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USGS2020

Design and operations of the Hydrate 01 Stratigraphic test well, Alaska North Slope

The National Energy Technology Laboratory, the Japan Oil, Gas and Metals National Corporation, and the U.S. Geological Survey are leading an effort to conduct an extended gas hydrate production test in northern Alaska. The proposed production test required the drilling of an initial stratigraphic test well (STW) to confirm the geologic conditions of the proposed test site. This well was completed in December 2018 in cooperation with the Prudhoe Bay Unit Interest Owners. With the success of the STW, the project leadership group is developing plans to drill a geologic data well and a production test well. Drilling plans for the STW were advanced in late 2018. The Prudhoe Bay Unit Hydrate-01 well was spudded on 10-December-2018. Downhole data acquisition was completed on 25-December-2018 and the rig was released on 01-January-2019. The STW was drilled in two sections. The surface hole was drilled to a depth of 2248 ft (MD, measured depth) and cased, and the “production hole section” was drilled to a depth of 3558 ft (MD) and also cased. A thermally chilled mineral-oilbased mud was used to maintain drillhole stability and quality of the borehole acquired data. The primary borehole data were acquired using a suite of Schlumberger logging-while-drilling tools. To gather grain size and other data needed to inform the design of the production test well, sidewall pressure cores were collected using Halliburton’s CoreVault tool. In addition to confirming the geologic conditions at the test site, the Hydrate-01 well was designed to serve as a monitoring well during future field operations. Therefore, two sets of fiber optic cables, each including bundled Distributed Acoustic Sensors (DAS) and Distributed Temperature Sensors (DTS), were clamped to the outside of the well casing and cemented in place. In March 2019, the project team worked with SAExploration to acquire 3D DAS Vertical Seismic Profiling (VSP) data in the Hydrate-01 well, which was the largest 3D DAS-VSP ever conducted. Additionally, since the December 2018 completion of the STW, several borehole temperature surveys have been acquired with the DTS deployed in the Hydrate-01 well.

Alaska↗

USGS2006

The giant Carlin gold province: A protracted interplay of orogenic, basinal, and hydrothermal processes above a lithospheric boundary

Northern Nevada hosts the only province that contains multiple world-class Carlin-type gold deposits. The first-order control on the uniqueness of this province is its anomalous far back-arc tectonic setting over the rifted North American paleocontinental margin that separates Precambrian from Phanerozoic subcontinental lithospheric mantle. Globally, most other significant gold provinces form in volcanic arcs and accreted terranes proximal to convergent margins. In northern Nevada, periodic reactivation of basement faults along this margin focused and amplified subsequent geological events. Early basement faults localized Devonian synsedimentary extension and normal faulting. These controlled the geometry of the Devonian sedimentary basin architecture and focused the discharge of basinal brines that deposited syngenetic gold along the basin margins. Inversion of these basins and faults during subsequent contraction produced the complex elongate structural culminations that characterize the anomalous mineral deposit "trends." Subsequently, these features localized repeated episodes of shallow magmatic and hydrothermal activity that also deposited some gold. During a pulse of Eocene extension, these faults focused advection of Carlin-type fluids, which had the opportunity to leach gold from gold-enriched sequences and deposit it in reactive miogeoclinal host rocks below the hydrologic seal at the Roberts Mountain thrust contact. Hence, the vast endowment of the Carlin province resulted from the conjunction of spatially superposed events localized by long-lived basement structures in a highly anomalous tectonic setting, rather than by the sole operation of special magmatic or fluid-related processes. An important indicator of the longevity of this basement control is the superposition of different gold deposit types (e.g., Sedex, porphyry, Carlin-type, epithermal, and hot spring deposits) that formed repeatedly between the Devonian and Miocene time along the trends. Interestingly, the large Cretaceous Alaska-Yukon intrusion-related gold deposits (e.g., Fort Knox) are associated with the northern extension of the same lithospheric margin in the Selwyn basin, which experienced an analogous series of geologic events. ?? Springer-Verlag 2006.

