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USGS2003

Correlation of the Klamath Mountains and Sierra Nevada

This report graphically portrays the broadly parallel tectonic development of the Klamath Mountains and Sierra Nevada from early Paleozoic to Early Cretaceous time. It is dedicated to J.S. Diller of the U.S. Geological Survey who, during his pioneer field studies a century ago, recognized significant similarities between these two important provinces. The report is based mainly on the numerous published reports of the field and laboratory studies by various geologists and students during the last century, and to a lesser extent on my own field work which has been substantial in the Klamath Mountains but minimal in the Sierra Nevada. For brevity, required by the format of this report, little of the extensive literature pertaining to these two provinces is referenced. This report is preliminary in nature and was prepared as an aid to further study of the tectonic relations between the Klamath Mountains and Sierra Nevada. This report consists of two sheets: Sheet 1, Map showing accreted terranes and plutons of the Klamath Mountains and Sierra Nevada, and Sheet 2, Successive accretionary episodes of the Klamath mountains and northern part of Sierra Nevada, showing related plutonic, volcanic, and metamorphic events. The map on Sheet 1 was compiled and modified from two Open-File maps (Irwin and Wooden, 1999 and 2001) which had been compiled and modified mainly from Jennings (1977), Harwood (1992), Irwin (1994), Jayko (1988), Graymer and Jones (1994), Edelman and Sharp (1989), Schweickert and others (1999), Saucedo and Wagner(1992), Saleeby and Sharp (1980), Wagner and others (1981), and various other sources. For detailed lists of the sources for the isotopic age data used in Sheets 1 and 2, see Irwin and Wooden (1999 and 2001). On Sheet 2, the accretionary episodes are shown sequentially from left to right in two tiers of figures. Episodes for the Klamath Mountains are in the upper tier; correlative episodes of the Sierra Nevada are directly below in the lower tier. The sequence shown for the Klamath Mountains is modified from Irwin and Mankinen (1998) and Irwin and Wooden (1999). The episodes are named for the accreting terranes of the Klamath Mountains, but those names may not be suitable for reference to the correlative episodes of the Sierra Nevada. In the figure for each episode, a heavy black line represents the active suture that separated oceanic crustal rocks on the left from the earlier accreted terranes on the right. Plutons are particularly useful for timing the accretionary episodes. The preaccretionary plutons, which commonly represent the roots of oceanic volcanic arcs, are shown in the accreting oceanic crustal rocks to the left of the heavy black line. The accretionary plutons consist of rock that has been subducted and remobilized as magma during the accretionary process and injected into an overlying earlier accreted terrane on the right of the heavy black line. Thus, isotopic dating of the accretionary plutons (preferably U/Pb dates measured on zircon extracted from the plutonic rock) provides a useful basis for assigning ages to the accretionary episodes. Many plutons are rootless at depth, as they tend to be truncated by the subduction zone sutures of younger accreting terranes. Volcanic deposits resulting from accretionary episodes apparently are uncommon except for those deposited on the backstop terranes. In the Klamath Mountains, the Eastern Klamath terrane, which consists of the Yreka, Trinity and Redding subterranes, was the backstop for the Central Metamorphic and younger accretionary episodes, and displays a remarkable record of sedimentation, volcanism and plutonism from Silurian-Devonian to Jurassic time. In the Sierra Nevada, the correlative backstop was the Northern Sierra terrane which shows a similar long record of volcanism in the Taylorsville, Permian, and Jurassic volcanic arc sequences. During some accretionary episodes the subducting oceanic rocks were dynamically metamorphosed to schist along the suture zone beneath the overriding accreted terranes. Examples of this in the Klamath Mountains are the Devonian Salmon and Abrams Schists of the Central Metamorphic terrane, the Triassic(?) schist of the Fort Jones terrane , and the Early Cretaceous South Fork Mountain Schist that structurally underlies Klamath Mountains terranes along much of the western edge of the province. The Fort Jones terrane and South Fork Mountains Schist were metamorphosed under blueschist-facies conditions. In the Sierra Nevada, schist that is correlative with the Central Metamorphic terrane is present in patches along the Feather River terrane (see Hacker and Peacock, 1990); the Triassic(?) Red Ant Schist is correlative with the Fort Jones terrane; but a correlative of the South Fork Mountain Schist is not present. In addition to the similarities in the sequences of accretion, plutonism, volcanism, and metamorphism, strong ties between the two provinces are also provided by paleontologic data. The Permian McCloud fusulinid fauna of the Redding subterrane also is present in the Northern Sierra terrane. Rare Tethyan fusulinids are found in Permian limestone of the Eastern Hayfork terrane of the Klamath Mountains and also in limestone blocks in the Central Belt of the Sierra Nevada. Ichthyosaur fossils have been collected from the Triassic of both the Redding subterrane and Northern Sierra terrane. Jurassic ammonites and the pelecypod Buchia concentrica occur in both the Galice Formation of the western Klamath Mountains and the Mariposa Formation of the western Sierra Nevada. Events that preceded the Central Metamorphic episode prior to Silurian-Devonian time are not clearly understood and are not shown in the succession of diagrams on Sheet 2. The oldest rocks of the Klamath Mountains are Neoproterozic and they predate the Central Metamorphic episode by possibly a hundred million years or more. They include ophiolitic rocks of the Trinity subterrane and the Antelope Mountain Quartzite of the Yreka subterrane (see Mankinen and others, 2002). In the Sierra Nevada, correlatives of the ancient ophiolitic rocks may be part of the Feather River terrane. Although Neoproterozoic fossils have not yet been found in the Sierra Nevada, petrologic study shows the quartzite of the Lang sequence is closely similar to the Antelope Mountain Quartzite (see Bond and Devay, 1980). Correlation of the two quartzite formations is also suggested by the similarity of their positions in the accretionary sequence.

