examples of O. plummeri has been reexamined and reillustrated. The slab came from the type-locality of O. plummeri in Eastland County, Tex., and is a shallow sub tidal sandstone of the Graham Formation; the sandstone, which has yielded additional specimens, is presumably a reworked delta-front deposit. Olivellites was also observed in the Caddo Creek Formation in Stephens County, Tex., but, to date, it has not been found elsewhere in north-central Texas. Interpretation of Paleozoic ichnofossils by analogy with modern traces is limited; behavioral characteristics may be the products of post-Paleozoic innovation. The internal morphology and path of Olivellites are unlike those of any modern gastropod trail, and the genus is removed from the Mollusca.

Texas↗
USGS2016

Unusually large tsunamis frequent a currently creeping part of the Aleutian megathrust

Current models used to assess earthquake and tsunami hazards are inadequate where creep dominates a subduction megathrust. Here we report geological evidence for large tsunamis, occurring on average every 300–340 years, near the source areas of the 1946 and 1957 Aleutian tsunamis. These areas bookend a postulated seismic gap over 200 km long where modern geodetic measurements indicate that the megathrust is currently creeping. At Sedanka Island, evidence for large tsunamis includes six sand sheets that blanket a lowland facing the Pacific Ocean, rise to 15 m above mean sea level, contain marine diatoms, cap terraces, adjoin evidence for scour, and date from the past 1700 years. The youngest sheet, and modern drift logs found as far as 800 m inland and >18 m elevation, likely record the 1957 tsunami. Modern creep on the megathrust coexists with previously unrecognized tsunami sources along this part of the Aleutian Subduction Zone.

Alaska↗
USGS2014

Geologic map of the west-central Buffalo National River region, northern Arkansas

This map summarizes the geology of the west-central Buffalo National River region in the Ozark Plateaus region of northern Arkansas. Geologically, the region lies on the southern flank of the Ozark dome, an uplift that exposes oldest rocks at its center in Missouri. Physiographically, the map area spans the Springfield Plateau, a topographic surface generally held up by Mississippian cherty limestone and the higher Boston Mountains to the south, held up by Pennsylvanian rocks. The Buffalo River flows eastward through the map area, enhancing bedrock erosion of an approximately 1,600-ft- (490-m-) thick sequence of Ordovician, Mississippian, and Pennsylvanian carbonate and clastic sedimentary rocks that have been mildly deformed by a series of faults and folds. Quaternary surficial units are present as alluvial deposits along major streams, including a series of terrace deposits from the Buffalo River, as well as colluvium and landslide deposits mantling bedrock on hillslopes. This report provides a geologic map database of the map area that improves understanding of the regional geologic framework and its influence on the regional groundwater flow system. Furthermore, additional edits were made to the Ponca and Jasper quadrangles in the following ways: new control points on important contacts were obtained using modern GPS; recent higher resolution elevation data allowed further control on placement of contacts; some new contacts were added, in particular the contact separating the upper and lower Everton Formation.

Arkansas↗
USGS1999

Geographic information systems (GIS) compilation of geophysical, geologic, and tectonic data for the circum-North Pacific

The accompanying directory structure contains a Geographic Information Systems (GIS) compilation of geophysical, geological, and tectonic data for the Circum-North Pacific. This area includes the Russian Far East, Alaska, the Canadian Cordillera, linking continental shelves, and adjacent oceans. This GIS compilation extends from 120°E to 115°W, and from 40°N to 80°N. This area encompasses: (1) to the south, the modern Pacific plate boundary of the Japan-Kuril and Aleutian subduction zones, the Queen Charlotte transform fault, and the Cascadia subduction zone; (2) to the north, the continent-ocean transition from the Eurasian and North American continents to the Arctic Ocean; (3) to the west, the diffuse Eurasian-North American plate boundary, including the probable Okhotsk plate; and (4) to the east, the Alaskan-Canadian Cordilleran fold belt. This compilation should be useful for: (1) studying the Mesozoic and Cenozoic collisional and accretionary tectonics that assembled this continental crust of this region; (2) studying the neotectonics of active and passive plate margins in this region; and (3) constructing and interpreting geophysical, geologic, and tectonic models of the region. Geographic Information Systems (GIS) programs provide powerful tools for managing and analyzing spatial databases. Geological applications include regional tectonics, geophysics, mineral and petroleum exploration, resource management, and land-use planning. This CD-ROM contains thematic layers of spatial data-sets for geology, gravity field, magnetic field, oceanic plates, overlap assemblages, seismology (earthquakes), tectonostratigraphic terranes, topography, and volcanoes. The GIS compilation can be viewed, manipulated, and plotted with commercial software (ArcView and ArcInfo) or through a freeware program (ArcExplorer) that can be downloaded from http://www.esri.com for both Unix and Windows computers using the button below.