Mineralium Deposita↗

USGS1953

Reconnaissance for radioactive deposits in the Fairbanks and Livengood Quadrangles, east-central Alaska, 1949

Several mines and prospects in the Fairbanks and Livengood quadrangles, east-central Alaska, were examined for the possible presence of radioactive materials in the summer of 1949. Also tested were pre-Cambrian and Paleozoic metamorphic and sedimentary rocks crossed by the Elliott Highway, which extends from Fox, near Fairbanks, northward about 70 miles to the town of Livengood. None of the lodes tested exhibited radioactivity in excess of 0.003 percent equivalent uranium, although nuggets consisting chiefly of native bismuth and containing as much as 0.1 percent equivalent uranium had been found previously in a placer on Fish Creek several miles below the reported bismuth-bearing lode on Melba Creek. The greatest radioactivity found in the rocks along the Elliott Highway was in an iron-stained schist of pre-Cambrian age and in carbonaceous shale of Middle Devonian or Carboniferous age. Respective samples of these rocks contain 0.003 and 0.004 percent equivalent uranium. A possible local bedrock source for a euxenite-polycrase mineral found in a placer concentrate containing about 0.04 percent equivalent uranium was sought in the watershed of Goodluck Creek, near Livengood. The bedrock source of this mineral could not be located; it is believed that the source could be outside of the Goodluck watershed, as drainage changes in the area during Quaternary time might well have introduced gravels from nearby areas.

Alaska↗

USGS1962

Chromite in the United States, exclusive of Alaska and Hawaii

The chromite deposits in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. In compiling the map, the deposits were classified in five size categories according to the estimated total quantity of chromite present before mining. The map shows, by different symbols, deposits of chromite in ultramafic rocks, beach sands in which chromite is an important constituent, and lateritic iron ores in which chromium has been concentrated by weathering of peridotite in situ. Although geologically significant amounts of chromium are known to occur in some gabbros and sedimentary rocks other than beach sands and laterite, the data are too fragmentary to show on the map.

Mineral Investigations Resource Map↗

USGS1967

Iron in the United States, exclusive of Alaska and Hawaii

The iron-ore deposits in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map; many iron-bearing deposits that are of lesser or only potential value are also shown. Because these deposits range widely in extent, two general categories of symbols are used, each of which is subdivided as explained below. The first category is for deposits of such restricted extent that they can be represented by a "spot": the second is for deposits which, although not necessarily extremely large in terms of volume or tonnage, are either continuous (or essentially so) or clustered in reasonably well-defined districts of numerous small occurrences.

Mineral Investigations Resource Map↗

USGS2017

Fuel-reduction management alters plant composition, carbon and nitrogen pools, and soil thaw in Alaskan boreal forest

Increasing wildfire activity in Alaska's boreal forests has led to greater fuel-reduction management. Management has been implemented to reduce wildfire spread, but the ecological impacts of these practices are poorly known. We quantified the effects of hand-thinning and shearblading on above- and belowground stand characteristics, plant species composition, carbon (C) and nitrogen (N) pools, and soil thaw across 19 black spruce ( Picea mariana ) dominated sites in interior Alaska treated 2-12 years prior to sampling. The density of deciduous tree seedlings was significantly higher in shearbladed areas compared to unmanaged forest (6.4 vs. 0.1 stems m −2 ), and unmanaged stands exhibited the highest mean density of conifer seedlings and layers (1.4 stems m −2 ). Understory plant community composition was most similar between unmanaged and thinned stands. Shearblading resulted in a near complete loss of aboveground tree biomass C pools while thinning approximately halved the C pool size (1.2 kg C m −2 compared to 3.1 kg C m −2 in unmanaged forest). Significantly smaller soil organic layer (SOL) C and N pools were observed in shearbladed stands (3.2 kg C m −2 and 116.8 g N m −2 ) relative to thinned (6.0 kg C m −2 and 192.2 g N m −2 ) and unmanaged (5.9 kg C m −2 and 178.7 g N m −2 ) stands. No difference in C and N pool sizes in the uppermost 10 cm of mineral soil was observed among stand types. Total C stocks for measured pools was 2.6 kg C m −2 smaller in thinned stands and 5.8 kg C m −2 smaller in shearbladed stands when compared to unmanaged forest. Soil thaw depth averaged 13 cm deeper in thinned areas and 46 cm deeper in shearbladed areas relative to adjacent unmanaged stands, although variability was high across sites. Deeper soil thaw was linked to shallower SOL depth for unmanaged stands and both management types, however for any given SOL depth, thaw tended to be deeper in shearbladed areas compared to unmanaged forest. These findings indicate that fuel-reduction management alters plant community composition, C and N pools, and soil thaw depth, with consequences for ecosystem structure and function beyond those intended for fire management.

