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At least 991 records · Page 55Linked to original sources
USGS2014

Historic and contemporary mercury exposure and potential risk to yellow-billed loons ( Gavia adamsii ) breeding in Alaska and Canada

The Yellow-billed Loon (Gavia adamsii) is one of the rarest breeding birds in North America. Because of the small population size and patchy distribution, any stressor to its population is of concern. To determine risks posed by environmental mercury (Hg) loads, we captured 115 Yellow-billed Loons between 2002 and 2012 in the North American Arctic and sampled their blood and/or feather tissues and collected nine eggs. Museum samples from Yellow-billed Loons also were analyzed to examine potential changes in Hg exposure over time. An extensive database of published Hg concentrations and associated adverse effects in Common Loons (G. immer) is highly informative and representative for Yellow-billed Loons. Blood Hg concentrations reflect dietary uptake of methylmercury (MeHg) from breeding areas and are generally considered near background levels if less than 1.0 µg/g wet weight (ww). Feather (grown at wintering sites) and egg Hg concentrations can represent a mix of breeding and wintering dietary uptake of MeHg. Based on Common Loon studies, significant risk of reduced reproductive success generally occurs when adult Hg concentrations exceed 2.0 µg/g ww in blood, 20.0 µg/g fresh weight (fw) in flight feathers and 1.0 µg/g ww in eggs. Contemporary mercury concentrations for 176 total samples (across all study sites for 115 Yellow-billed Loons) ranged from 0.08 to 1.45 µg/g ww in blood, 3.0 to 24.9 µg/g fw in feathers and 0.21 to 1.23 µg/g ww in eggs. Mercury concentrations in blood, feather and egg tissues indicate that some individual Yellow-billed Loons in breeding populations across North America are at risk of lowered productivity resulting from Hg exposure. Most Yellow-billed Loons breeding in Alaska overwinter in marine waters of eastern Asia. Although blood Hg concentrations from most breeding loons in Alaska are within background levels, some individuals exhibit elevated feather and egg Hg concentrations, which likely indicate the uptake of MeHg originating from eastern Asia. Feather Hg concentrations tended to be highest in individuals overwintering farthest west (closer to Asia). A retrospective analysis of museum specimens (n = 25) found a two-fold increase in Yellow-billed Loon feather Hg concentrations from the pre-1920s (as early as 1845) to the present. The projected increase in Hg deposition (approximately four-fold by 2050) along with the uncertainty of Hg being released through the thawing of permafrost and Arctic sea ice suggest that Hg body burdens in Yellow-billed Loons may increase. These findings indicate that Hg is a current and potentially increasing environmental stressor for the Yellow-billed Loon and possibly other Nearctic-Palearctic migrant birds.

Alaska↗
USGS2022

Interspecific and local variation in Tern chick diets across nesting colonies in the Gulf of Maine

The Gulf of Maine, USA is home to four colonial co-nesting tern species: Least Tern ( Sternula antillarum ), Common Tern ( Sterna hirundo ), Arctic Tern ( Sterna paradisaea ), and the federally endangered Roseate Tern ( Sterna dougallii ). Over three decades of visual observations of chick provisioning were compiled for a comparative dietary study in the region, including the first detailed descriptions of Least and Roseate Tern chick diets. Three prey groups comprised the majority of chick diets among tern species between 1986–2017: hake ( Urophycis spp. or Enchelyopus cimbrius ) 28–37% frequency of occurrence (FO), sand lance ( Ammodytes americanus or A. dubius ) 8–22% FO, and herring ( Clupea spp . or Alosa spp.) 3–30% FO. Dietary contributions varied across species and islands. At two inshore colonies, Common Tern diets contained higher amounts of sand lance (30–42% FO), while offshore islands contained lesser amounts (5–9% FO). Overall dietary diversity (H′) was similar between Common (H′ = 1.57) and Arctic Terns (H′ = 1.74) and notably lower in Roseate (H′ = 1.24) and Least Terns (H′ = 1.37), whose diets were primarily piscivorous. The degree of dietary plasticity and general feeding ecology provided by baseline dietary information can inform holistic assessments of risk to ongoing and future disturbances from fishing and climate change.

