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USGS1999

Digital data for the geologic framework of the Alaska Peninsula, southwest Alaska, and the Alaska Peninsula terrane

These digital databases are the result of the compilation and reinterpretation of published and unpublished 1:250,000- and 1:63,360-scale mapping. The map area covers approximately 62,000 sq km (23,000 sq mi) in land area and encompasses much of 13 1:250,000-scale quadrangles on the Alaska Peninsula in southwestern Alaska. The compilation was done as part of the U.S. Geological Survey's Alaska Mineral Resource Assessment project (AMRAP), whose goal was create and assemble geologic, geochemical, geophysical, and other data in order to perform mineral resource assessments on a quadrangle, regional or statewide basis. The digital data here was created to assist in the completion of a regional mineral resource assessment of the Alaska Peninsula. Mapping on the Alaska Peninsula under AMRAP began in 1977 in the Chignik and Sutwik Island 1:250,000 quadrangles (Detterman and others, 1981). Continued mapping in the Ugashik, bristol bay, and northwestern Karluk quadrangles (Detterman and others, 1987) began in 1979, followed by the Mount Katmai, eastern Naknek, and northwestern Afognak quadrangles (Riehle and others, 1987; Riehle and others, 1993), the Port Moller, Stepovak bay, and Simeonof Island quadrangles (Wilson and others, 1995) beginning in 1983. Work in the Cold bay and False Pass quadrangles (Wilson and others, 1992 [Superseded by Wilson and others 1997, but not incorporated herein]) began in 1986. The reliability of the geologic mapping is variable, based, in part, on the field time spent in each area of the map, the available support, and the quality of the existing base maps. In addition, our developing understanding of the geology of the Alaska Peninsula required revision of earlier maps, such as the Chignik and Sutwik Island quadrangles map (Detterman and others, 1981) to reflect this new knowledge. We have revised the stratigraphic nomenclature (Detterman and others, 1996) and our assignment of unit names to some rocks has been changed. All geologic maps on which this compilation is based were published using the Universal Transverse Mercator projection (UTM; Zones 3, 4, and 5). because of the distortions use of the UTM projection would produce on a map of small scale and large area, the plot and graphics files derived from this data are plotted using a more appropriate Albers Equal-area projection for publication.

Alaska↗

USGS1989

Turbidity-current channels in Queen Inlet, Glacier Bay, Alaska

Queen Inlet is unique among Glacier Bay fjords because it alone has a branching channel system incised in the Holocene sediment fill of the fjord floor. Bathymetry and seismic-reflection profiles show that four channels begin on, or at the base of, the delta front of this marine-outwash fjord. By midpoint of the fjord, these channels have merged into one main channel that extends the length of the fjord. The main channel cuts deeply into the scarp that separates this hanging tributary from the West Arm of Glacier Bay. The Queen Inlet channel ends on the main fjord floor as several small distributaries that form part of a lobate-fan deposit. Sand from the channel and lobate fan, in contrast to fjord-floor mud, plus steep truncated channel walls indicate that turbidity currents created this apparently active channel system. Queen Inlet and other known channel-containing fjords are marine-outwash fjords; the tidewater glacial fjords do not have steep delta fronts on which slides are generated and may not have a sufficient reservoir of potentially unstable coarse sediment to generate channel-cutting turbidity currents. Presence or absence of channels, as revealed in the ancient rock record, may be one criterion for interpreting types of fjords.

