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Research about Canada;United States

Source-linked reports with geographic coverage including Canada;United States.

At least 73 records · Page 4Linked to original sources
USGS2010

A model for Iapetan rifting of Laurentia based on Neoproterozoic dikes and related rocks

Geologic evidence of the Neoproterozoic rifting of Laurentia during breakup of Rodinia is recorded in basement massifs of the cratonic margin by dike swarms, volcanic and plutonic rocks, and rift-related clastic sedimentary sequences. The spatial and temporal distribution of these geologic features varies both within and between the massifs but preserves evidence concerning the timing and nature of rifting. The most salient features include: (1) a rift-related magmatic event recorded in the French Broad massif and the southern and central Shenandoah massif that is distinctly older than that recorded in the northern Shenandoah massif and northward; (2) felsic volcanic centers at the north ends of both French Broad and Shenandoah massifs accompanied by dike swarms; (3) differences in volume between massifs of cover-sequence volcanic rocks and rift-related clastic rocks; and (4) WNW orientation of the Grenville dike swarm in contrast to the predominately NE orientation of other Neoproterozoic dikes. Previously proposed rifting mechanisms to explain these features include rift-transform and plume–triple-junction systems. The rift-transform system best explains features 1, 2, and 3, listed here, and we propose that it represents the dominant rifting mechanism for most of the Laurentian margin. To explain feature 4, as well as magmatic ages and geochemical trends in the Northern Appalachians, we propose that a plume–triple-junction system evolved into the rift-transform system. A ca. 600 Ma mantle plume centered east of the Sutton Mountains generated the radial dike swarm of the Adirondack massif and the Grenville dike swarm, and a collocated triple junction generated the northern part of the rift-transform system. An eastern branch of this system produced the Long Range dike swarm in Newfoundland, and a subsequent western branch produced the ca. 554 Ma Tibbit Hill volcanics and the ca. 550 Ma rift-related magmatism of Newfoundland.

GSA Memoirs↗
USGS2009

Comparison of precipitation chemistry measurements obtained by the Canadian Air and Precipitation Monitoring Network and National Atmospheric Deposition Program for the period 1995-2004

Precipitation chemistry and depth measurements obtained by the Canadian Air and Precipitation Monitoring Network (CAPMoN) and the US National Atmospheric Deposition Program/National Trends Network (NADP/NTN) were compared for the 10-year period 1995–2004. Colocated sets of CAPMoN and NADP instrumentation, consisting of precipitation collectors and rain gages, were operated simultaneously per standard protocols for each network at Sutton, Ontario and Frelighsburg, Ontario, Canada and at State College, PA, USA. CAPMoN samples were collected daily, and NADP samples were collected weekly, and samples were analyzed exclusively by each network’s laboratory for pH, H + , Ca 2+ , Mg 2+ , Na + , K + , NH + 4 , Cl − , NO − 3 , and SO 2− 4 . Weekly and annual precipitation-weighted mean concentrations for each network were compared. This study is a follow-up to an earlier internetwork comparison for the period 1986–1993, published by Alain Sirois, Robert Vet, and Dennis Lamb in 2000. Median weekly internetwork differences for 1995–2004 data were the same to slightly lower than for data for the previous study period (1986–1993) for all analytes except NO − 3 , SO 2− 4 , and sample depth. A 1994 NADP sampling protocol change and a 1998 change in the types of filters used to process NADP samples reversed the previously identified negative bias in NADP data for hydrogen-ion and sodium concentrations. Statistically significant biases (α = 0.10) for sodium and hydrogen-ion concentrations observed in the 1986–1993 data were not significant for 1995–2004. Weekly CAPMoN measurements generally are higher than weekly NADP measurements due to differences in sample filtration and field instrumentation, not sample evaporation, contamination, or analytical laboratory differences.