Maine↗
USGS2011

Indigenous observations of climate change in the Lower Yukon River Basin, Alaska

Natural science climate change studies have led to an overwhelming amount of evidence that the Arctic and Subarctic are among the world's first locations to begin experiencing climate change. Indigenous knowledge of northern regions is a valuable resource to assess the effects of climate change on the people and the landscape. Most studies, however, have focused on coastal Arctic and Subarctic communities with relatively little focus on inland communities. This paper relates the findings from fieldwork conducted in the Lower Yukon River Basin of Alaska in the spring of 2009. Semi-structured interviews were conducted with hunters and elders in the villages of St. Mary's and Pitka's Point, Alaska to document observations of climate change. This study assumes that scientific findings and indigenous knowledge are complementary and seeks to overcome the false dichotomy that these two ways of knowing are in opposition. The observed changes in the climate communicated by the hunters and elders of St. Mary's and Pitka's Point, Alaska are impacting the community in ways ranging from subsistence (shifting flora and fauna patterns), concerns about safety (unpredictable weather patterns and dangerous ice conditions), and a changing resource base (increased reliance on fossil fuels). Here we attempt to address the challenges of integrating these two ways of knowing while relating indigenous observations as described by elders and hunters of the study area to those described by scientific literature.

Human Organization↗
USGS2014

Wildlife health in a rapidly changing North: focus on avian disease

Climate-related environmental changes have increasingly been linked to emerging infectious diseases in wildlife. The Arctic is facing a major ecological transition that is expected to substantially affect animal and human health. Changes in phenology or environmental conditions that result from climate warming may promote novel species assemblages as host and pathogen ranges expand to previously unoccupied areas. Recent evidence from the Arctic and subarctic suggests an increase in the spread and prevalence of some wildlife diseases, but baseline data necessary to detect and verify such changes are still lacking. Wild birds are undergoing rapid shifts in distribution and have been implicated in the spread of wildlife and zoonotic diseases. Here, we review evidence of current and projected changes in the abundance and distribution of avian diseases and outline strategies for future research. We discuss relevant climatic and environmental factors, emerging host–pathogen contact zones, the relationship between host condition and immune function, and potential wildlife and human health outcomes in northern regions.

Frontiers in Ecology and the Environment↗
USGS2016

Demography of an apex predator at the edge of its range: impacts of changing sea ice on polar bears in Hudson Bay

Changes in the abundance and distribution of wildlife populations are common consequences of historic and contemporary climate change. Some Arctic marine mammals, such as the polar bear ( Ursus maritimus ), may be particularly vulnerable to such changes due to the loss of Arctic sea ice. We evaluated the impacts of environmental variation on demographic rates for the Western Hudson Bay (WH), polar bear subpopulation from 1984 to 2011 using live-recapture and dead-recovery data in a Bayesian implementation of multistate capture–recapture models. We found that survival of female polar bears was related to the annual timing of sea ice break-up and formation. Using estimated vital rates (e.g., survival and reproduction) in matrix projection models, we calculated the growth rate of the WH subpopulation and projected population responses under different environmental scenarios while accounting for parametric uncertainty, temporal variation, and demographic stochasticity. Our analysis suggested a long-term decline in the number of bears from 1185 (95% Bayesian credible interval [BCI] = 993–1411) in 1987 to 806 (95% BCI = 653–984) in 2011. In the last 10 yr of the study, the number of bears appeared stable due to temporary stability in sea ice conditions (mean population growth rate for the period 2001–2010 = 1.02, 95% BCI = 0.98–1.06). Looking forward, we estimated long-term growth rates for the WH subpopulation of ~1.02 (95% BCI = 1.00–1.05) and 0.97 (95% BCI = 0.92–1.01) under hypothetical high and low sea ice conditions, respectively. Our findings support previous evidence for a demographic linkage between sea ice conditions and polar bear population dynamics. Furthermore, we present a robust framework for sensitivity analysis with respect to continued climate change (e.g., to inform scenario planning) and for evaluating the combined effects of climate change and management actions on the status of wildlife populations.