Alaska↗

USGS1995

Geochemical data of fumarolically altered rocks, Valley of Ten Thousand Smokes, Alaska

Samples from a fossil fumarole originating in the 1912 ash-flow tuffin the Valley of Ten Thousand Smokes have been analyzed to ascertain chemical changes resulting from high-temperature fumarolic alteration and subsequent cooling and weathering of the protolith. Samples of the underlying, dominantly leached, dacite-rich portion of the ash-flow tuff adjacent to the fumarolic conduit and samples of encrusted fallout from the shallow part of the fossil fumarole were interpreted using the isocon method of Grant (1986). The results show that, relative to unaltered l9l2 dacite, chosen as a standard composition for the protolith in this fossil fumarole, mass was conserved during the alteration reactions for most of the system, but mass gains of l4–2D% were determined for three samples in the leached ash-flow tuff Relative to unaltered dacite protolith, significant enrichments occurred in SO 3 , LOI (~H 2 O), Cl, F, Zn, Pb, Cu, Sn, Cr, Ni, As, Sb, Au, Br in various parts of the fossil fumarole. Some of these were during the high-temperature part of the alteration, and some were during cooling processes when acid alteration becomes prominent. The REEs indicate some depletion in highly altered samples relative to dacite protolith and differential mobility of Eu 2+ relative to trivalent REEs. This is manifested by positive Eu anomalies in REE patterns normalized against REE in the dacite protolith. Mineral phases introduced in the alteration assemblages include alunite reflecting high SO 3 , activity, hydrated aluminum hydroxy-fluoride (a ralstonite-like phase) and fluorite reflecting high F activity, smectite, magnetite, hematite, and goethite reflecting oxidation and hydration reactions. Opal and a portion of the α-cristobalite reflect SiO 2 , mobility; however, the abundance of α-cristobalite is formed from pumice leached during high-temperature vapor-phase processes and devitrification of the altered glass.

Open-File Report↗

USGS2019

Integration of microfacies analysis, inorganic geochemical data, and hyperspectral imaging to unravel mudstone depositional and diagenetic processes in two cores from the Triassic Shublik Formation, Northern Alaska

The Middle – Upper Triassic Shublik Formation is an organic-rich heterogeneous carbonate-siliciclastic-phosphatic unit that generated much of the oil in the Prudhoe Bay field and other hydrocarbon accumulations in northern Alaska. A large dataset, including total organic carbon (TOC), X-ray diffraction (XRD), X-ray fluorescence (XRF) and inductively coupled plasma – mass spectrometry (ICP-MS) measurements, has been built from core and outcrop samples of the Shublik, with a focus on the organic-rich intervals. In addition, two core intervals from the Shublik were analyzed using a hyperspectral imaging system in the visible, near-infrared and shortwave-infrared range. Integration of the hyperspectral results with core descriptions, microfacies interpretations, and analytical data is being used to decipher mudstone depositional and diagenetic processes. Petrographic analysis of Upper Triassic organic-rich intervals within the Shublik suggests that the main microfacies is a laminated bioclastic wackestone/packstone that was episodically disrupted by energetic events of variable intensity. These energetic events produced transitional and sparry calcite bioclastic packstone to grainstone intervals, depending on the depth of sediment column disturbance. By using hyperspectral imaging data from the Ikpikpuk core, individual distribution maps for minerals of interest have been generated and corroborate the microfacies interpretations. These maps also illustrate small-scale vertical changes in mineralogy. The laminated bioclastic wackestone/packstone intervals contain less calcite than the adjacent sparry bioclastic packstone to grainstone intervals. The calcite in these laminated intervals is more iron rich. This interpretation suggests that lower iron concentrations should be expected in the disrupted intervals than in nearby laminated intervals. Textural features are also enhanced in the hyperspectral images relative to visual description of the cores by combining the extraction of the average reflectance in the visible part of the electromagnetic spectrum and the depth of the main carbonate-related feature belonging to calcite. Examples noted in the enhanced imagery include low-angle features, calcite grain-size, and the size, shape and orientation of phosphatic nodules. This enhancement is being used to differentiate laminated from sparry bioclastic packstone to grainstone-rich intervals and provides a more comprehensive assessment of the microfacies than is practical by thin-section analysis.