Environmental Monitoring and Assessment↗
USGS2009

Statistical and Spatial Analysis of Bathymetric Data for the St. Clair River, 1971-2007

To address questions concerning ongoing geomorphic processes in the St. Clair River, selected bathymetric datasets spanning 36 years were analyzed. Comparisons of recent high-resolution datasets covering the upper river indicate a highly variable, active environment. Although statistical and spatial comparisons of the datasets show that some changes to the channel size and shape have taken place during the study period, uncertainty associated with various survey methods and interpolation processes limit the statistically certain results. The methods used to spatially compare the datasets are sensitive to small variations in position and depth that are within the range of uncertainty associated with the datasets. Characteristics of the data, such as the density of measured points and the range of values surveyed, can also influence the results of spatial comparison. With due consideration of these limitations, apparently active and ongoing areas of elevation change in the river are mapped and discussed.

Michigan;Ontario↗
USGS2007

Tectonic setting and metallogenesis of volcanogenic massive sulfide deposits in the Bonnifield Mining District, Northern Alaska Range: Chapter B in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

This paper summarizes the results of field and laboratory investigations, including whole-rock geochemistry and radiogenic isotopes, of outcrop and drill core samples from volcanogenic massive sulfide (VMS) deposits and associated metaigneous rocks in the Wood River area of the Bonnifield mining district, northern Alaska Range (see fig. 1 of Editors’ Preface and Overview). U-Pb zircon igneous crystallization ages from felsic rocks indicate a prolonged period of Late Devonian to Early Mississippian (373±3 to 357±4 million years before present, or Ma) magmatism. This magmatism occurred in a basinal setting along the ancient Pacific margin of North America. The siliceous and carbonaceous compositions of metasedimentary rocks, Precambrian model ages based on U-Pb dating of zircon and neodymium ages, and for some units, radiogenic neodymium isotopic compositions and whole-rock trace-element ratios similar to those of continental crust are evidence for this setting. Red Mountain (also known as Dry Creek) and WTF, two of the largest VMS deposits, are hosted in peralkaline metarhyolite of the Mystic Creek Member of the Totatlanika Schist. The Mystic Creek Member is distinctive in having high concentrations of high-field-strength elements (HFSE) and rare-earth elements (REE), indicative of formation in a within-plate (extensional) setting. Mystic Creek metarhyolite is associated with alkalic, within-plate basalt of the Chute Creek Member; neodymium isotopic data indicate an enriched mantle component for both members of this bimodal (rhyolite-basalt) suite. Anderson Mountain, the other significant VMS deposit, is hosted by the Wood River assemblage. Metaigneous rocks in the Wood River assemblage span a wide compositional range, including andesitic rocks, which are characteristic of arc volcanism. Our data suggest that the Mystic Creek Member likely formed in an extensional, back-arc basin that was associated with an outboard continental-margin volcanic arc that included rocks of the Wood River assemblage. We suggest that elevated HFSE and REE trace-element contents of metavolcanic rocks, whose major-element composition may have been altered, are an important prospecting tool for rocks of VMS deposit potential in east-central Alaska.

Alaska;Yukon↗
USGS2007

Matching magnetic trends and patterns across the Tintina fault, Alaska and Canada--evidence for offset of about 490 kilometers: Chapter C in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

Magnetic anomaly patterns on opposite sides of the mapped Tintina fault in eastern Alaska and western Canada show an apparent offset of about 490 kilometers (km), probably of Eocene age. This estimate is compared with previous geologically based estimates of 400 to 430 km and paleomagnetically based estimates of more than 1,100 km. The apparent geophysical alignments have geologic implications that deserve further study.

Alaska;Yukon↗
USGS2007

The Black Mountain tectonic zone--a reactivated northeast-trending crustal shear zone in the Yukon-Tanana Upland of east-central Alaska: Chapter D in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