Hudson Bay↗
USGS2009

Organochlorine contaminants in fishes from coastal waters west of Amukta Pass, Aleutian Islands, Alaska, USA

Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus) , Pacific halibut (Hippoglossus stenolepis) , and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Σ) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (ΣDDTs, Σchlordane cyclodienes, Σother cyclodienes, and Σchlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by ΣDDTs and Σchlordanes; dichlorodiphenyldi-chloroethylene ( p , p ′DDE) composed 52 to 66% of ΣDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but ΣPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with δ 15 N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of ΣPCBs and p , p ′DDE among species and locations.

Alaska↗
USGS2004

A geologic framework for mineralization in the western Brooks Range

The Brooks Range is a 950-km-long north-vergent fold and thrust belt, which was formed during Mesozoic convergence of the continental Arctic Alaska terrane and the oceanic Angayucham terrane and was further shortened and uplifted in Tertiary time. The Arctic Alaska terrane consists of parautochthonous rocks and the Endicott Mountains and De Long Mountains subterranes. The Endicott Mountains allochthon of the western Brooks Range is the setting for many sulfide and barite occurrences, such as the supergiant Red Dog zinc-lead mine. Mineralization is sediment hosted and most commonly is present in black shale and carbonate turbidites of the Mississippian Kuna Formation. The reconstructed Kuna basin is a 200 by +600 km feature that represents the culmination of a remarkable chain of events that includes three fluvial-deltaic and two or more orogenic cycles, Middle Devonian to Mississippian episodes of extension and igneous activity, and the emergence of a seaward Lower Proterozoic landmass that may have constituted a barrier to marine circulation. Mississippian extension and related horst-and-graben architecture in the western Brooks Range is manifested in part by strong facies variability between coeval units of allochthons and structural plates. Shallow marine to possibly nonmarine arkose, platform to shelf carbonate, slope-to-basin shale, chert and carbonate turbidites, and submarine volcanic rocks are all represented in Mississippian time. The structural setting of Mississippian sedimentation, volcanism, and mineralization in the Kuna basin may be comparable to documented Devono-Mississippian extensional sags or half-grabens in the subsurface north of the Brooks Range. Climate, terrestrial ecosystems, multiple fluvial-deltaic aquifers, and structural architecture affected the liberation, movement, and redeposition of metals in ways that are incompletely understood.

Alaska↗
USGS1994

Emperor goose (Chen canagica)

Early naturalists exploring western Alaska were intrigued to find a stocky, blue-gray species of coastal goose unique to that area and nearby Russia. As E. W. Nelson (1887) wrote, "Among the various species of birds more or less peculiar to Alaska this goose is perhaps the most noteworthy." The Emperor Goose nests in the extensive coastal salt marsh habitats of arctic and sub-arctic Alaska and Russia and winters primarily on coastal beaches along ice-free areas of the Aleutian Islands and the Alaska Peninsula. Locally known as the "Beach Goose" from its habit of roosting and feeding near the waters' edge, the diet of this species consists largely of clams, mussels, and algae when wintering and staging in marine and estuarine habitats. When nesting in terrestrial habitats, it eats mostly roots, bulbs, and shoots of vegetation. Although the breeding biology and habitat requirements of this goose have been examined in detail, mostly on the Yukon-Kuskokwim Delta (Y-K Delta) of Alaska, there have been no intensive studies of its wintering or staging biology. Recent studies of migration have confirmed pathways and timing between the Y-K Delta and staging areas on the Alaska Peninsula and wintering areas largely on the Aleutian Islands (Hupp et al. 2007). Observations of substantial molt migrations to the Chukotka Peninsula in eastern Russia (Hupp et al. 2007) suggest a possible change in distribution, or at least a clarification, and raise the possibility of harvest mortality on both continents. Alaska's Emperor Goose population declined precipitously from 139,000 in 1964 to 42,000 in 1986, although its numbers have recovered slightly since then (Fischer et al. 2008). The factors responsible for this quick decline and slow recovery remain poorly known. Hunting, especially subsistence hunting by Native Americans, is probably a factor (Hupp et al. 2008b); coastal oil pollution could also be reducing the survival of overwintering individuals (Byrd et al. 1995); and interspecific competition among brood rearing geese may limit recovery through recruitment (Schmutz and Laing 2002, Lake et al. 2008).