Alaska↗

USGS2015

Soil nitrogen accretion along a floodplain terrace chronosequence in northwest Alaska: Influence of the nitrogen-fixing shrub Shepherdia canadensis

Nitrogen enters terrestrial ecosystems through multiple pathways during primary succession. We measured accumulation of total soil nitrogen and changes in inorganic nitrogen (N) pools across a 300-y sequence of river terraces in northwest Alaska and assessed the contribution of the nitrogen-fixing shrub Shepherdia canadensis . Our work compared 5 stages of floodplain succession, progressing from a sparsely vegetated silt cap to dense shrubby vegetation, balsam poplar-dominated ( Populus balsamifera ) and white spruce-dominated ( Picea glauca ) mixed forests, and old-growth white spruce forest. Total soil N (0–30 cm depth) increased throughout the age sequence, initially by 2.4 g N·m −2 ·y −1 during the first 120 y of terrace development, then by 1.6 g N·m −2 ·y −1 during the subsequent 2 centuries. Labile soil N, measured by anaerobic incubation, increased most rapidly during the first 85 y of terrace formation, then remained relatively constant during further terrace development. On recently formed terraces, Shepherdia shrubs enriched soil N pools several-fold compared to soil beneath Salix spp. shrubs or intercanopy sites. Total and labile soil N accretion was proportional to Shepherdia cover during the first century of terrace development, and mineral soil δ 15 N content indicated that newly formed river terraces receive substantial N through N-fixation. About half the 600 g total N·m −2 accumulated across the river terrace chronosequence occurred during the 120 y when S. canadensis was dominant. Sediment deposited by periodic flooding continued to add N to terrace soils after the decline in Shepherdia abundance and may have contributed 25% of the total N found in the floodplain terrace soils.

Alaska↗

USGS1962

Antimony in the United States, exclusive of Alaska and Hawaii

The principal sources of antimony in the United States (exclusive of Alaska and Hawaii) are shown on the accompanying map. The types of deposits are indicated by shape of symbols and the relative importance of the deposits is indicated by size of symbols. In the locality index the localities are listed by States and are keyed by numbers to the map. Localities are distinguished by name of mine, prospect, or geographic area, and their coordinates are given to the nearest minute of latitude and longitude. Geologic relations of each occurrence are characterized briefly. The text and map were compiled from published and unpublished information, and at least one reference is given for each locality if reports on it have been published.

Continental United States↗

USGS2006

Gravity and Aeromagnetic Gradients within the Yukon-Tanana Upland, Black Mountain Tectonic Zone, Big Delta Quadrangle, east-central Alaska

The Yukon-Tanana Upland is a complex composite assemblage of variably metamorphosed crystalline rocks with strong North American affinities. At the broadest scale, the Upland has a relatively neutral magnetic character. More detailed examination, however, reveals a fundamental northeast-southwest-trending magnetic gradient, representing a 20-nT step (as measured at a flight height of 300 m) with higher values to the northwest, that extends from the Denali fault to the Tintina fault and bisects the Upland. This newly recognized geophysical gradient is parallel to, but about 100 km east of, the Shaw Creek fault. The Shaw Creek fault is mapped as a major left-lateral, strike-slip fault, but does not coincide with a geophysical boundary. A gravity gradient coincides loosely with the southwestern half of the magnetic gradient. This gravity gradient is the eastern boundary of a 30-mGal residual gravity high that occupies much of the western and central portions of the Big Delta quadrangle. The adjacent lower gravity values to the east correlate, at least in part, with mapped post-metamorphic granitic rocks. Ground-based gravity and physical property measurements were made in the southeastern- most section of the Big Delta quadrangle in 2004 to investigate these geophysical features. Preliminary geophysical models suggest that the magnetic boundary is deeper and more fundamental than the gravity boundary. The two geophysical boundaries coincide in and around the Tibbs Creek region, an area of interest to mineral exploration. A newly mapped tectonic zone (the Black Mountain tectonic zone of O'Neill and others, 2005) correlates with the coincident geophysical boundaries.