Klamath Mountains, Sierra Nevada↗

USGS2003

Regional sediment budget of the Columbia River littoral cell, USA: Analysis of bathymetric- and topographic-volume change

In this Open-File Report we present calculations of changes in bathymetric and topographic volumes for the Grays Harbor, Willapa Bay, and Columbia River entrances and the adjacent coasts of North Beach, Grayland Plains, Long Beach, and Clatsop Plains for four intervals: pre-jetty - 1920s (Interval 1), 1920s - 1950s (Interval 2), 1950s - 1990s (Interval 3), and 1920s 1990s (Interval 4). This analysis is part of the Southwest Washington Coastal Erosion Study (SWCES), the goals of which are to understand and predict the morphologic behavior of the Columbia River littoral cell on a management scale of tens of kilometers and decades. We obtain topographic Light Detection and Ranging (LIDAR) data from a joint project by the U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), National Aeronautic and Space Administration (NASA), and the Washington State Department of Ecology (DOE) and bathymetric data from the U.S. Coast and Geodetic Survey (USC&GS), U.S. Army Corps of Engineers (USACE), USGS, and the DOE. Shoreline data are digitized from T-Sheets and aerial photographs from the USC&GS and National Ocean Service (NOS). Instead of uncritically adjusting each survey to NAVD88, a common vertical land-based datum, we adjust some surveys to produce optimal results according to the following criteria. First, we minimize offsets in overlapping surveys within the same era, and second, we minimize bathymetric changes (relative to the 1990s) in deep water, where we assume minimal change has taken place. We grid bathymetric and topographic datasets using kriging and triangulation algorithms, calculate bathymetric-change surfaces for each interval, and calculate volume changes within polygons that are overlaid on the bathymetric-change surfaces. We find similar morphologic changes near the entrances to Grays Harbor and the Columbia River following jetty construction between 1898 and 1916 at the Grays Harbor entrance and between 1885 and 1913 at the Columbia River entrance. The inlets and inner deltas eroded and the outer deltas moved offshore and accreted. The adjacent coasts experienced accretion over alongshore distances of tens of kilometers. North of the Grays Harbor entrance along North Beach and north of the Columbia River entrance along Long Beach the shoreface and the beach-dune complex mainly prograded, whereas south of the Grays Harbor entrance along Grayland Plains and south of the Columbia River entrance along Clatsop Plains the beach-dune complex above -10 m NAVD88 prograded and the shoreface between approximately -30 m and -10 m NAVD88 eroded. In the decades following jetty construction, the rates of erosion and accretion at the entrances decreased and the centers of deposition along the adjacent coasts moved away from the entrances. The rates of change have decreased, suggesting the systems are approaching dynamic equilibrium. Exceptions to this behaviour are the accretion of the beach-dune complex of Long Beach, the erosion of Cape Shoalwater, and the northward migration of the Willapa Bay ebb-tidal delta during all intervals. The net shoreline advance of Long Beach increases from 0.28 m/yr in pre-jetty conditions to 3.78 m/yr during Interval 4. The erosion of Cape Shoalwater and the northward migration of the Willapa Bay ebb-tidal delta are related to the northern migration of the Willapa Bay North Channel. Volume changes at the Grays Harbor, Willapa Bay, and Columbia River entrances and the Columbia River estuary are balanced against losses and gains due to littoral transport and sand supply from the Columbia River. Based on these sediment balances, we infer the following pathways: sand that eroded from the inlets and inner deltas at the Grays Harbor and Columbia River entrances moved offshore and northward to accrete the outer deltas and the beaches to the north; sand from the south flank of the Grays Harbor delta and shelf along Grayland Plains moved onshore to accrete the beach dune complex of Grayland Plains and moved northward to maintain accretion of the outer delta and the beach-dune complex of North Beach; sand that eroded from the south flank of the Columbia River delta and shelf along Clatsop Plains contributed to the accretion of the beach-dune complex of Clatsop Plains and the Columbia River outer delta. The net volume change for Interval 1 and 3 at the Grays Harbor entrance and for Interval 1 at the Columbia River entrance is erosion, whereas the net change for the other intervals is accretion. For the entire CRLC, there is a net loss of 185 Mm 3 for Interval 1, a net gain of 357 Mm 3 for Interval 2, and a net gain of 187 Mm 3 for Interval 3. These imbalances can be the result of incomplete bathymetric coverage of the bays and shoreface, uncertainties in the adjustments of vertical tidal datums, inconsistencies in the bathymetric data, and uncertainties in the sediment supply of the Columbia River.

Oregon, Washington↗

USGS2013

Hydraulic and Geomorphic Assessment of the Merced River and Historic Bridges in Eastern Yosemite Valley, Yosemite National Park, California: Sacramento, California