North Pacific↗
USGS2022

Maturation study of vitrinite in carbonaceous shales and coals: Insights from hydrous pyrolysis

The presence of vitrinite in sedimentary rocks of post-Silurian age allows its reflectance to be used to estimate the thermal maturation of organic matter in petroleum systems. Increasing reflectance of vitrinite, which is primarily driven by aromaticity, depends primarily on the time and temperature attributes of its evolutionary pathway. This study evaluated carbonaceous shales proximal to coal measures and coal samples via isothermal hydrous pyrolysis (HP) to compare differences in the maturation pathways of vitrinite. Sample residues were analysed via vitrinite reflectance (VRo), geochemical screening tests (organic carbon and programmed temperature pyrolysis), and infrared spectroscopy. The study included samples from Indian and North American basins, to observe differences in vitrinite evolution with respect to enclosing mineral matrix, starting degree of aromaticity, organic matter types, stratigraphic age, and depositional environment. The organic content of HP residues shows an intuitive response to the thermal stress of HP, e.g., a general depletion of total organic carbon (TOC) content, pyrolyzate (S2), and hydrogen index with increasing HP temperature. Infrared proxies including C-factor and CH2/CH3 generally decrease with increasing thermal maturity indicating loss of O via CO2 generation and the thermal cracking of aliphatic organic matter. Tmax, production index (PI), and VRo show intuitive increasing values with respect to HP temperature. The least mature sample (0.48 ± 0.05% VRo) generally experienced the maximum change in these parameters during maturation, whereas the most mature sample (0.99 ± 0.06% VRo) generally showed the least change. This observation is consistent with higher kinetic barriers to reaction in more aromatic vitrinite which contains higher bond dissociation energies. Devolatilization of vitrinite during HP causes formation of gas evacuation vacuoles and contraction cracks in the vitrinite grains of both coal and carbonaceous shale. Similarities in vitrinite response to HP between coal and carbonaceous shale suggest that thermal evolution of the vitrinite maceral is principally controlled by inherent rate-limiting kinetic parameters related to its molecular structure. Whereas, the stratigraphic age, sedimentary environment, surrounding organic matter, lithology, and catalysis by mineral composition have less effect. To further improve our understanding of vitrinite aromatization and kinetic parameters, future studies of vitrinite reflectance thermal evolution with temperature should include coal and carbonaceous shale from the same stratigraphic section and extant woody tissue from modern vascular plants.

International Journal of Coal Geology↗
USGS1995

An update on USGS studies of the Summitville Mine and its downstream environmental effects

The Summitville gold mine, located at ~3800 meters (11,500 ft) elevation in the San Juan Mountains of southwestern Colorado, was the focus of extensive public attention in 1992 and 1993 for environmental problems stemming from recent open-pit mining activities. Summitville catalyzed national debates about the environmental effects of modern mining activities, and became the focus of arguments for proposed revisions to the 1872 Mining Law governing mining activities on public lands. In early 1993, the State of Colorado, U.S. Environmental Protection Agency (EPA), U.S. Geological Survey (USGS), U.S. Fish and Wildlife Service (USFWS), Colorado State University, San Luis Valley agencies, downstream water users, private companies, and individuals began a multi-disciplinary research program to provide needed scientific information on Summitville's environmental problems and downstream environmental effects. Detailed results of this multi-agency effort were presented, along with legal and policy issues, at the Summitville Forum in January, 1995, at Colorado State University, Fort Collins, Colorado.