Birds of North America↗
USGS2010

Effects of earlier sea ice breakup on survival and population size of polar bears in western Hudson Bay

Some of the most pronounced ecological responses to climatic warming are expected to occur in polar marine regions, where temperature increases have been the greatest and sea ice provides a sensitive mechanism by which climatic conditions affect sympagic (i.e., with ice) species. Population-level effects of climatic change, however, remain difficult to quantify. We used a flexible extension of Cormack-Jolly-Seber capture-recapture models to estimate population size and survival for polar bears (Ursus maritimus), one of the most ice-dependent of Arctic marine mammals. We analyzed data for polar bears captured from 1984 to 2004 along the western coast of Hudson Bay and in the community of Churchill, Manitoba, Canada. The Western Hudson Bay polar bear population declined from 1,194 (95% CI = 1,020-1,368) in 1987 to 935 (95% CI = 794-1,076) in 2004. Total apparent survival of prime-adult polar bears (5-19 yr) was stable for females (0.93; 95% CI = 0.91-0.94) and males (0.90; 95% CI = 0.88-0.91). Survival of juvenile, subadult, and senescent-adult polar bears was correlated with spring sea ice breakup date, which was variable among years and occurred approximately 3 weeks earlier in 2004 than in 1984. We propose that this correlation provides evidence for a causal association between earlier sea ice breakup (due to climatic warming) and decreased polar bear survival. It may also explain why Churchill, like other communities along the western coast of Hudson Bay, has experienced an increase in human-polar bear interactions in recent years. Earlier sea ice breakup may have resulted in a larger number of nutritionally stressed polar bears, which are encroaching on human habitations in search of supplemental food. Because western Hudson Bay is near the southern limit of the species' range, our findings may foreshadow the demographic responses and management challenges that more northerly polar bear populations will experience if climatic warming in the Arctic continues as projected.

Journal of Wildlife Management↗
USGS2017

Part I, the development of the method

A freshly exposed surface of obsidian will take up water from the atmosphere to form a hydrated surface layer. This layer has a different density and refractive index than does the remainder of the obsidian. Using special techniques, a thin section of the obsidian cut at right angles to the surface can be prepared. When examined under the microscope the hydrated layer is visible and its thickness can be measured. Photomicrographs of such thin sections are shown. Factors that determine the rate of hydration were considered. Using artifacts from archaeological sites of known age, the influence of temperature, relative humidity, chemical composition of the obsidian, burning and erosion of the obsidian on the rates of hydration was determined. Temperature and chemical composition are the main factors controlling the rate of hydration. Obsidian hydrates more rapidly at a higher temperature, and thus progresses at a faster rate in tropical than in arctic climates. Rhyolitic obsidian hydrates more slowly than does trachytic obsidian. Using archaeological data from various parts of the world, several tentative hydration rates were determined for tropical, temperate, and arctic climates. The method in its present state of development is especially suited to determine relative chronologies in layered sequences of artifacts from a single site, or region. It is also useful for detecting fake artifacts. Future work to refine the method is suggested.