The Merced River in the popular and picturesque eastern-most part of Yosemite Valley in Yosemite National Park, California, USA, has been extensively altered since the park was first conceived in 1864. Historical human trampling of streambanks has been suggested as the cause of substantial increases in stream width, and the construction of undersized stone bridges in the 1920s has been suggested as the major factor leading to an increase in overbank flooding due to deposition of bars and islands between the bridges. In response, the National Park Service at Yosemite National Park (YNP) requested a study of the hydraulic and geomorphic conditions affecting the most-heavily influenced part of the river, a 2.4-km reach in eastern Yosemite Valley extending from above the Tenaya Creek and Merced River confluence to below Housekeeping Bridge. As part of the study, present-day conditions were compared to historical conditions and several possible planning scenarios were investigated, including the removal of an elevated road berm and the removal of three undersized historic stone bridges identified by YNP as potential problems: Sugar Pine, Ahwahnee and Stoneman Bridges. This Open-File Report will be superseded at a later date by a Scientific Investigations Report. A two-dimensional hydrodynamic model, the USGS FaSTMECH (Flow and Sediment Transport with Morphological Evolution of Channels) model, within the USGS International River Interface Cooperative (iRIC) model framework, was used to compare the scenarios over a range of discharges with annual exceedance probabilities of 50-, 20-, 10-, and 5- percent. A variety of topographic and hydraulic data sources were used to create the input conditions to the hydrodynamic model, including aerial LiDAR (Light Detection And Ranging), ground-based LiDAR, total station survey data, and grain size data from pebble counts. A digitized version of a historical topographic map created by the USGS in 1919, combined with estimates of grain size, was used to simulate historical conditions, and the planning scenarios were developed by altering the present-day topography. Roughness was estimated independently of measured water-surface elevations by using the mapped grain-size data and the Keulegan relation of grain size to drag coefficient. The FaSTMECH hydrodynamic model was evaluated against measured water levels by using a 130.9 m 3 s -1 flow (approximately a 33-percent annual exceedance probability flood) with 36 water-surface elevations measured by YNP personnel on June 8, 2010. This evaluation run had a root mean square error of 0.21 m between the simulated- and observed water-surface elevations (less than 10 percent of depth), though the observed water-surface elevations had relatively high variation due to the strong diurnal stage changes over the course of the 4.4-hour collection period, during which discharge varied by about 15 percent. There are presently no velocity data with which to test the model. A geomorphic assessment was performed that consisted of an estimate of the magnitude and frequency of bedload and suspended-sediment transport at “Tenaya Bar”, an important gravel-cobble bar located near the upstream end of the study site that determines the amount of flow across the floodplain at the Sugar Pine – Ahwahnee bend. An analysis of select repeat cross-sections collected by YNP since the late 1980s was done to investigate changes in channel cross-sectional area near the Tenaya Bar site. The results of the FaSTMECH models indicate that the maximum velocities in the present-day channel within the study reach are associated with Stoneman and Sugar Pine Bridges, at close to 3.0 m s -1 for the 5-percent annual exceedance probability flood. The modeled maximum velocities at Ahwahnee Bridge are comparatively low, at between 1.5 and 2.0 m s -1 , most likely due to the bridge's orientation parallel to down-valley floodplain flows. The results of the FaSTMECH models for the bridge removal scenarios indicate a reduction in average velocity at the bridge sites for the range of flows by approximately 23-38 percent (Sugar Pine Bridge), 32-42 percent (Ahwahnee Bridge), and 33-39 percent (Stoneman Bridge), though a side channel of concern to YNP management did not appear to be substantially affected by the removal scenarios. In comparison to the historical data, the FaSTMECH results suggest that flows for present-day conditions do not inundate the floodplain until between the 50- and 20-percent annual exceedance probability flood, whereas historically, a large portion of the floodplain was inundated during the 50-percent annual exceedance probability flood. Modeled maximum velocities in the present-day channel commonly exceed 2.0 m s -1 , whereas with the historical scenario, modeled maximum in-channel velocities rarely exceeded 2.0 m s -1 . The geomorphic analysis of the magnitude-frequency of bedload and suspended-sediment transport suggests that at the important Tenaya Bar site, the majority of bed sediment is mobile during most snowmelt-dominated floods. In contrast to sediment transport capacity, the analysis of repeat cross-sections suggests that bedload sediment supply into the eastern Yosemite Valley may be quite different between rain-on-snow floods and snowmelt-dominated floods, potentially with most sediment supply occurring during rain-on-snow floods, such as the 1997 flood. In contrast, the magnitude-frequency analysis of bedload and suspended-sediment transport suggests that long-term bedload sediment transport is likely dominated by snowmelt floods, and suspended-sediment transport is relatively low compared to bedload transport. Obtaining measured velocity data throughout the study reach would aid in model calibration, and thus would improve confidence in model results. Improved confidence in the model velocity results would allow additional substantial analyses of reach-scale effects of the planning scenarios and would enable the development of geomorphic models to evaluate the long-term geomorphic responses of the site. In addition, the collection of watershed sediment-supply data, about which little is presently known, would give planners helpful tools to plan restoration scenarios for this nationally important river.

California↗

USGS2007

Report on the final completion of the Unified Lunar Control Network 2005 and Lunar Topographic Model

In order to highlight this project to the extraterrestrial mapping community, we repeat here our earlier abstract [1], with a corrected Figure 2. A report describing the Unified Lunar Control Network 2005 and the files associated with that network is now available as an on-line USGS Open-File Report [2] at the location http://pubs.usgs.gov/of/2006/1367/. A “Readme” file describes the available files, including the report text, the original photogrammetric solution input and output files, derived files such as information on all the control point positions, the expected vertical precision (EVP) of the points and the solution residuals, and a directory containing global DEMs derived from the point positions. While a paper providing further details about the solution is in preparation, we provide some useful additional information about the solution and possible uses for it here.

Conference Paper↗

USGS2006

Digital geologic map and GIS database of Venezuela

The digital geologic map and GIS database of Venezuela captures GIS compatible geologic and hydrologic data from the 'Geologic Shaded Relief Map of Venezuela,' which was released online as U.S. Geological Survey Open-File Report 2005-1038. Digital datasets and corresponding metadata files are stored in ESRI geodatabase format; accessible via ArcGIS 9.X. Feature classes in the geodatabase include geologic unit polygons, open water polygons, coincident geologic unit linework (contacts, faults, etc.) and non-coincident geologic unit linework (folds, drainage networks, etc.). Geologic unit polygon data were attributed for age, name, and lithologic type following the Lexico Estratigrafico de Venezuela. All digital datasets were captured from source data at 1:750,000. Although users may view and analyze data at varying scales, the authors make no guarantee as to the accuracy of the data at scales larger than 1:750,000.