Open-File Report↗
USGS1989

IRIS/USGS plans for upgrading the Global Seismograph Network

This report has been prepared to provide information to organizations that may be asked to participate in a program to upgrade the global seismographic network. In most cases, the organizations that will be offered new instrumentation by the U.S. Geological Survey currently operate stations in the World-Wide Standardized Seismograph Network (WWSSN) or the Global Digital Seismograph Network (GDSN). The deployment of the WWSSN in the 1960's and the subsequent equipping of some WWSSN stations with digital equipment and borehole seismometers during the 1970's has been a remarkably successful program that generated the high- quality data needed to fuel an unprecedented period of progress in earthquake and tectonic research. The success of the WWSSN can be attributed to the importance of the data, to the strong commitment by participating organizations to international scientific cooperation, to the dedication and skill of the station operators, and to the resourcefulness of the staff supporting the network. Benefits have been widespread. The community of scientists world-wide has benefited from unrestricted access to a standardized base of calibrated data, and the participating stations have benefited from the donation of modern observatory instruments that have been useful for local earthquake studies and for the training of scientists and engineers. Now, an exciting opportunity has arisen to deploy a new generation of seismograph systems to replace the outdated equipment at many of the WWSSN and GDSN stations. The U.S. Geological Survey (USGS) is cooperating with the Incorporated Research Institutions for Seismology (IRIS) in a program to upgrade the global seismograph network. The equipment development phase is nearly complete with a prototype of the new broadband seismograph system currently undergoing final testing at the USGS Albuquerque Seismological Laboratory. Deployment of the new equipment is expected to begin in early 1990. As this report will demonstrate, the IRIS broadband seismograph system combines the very latest data acquisition and computer technology to produce seismic data with unprecedented bandwidth and dynamic range. Moreover, the system has been designed so that the high-quality digital data are accessible for local display and analysis. The functional design of the new system, which uses off-the-shelf modules and a standard computer bus, will make it much easier than it has been in the past to modify and upgrade the data acquisition system as improvements in technology become available. With adequate support for the program, the new IRIS seismograph system need never become obsolete. We want you to be aware of our plans and the possibility that you may be asked to participate in this ,program. The schedule for upgrading WWSSN and GDSN stations depends on the level of funding earmarked for the program by our National Science Foundation. We hope to deploy at least ten new GSN data systems each year. If you have any questions concerning this program, please contact the Albuquerque Seismological Laboratory, U.S. Geological Survey, Albuquerque, New Mexico 87115-5000. This report was revised in February 1992 in order to update information concerning the current program and instrumentation. The amp in Figure 1 was revised in June 1993, April 1994, December 1994, and September 1996 to reflect updated siting information. In September 1996 a composite photo of standard and optional components of the IRIS-2 GSN system hardware was added as a separate page between Figures 9 and 10.

Open-File Report↗
USGS2022

Shallow faulting and folding in the epicentral area of the 1886 Charleston, South Carolina, earthquake

The moment magnitude ( ⁠ M w "> M w �w ⁠ ) ∼7 earthquake that struck Charleston, South Carolina, on 31 August 1886 is the largest historical earthquake in the United States east of the Appalachian Mountains. The fault(s) that ruptured during this earthquake has never been conclusively identified, and conflicting fault models have been proposed. Here we interpret reprocessed seismic reflection profiles, reprocessed legacy aeromagnetic data, and newly collected ground penetrating radar (GPR) profiles to delineate faults deforming the Cretaceous and younger Atlantic Coastal Plain (ACP) strata in the epicentral area of the 1886 earthquake. The data show evidence for faults folding or vertically displacing ACP strata, including apparent displacements of near‐surface strata (upper ∼20 m). Aeromagnetic data show several northeast (NE)‐trending lineaments, two of which correlate with faults and folds with vertical displacements as great as 55 m on the seismic reflection and radar profiles. ACP strata show only minor thickness changes across these structures, indicating that much of the displacement postdates the shallowest well‐imaged ACP strata of Eocene age. Faults imaged on the seismic reflection profiles appear on GPR profiles to displace the erosional surface at the top of the upper Eocene to Oligocene Cooper Group, including where railroad tracks were bent during the 1886 earthquake. Some faults coincide with changes in river trends, bifurcations of river channels, and unusual river meanders that could be related to recent fault motion. In contrast to our interpreted NE fault trends, earthquake locations and some focal mechanisms in the modern seismic zone have been interpreted as defining a nearly north‐striking, west‐dipping zone of aftershocks from the 1886 earthquake. The relationship between the modern seismicity and the faults we image is therefore enigmatic. However, multiple faults in the area clearly have been active since the Eocene and deform strata in the upper 20 m, providing potential targets for field‐based geologic investigations.