The Black Mountain tectonic zone in the YukonTanana terrane of east-central Alaska is a belt of diverse northeast-trending geologic features that can been traced across Black Mountain in the southeast corner of the Big Delta 1°×3° degree quadrangle. Geologic mapping in the larger scale B1 quadrangle of the Big Delta quadrangle, in which Black Mountain is the principal physiographic feature, has revealed a continuous zone of normal and left-lateral strikeslip high-angle faults and shear zones, some of which have late Tertiary to Quaternary displacement histories. The tectonic zone includes complexly intruded wall rocks and intermingled apophyses of the contiguous mid-Cretaceous Goodpaster and Mount Harper granodioritic plutons, mafic to intermediate composite dike swarms, precious metal mineralization, early Tertiary volcanic activity and Quaternary fault scarps. These structures define a zone as much as 6 to 13 kilometers (km) wide and more than 40 km long that can be traced diagonally across the B1 quadrangle into the adjacent Eagle 1°×3° quadrangle to the east. Recurrent activity along the tectonic zone, from at least mid-Cretaceous to Quaternary, suggests the presence of a buried, fundamental tectonic feature beneath the zone that has influenced the tectonic development of this part of the Yukon-Tanana terrane. The tectonic zone, centered on Black Mountain, lies directly above a profound northeast-trending aeromagnetic anomaly between the Denali and Tintina fault systems. The anomaly separates moderate to strongly magnetic terrane on the northwest from a huge, weakly magnetic terrane on the southeast. The tectonic zone is parallel to the similarly oriented left-lateral, strike-slip Shaw Creek fault zone 85 km to the west.

Alaska;Yukon↗
USGS2007

Mapping known and potential mineral occurrences and host rocks in the Bonnifield Mining District using minimal cloud- and snow-cover ASTER data: Chapter E in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

On July 8, 2003, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor acquired satellite imagery of a 60-kilometer-wide swath covering a portion of the Bonnifield mining district within the southernmost part of the Tintina Gold Province, Alaska, under unusually favorable conditions of minimal cloud and snow cover. Although rocks from more than eight different lithotectonic terranes are exposed within the extended swath of data, we focus on volcanogenic massive sulfides (VMS) and porphyry deposits within the Yukon-Tanana terrane (YTT), the largest Mesozoic accretionary terrane exposed between the Denali fault system to the south of Fairbanks and the Tintina fault system to the north of Fairbanks. Comparison of thermal-infrared region (TIR) decorrelation stretch data to available geologic maps indicates that rocks from the YTT contain a wide range of rock types ranging in composition from mafic metavolcanic rocks to felsic rock types such as metarhyolites, pelitic schists, and quartzites. The nine-band ASTER visible-near-infrared region--short-wave infrared region (VNIR-SWIR) reflectance data and spectral matched-filter processing were used to map hydrothermal alteration patterns associated with VMS and porphyry deposit types. In particular, smectite, kaolinite, opaline silica, jarosite and (or) other ferric iron minerals defined narrow (less than 250-meter diameter) zonal patterns around Red Mountain and other potential VMS targets. Using ASTER we identified some of the known mineral deposits in the region, as well as mineralogically similar targets that may represent potential undiscovered deposits. Some known deposits were not identified and may have been obscured by vegetation or snow cover or were too small to be resolved.

Alaska;Yukon↗
USGS2007

Aufeis accumulations in stream bottoms in arctic and subarctic environments as a possible indicator of geologic structure: Chapter F in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

Thick accumulations of ice, called “aufeis,” form during winter along stream and river valleys in arctic and subarctic regions. In high-gradient alpine streams, aufeis forms mostly as a result of ground-water discharge into the stream channel. The ice occludes this discharge, perturbing the steady-state condition, and causing an incremental rise in the local water table until discharge occurs higher on the stream bank above the previously formed ice. Successive freezing of onlapping ice layers can lead to aufeis accumulations several meters thick. The location and extent of aufeis in high-gradient streams may be useful to relate local hydrology to geologic structure. In the Goodpaster River basin study area, mineral deposits are known to occur, the location of which may be structurally controlled. Therefore, a more thorough understanding of regional geologic structures may facilitate a more detailed understanding of the genesis of the mineral deposits. Extensive aufeis was observed during visits to the Goodpaster River basin in east-central Alaska during 1999, 2001, and 2002. Seeps from the sides of the valleys caused ice to build up, giving the ice surface a concave-upward shape perpendicular to the stream direction. This concavity is evidence for ground-water discharge along the length of the aufeis, as opposed to discharge from a single upstream point. During thaw, streamflow is commonly observed out of the normal channel, evidence that occlusion of the channel (and shallow sediments) by ice is a viable mechanism for causing the water table to rise. The thickest (>3 meters) and most extensive aufeis (100’s of meters to kilometers along valleys) coincided with locations of laterally extensive (>5 kilometers) mapped high-angle brittle fault zones, suggesting that the fault zones are hydraulically conductive. Additional evidence of water flow is provided by observed changes in stream-water chemistry in reaches in which aufeis forms, despite a lack of surface tributaries. Minor or no aufeis was observed in many other drainage valleys where no laterally extensive structures have been mapped, implying that aufeis formation results from more than a topographic effect or discharge from bank storage. Thus, the presence of thick, laterally extensive aufeis in highgradient streams may be a useful aid to geologic structural mapping in arctic and subarctic climates.