Data Series↗

USGS2019

Surficial materials of Massachusetts—A 1:24,000-scale geologic map database

The surficial materials geologic map database defines the distribution of nonlithified earth materials at the land surface in the 189 7.5-minute, 1:24,000-scale quadrangles that cover the Commonwealth of Massachusetts (index map). Across the State, these materials range in thickness from a few feet to more than 500 feet (ft). In some places, surficial materials are absent where bedrock is at the land surface. The geologic map database differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. The mapped distribution of surficial materials defines the areas of exposed bedrock and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits at a 1:24,000-scale level of accuracy. Most of the surficial materials in Massachusetts are deposits of the last two continental ice sheets that covered all of New England in the latter part of the Pleistocene ice age. The glacial deposits are divided into two broad categories, glacial till and moraine deposits, and glacial stratified deposits. Widespread till deposits were laid down directly on bedrock or on semi-consolidated coastal plain strata by glacier ice. Tills in thick-till (>15 ft thick) drumlin landforms are found in all parts of the State. Areas of shallow bedrock contain thin discontinuous till deposits and numerous bedrock outcrops, and are located chiefly in rocky upland areas. Moraine deposits related to glacial ice lobes of the last ice sheet are located mostly in southeastern Massachusetts. Glacial stratified deposits are concentrated in valleys and lowland areas and were laid down by glacial meltwater in streams, lakes, and the sea in front of the retreating ice margin during the last deglaciation. Postglacial deposits, primarily flood-plain alluvium and swamp deposits, make up a lesser proportion of the unconsolidated materials. The geodatabase included with this report contains MapUnitPolys, MapUnitOverlayPolys, and OverlayPolys, which show the distribution of geologic units that cover the entire map area and are intended for use at quadrangle scale (1:24,000). These data layers can be clipped by quadrangle or by town boundary. Unlike the units in conventional geologic maps, the digitally defined MapUnitOverlayPolys are arranged in order according to superposition. The polygons for till and bedrock are on the bottom and are overlain by the succeeding stratified deposits; these materials are shown everywhere they occur, including beneath postglacial deposits such as swamp deposits, and also beneath water bodies. The postglacial deposits are on top because these materials overlie the other, older deposits. Instructions for using the digital files are included in the README file. A series of map figures in the pamphlet illustrates the stacking of geologic units in a portion of the Mount Toby quadrangle. The BaseMaps folder contains the 1:24,000-scale topographic base map images (1944–1977 editions) used for this compilation. This report supersedes U.S. Geological Survey Open-File Reports 2006-1260-A, -B, -C, -D, -E, -F, -G, and -I.

Massachusetts↗

USGS1992

Map showing bottom topography of the Pacific continental margin, Point Conception to Point Loma

All contours, geographic outlines, and political boundaries shown on this map of the bottom topography, or bathymetry, of the Pacific continental margin between 34° and 41° N. latitudes were plotted from digital data bases in the library of the U.S. Geological Survey (USGS)-National Oceanic and Atmospheric Administration (NOAA) Joint Office for Mapping and Research (JOMAR). These digital data were obtained and compiled from many sources; consequently, data quality varies within particular data bases as well as from one data base to another. Bathymetric contours north of 32°N. were digitized from a map by Chase and others (1981) and from the unpublished large scale versions of that map (T. E. Chase, unpublished maps, 1981). South of 32°N, the contours are from unpublished maps (T.E. Chase and B.A. Seekins, unpublished maps, 1989). Chase and others (1981 and unpublished maps) obtained the data for the area seaward of the continental slope (-2000 m depth) primarily from the U.S. Coast and Geodetic Survey (C&GS) 1955 Pacific Exploratory Survey, a systematic and detailed (~8-nmi-trackline spacing) survey between Mexico and Canada. The USGS provided data from cruises S3-78-NC, L2-77-NC, L10-76-NC, K-73-NC, and Bartlett 72. Data were also obtained from Scripps Institution of Oceanography cruises Blue Flash, Kayak B, Scan I, and Seven Tow (Chase and Menard, 1971; Chase and others, 1975). The 200-m contour was derived from the National Ocean Survey charts 1206N-16 (1975a) and 1306N-20 (1975b), and C&GS charts 1206N-15 (1967a) and 1306N-19 (1967b). Sea-floor depths were corrected for sound velocity in sea water using Matthew's (1939) tables. Onshore topographic contours were generated by computer from a modified version of 3-arc-second elevation data provided by the Defense Mapping Agency. The United States digital shoreline was obtained from the NOAA, NOS, Nautical Charting Division, National Atlas files. The coastline of Canada was digitized from Canadian Hydrographic Service bathymetric maps. The primary source of names of the sea floor features was the "Gazetteer of Undersea Features" (Defense Mapping Agency, 1990). Acknowledgments Christopher Hines assisted in the construction of the digital data bases. Reviews and suggestions by Edward C. Escowitz and Florence Wong and advice provided by Will Stettner regarding the cartographic design substantially improved the quality of this map. References Cited Chase, T.E., and Menard, H.W., 1971, Bathymetric atlas of the northeastern Pacific Ocean: U.S. Naval Oceanographic Office Publication 1303, scale 1:2,000,000 at 33° latitude, 48 p. Chase, T.E., Wilde, Pat, and Normark, W.R., 1975, Oceanographic data of the Monterey Deep Sea Fan: San Diego, University of California, Institute of Marine Resources Publication TR 58, scale 1:898,524 at 35° latitude. Chase, T.E., Wilde, Pat, Normark, W.R., Miller, C.P., Seekins, B.A., and Young, J.D., 1981, Offshore topography of the Western United States between 32° and 49° North latitudes: U.S. Geological Survey Open-File Report 81-443, scale 1:864,518 at 38° latitude, 2 sheets. Coast and Geodetic Survey, 1967a, Santa Barbara to Huntington Beach : Coast and Geodetic Survey Bathymetric Map 1206N-15, scale 1:250,000. Coast and Geodetic Survey, 1967b, Southwest of Santa Rosa Island: Coast and Geodetic Survey Bathymetric Map 1306N-19, scale 1:250,000. Defense Mapping Agency, 1990, Gazetteer of undersea features (4th ed.): Washington, D.C., Defense Mapping Agency. Matthews, D.J., 1939, Tables of the velocity of sound in pure water and sea water (2d ed.): London, Admiralty, Hydrographic Department, H.D. 282, 52 p. National Ocean Survey, 1975a, Hungington Beach to Punta Sal Si Puedes: National Ocean Survey Bathymetric Map 1206N-16, scale 1:250,000. National Ocean Survey, 1975b, Cape San Martin to Point Conception: National Ocean Survey Bathymetric Map 1306N-20, scale 1:250,000. index map for I-2089-A