South Carolina↗
USGS2018

The 3D Elevation Program—Flood risk management

Flood-damage reduction in the United States has been a longstanding but elusive societal goal. The national strategy for reducing flood damage has shifted over recent decades from a focus on construction of flood-control dams and levee systems to a three-pronged strategy to (1) improve the design and operation of such structures, (2) provide more accurate and accessible flood forecasting, and (3) shift the Federal Emergency Management Agency (FEMA) National Flood Insurance Program to a more balanced, less costly flood-insurance paradigm. Expanding the availability and use of high-quality, three-dimensional (3D) elevation information derived from modern light detection and ranging (lidar) technologies to provide essential terrain data poses a singular opportunity to dramatically enhance the effectiveness of all three components of this strategy. Additionally, FEMA, the National Weather Service, and the U.S. Geological Survey (USGS) have developed tools and joint program activities to support the national strategy. The USGS 3D Elevation Program (3DEP) has the programmatic infrastructure to produce and provide essential terrain data. This infrastructure includes (1) data acquisition partnerships that leverage funding and reduce duplicative efforts, (2) contracts with experienced private mapping firms that ensure acquisition of consistent, low-cost 3D elevation data, and (3) the technical expertise, standards, and specifications required for consistent, edge-to-edge utility across multiple collection platforms and public access unfettered by individual database designs and limitations. High-quality elevation data, like that collected through 3DEP, are invaluable for assessing and documenting flood risk and communicating detailed information to both responders and planners alike. Multiple flood-mapping programs make use of USGS streamflow and 3DEP data. Flood insurance rate maps, flood documentation studies, and flood-inundation map libraries are products of these programs.

Fact Sheet↗
USGS2002

The last interglacial period on the Pacific Coast of North America: Timing and paleoclimate

New, high-precision U-series ages of solitary corals ( Balanophyllia elegans ) coupled with molluscan faunal data from marine terraces on the Pacific Coast of North America yield information about the timing and warmth of the last interglacial sea-level highstand. Balanophyllia elegans takes up U in isotopic equilibrium with seawater during growth and shortly after death. Corals from the second terrace on San Clemente Island (offshore southern California), the third terrace on Punta Banda (on the Pacific Coast of northern Baja California), and the Discovery Point Formation on Isla de Guadalupe (in the Pacific Ocean offshore Baja California) date to the peak of the last interglacial period and have U-series ages ranging from ca. 123 to 114 ka. The first terrace on Punta Banda has corals with ages ranging from ca. 83 to 80 ka, which corresponds to a sea-level highstand formed in the late last interglacial period. U-series analyses of corals from the Cayucos terrace (central California) and the Nestor terrace at Point Loma (southern California) show that these fossils have evidence of open-system history, similar to what has been reported by other workers for the same localities. Nevertheless, a model of continuous, secondary U and Th uptake shows that two ages of corals are likely present at these localities, representing the ca. 105 and ca. 120 ka sea-level highstands reported elsewhere. U-series ages of last interglacial corals from the Pacific Coast overlap with, but are on average younger than the ages of corals from Barbados, the Bahamas, and Hawaii. This age difference is explained by the nature of the geomorphic response to sea-level change: fringing or barrier reefs on low-latitude coastlines have an accretionary growth style that keeps pace with rising sea level, whether on a tectonically rising or stable coastline. In contrast, midlatitude, high-energy coastlines are sites of platform cutting during the early part of a sea-level high stand and terrace scouring and concomitant sediment and fossil deposition as sea level starts to recede. The youngest ages of corals from the Pacific Coast suggest that sea level was still relatively high at ca. 116 ka, which is not in agreement with other estimates of relatively large global ice volume at that time. Reliably dated, ca. 120 ka marine-terrace deposits on the Pacific Coast have fossil mollusks that indicate water temperatures as warm or warmer than at present. In contrast, ca. 80 ka marine deposits reported here and elsewhere have fossil mollusks indicating cooler-than-modern water temperatures. The presence of both ca. 105 ka and ca. 120 ka corals on the Nestor and Cayucos terraces explains a previously enigmatic mixture of warm-water and cool-water mollusks. At ca. 105 ka, a relatively high sea level with cool waters may have "captured" the terrace formed during the 120 ka sea-level highstand, in areas of low uplift rate. The inference of cooler-than-modern waters off the Pacific Coast of North America at ca. 80 ka and ca. 105 ka, based on marine-terrace faunas, does not agree with estimates of sea-surface temperatures derived from alkenone studies in the Santa Barbara Basin. However, cooler water temperatures at these times are in agreement with paleo-temperature estimates from planktonic foraminiferal data for the Santa Barbara Basin. All records, from central California to Baja California, whether from marine terraces or offshore cores, indicate at least seasonably warmer-than-modern waters during the peak of the last interglacial period at ca. 120 ka.