Alaska;Yukon↗
USGS2007

Surface-water, ground-water, and sediment geochemistry of epizonal and shear-hosted mineral deposits in the Tintina Gold Province--arsenic and antimony distribution and mobility: Chapter G in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

Epigenetic mineral deposits in the Tintina Gold Province are generally characterized by high concentrations of arsenic and antimony in their mineral assemblage. A total of 347 samples (ground water, surface water, and stream sediment) were collected to investigate the distribution and mobility of arsenic and antimony in the environment near known mineral deposits. Samples were collected from east to west at Keno Hill and Brewery Creek, Yukon, Canada; and Cleary Hill, True North, Scrafford Mine, Fairbanks, Ryan Lode, Stampede Creek, Slate Creek, and Donlin Creek, all in Alaska. Surface- and ground-water samples are all slightly acidic to near-neutral in pH (5-8), have a wide range in specific conductance (surface water 17-2,980 microsiemens per centimeter and ground water 170-2,940 microsiemens per centimeter), and show elevated dissolved arsenic and antimony concentrations (arsenic in surface water is less than 1 to 380 micrograms per liter and in ground water is less than 1 micrograms per liter to 1.5 milligrams per liter; antimony in surface water is less than 2 to 660 micrograms per liter and in ground water is less than 2 to 60 micrograms per liter). Stream sediments downstream from these deposits have high concentrations of arsenic and antimony (arsenic median is 1,670 parts per million, maximum is 10,000 parts per million; antimony median is 192 parts per million, maximum is 7,200 parts per million). The mobility of arsenic and antimony is controlled by the local redox environment, with arsenic being less mobile in oxidized surface waters relative to antimony, and arsenic more mobile in reduced ground water. These factors suggest that both antimony and arsenic may be useful pathfinder elements in water and sediment for targeting similar style deposits elsewhere in the Tintina Gold Province.

Alaska;Yukon↗
USGS2007

Landscape geochemistry near mineralized areas of eastern Alaska: Chapter H in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