American Antiquity↗
USGS1991

Growth rate is negatively correlated with hatch date in Black Brant

Arctic geese nest in a highly seasonal environment in which ungrazed plants reach peak nitrogen concentrations when goslings hatch (Sedinger and Raveling 1986). Grazing by geese prolongs peak nutrient concentrations but reduces food availability. This should cause nutrient availability to decline seasonally. Here, we test the hypothesis that late-hatching goslings of Black Brant ( Branta bernicla nigricans ) grow more slowly than those hatching early. We substracted the sizes of wild goslings from those of captive-reared goslings of the same age and regressed the differences against hatch date. Differences between wild- and captive-reared goslings for body mass, tarsus length, and culmen length were significantly negatively related to hatch date; i.e., late-hatching wild goslings were smaller than those hatching early, after accounting for age. We detected no between-year difference in gosling size, but male goslings were larger than females of the same age for all measures. Egg size was only weakly associated with size of goslings 1 mo after hatching, but we detected no effect of other brood characteristics on growth. Seasonal variation in gosling growth rate may favor early nesting in arctic geese.

Alaska↗
USGS1996

DDE decreases in plasma of spring migrant peregrine falcons, 1978-94

Mean p,p'-DDE (DDE) residues in plasma of combined adult and subadult female peregrine falcons (Falco peregrinus) decreased significantly in spring migrants captured at Padre Island, Texas, between 1978 and 1979 (1.00 μg /g wet wt), 1980 (0.57), 1984 (0.50), and 1994 (0.34). No other organochlorine pesticides were detected (detection limit, 0.02 μ g/g) in 1994. Mirex, oxychlordane, dieldrin, heptachlor epoxide, and the parent material DDT were routinely found in plasma samples in earlier years. Polychlorinated biphenyls (PCBs) were found in 75% of the adult females in 1994, but PCB data collected in 1984 were not comparable. The decrease in organochlorine pesticide residues was associated with peregrine population increases in the Arctic and elsewhere in North America. The arctic peregrine ( F. p. tundrius ) was removed from the list of Threatened and Endangered Species by the U.S. Fish and Wildlife Service in 1994. Satellite telemetry and plasma sampling provide new insight into continuing sources of DDE and PCBs. Chemicals that replaced organochlorine pesticides require additional investigation in North and South America.

Texas↗
USGS1998

Genetic differentiation between wintering populations of lesser snow geese nesting on Wrangel Island, Russia

Arctic breeding populations of Lesser Snow Geese ( Chen c. caerulescens ) range from Baffin Island in eastern Canada to Wrangel Island, Russia, which is located 650 km west of Alaska (Bellrose 1980). Although hundreds of thousands of Lesser Snow Geese may have occupied the Russian arctic in the mid1800s (see Takekawa et al., 1994), the Wrangel Island birds constitute the only remnant colony on the Asian continent (Syroechkovsky and Litvin 1986) and may represent a matriarchal population for the species (Quinn 1992). In the past 30 years, the Wrangel Island colony has declined from more than 200,000 to less than 75,000 breeding adults (Pacific Flyway Technical Subcommittee 1992, V. Baranyuk unpubl. data), which has resulted in increasing concern about its conservation and management. The Wrangel Island colony consists of two wintering populations that migrate to different regions and are faithful to their wintering areas (McKelvey et al. 1989). The larger northern population (about 60% of the total from Wrangel) migrates to the Fraser River delta of British Columbia and the Skagit River delta of northern Washington, whereas the southern population flies 600 km farther south to the Central Valley of California (Rienecker 1965, Teplov and Shev. aryova 1965, Jeffrey and Kaiser 1979, Priklonsky and Sapetin 1979). The northern population is isolated from other Lesser Snow Geese during the winter, but the southern population mixes with geese from Banks Island, Canada and from the smaller Anderson and Sagaviriniktok River deltas (Dzubin 1974, Johnson 1995, Syroechkovsky et al. 1994).