Pacific Coast↗
USGS2025

Favorability mapping for hydrothermal power resource assessments of the Great Basin, USA

The U.S. Geological Survey (USGS) is updating the 2008 assessment of conventional hydrothermal resources for the Great Basin in the western United States. As part of this work, the workflow for hydrothermal resource favorability maps is being modified to integrate modern data-driven machine learning (ML) methods. Improvements include: [1] using new and refined evidence layers (features); [2] using an order of magnitude more training sites (labeled examples); [3] utilizing simple but non-linear supervised ML algorithms; [4] representing positive training sites (wells with measured heat flow) with their ordinal value proportional to the magnitude of convective upflow (i.e., low, high, or very high convective signals instead of past strategies using positive-negative labels); [5] supplementing training sites with additional sites with low convective signals to represent diverse under-sampled areas where hydrothermal systems are unlikely to exist; [6] comparing with competing approaches; and [7] utilizing Monte Carlo cross-validation to estimate and evaluate prediction uncertainty. For the new favorability map, over half of the power-producing systems (i.e., 15 of 28) are predicted in the 99th percentile of most favorable locations (i.e., the highest 1 % of favorability, corresponding to 1 % of the map area), exceeding the performance of past models that have explicitly used power plants as training sites. Previous favorability maps predicted approximately half of the power-producing hydrothermal systems above the 80th percentile (i.e., 20 % of the map area). For the new favorability map, 93 % of power-producing systems (i.e., 26 of 28) are above the 80th percentile. The power-producing systems for which the new model does not perform well are either comparatively small, low-temperature systems or systems also not predicted well by prior modeling approaches, suggesting that these few systems are unusual when compared with most power-producing systems. Focusing research on these known, seemingly different systems may yield new insights and subsequent discovery of new prospects.

California, Idaho, Nevada, Oregon, Utah↗
USGS1984

Fossils of hydrothermal vent worms from Cretaceous sulfide ores of the Samail ophiolite, Oman

Fossil worm tubes of Cretaceous age preserved in the Bayda massive sulfide deposit of the Samail ophiolite, Oman, are apparently the first documented examples of fossils embedded in massive sulfide deposits from the geologic record. The geologic setting of the Bayda deposit and the distinctive mineralogic and textural features of the fossiliferous samples suggest that the Bayda sulfide deposit and fossil fauna are remnants of a Cretaceous sea-floor hydrothermal vent similar to modern hot springs on the East Pacific Rise and the Juan de Fuca Ridge.

Science↗
USGS2005

Evidence of cold climate slope processes from the New Jersey Coastal Plain: Debris flow stratigraphy at Haines Corner, Camden County, New Jersey

Excavations through surficial deposits across the New Jersey Coastal Plain commonly reveal homogenized surficial sediments, deformed sedimentary structures, chaotically rearranged bed-forms, and wedge-shaped cracks filled with sand from the top-most layers of extant soil profiles. As a whole, these abundant, broadly distributed phenomena are best explained as artifacts of an era of frozen ground during the last Pleistocene glacial maximum. Vigorous freeze-thaw processes and abundant seasonal rainfall created a landscape of low relief covered by highly mobile surficial deposits. The surficial deposits are at grade into broad, flat bottomed valleys now drained by small, tightly meandering, under-fit streams. Modern fluvial, aeolian, and slope processes are ineffectual in either creating or modifying these landscapes. One particularly brief exposure of complex slope deposits was documented at Haines Corner, Camden County, during the field work (1986) for the Surficial Geologic Map of southern and central New Jersey. The exposure, now presented and interpreted here, provides previously unavailable details of a system of freeze-thaw driven processes that unfolded upon a frozen, impermeable substrate 80 miles south of the southern margin of the Wisconsinan glacial advance to Long Island, N.Y. At the time of these extreme processes, the presently sub-aerial New Jersey Coastal Plain was not proximal to moderating effects of the Atlantic Ocean, being about 100 miles inland and 300 feet above the lowered sea level. Current studies of analogous deposits across the mid-Atlantic Coastal Plain now benefit from dating techniques that were not available during the geologic mapping field work (1985-'92). During the mapping in New Jersey, hundreds of exposures failed to produce datable carbon remains within the stratigraphy of the surficial deposits. Recently reported TL dates from wind-blown sand filling frost wedges, exposed elsewhere in New Jersey, indicate that the widely distributed surficial deposits of the New Jersey Coastal Plain were active during the maximum cold period of the late Pleistocene (around 18,000 years ago).