The Pogo lode gold deposit was discovered in eastern Alaska in the early 1990s and provided the opportunity to study elemental distribution and mobility in the natural environment prior to mine development. Studying mineralized systems prior to mining allows us to compare the natural biogeochemical signature in mineralized versus nonmineralized areas. The resultant data and interpretation also provide a baseline for evaluating what, if any, changes in elemental distribution result from development. This report investigates the chemistry of stream water, streambed sediment, and soil in the context of regional bedrock geology. The major-ion chemistry of the waters reflects a rock-dominated aqueous system, and the waters are classified as Ca 2+ and Mg 2+ - HCO 3 - to Ca 2+ and Mg 2+ - SO 4 -2 waters. Creeks draining the gneissic lithologies tend to be more sulfate dominated than those draining the intrusive units. Sulfate also dominated creeks draining mineralized areas; however, the underlying paragneiss unit could be contributing substantially to the sulfate concentration, and the sulfate concentration in these creeks may reflect a complex baltholith-paragneiss boundary rather than mineralization. Arsenic concentrations in bed sediments were elevated in mineralized areas relative to nonmineralized areas. Elevated concentrations of nickel, chromium, iron, manganese, and cobalt appear to reflect the presence of ultramafic rocks in the drainage. In general, aqueous metal concentrations were below the State of Alaska’s Aquatic Life Criteria and Drinking Water Standards, with the exception of arsenic in stream water, which ranged in concentration from less than 1 to 14 micrograms per liter (μg/L) and exceeded the drinking water standard at one site. The arsenic and antimony concentration in the A, B, and C soil horizons ranged from 3 to 410 milligrams per kilogram (mg/kg), 6.1 to 440 mg/kg, and 2 to 300 mg/kg, respectively, for arsenic and 0.4 to 24 mg/kg, 0.6 to 25 mg/kg, and 0.2 to 16 mg/kg, respectively, for antimony. The arsenic and antimony concentrations in stream waters correlate well with the concentrations in soils. However, significantly less arsenic and antimony was extracted from C horizon soils in water leaching experiments, indicating that the arsenic and antimony in the C horizon is present in a less available form than in the A or B horizons. Arsenic and antimony uptake by grayleaf willow (Salix glauca L.) appears minimal, with arsenic concentrations ranging from less than 0.01 to 0.14 mg/kg and antimony concentrations ranging from less than 0.003 to 0.23 mg/kg in willow leaves. In general, the highest concentrations of both arsenic and antimony in water and soils were found near mineralized areas. Elevated arsenic concentrations were also found in bed sediments from mineralized areas. In these sample matrices, the presence of arsenic and (or) antimony was a good indicator of contact with mineralized rock units.

Alaska;Yukon↗
USGS2007

Environmental geochemical study of Red Mountain--an undisturbed volcanogenic massive sulfide deposit in the Bonnifield District, Alaska range, east-central Alaska: Chapter I in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

The Red Mountain volcanogenic massive sulfide (VMS) deposit exhibits well-constrained examples of acid-generating, metal-leaching, metal-precipitation, and self-mitigation (via co-precipitation, dilution, and neutralization) processes that occur in an undisturbed natural setting, a rare occurrence in North America. The unmined pyrite-rich deposit displays a remarkable environmental footprint of natural acid generation, high metal concentrations, and exceedingly high rare-earth-element (REE) concentrations in surface waters. Dissolution of pyrite and associated secondary reactions under near-surface, oxidizing conditions are the primary causes for the acid generation and metal leaching. The deposit is hosted in Devonian to Mississippian felsic metavolcanic rocks of the Mystic Creek Member of the Totatlanika Schist. Water samples with the lowest pH values, highest specific conductances, and highest major- and trace-element concentrations are from springs and streams within the quartz-sericite-pyrite alteration zone. Aluminum, As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Y, and particularly Zn and the REEs are all found in high concentrations, ranging across four orders of magnitude. Waters collected upstream from the alteration zone have near-neutral pH values, lower specific conductances, lower metal concentrations, and measurable alkalinities. Water samples collected downstream of the alteration zone have pH values and metal concentrations intermediate between these two extremes. Stream sediments are anomalous in Zn, Pb, S, Fe, Cu, As, Co, Sb, and Cd relative to local and regional background abundances. Red Mountain Creek and its tributaries do not support, and probably never have supported, significant megascopic faunal aquatic life.

Alaska;Yukon↗
USGS2007

The biogeochemistry and occurrence of unusual plant species inhabiting acidic, metal-rich water, Red Mountain, Bonnifield district, Alaska Range: Chapter J in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year project

This report presents results on the occurrence and biogeochemistry of unusual plant species, and of their supporting sediment, in an undisturbed volcanogenic massive sulfide deposit in the Tintina Gold Province (see fig. 1 of Editors’ Preface and Overview). The extraordinary plant assemblage found growing in the acidic metal-rich waters that drain the area is composed predominantly of bryophytes (liverworts and mosses). Ferricrete-cemented silty alluvial sediments within seeps and streams are covered with the liverwort Gymnocolea inflata, whereas the mosses Polytrichum commune and P. juniperinum inhabit the area adjacent to the water and within the splash zone. Both the liverwort-encrusted sediment and Polytrichum thalli have high concentrations of major- and trace-metal cations (for example, Al, As, Cu, Fe, Hg, La, Mn, Pb, and Zn). Soils in the area do not reflect the geochemical signature of the mineral deposit, and we suspect that they are most influenced by the chemistry of airborne dust (aeolian material) derived from outside the area.