California↗

USGS1992

Map showing bottom topography of the Pacific Continental Margin, Cape Mendocino to Point Conception

All contours, geographic outlines, and political boundaries shown on this map of the bottom topography, or bathymetry, of the Pacific continental margin between 34? and 41? N. latitudes were plotted from digital data bases in the library of the U.S. Geological Survey (USGS)-National Oceanic and Atmospheric Administration (NOAA) Joint Office for Mapping and Research (JOMAR). These digital data were obtained and compiled from many sources; consequently, data quality varies within particular data bases as well as from one data base to another. Bathymetric contours were digitized from a map compiled by Chase and others (1981) and from the unpublished large scale versions of that map (T.E. Chase, unpub. maps, 1981). Data for the area seaward of the continental slope (~2000 m depth) were obtained primarily from the U.S. Coast and Geodetic Survey (C&GS) 1955 Pacific Exploratory Survey, a systematic and detailed (~8 -nmi trackline spacing) survey between Mexico and Canada. The USGS provided data from cruises S3-78-NC, S15-79-NC, L2-77-NC, Ll0-76-NC, and Bartlett 72. Data were also obtained from Scripps Institution of Oceanography cruises Merazine, Blue Flash, Kayak B, Scan I, and Seven Tow (Chase and Menard, 1971; Chase and others, 1975; Wilde and others, 1976; Wilde and others, 1978). The 200-m contour was derived from the National Ocean Survey charts 1306N-20 (1975), 1307N-l1B (1974a), 1307N-18B (1974b), and C&GS chart 1308N-12 (1969). Sea-floor depths were corrected for sound velocity in sea water using Matthew's (1939) tables. Onshore topographic contours were generated by computer from a modified version of 3-arc-second elevation data provided by the Defense Mapping Agency. The United States digital shoreline was obtained from the NOAA, NOS, Nautical Charting Division, National Atlas files. The coastline of Canada was digitized from Canadian Hydrographic Service bathymetric maps. The primary source of names of the sea floor features was the "Gazetteer of Undersea Features" (Defense Mapping Agency, 1990). Acknowledgments Christopher Hines assisted in the construction and verification of the digital data bases. Reviews and suggestions by Edward C. Escowitz and Florence Wong and advice provided by Will Stettner regarding the cartographic design substantially improved the quality of this map. References Cited Chase, T.E., and Menard, H.W., 1971, Bathymetric atlas of the northeastern Pacific Ocean: U.S. Naval Oceanographic Office Publication 1303, scale 1:2,000,000 at 33° latitude, 48 p. Chase, T.E., Wilde, Pat, and Normark, W.R., 1975, Oceanographic data of the Monterey Deep Sea Fan: San Diego, University of California, Institute of Marine Resources Publication TR 58, scale 1:898,524 at 35° latitude. Chase, T.E., Wilde, Pat, Normark, W.R., Miller, C.P., Seekins, B.A., and Young, J.D., 1981, Offshore topography of the Western United States between 32° and 49° North latitudes: U.S. Geological Survey Open-File Report 81-443, scale 1:864,518 at 38° latitude, 2 sheets. Coast and Geodetic Survey, 1969, Point St. George to Point Delgada: Coast and Geodetic Survey Bathymetric Map 1308N-12, scale 1:250,000. Defense Mapping Agency, 1990, Gazetteer of undersea features (4th ed.): Washington, D.C., Defense Mapping Agency. Matthews, D.J., 1939, Tables of the velocity of sound in pure water and sea water (2d ed.): London, Admiralty, Hydrographic Department, H.D. 282, 52 p. National Ocean Survey, 1974a, Vicinity Pt. Sur to Pt. Reyes: National Ocean Survey Bathymetric Map 1307N-11B, scale 1:250,000. National Ocean Survey, 1974b, Pt. Reyes to Tolo Bank: National Ocean Survey Bathymetric Map 1307N-18B, scale 1:250,000. National Ocean Survey, 1975, Cape San Martin to Point Conception: National Ocean Survey Bathymetric Map 1306N-20, scale 1:250,000. Wilde, Pat, Normark, W.R., and Chase, T.E., 1976, Oceanographic data off central California 37° to 40° North including the Delgada Deep Sea Fan: Berkeley, University of California, Lawrence Berkeley Laboratory Publication 92, scale 1 :864,581 at 38° latitude. Wilde, Pat, Chase, T.E., Holmes, M.L., Normark, W.R., Thomas, J.A., McCulloch, D.S., and Kulm, L.D., 1978, Oceanographic data off northern California-southern Oregon 40° to 43° North including the Gorda Deep Sea Fan: Berkeley, University of California, Lawrence Berkeley Laboratory Publication 251, scale 1:815,482 at 42° latitude.

IMAP↗

USGS1992

Map showing bottom topography of the Pacific Continental Margin, Strait of Juan de Fuca to Cape Mendocino