New Jersey↗
USGS2017

A seasonal and spatial comparison of metals, and stable carbon and nitrogen isotopes, in Chincoteague Bay and the marsh deposits of Assateague Island and the adjacent vicinity, Maryland and Virginia

After Hurricane Sandy, scientists from the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center conducted a seasonal collection of estuarine, marsh, and sandy overwash surface sediments from Chincoteague Bay, Tom’s Cove, and the surrounding Assateague Island and Delmarva Peninsula in March–April and October 2014. Surplus surface sediment was analyzed for metals, percent carbon and nitrogen, δ 13 C, and δ 15 N as part of a complementary U.S. Geological Survey Coastal and Marine Geology Program Sea-level and Storm Impacts on Estuarine Environments and Shorelines project study. The geochemical subsample analyzed for metals and stable isotopes at each site may be used for comparison with past data sets, to create a modern baseline of the natural distribution of the area, to understand seasonal variability as it relates to the health of the local environment, and to assess marsh-to-bay interactions. The use of metals, stable carbon, and stable nitrogen isotopes allows for a more cohesive snapshot of factors influencing the environment and could aid in tracking environmental change. This report serves as an archive for chemical data derived from the surface sediment. Data are available for a seasonal comparison between the March–April 2014 and October 2014 sampling trips. Downloadable data are available as Microsoft Excel spreadsheets. These additional files include formal Federal Geographic Data Committee metadata ( data downloads ).

Maryland, Virginia↗
USGS2003

Map and digital database of sedimentary basins and indications of petroleum in the Central Alaska Province

This database and accompanying text depict historical and modern reported occurrences of petroleum both in wells and at the surface within the boundaries of the Central Alaska Province. These data were compiled from previously published and unpublished sources and were prepared for use in the 2002 U.S. Geological Survey petroleum assessment of Central Alaska, Yukon Flats region. Indications of petroleum are described as oil or gas shows in wells, oil or gas seeps, or outcrops of oil shale or oil-bearing rock and include confirmed and unconfirmed reports. The scale of the source map limits the spatial resolution (scale) of the database to 1:2,500,000 or smaller.

Open-File Report↗
USGS2000

Hydrogeology of the Beaver Kill Basin in Sullivan, Delaware, and Ulster Counties, New York

The hydrogeology of the 299-square-mile Beaver Kill basin in the southwestern Catskill Mountains of southeastern New York is depicted in a surficial geologic map and five geologic sections, and is summarized through an analysis of low-flow statistics for the Beaver Kill and its major tributary, Willowemoc Creek. Surficial geologic data indicate that the most widespread geologic units within the basin are ablation and lodgment till. Large masses of ablation till as much as 450 feet thick were deposited as lateral embankments within the narrow Beaver Kill and Willowemoc Creek valleys and have displaced the modern stream courses by as much as 1,000 feet from the preglacial bedrock-valley axis. Low-flow statistics for the Beaver Kill and Willowemoc Creeks indicate that the base flows (discharges that are exceeded 90 percent of the time) of these two streams—0.36 and 0.39 cubic feet per square mile,respectively—are the highest of 13 Catskill Mountain streams studied. High base flows elsewhere in the glaciated northeastern United States are generally associated with large stratified-drift aquifers, however, stratified drift in these two basins accounts for only about 5 percent and 4.4 percent of their respective surface areas, respectively. The high base flows in these two basins appear to correlate with an equally high percentage of massive sandstone members of the Catskill Formation, which underlies the entire region. Ground-water seepage from these sandstone members may be responsible for the high base flows of these two streams.

Water-Resources Investigations Report↗