Alaska;Yukon↗
USGS2005

Simulation of hydraulic characteristics in the white sturgeon spawning habitat of the Kootenai River near Bonners Ferry, Idaho

Hydraulic characterization of the Kootenai River, especially in the white sturgeon spawning habitat reach, is needed by the Kootenai River White Sturgeon Recovery Team to promote hydraulic conditions that improve spawning conditions for the white sturgeon (Acipenser transmontanus) in the Kootenai River. The decreasing population and spawning failure of white sturgeon has led to much concern. Few wild juvenile sturgeons are found in the river today. Determining the location of the transition between backwater and free-flowing water in the Kootenai River is a primary focus for biologists who believe that hydraulic changes at the transition affect the location where the sturgeon choose to spawn. The Kootenai River begins in British Columbia, Canada, and flows through Montana, Idaho, and back into British Columbia. The 65.6-mile reach of the Kootenai River in Idaho was studied. The study area encompasses the white sturgeon spawning reach that has been designated as a critical habitat. A one-dimensional hydraulic-flow model of the study reach was developed, calibrated, and used to develop relations between hydraulic characteristics and water-surface elevation, discharge, velocity, and backwater extent. The model used 164 cross sections, most of which came from a previous river survey conducted in 2002-03. The model was calibrated to water-surface elevations at specific discharges at five gaging stations. Calibrated water-surface elevations ranged from about 1,743 to about 1,759 feet, and discharges used in calibration ranged from 5,000 to 47,500 cubic feet per second. Model calibration was considered acceptable when the difference between measured and simulated water-surface elevations was ?0.15 foot or less. Measured and simulated average velocities also were compared. These comparisons indicated agreement between measured and simulated values. The location of the transition between backwater and free-flowing water was determined using the calibrated model. The model was used to simulate hydraulic characteristics for a range of water-surface elevations from 1,741 to 1,762 feet and discharges from 4,000 to 75,000 cubic feet per second. These simulated hydraulic characteristics were used to develop a three-parameter relation-discharge in the study reach, water-surface elevation at Kootenai River at Porthill gaging station (12322000), and the location of the transition between backwater and free-flowing water. Simulated hydraulic characteristics produced backwater locations ranging from river mile (RM) 105.6 (Porthill) to RM 158 (near Crossport), a span of about 52 miles. However, backwater locations from measured data ranged primarily from RM 152 to RM 157, a 5-mile span. The average backwater location from measured data was at about RM 154. Three-parameter relations also were developed for determining the amount of discharge in the Shorty Island side channel and average velocity at selected cross sections in the study reach. Simulated discharge for the side channel relative to measured data ranged from 0 to about 5,500 cubic feet per second, and simulated average velocity relative to measured data ranged from 0 to about 3.5 feet per second. Relations using other hydraulic, sediment/incipient motion, ecological, and biological characteristics also could be developed. The relations also can be used in real time by accessing data from the Web. Discharge and stage data for two gaging stations, Tribal Hatchery (12310100) and Porthill (12322500), are available from the Idaho U.S. Geological Survey web page (URL: http://waterdata.usgs.gov/id/nwis/current/?type=flow). Because the coordinate axes of the three-parameter relations use discharge from the Tribal Hatchery gaging station and water-surface elevation from the Porthill gaging station, the location of the transition between backwater and free-flowing water can be determined for current conditions using the real-time data. Similarly, discharge in the Shorty Island side channel and (or) average velocity at selected cross sections also can be determined for current conditions.