Alaska↗

USGS1969

Environmental impact of oil development in northern Alaska

It is reported that in the spring of 1969 a high official of one of the oil companies was flying over the area of oil development in the vicinity of Prudhoe Bay. He is quoted as saying "If the American people could see what we are doing to their land here, they would want to abolish the use of the reciprocating engine." The last really large area of wilderness in the United States is the' Brooks Range and the Arctic Coastal Plain which stretches from that range to the Arctic Ocean. The proving of the exploratory oil wells which have been drilled on the coastal plain in the vicinity of Prudhoe Bay makes it virtually certain that this heretofore mostly unknown country will rapidly and vigorously be exposed to a variety of changes caused by the influx of men and their equipment. Even within the first four months of 1969 the whole aspect of the central part of the region has been importantly changed by the drilling programs of several large oil companies. So suddenly was this change brought about that no long-range plans have been developed either to soften the effect of such development on the natural environment or even to record the progress of these effects. Yet the absence of a plan provides an inadvertent potential advantage in that there has' been no history of increasingly firm Federal policy which, in other places, has often made it difficult to take newly conceived action in line with the increasing societal interest in environmental preservation. The lack of firm Federal policy provides here a unique opportunity for the application of new rules and investigative techniques aimed at minimizing the adverse effects on the environment while5.at the same time, not unduly hindering the development of the natural resources. But the speed with which the changes are being wrought makes it imperative that the principles applicable here to environmental protection or preservation, be enunciated immediately and that from these principles flow farsighted regulations which reflect the new interest in combining resource development with environmental protection. The present report constitutes a brief summary of the conditions existing in northern Alaska in the spring of 1969, presenting some inferences on the environmental changes which can be expected in the future and offering some specific steps which, if taken immediately and positively, could greatly ameliorate the adverse effects of rapid development in the absence of positive steps for environmental protection. In that regard, then, this report is ephemeral in character because the conditions in northern Alaska will surely change with great rapidity. Considering the"fragility and sensitivity of the ecosystems existing there, the changes can be both harsh and permanent. Therefore, whatever value lies in the recommendations made here., the results of their application will depend on the promptness of their consideration, amendment, and application. Whatever form the actions might take for minimizing the harm to the environment, the urgency of the matter can hardly be overestimated.

Alaska↗

USGS2015

Mapping surficial minerals at high latitudes: The USGS 2014 imaging spectrometer data collection in Alaska

Passive optical remote sensing of high latitude regions faces many challenges including a short acquisition season and poor illumination due to low solar elevation. Additional complications are encountered in the identification of surface minerals for mineral resource characterization because minerals of interest commonly are exposed on steep terrain, further challenging reflectance retrieval and detection of mineral signatures. On shallow slopes and flat terrain, vegetation cover can interfere with or obscure the absorption features of minerals in rock and soil. The USGS is conducting a study to examine the viability of using remote sensing techniques for identification of large-tonnage, base metal-rich deposits in Alaska.

Alaska↗

USGS2021

Bar-tailed Godwits Limosa lapponica in Alaska: Revisiting population estimates from the staging grounds

Bar-tailed Godwits Limosa lapponica baueri breed in Alaska and spend the nonbreeding season primarily in eastern Australia and New Zealand. Long-term declines spurred recent surveys at nonbreeding sites that yielded a revised population estimate of ~126,000 godwits. We conducted aerial surveys for Bar-tailed Godwits in 2018 and 2019 at pre-migratory staging sites in western Alaska. Counts from similar surveys in 1997 accorded with counts of baueri from the nonbreeding range. Instead of relying on observer estimates of flock sizes, we enumerated 97% of our survey totals using digital photography. Our survey results differed markedly between 2018 (39,751) and 2019 (100,926), differences that reflected a relatively late autumn survey period in 2018, when some godwits were likely to have left the area, compared to 2019. In contrast to the 1997 surveys, we found few Bar-tailed Godwits at estuaries on the Alaska Peninsula. However, we counted nearly 93,000 godwits (~92% of survey total) along ~60 km of coast at the Kuskokwim River Delta in 2019, a value constituting nearly three-quarters of the subspecies’ current population estimate. Our survey totals for 2019 were in agreement with contemporaneous counts at austral nonbreeding sites, demonstrating how aerial surveys from Alaska can provide useful insights into counts conducted elsewhere in the subspecies’ range. When combined with measures of reproductive output, estimates of seasonal survival, and dedicated studies of the movement and survival of juvenile godwits, future surveys from Alaska can further contribute to efforts to determine mechanisms of population changes in baueri Bar-tailed Godwits.