All contours, geographic outlines, and political boundaries shown on this map of the bottom topography, or bathymetry, of the Pacific continental margin between 34° and 41° N. latitudes were plotted from digital data bases in the library of the U.S. Geological Survey (USGS)-National Oceanic and Atmospheric Administration (NOAA) Joint Office for Mapping and Research (JOMAR). These digital data were obtained and compiled from many sources; consequently, data quality varies within particular data bases as well as from one data base to another. Bathymetric contours were digitized from a map compiled by Chase and others (1981) and from the unpublished large scale versions of that map (T.E. Chase, unpub. maps, 1981). Data for the area seaward of the continental slope (~2000 m depth) were obtained primarily from the U.S. Coast and Geodetic Survey (C&GS) 1955 Pacific Exploratory Survey, a systematic and detailed (~8 -nmi trackline spacing) survey between Mexico and Canada. The USGS provided data from cruises S3-78-NC, S15-79-NC, L2-77-NC, Ll0-76-NC, and Bartlett 72. Data were also obtained from Scripps Institution of Oceanography cruises Merazine, Blue Flash, Kayak B, Scan I, and Seven Tow (Chase and Menard, 1971; Chase and others, 1975; Wilde and others, 1976; Wilde and others, 1978). The 200-m contour was derived from the National Ocean Survey charts 1306N-20 (1975), 1307N-l1B (1974a), 1307N-18B (1974b), and C&GS chart 1308N-12 (1969). Sea-floor depths were corrected for sound velocity in sea water using Matthew's (1939) tables. Onshore topographic contours were generated by computer from a modified version of 3-arc-second elevation data provided by the Defense Mapping Agency. The United States digital shoreline was obtained from the NOAA, NOS, Nautical Charting Division, National Atlas files. The coastline of Canada was digitized from Canadian Hydrographic Service bathymetric maps. The primary source of names of the sea floor features was the "Gazetteer of Undersea Features" (Defense Mapping Agency, 1990). Acknowledgments Christopher Hines assisted in the construction and verification of the digital data bases. Reviews and suggestions by Edward C. Escowitz and Florence Wong and advice provided by Will Stettner regarding the cartographic design substantially improved the quality of this map. References Cited Chase, T.E., and Menard, H.W., 1971, Bathymetric atlas of the northeastern Pacific Ocean: U.S. Naval Oceanographic Office Publication 1303, scale 1:2,000,000 at 33° latitude, 48 p. Chase, T.E., Wilde, Pat, and Normark, W.R., 1975, Oceanographic data of the Monterey Deep Sea Fan: San Diego, University of California, Institute of Marine Resources Publication TR 58, scale 1:898,524 at 35° latitude. Chase, T.E., Wilde, Pat, Normark, W.R., Miller, C.P., Seekins, B.A., and Young, J.D., 1981, Offshore topography of the Western United States between 32° and 49° North latitudes: U.S. Geological Survey Open-File Report 81-443, scale 1:864,518 at 38° latitude, 2 sheets Coast and Geodetic Survey, 1969, Point St. George to Point Delgada: Coast and Geodetic Survey Bathymetric Map 1308N-12, scale 1:250,000. Defense Mapping Agency, 1990, Gazetteer of undersea features (4th ed.): Washington, D.C., Defense Mapping Agency. Matthews, D.J., 1939, Tables of the velocity of sound in pure water and sea water (2d ed.): London, Admiralty, Hydrographic Department, H.D. 282, 52 p. National Ocean Survey, 1974a, Vicinity Pt. Sur to Pt. Reyes: National Ocean Survey Bathymetric Map 1307N-11B, scale 1:250,000. National Ocean Survey, 1974b, Pt. Reyes to Tolo Bank: National Ocean Survey Bathymetric Map 1307N-18B, scale 1:250,000. National Ocean Survey, 1975, Cape San Martin to Point Conception: National Ocean Survey Bathymetric Map 1306N-20, scale 1:250,000. Wilde, Pat, Normark, W.R., and Chase, T.E., 1976, Oceanographic data off central California 37° to 40° North including the Delgada Deep Sea Fan: Berkeley, University of California, Lawrence Berkeley Laboratory Publication 92, scale 1 :864,581 at 38° latitude. Wilde, Pat, Chase, T.E., Holmes, M.L., Normark, W.R., Thomas, J.A., McCulloch, D.S., and Kulm, L.D., 1978, Oceanographic data off northern California-southern Oregon 40° to 43° North including the Gorda Deep Sea Fan: Berkeley, University of California, Lawrence Berkeley Laboratory Publication 251, scale 1:815,482 at 42° latitude.

IMAP↗

USGS1993

Undiscovered oil and gas resources and leasing status of forestlands in Wyoming

All of four national forests, one national grassland, and parts of four additional forests lie within the State of Wyoming. Some of these National Forest System lands have moderate to high potential for undiscovered oil and gas resources. In the 1989 National Assessment of undiscovered oil and gas and in various Open-File Reports, the U.S. Geological Survey described oil and gas plays and presented estimates of recoverable conventional oil and gas resources for these plays. Estimated resources in plays affecting NFS lands in Wyoming are substantial. Of special significance are undiscovered recoverable conventional resources (mean estimate) of approximately 1,010 million barrels of oil, 10,611 billion cubic feet of gas, and 188 million barrels of natural gas liquids assessed in ten plays that include National Forest System lands in the Thunder Basin National Grassland and the Bridger-Teton, Targhee, Caribou, and Shoshone National Forests in Wyoming. Approximately 5,715,570 acres in the forests and grassland are available for leasing or are expected to be available for leasing by mid-1993. Poor accessibility, environmental concerns, and geologic factors such as complex structure and greater drilling depths to potential reservoirs may cause higher exploration risks and operating costs on NFS lands. However, cooperative arrangements with the U.S. Forest Service, in addition to carefully planned exploration and development programs, can facilitate operations in remote and environmentally sensitive areas, and could result in opening new exploration frontiers in Wyoming.

Book chapter↗

USGS2011

Mars Global Digital Dune Database (MGD3): North polar region (MC-1) distribution, applications, and volume estimates

The Mars Global Digital Dune Database (MGD 3 ) now extends from 90°N to 65°S. The recently released north polar portion (MC‐1) of MGD 3 adds ~844 000 km 2 of moderate‐ to large‐size dark dunes to the previously released equatorial portion (MC‐2 to MC‐29) of the database. The database, available in GIS‐ and tabular‐format in USGS Open‐File Reports, makes it possible to examine global dune distribution patterns and to compare dunes with other global data sets (e.g. atmospheric models). MGD 3 can also be used by researchers to identify areas suitable for more focused studies. The utility of MGD 3 is demonstrated through three example applications. First, the uneven geographic distribution of the dunes is discussed and described. Second, dune‐derived wind direction and its role as ground truth for atmospheric models is reviewed. Comparisons between dune‐derived winds and global and mesoscale atmospheric models suggest that local topography may have an important influence on dune‐forming winds. Third, the methods used here to estimate north polar dune volume are presented and these methods and estimates (1130 km 3 to 3250 km 3 ) are compared with those of previous researchers (1158 km 3 to 15 000 km 3 ). In the near future, MGD 3 will be extended to include the south polar region.