British Columbia;Idaho;Montana↗
USGS2004

Surveying Cross Sections of the Kootenai River Between Libby Dam, Montana, and Kootenay Lake, British Columbia, Canada

The declining population of Kootenai River white sturgeon, which was listed as an Endangered Species in 1994, has prompted a recovery team to assess the feasibility of various habitat enhancement scenarios to reestablish white sturgeon populations. As the first phase in this assessment, the U.S. Geological Survey collected stream channel cross-section and longitudinal data during 2002—03 at about 400 locations along the Kootenai River from Libby Dam near Libby, Montana, to where the river empties into Kootenay Lake near Creston, British Columbia, Canada. Survey control stations with a horizontal and vertical accuracy of less than 0.1 foot were established using a global positioning system (GPS) prior to collection of stream channel cross-section data along the Kootenai River. A total of 245 cross sections were surveyed. Six cross sections upstream from Kootenai Falls were surveyed using a total station where the river was too shallow or dangerous to navigate by vessel. The remaining 239 cross sections were surveyed by interfacing real-time GPS equipment with an echo sounder to obtain bathymetric data and with a laser range- finder to obtain streambank data. These data were merged, straightened, ordered, and reduced in size to be useful. Spacing between these cross sections ranged from about 600 feet in the valley flat near Deep Creek and Shorty Island and near bridges to as much as several miles in other areas. These stream channel cross sections will provide information that can be used to develop hydraulic flow models of the Kootenai River from Libby Dam, Montana, to Queens Bay on Kootenay Lake in British Columbia, Canada.

Montana;Idaho↗
USGS2003

Cascadia Tsunami Deposit Database

The Cascadia Tsunami Deposit Database contains data on the location and sedimentological properties of tsunami deposits found along the Cascadia margin. Data have been compiled from 52 studies, documenting 59 sites from northern California to Vancouver Island, British Columbia that contain known or potential tsunami deposits. Bibliographical references are provided for all sites included in the database. Cascadia tsunami deposits are usually seen as anomalous sand layers in coastal marsh or lake sediments. The studies cited in the database use numerous criteria based on sedimentary characteristics to distinguish tsunami deposits from sand layers deposited by other processes, such as river flooding and storm surges. Several studies cited in the database contain evidence for more than one tsunami at a site. Data categories include age, thickness, layering, grainsize, and other sedimentological characteristics of Cascadia tsunami deposits. The database documents the variability observed in tsunami deposits found along the Cascadia margin.

British Columbia;California;Oregon;Washington↗
USGS2003

Wide-angle seismic recording from the 2002 Georgia Basin Geohazards Initiative, northwestern Washington and British Columbia

This report describes the acquisition and processing of shallow-crustal wide-angle seismicreflection and refraction data obtained during a collaborative study in the Georgia Strait, western Washington and southwestern British Columbia. The study, the 2002 Georgia Strait Geohazards Initiative, was conducted in May 2002 by the Pacific Geoscience Centre, the U.S. Geological Survey, and the University of Victoria. The wide-angle recordings were designed to image shallow crustal faults and Cenozoic sedimentary basins crossing the International Border in southern Georgia basin and to add to existing wide-angle recordings there made during the 1998 SHIPS experiment. We recorded, at wide-angle, 800 km of shallow penetration multichannel seismic-reflection profiles acquired by the Canadian Coast Guard Ship (CCGS) Tully using an air gun with a volume of 1.967 liters (120 cu. in.). Prior to this reflection survey, we deployed 48 Refteks onshore to record the airgun signals at wide offsets. Three components of an oriented, 4.5 Hz seismometer were digitally recorded at all stations. Nearly 160,300 individual air gun shots were recorded along 180 short seismic reflection lines. In this report, we illustrate the wide-angle profiles acquired using the CCGS Tully, describe the land recording of the air gun signals, and summarize the processing of the land recorder data into common-receiver gathers. We also describe the format and content of the archival tapes containing the SEGY-formated, common-receiver gathers for the Reftek data. Data quality is variable but the experiment provided useful data from 42 of the 48 stations deployed. Three-fourths of all stations yielded useful first-arrivals to source-receiver offsets beyond 10 km: the average maximum source-receiver offset for first arrivals was 17 km. Six stations yielded no useful data and useful firstarrivals were limited to offsets less than 10 km at five stations. We separately archived our recordings of 86 local and regional earthquakes ranging in magnitude from 0.2 to 4.3 and 16 teleseisms ranging in magnitude 5.5 to 6.5.

British Columbia;Washington↗