Alaska↗

USGS2010

Persistent organic pollutants in the blood of free-ranging sea otters (Enhydra lutris ssp.) in Alaska and California

As part of tagging and ecologic research efforts in 1997 and 1998, apparently healthy sea otters of four age-sex classes in six locations in Alaska and three in California were sampled for persistent organic pollutants (POPs) and other chemicals of ecologic or environmental concern (COECs). Published techniques for the detection of POPs (specifically Σpolychlorinated biphenyls [PCBs], ΣDDTs, Σhexachlorocyclohexanes [HCHs], Σpolycyclic aromatic hydrocarbons [PAHs], Σchlordanes [CHLs], hexachlorobenzene [HCB], dieldrin, and mirex) in the tissue of dead otters were modified for use with serum from live sea otters. Toxic equivalencies (TEQs) were calculated for POPs with proven bioactivity. Strong location effects were seen for most POPs and COECs; sea otters in California generally showed higher mean concentrations than those in Alaska. Differences in contaminant concentrations were detected among age and sex classes, with high levels frequently observed in subadults. Very high levels of ΣDDT were detected in male sea otters in Elkhorn Slough, California, where strong freshwater outflow from agricultural areas occurs seasonally. All contaminants except mirex differed among Alaskan locations; only ΣDDT, HCB, and chlorpyrifos differed within California. High levels of ΣPCB (particularly larger, more persistent congeners) were detected at two locations in Alaska where associations between elevated PCBs and military activity have been established, while higher PCB levels were found at all three locations in California where no point source of PCBs has been identified. Although POP and COEC concentrations in blood may be less likely to reflect total body burden, concentrations in blood of healthy animals may be more biologically relevant and less influenced by state of nutrition or perimortem factors than other tissues routinely sampled.

Alaska, California↗

USGS2012

Cenozoic tectono-thermal history of the Tordrillo Mountains, Alaska: Paleocene-Eocene ridge subduction, decreasing relief, and late Neogene faulting

Topographic development inboard of the continental margin is a predicted response to ridge subduction. New thermochronology results from the western Alaska Range document ridge subduction related orogenesis. K-feldspar thermochronology (KFAT) of bedrock samples from the Tordrillo Mountains in the western Alaska Range complement existing U-Pb, 40 Ar/ 39 Ar and AFT (apatite fission track) data to provide constraints on Paleocene pluton emplacement, and cooling as well as Late Eocene to Miocene vertical movements and exhumation along fault-bounded blocks. Based on the KFAT analysis we infer rapid exhumation-related cooling during the Eocene in the Tordrillo Mountains. Our KFAT cooling ages are coeval with deposition of clastic sediments in the Cook Inlet, Matanuska Valley and Tanana basins, which reflect high-energy depositional environments. The Tordrillo Mountains KFAT cooling ages are also the same as cooling ages in the Iliamna Lake region, the Kichatna Mountains of the western Alaska Range, and Mt. Logan in the Wrangell-St. Elias Mountains, thus rapid cooling at this time encompasses a broad region inboard of, and parallel to, the continental margin extending for several hundred kilometers. We infer these cooling events and deposition of clastic rocks are related to thermal effects that track the eastward passage of a slab window in Paleocene-Eocene time related to the subduction of the proposed Resurrection-Kula spreading ridge. In addition, we conclude that the reconstructed KFAT max negative age-elevation relationship is likely related to a long period of decreasing relief in the Tordrillo Mountains.

Alaska↗

USGS2013

Extending airborne electromagnetic surveys for regional active layer and permafrost mapping with remote sensing and ancillary data, Yukon Flats ecoregion, central Alaska

Machine-learning regression tree models were used to extrapolate airborne electromagnetic resistivity data collected along flight lines in the Yukon Flats Ecoregion, central Alaska, for regional mapping of permafrost. This method of extrapolation (r = 0.86) used subsurface resistivity, Landsat Thematic Mapper (TM) at-sensor reflectance, thermal, TM-derived spectral indices, digital elevation models and other relevant spatial data to estimate near-surface (0–2.6-m depth) resistivity at 30-m resolution. A piecewise regression model (r = 0.82) and a presence/absence decision tree classification (accuracy of 87%) were used to estimate active-layer thickness (ALT) (< 101 cm) and the probability of near-surface (up to 123-cm depth) permafrost occurrence from field data, modelled near-surface (0–2.6 m) resistivity, and other relevant remote sensing and map data. At site scale, the predicted ALTs were similar to those previously observed for different vegetation types. At the landscape scale, the predicted ALTs tended to be thinner on higher-elevation loess deposits than on low-lying alluvial and sand sheet deposits of the Yukon Flats. The ALT and permafrost maps provide a baseline for future permafrost monitoring, serve as inputs for modelling hydrological and carbon cycles at local to regional scales, and offer insight into the ALT response to fire and thaw processes.