Earth Surface Processes and Landforms↗

USGS1991

A microcomputer program for energy assessment and aggregation using the triangular probability distribution

A general risk-analysis method was developed for petroleum-resource assessment and other applications. The triangular probability distribution is used as a model with an analytic aggregation methodology based on probability theory rather than Monte-Carlo simulation. Among the advantages of the analytic method are its computational speed and flexibility, and the saving of time and cost on a microcomputer. The input into the model consists of a set of components (e.g. geologic provinces) and, for each component, three potential resource estimates: minimum, most likely (mode), and maximum. Assuming a triangular probability distribution, the mean, standard deviation, and seven fractiles (F100, F95, F75, F50, F25, F5, and F0) are computed for each component, where for example, the probability of more than F95 is equal to 0.95. The components are aggregated by combining the means, standard deviations, and respective fractiles under three possible siutations (1) perfect positive correlation, (2) complete independence, and (3) any degree of dependence between these two polar situations. A package of computer programs named the TRIAGG system was written in the Turbo Pascal 4.0 language for performing the analytic probabilistic methodology. The system consists of a program for processing triangular probability distribution assessments and aggregations, and a separate aggregation routine for aggregating aggregations. The user's documentation and program diskette of the TRIAGG system are available from USGS Open File Services. TRIAGG requires an IBM-PC/XT/AT compatible microcomputer with 256kbyte of main memory, MS-DOS 3.1 or later, either two diskette drives or a fixed disk, and a 132 column printer. A graphics adapter and color display are optional. ?? 1991.

Computers & Geosciences↗

USGS1994

JKPLOT version 2.00: A device-independent plotting system written in QuickBasic for an IBM PC

Version 2.0 of JKPLOT is a simple, device-independent plotting system that can provide a base for building plotting facilities tailored to the needs of geologists. The programs were written in Microsoft QuickBasic for use on equipment compatible with an IBM personal computer. The system provides subroutines and functions for plotting in both 2 and 3 dimensions with the capability for making scaled plots with annotated axes. Plot output can be directed to the PC screen, an Epson printer, any HPGL pen plotter, or an HP laser printer. The user's documentation and program diskettes of the JKPLOT system are available from U.S. Geological Survey Open File Services. ?? 1994.

Computers & Geosciences↗

USGS1990

Modern aerial gamma-ray spectrometry and regional potassium map of the conterminous United States

Aerial gamma-ray surveys of the natural environment measure the flux of gamma rays produced by the radioactive decay of 40 K, 214 Bi, and 208 Tl in the upper 10–20 cm of surface materials. 40 K is a radioactive potassium isotope which can be used to estimate the total amount of potassium in the soils and rocks. 214 Bi is a decay product of the 238 U radioactive decay series and is used to estimate the uranium concentrations, and 208 Tl, a decay product of the 232 Th radioactive decay series, is used to estimate thorium concentrations. Aerial gamma-ray data covering the 48 contiguous states of the United States have been compiled to produce maps showing the distributions of equivalent uranium, equivalent thorium, and potassium. This compilation involved processing the aerial survey data from about 470 1° × 2° quadrangle maps. The aerial gamma-ray data were obtained as part of the National Uranium Resource Evaluation (NURE) Program sponsored by the U.S. Department of Energy during the period 1975-1983. References for the Open-File Reports that describe the surveys and data collection can be found in Bendix Field Engineering Corp. (1983). The aerial surveys were flown by contractors using fixed-wing and helicopter systems with 33-50 L (liters) of thallium-activated sodium iodide (NaI (TI)) crystals. The nominal survey altitude used is 122 m. The survey lines were generally east-west with line spacings of 1.6-10 km. Tie lines were flown perpendicular to the flight lines at intervals of 16- 30 km. The data were corrected for background from aircraft contamination and cosmic rays, altitude variations, airborne 214Bi, and Compton scattering. The gamma-ray systems were calibrated using the calibrations pads at Grand Junction, Colorado (Ward, 1978 ) and the dynamic test strip at Lake Mead, Arizona (Geodata International, Inc., 1977).

Journal of Geochemical Exploration↗

USGS2004

Gas evolution in eruptive conduits: Combining insights from high temperature and pressure decompression experiments with steady-state flow modeling

In this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma. We use the results of published high temperature and pressure decompression experiments as input to a modified version of CONFLOW, the numerical model of Mastin and Ghiorso [(2000) U.S.G.S. Open-File Rep. 00-209, 53 pp.] and Mastin [(2002) Geochem. Geophys. Geosyst. 3, 10.1029/2001GC000192] for steady, two-phase flow in vertical conduits. Synthesis of the available experimental data shows that heterogeneous nucleation is triggered at ΔP <5–20 MPa in water-saturated rhyolite and leads to equilibrium degassing through a discrete nucleation event. Typically 10 5 –10 7 bubbles/cm 3 are produced which evolve Gaussian bubble size distributions. Homogeneous nucleation requires ΔP >120–150 MPa, and leads to disequilibrium degassing at extreme H 2 O supersaturation. In this latter case, nucleation is an ongoing process controlled by changing supersaturation conditions. Exponential bubble size distributions are often produced with number densities of 10 6 –10 9 bubbles/cm 3 . Our numerical analysis adopts an end-member approach that specifically compares equilibrium degassing with delayed, disequilibrium degassing characteristic of homogeneously-nucleating systems. The disequilibrium simulations show that delaying nucleation until ΔP =150 MPa restricts degassing to within ∼1500 m of the surface. Fragmentation occurs at similar porosity in both the disequilibrium and equilibrium modes (∼80 vol%), but at the distinct depths of ∼500 m and ∼2300 m, respectively. The vesiculation delay leads to higher pressures at equivalent depths in the conduit, and the mass flux and exit pressure are each higher by a factor of ∼2.0. Residual water contents in the melt reaching the vent are between 0.5 and 1.0 wt%, roughly twice that of the equilibrium model.