Open-File Report↗

USGS1991

Geochemistry and mineralogy of fumarolic deposits, Valley of Ten Thousand Smokes, Alaska: Bulk chemical and mineralogical evolution of dacite-rich protolith

Alaska↗

USGS2014

Effects of permafrost thaw on CO2 and CH4 exchange in a western Alaska peatland chronosequence

Permafrost soils store over half of global soil carbon (C), and northern frozen peatlands store about 10% of global permafrost C. With thaw, inundation of high latitude lowland peatlands typically increases the surface-atmosphere flux of methane (CH 4 ), a potent greenhouse gas. To examine the effects of lowland permafrost thaw over millennial timescales, we measured carbon dioxide (CO 2 ) and CH 4 exchange along sites that constitute a ~1000 yr thaw chronosequence of thermokarst collapse bogs and adjacent fen locations at Innoko Flats Wildlife Refuge in western Alaska. Peak CH 4 exchange in July (123 ± 71 mg CH 4 –C m −2 d −1 ) was observed in features that have been thawed for 30 to 70 (<100) yr, where soils were warmer than at more recently thawed sites (14 to 21 yr; emitting 1.37 ± 0.67 mg CH 4 –C m −2 d −1 in July) and had shallower water tables than at older sites (200 to 1400 yr; emitting 6.55 ± 2.23 mg CH 4 –C m −2 d −1 in July). Carbon lost via CH 4 efflux during the growing season at these intermediate age sites was 8% of uptake by net ecosystem exchange. Our results provide evidence that CH 4 emissions following lowland permafrost thaw are enhanced over decadal time scales, but limited over millennia. Over larger spatial scales, adjacent fen systems may contribute sustained CH 4 emission, CO 2 uptake, and DOC export. We argue that over timescales of decades to centuries, thaw features in high-latitude lowland peatlands, particularly those developed on poorly drained mineral substrates, are a key locus of elevated CH 4 emission to the atmosphere that must be considered for a complete understanding of high latitude CH 4 dynamics.

Environmental Research Letters↗

USGS2009

Geochemistry and geochronology of carbonate-hosted base metal deposits in the southern Brooks Range, Alaska: Temporal association with VMS deposits and metallogenic implications

The Brooks Range contains enormous accumulations of zinc and copper, either as VMS or sediment-hosted deposits. The Ruby Creek and Omar deposits are Cu-Co stratabound deposits associated with dolomitic breccias. Numerous volcanogenic Cu-Zn (+/-Ag, Au) deposits are situated ~20 km north of the Ruby Creek deposit. The carbonate-hosted deposits consist of chalcopyrite and bornite that fill open spaces, replace the matrix of the breccias, and occur in later cross-cutting veins. Cobaltiferous pyrite, chalcocite, minor tennantite-tetrahedrite, galena, and sphalerite are also present. At Ruby Creek, phases such as carrollite, renierite, and germanite occur rarely. The deposits have undergone post-depositional metamorphism (Ruby Creek, low greenschist facies; Omar, blueschist facies). The unusual geochemical signature includes Cu-Co +/- Ag, As, Au, Bi, Ge, Hg, Sb, and U with sporadic high Re concentrations (up to 2.7 ppm). New Re-Os data were obtained for chalcopyrite, bornite, and pyrite from the Ruby Creek deposit (analyses of sulfides from Omar are in progress). The data show extremely high Re abundances (hundreds of ppb, low ppm) and contain essentially no common Os. The Re-Os data provide the first absolute ages of ore formation for the Ruby Creek deposit and demonstrate that the Re-Os systematics of pyrite, chalcopyrite, and bornite are unaffected by greenschist metamorphism. The Re-Os data show that the main phase of Cu mineralization occurred at 384 +/-4.2 Ma, which coincides with zircon U-Pb ages from igneous rocks that are spatially and genetically associated with VMS deposits. This suggests a temporal link between regional magmatism and hydrothermal mineralization.