Alaska↗

USGS2025

Toward co-designed Earth System Models: Reflecting end-user priorities in local applications from a modeler's perspective

Earth System Models (ESM) are crucial for quantifying climate impacts across Earth's interconnected systems and supporting science-based adaptation and mitigation. However, not including end-users, especially decision-makers representing communities vulnerable to climate change, can limit model utility, increase epistemic risks, and lead to information misuse in decision-making. While the ESM community increasingly values broad community engagement, end-users may not initially perceive models as useful for local planning. Co-designing models with end-users fosters two-way learning: users better understand models and their outputs, while modelers gain insights into fine-scale local processes like monitoring practices and management priorities. Higher-level co-design can lead to more customized, priority-driven, and useful modeling products. Despite these benefits, modelers often struggle to initiate meaningful partnerships with local communities. Therefore, this paper explores model co-design from the perspective of modelers. This study presents two case studies where modelers and social scientists collaborated with Indigenous communities' decision-makers to reflect their priorities in model design and application. In the Arctic Rivers Project, high-resolution climate and hydrology data sets for Alaska were developed with guidance from an Indigenous Advisory Council, using optimized, coupled land-atmosphere models. In the Mid-Klamath Project, we partnered with the Karuk Tribe's Department of Natural Resources to assess climate change and prescribed burning impacts on terrestrial hydrology in the Klamath River Basin. Drawing from these studies, we introduce a four-level framework: (a) Co-design Configuration; (b) Model Tuning; (c) Incorporate Contextual Knowledge; (d) Co-develop New Model Functions. We aim to help researchers consider and compare co-design across diverse modeling projects systematically and coherently.

Alaska, California, Oregon↗

USGS2015

Reconnaissance surficial geologic map of the Taylor Mountains quadrangle, southwestern Alaska

This map and accompanying digital files are the result of the interpretation of aerial photographs from the 1950s as well as more modern imagery. The area, long considered a part of Alaska that was largely not glaciated (see Karlstrom, 1964; Coulter and others, 1965; or Péwé, 1975), actually has a long history reflecting local and more distant glaciations. An unpublished photogeologic map of the Taylor Mountains quadrangle from the 1950s by J.N. Platt Jr. was useful in the construction of this map. Limited new field mapping in the area was conducted as part of a mapping project in the Dillingham quadrangle to the south (Wilson and others, 2003); however, extensive aerial photograph interpretation represents the bulk of the mapping effort. The accompanying digital files show the sources for each line and geologic unit shown on the map. I used the Platt and Muller 1950s-era aerial photographic interpretation map as the starting point for the surficial geology; their unpublished data were produced using a reconnaissance quality topographic base map. In addition to transferring their data to a modern base to use as a guide, all of the photographs were re-examined. As result, in a number of areas, the features have been reinterpreted and the linework revised. A major difference between the maps is the recognition of much more extensive glacially dammed lake deposits and reassignment of some glacial deposits to different glacial events.

Alaska↗

USGS2017

Paleoseismic potential of sublacustrine landslide records in a high-seismicity setting (south-central Alaska)

Sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low-seismicity settings. However, as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures, it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking. To test this, we selected three lakes in south-central Alaska that experienced a strong historical megathrust earthquake (the 1964 M w 9.2 Great Alaska Earthquake) and exhibit high sedimentation rates in their main basins (0.2 cm yr − 1 –1.0 cm yr − 1 ). We present high-resolution reflection seismic data (3.5 kHz) and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record. Seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill. Most of these landslide deposits can be attributed to specific landslide events, as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon. We identify numerous events in the lakes: Eklutna Lake proximal basin (14 events), Eklutna Lake distal basin (8 events), Skilak Lake (7 events) and Kenai Lake (7 events). The most recent event in each basin corresponds to the historic 1964 megathrust earthquake. All events are characterized by multiple landslide deposits, which hints at a regional trigger mechanism, such as an earthquake (the synchronicity criterion). This means that the landslide record in each basin represents a record of past seismic events. Based on extrapolation of sedimentation rates derived from radionuclide dating, we roughly estimate a mean recurrence interval in the Eklutna Lake proximal basin, Eklutna Lake distal basin, Skilak Lake and Kenai Lake, at ~ 250 yrs., ~ 450 yrs., ~ 900 yrs. and ~ 450 yrs., respectively. This distinct difference in recording can be explained by variations in preconditioning factors like slope angle, slope recharging (sedimentation rate) and the sediment source area: faster slope recharging and a predominance of delta and alluvial fan failures, increase the sensitivity and lower the intensity threshold for slope instability. Also, the seismotectonic setting of the lakes has to be taken into account. This study demonstrates that sublacustrine landslides in several Alaskan lakes can be used as reliable recorders of strong earthquake shaking, when a multi-lake approach is used, and can enhance the temporal and spatial resolution of the paleoseismic record of south-central Alaska.

Alaska↗

USGS1982

Active geologic processes in Barrow Canyon, northeast Chukchi Sea

Circulation patterns on the shelf and at the shelf break appear to dominate the Barrow Canyon system. The canyon's shelf portion underlies and is maintained by the Alaska Coastal Current (A.C.C.), which flows northeastward along the coast toward the northeast corner of the broad Chukchi Sea. Offshelf and onshelf advective processes are indicated by oceanographic measurements of other workers. These advective processes may play an important role in the production of bedforms that are found near the canyon head as well as in processes of erosion or non-deposition in the deeper canyon itself. Coarse sediments recovered from the canyon axis at 400 to 570 m indicate that there is presently significant flow along the canyon. The canyon hooks left at a point north of Point Barrow where the A.C.C. loses its coastal constriction. The left hook, as well as preferential west-wall erosion, continues down to the abyssal plain of the Canada Basin at 3800 m. A possible explanation for the preferential west-wall erosion along the canyon, at least for the upper few hundred meters, is that the occasional upwelling events, which cause nutrient-rich water to flow along the west wall would in turn cause larger populations of burrowing organisms to live there than on the east wall, and that these organisms cause high rates of bioerosion. This hypothesis assumes that the dominant factor in the canyon's erosion is biological activity, not current velocity. Sedimentary bedforms consisting of waves and furrows are formed in soft mud in a region on the shelf west of the canyon head; their presence there perhaps reflects: (a) the supply of fine suspended sediments delivered by the A.C.C. from sources to the south, probably the Yukon and other rivers draining northwestern Alaska; and (b) the westward transport of these suspended sediments by the prevailing Beaufort Gyre which flows along the outer shelf.

Alaska↗

USGS1990

The Denali fault system and Alaska Range of Alaska: Evidence for underplated Mesozoic flysch from magnetotelluric surveys

Regional magnetotelluric surveys recently completed across the central and eastern Alaska Range of Alaska provide evidence for large volumes of conductive rocks beneath the core of the range. These conductive rocks may represent a formerly extensive, but now collapsed, Mesozoic flysch basin formed on the leading edge of the Talkeetna superterrane (amalgamated Wrangellia, Peninsular, and Alexander terranes). The docking of the Talkeetna superterrane caused large-scale oblique thrusting, folding, and metamorphism in the flysch basin, and formation of a megasuture along which the Cenozoic strike-slip Denali fault system developed. The deep magnetotelluric soundings and seismic reflection data suggest the possibility that the highly conductive rocks were tectonically emplaced beneath the thin crystalline sheet constituting the southern Yukon-Tanana terrane over a broad region of the Alaska Range. The conductive rocks are locally correlated with surface outcrops of Mesozoic black shales that are part of Upper Jurassic and Cretaceous flysch but may be composed of Paleozoic carbonaceous shales as well. In either case, their extremely low resistivities make them a valuable marker horizon for tectonic studies. The conductive rocks are interpreted to extend to depths of greater than 20 km and were mapped north and northeast of the Denali fault for more than 50 km. The magnetotelluric surveys represent the first large-scale surveys done in Alaska, but the structures mapped are similar to those observed in large, compressed flysch basins in the eastern Alps and Carpathian Mountains of Europe. The results of these surveys bear on several key tectonic questions, including development of the ancestral Denali fault, and collapse and possible underplating of an extensive Mesozoic flysch system and associated igneous arc.