Journal of Volcanology and Geothermal Research↗

USGS2011

Studying geodesy and earthquake hazard in and around the New Madrid Seismic Zone

Workshop on New Madrid Geodesy and the Challenges of Understanding Intraplate Earthquakes; Norwood, Massachusetts, 4 March 2011 Twenty-six researchers gathered for a workshop sponsored by the U.S. Geological Survey (USGS) and FM Global to discuss geodesy in and around the New Madrid seismic zone (NMSZ) and its relation to earthquake hazards. The group addressed the challenge of reconciling current geodetic measurements, which show low present-day surface strain rates, with paleoseismic evidence of recent, relatively frequent, major earthquakes in the region. The workshop presentations and conclusions will be available in a forthcoming USGS open-file report (http://pubs.usgs.gov).

Eos, Transactions, American Geophysical Union↗

USGS1981

New maps of Federal coal

Compilation and analysis of publicly available data on Federal coal are resulting in voluminous map sets showing coal isopachs, structure contours, and overburden isopachs on each known minable coal bed. As of the spring of 1981, there are available from the U.S. Geological Survey Open-File Services Section in Denver map sets at 1:24,000 scale or microfiche sets covering approximately 470 of the ultimately 1,400 quadrangles in the program. Because Congress in 1976 mandated the prompt “inventorying” of all unleased Federal coal for Government land-use planning, and because dollars but not employee positions were provided for the work, the U.S. Geological Survey was obliged to contract for the compilations. A typical map set has a short text and about 20 plates, including a data sheet; a Federal mineral ownership map; and correlation charts. For each coal bed, there are isopachs, structure contours, stripping limits, and mining ratios extending as far as the data will permit, regardless of coal ownership. Reserve base tonnages and relative development potentials are calculated, but only for unleased Federal coal areas. Termed “minable” are coal beds at least 1.524 m (5 ft) thick and less than 914.4 m (3,000 ft) deep. For conventional underground mining methods, beds dipping more than 15° are excluded; also excluded are all but 3.66 m (12 ft) of thick beds. For in situ conversion methods, the minimum dip is 15° except for the deep thick beds in the Powder River Basin. Arbitrary parameters classify the development potential of each unleased 16.19-hectare (40-acre) tract as high, moderate, low, unknown, or negative. The former Secretary of the Interior announced his intention to restrict leasing in general to tracts classified as having high to moderate potential for development. Many geologists will find these systematic map compilations to be useful bases for adding new data points and making their own interpretations, correlations, extrapolations, and reserve estimates.

Geological Society of America Bulletin↗

USGS2021

Paleozoic and Mesozoic tectonic events west of the Waterbury Dome: Results of new mapping in the western Connecticut Highlands

This field trip highlights the results of recent U.S. Geological Survey (USGS) bedrock geologic mapping in four 7.5 min quadrangles in the western Connecticut highlands near Southbury, Connecticut, USA. The rocks are broadly within what Rodgers (1985) called the Hartland and Gneiss Dome belts of the Connecticut Valley Synclinorium ( Rodgers, 1985 ; Fig. 1 ), the latter of which is now known as the Connecticut Valley–Gaspe Trough (Hibbard et al., 2006). The mapping occurred over two intervals: 2003–2005 and 2016–present. In the first, the goal was a detailed map of the early Mesozoic Pomperaug basin, which overlaps the four quadrangles. Portions of the basin had been separately mapped during the statewide 7.5 min quadrangle mapping campaign spanning the 1950s–1970s, resulting in an inaccurate depiction of the basin on the 1985 state geologic map ( Rodgers, 1985 ). A new map of the basin was proposed in part to benefit an ongoing project by the USGS Connecticut Water Science Center to determine the contributions of natural and artificial contaminants to a public water-supply well in Woodbury, Connecticut, under the National Water-Quality Assessment (NAWQA) Program ( Starn and Brown, 2007) . The NAWQA project was partially funded by the Pomperaug River Watershed Coalition, which also provided logistical support to the geologic mapping project. Mapping of the basin was also a high priority for the Connecticut State Geologist at the time (Ralph Lewis, 2002, pers. comm.). The mapping resulted in an NEIGC (New England Intercollegiate Geologic Conference) field guide ( Burton et al., 2005) and a 1:12,000-scale USGS open-file map ( Burton, 2006) and was funded by the USGS National Cooperative Geologic Mapping Program (NCGMP). The second phase of the mapping began in 2016 after the discovery of elevated levels of uranium and arsenic in domestic water wells in the igneous and metamorphic rocks that surround the sedimentary and volcanic rocks of the Pomperaug basin ( Flanagan and Brown, 2017) . Structural measurements in the surrounding crystalline rocks were made during Pomperaug basin mapping to better understand the tectonic setting, but a revision of the crystalline map units on Rodgers’ 1985 geologic map was not attempted. Nonetheless, discrepancies were noted between the new mapping and the 1985 map, particularly within the two northern quadrangles of Woodbury and Roxbury, which were originally mapped by Gates (1954) and Gates (1959) , respectively. Based on these discrepancies, a new NCGMP project was proposed to remap the Woodbury and Roxbury 7.5 min quadrangles, commencing in the fall of 2016. The expected USGS product will be a two-quadrangle, 1:24,000-scale Scientific Investigations Map (SIM). This field guide is not meant as a comprehensive review of all of the geologic research done in this area of Connecticut; rather, it looks at previous bedrock geologic mapping from the perspective of new and recent mapping in the four-quadrangle area and discusses the structural, stratigraphic, and nomenclatural revisions necessary for the next revision of the state geologic map.

Connecticut↗