Alaska↗

USGS1962

Gold in the United States, exclusive of Alaska and Hawaii

The accompanying map shows the distribution of the principal gold mining districts in the United States (excluding Alaska and Hawaii). Only those districts that have produced 10,000 ounces of gold or more are shown. Gold ore reserves were not considered, and the types of deposits are not shown. Based on total output, the gold-producing districts have been classified into three categories on the map: (1) those that have an output of 10,000 to 100,000 ounces, (2) those with an output of 100,000to 1,000,000 ounces, and (3) and those with an output of more than 1,000,000 ounces. Each category is represented by a particular map symbol, and the symbol is placed at the approximate center of the mining district.

Mineral Investigations Resource Map↗

USGS1979

Outer Continental Shelf oil and gas information program; Pacific index

The Outer Continental Shelf Lands Act of 1953, as amended in 1978, (43 U.S.C. 1331 et seq.), grants to the Secretary of the Interior the authority to issue leases for minerals on the U.S. Outer Continental Shelf (OCS). It provides the authority and guidelines which the Secretary utilizes for expeditious exploration and development of the OCS while ensuring timely access to information by affected states and local governments in order that appropriate planning will anticipate and ameliorate impacts from such OCS activities. This document is prepared in accordance with Part 30 of the Code of Federal Regulations (CFR), Section 252.5 and 43 CFR, Section 3300.2, which require that the Directors of the U.S. Geological Survey and the Bureau of Land Management shall make available an Index, listing all relevant, actual or proposed programs, plans, reports, environmental impact statements and other lease sale information, on a regular basis, to each affected state and, upon request, to the executive of any local government whose jurisdiction covers an area affected by OCS activities. Accordingly, the Geological Survey and the Bureau of Land Management are cooperating in a joint effort to compile all relevant information on the OCS Oil and Gas Leasing Program in an Index with four volumes; Alaska, Atlantic, Gulf of Mexico and Pacific. This volume is a listing of documents used in the Pacific Area OCS decisionmaking process, and the sequence of information presented parallels this process. The bibliographic references are presented by lease sale number, in the sequence in which the documents are generated in the Federal OCS leasing program. Thus, the reader may compare all documents of one type in the Pacific Area or trace a single lease sale throughout the entire leasing process. Activities which generate information throughout the OCS lease sale process are described under Other Documentation and Supplemental Reading. Other Documentation pertains to Federal data gathering and analysis programs which are an integral part of the OCS decisionmaking process and are used throughout the process due to the usefulness of their subject matter. The Supplemental Reading documents (Appendix A) are not used in decisionmaking but are invaluable sources of general OCS information.

California, Oregon, Washington↗

USGS1991

Oxygen, hydrogen, and sulfur isotope studies in the Juneau gold belt, southeastern Alaska: Constraints on the origin of hydrothermal fluids

The delta 18 O values of gold-bearing quartz from the Juneau gold belt range from 15.2 to 20.8 per mil, indicating that ore fluid values ranged from 7.2 to 12.8 per mil at an estimated temperature of 300 degrees C. Hydrothermal micas from many of the deposits are characterized by delta D values of -75 to -53 per mil, and ore fluids were calculated to have values of -35 to -15 per mil. In contrast, extracted fluid inclusion waters have a broad range of delta D values, from -48 in relatively undeformed quartz to about -110 per mil for some of the more deformed quartz veins. This range of more than 60 per mil reflects various mixtures from inclusions containing isotopically heavy, primary ore fluids and those containing low-temperature, isotopically light meteoric waters that were trapped in late fractures during uplift of the veins to shallow crustal levels. These results indicate a deep crustal source for the ore fluids, most likely of metamorphic origin. Values of delta D for muscovite, biotite, and hornblende from country rocks, as well as of delta 18 O for quartz-feldspar and quartz-plagioclase, provide little evidence of deep circulation of meteoric water along the length of the gold belt.The provinciality of delta 34 data suggests a regional metamorphic fluid of approximately -6 per mil that acquired much of its sulfur from lithologies near sites of ore deposition. Sulfur ratios of sulfide minerals from auriferous quartz range from -17.8 to -5.6 per mil in black phyllite hosts, from -6.0 to -1.3 per mil in less reduced metasedimentary rocks, and from -3.8 to +1.2 per mil in relatively oxidized igneous rocks. The regional fluid is interpreted to have driven desulfidation reactions in relatively 34 S-depleted sulfur reservoirs in the phyllites and 34 S-enriched reservoirs in the more oxidized lithologies.

Economic Geology↗

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↗