Alaska↗

USGS2011

An overview of the petroleum geology of the Arctic

Nine main petroleum provinces containing recoverable resources totalling 61 Bbbl liquids+269 Bbbloe of gas are known in the Arctic. The three best known major provinces are: West Siberia–South Kara, Arctic Alaska and Timan–Pechora. They have been sourced principally from, respectively, Upper Jurassic, Triassic and Devonian marine source rocks and their hydrocarbons are reservoired principally in Cretaceous sandstones, Triassic sandstones and Palaeozoic carbonates. The remaining six provinces except for the Upper Cretaceous–Palaeogene petroleum system in the Mackenzie Delta have predominantly Mesozoic sources and Jurassic reservoirs. There are discoveries in 15% of the total area of sedimentary basins ( c. 8×10 6 km 2 ), dry wells in 10% of the area, seismic but no wells in 50% and no seismic in 25%. The United States Geological Survey estimate yet-to-find resources to total 90 Bbbl liquids+279 Bbbloe gas, with four regions – South Kara Sea, Alaska, East Barents Sea, East Greenland – dominating. Russian estimates of South Kara Sea and East Barents Sea are equally positive. The large potential reflects primarily the large undrilled areas, thick basins and widespread source rocks.

Geological Society Memoir↗

USGS2015

Preliminary interpretation of industry two-dimensional seismic data from Susitna Basin, south-central Alaska

Located approximately 80 kilometers northwest of Anchorage, Alaska, the Susitna Basin is a complex sedimentary basin whose tectonic history has been poorly understood. Recent interpretation of two-dimensional seismic reflection data integrated with well, aeromagnetic, and gravity data provides new insights into the structural and stratigraphic nature of the basin. This report presents an interpretation of 41 two-dimensional seismic reflection lines, acquired by industry from the 1960s to the 1980s. Our interpretation of the seismic data focused mainly on picking two Eocene stratigraphic units and a presumed base of Tertiary horizon. Based on our interpretation of the seismic data, the structural features in the basin appear to be generally contractional, as evidenced by the presence of many reverse faults, thrust faults, and folds, with the contraction mainly oriented east-west. This result is contrary to prior inferences of most previous geologic studies that showed normal faults. Several regional reverse faults have been identified in the seismic data and appear to divide the basin into three regions or “sides”: east, west, and south. The eastern seismic lines show evidence of numerous short-wavelength antiforms that appear to correspond to a series of northeast-trending lineations observed in aeromagnetic data, which have been interpreted as being due to folding of Paleogene volcanic strata. The eastern side of the basin is also cut by a number of reverse faults and thrust faults, the majority of which strike north-south. The western side of the Susitna Basin is cut by a series of regional reverse faults and is characterized by synformal structures in two fault blocks between the Kahiltna River and Skwentna faults. These synforms are progressively deeper to the west in the footwalls of the east-vergent Skwentna and northeast-vergent Beluga Mountain reverse faults. Although the seismic data are limited to the south, we interpret a potential regional south-southeast-directed reverse fault striking east-northeast on the east side of the basin that may cross the entire southern portion of the basin.

Alaska↗

USGS1969

Bathymetry and isopach map of stratified Holocene sediments of Nuka Bay, Alaska

The bathymetric chart of the Nuka Bay area, Alaska, is based on U.S.C.&G.S. Chart 8530, and over 750 km of additional sounding lines made in 1965 and in 1968. Continuous reflection seismic records made along the same tracks as the bathymetric profiles served as the basis for the Isopach map. For the determination of sediment thicknesses a sound velocity in sediment of 1.5 km/sec was used. Scale of both maps is 1:83, 074 at Latitude N59°20'.

Open-File Report↗

USGS1976

Preliminary space image lineament maps of Alaska

Examination of images from Nimbus, NOAA and Landsat satellites has revealed a series of lineaments in the earth's surface in Alaska 1000 km or more in length (fig. 1). These lineaments occur as alinements of surface geologic structures, linear valleys or ridges, and linear changes in tonal contrast marking differences in soil type, soil moisture, or vegetation. The lineaments are believed to represent the surface traces of zones of weakness deep within the earth's crust along which vertical or horizontal adjustments to earth stresses persistently recurred since at least Precambrian time. A consistent pattern in the lineaments can be discerned in Alaska (fig. 1D), and throughout the North American Cordillera (fig. 2). This pattern is believed to represent a mosaic of crustal blocks, whose differential movements have guided the tectonic development of the Cordillera. Areas in which mineral deposits are known to be concentrated are alined along many of the lineaments or occur at lineament intersections, suggesting that the zones of weakness reflected by the lineaments provided felicitous pathways for upward movement of mineralizing agents. Other lineaments bound areas of high mineral concentration suggesting that some crustal blocks have had a tectonic history more favorable for mineralization than others. These conclusions suggest that the study of space image lineaments can provide new and fruitful approaches to the search for concealed mineral deposits. In Alaska, some lineaments coincide in part with active fault traces and some separate areas of significantly different structure and geologic history. However, the movements along the zones of weakness which these lineaments are believed to reflect have been too slow and spread over too many millions of years for the lineaments to be considered as marking zones of present earthquake hazard. Detailed discussion of the lineaments, and of interpretations as to their meaning, are contained in: 1) a paper presented by Lathram and Raynolds at the First William T. Pecora Memorial Symposium, Sioux Falls, South Dakota, October 28-31, 1975, and 2) Lathram and Albert, 1976, Significance of space image linears in Alaska, in Hodgson, R.A., Gay, S.P., and Benjamins, J.Y., eds., Proceedings of the First International Conference on the New Basement Tectonics: Utah Geol. Assoc. Pub. 5, p. 11-26.

Alaska↗

USGS1979

Notes on the acquisition of high resolution seismic reflection profiles, side-scanning sonar records, and sediment samples from lower Cook Inlet and Kodiak Shelf, R/V Sea Sounder Cruise S8-78-WG, August 1978

The third U.S. Geological Survey geo-environmental cruise in lower Cook Inlet and on the Kodiak shelf and adjacent continental slope, Gulf of Alaska, was conducted aboard the R/V SEA SOUNDER from 2 August to 22 August, 1978 (Fig. 1, 2, and 3). The objectives of the cruise were to study in detail specific potentially hazardous environmental conditions identified as a result of the first reconnaissance cruise conducted in June and July of 1976 and from work by other investigators, and to initiate reconnaissance characterization studies on the continental slope. High-resolution seismic reflection profiling (sparker, Uniboam: 3.5 kHz, 12 kHz) and side-scanning sonar surveys formed the basis for selecting stations for observation with bottom television and 70 mm bottom camera as well as for sampling of surficial sediments (gravity corer, grab sampler), Generalized trackline charts are given in Figures 2 and 3. Detailed shot-point charts could not be constructed clearly, because of the overlap and coincidence of many of the lines. Station locations are shown in Figure 4 and 5, and sampling information is given in Table 4. Table 5 contains the navigation records from the cruise. The results of our investigations to date can be found in the references listed at the end of this text, Background information in lower Cook Inlet with several references is given in Open-File Report 75-429 (Magoon and others, 1975), and on the Kodiak shelf in Open-File Report 76-325 (von Huene and others, 1976). In addition, this report accompanies the basic seismic-reflection and side-scanning sonar records acquired on the cruise. The seismic-reflection records are publicly available from the National Geophysical and Solar Terrestrial Data Center EDS/NOAA, Boulder, Colorado 80302. These records can be inspected at U.S. Geological Survey offices at Rm B-164, Deer Creek Facility, 3475 Deer Creek Road, Palo Alto, California 94303.

Alaska↗