The Auk↗
USGS1999

At-sea distribution of Spectacled Eiders: A 120-year-old mystery resolved

The at-sea distribution of the threatened Spectacled Eider ( Somateria fischeri ) has remained largely undocumented. We identified migration corridors, staging and molting areas, and wintering areas of adult Spectacled Eiders using implanted satellite-transmitters in birds from each of the three extant breeding grounds (North Slope and Yukon-Kuskokwim Delta in Alaska and arctic Russia). Based on transmitter locations, we conducted aerial surveys to provide visual confirmation of eider flocks and to estimate numbers of birds. We identified two principal molting and staging areas off coastal Alaska (Ledyard Bay and eastern Norton Sound) and two off coastal Russia (Mechigmenskiy Bay on the eastern Chukotka Peninsula, and the area between the Indigirka and Kolyma deltas in the Republic of Sakha). We estimated that >10,000 birds molt and stage in monospecific flocks at Mechigmenskiy and Ledyard bays, and several thousand molt and stage in eastern Norton Sound. We further identified eastern Norton Sound as the principal molting and staging area for females nesting on the Yukon-Kuskokwim Delta, and Ledyard Bay and Mechigmenskiy Bay as the principal molting and staging areas for females nesting on the North Slope. Males marked at all three breeding grounds molt and stage in Mechigmenskiy Bay, Ledyard Bay, and the Indigirka-Kolyma delta region. Males from the Yukon-Kuskokwim Delta molt and stage mainly at Mechigmenskiy Bay. Equal numbers of males from the North Slope molt and stage at all three areas, and most males from arctic Russia molt and stage at the Indigirka-Kolyma delta region. Postbreeding migration corridors were offshore in the Bering, Chukchi, and Beaufort seas. In winter, eiders were in the Bering Sea south of St. Lawrence Island. Our estimates from surveys in late winter and early spring suggest that at least 333,000 birds winter in single-species flocks in the pack ice in the Bering Sea.

Alaska↗
USGS2019

Managing effects of drought and other water resource challenges in Alaska and the Pacific Northwest

This is a Cooperator Report. As such, there is no specific abstract. The physical, ecological, and social environments of Alaska and the Pacific Northwest (PNW) region of the United States are extremely diverse. Alaska ranges from the Arctic Ocean and the very cold, dry environments of the North Slope to the cool and very rainy coastal North Pacific region of Southeast Alaska. Most precipitation falls as snow at higher elevations. In Arctic Alaska, average annual temperature is 14.6 F, and average annual precipitation is 11 inches. By contrast, in Southeast Alaska, average annual temperature is 35.8 F, and annual average precipitation is 143 inches. The PNW, defined here as Idaho, Oregon, and Washington, ranges from the Pacific Coast (annual precipitation of 200 inches) to interior semi-arid regions (annual precipitation of 8 inches). Precipitation patterns in the PNW are strongly governed by orographic phenomena, with high, persistent snowpack in the higher mountains (e.g., record annual snowfall of 1,130 in at Mount Baker, Washington in 1999-2000). Ecosystems in the PNW include productive temperate coniferous forests near the Pacific coast and along the (wet) west slope of the Cascade Range, less productive mixed-conifer forest along the (dry) east slope of the Cascades and in interior mountain ranges, and sagebrush-steppe and shrublands at lower elevations in much of the interior and mountain valleys. Large rivers and thousands of smaller tributaries form an extensive network of riparian, wetland, and estuarine systems that provide both critical hydrologic function and biological diversity at broad and fine spatial scales. Although Alaska and the Pacific Northwest differ in important physical, ecological, and social features, the importance of natural resources is evident in both regions. Water is important for wildlife and people. Water provides critical habitat for salmon, which are culturally and economically valuable species. Timber production has declined in recent decades. Recreation has emerged as a major revenue source.

Alaska, Oregon, Washington↗
USGS2005

Beringia: Intercontinental exchange and diversification of high latitude mammals and their parasites during the Pliocene and Quaternary

Beringia is the region spanning eastern Asia and northwestern North America that remained ice-free during the full glacial events of the Pleistocene. Numerous questions persist regarding the importance of this region in the evolution of northern faunas. Beringia has been implicated as both a high latitude refugium and as the crossroads (Bering Land Bridge) of the northern continents for boreal mammals. The Beringian Coevolution Project (BCP) is an international collaboration that has provided material to assess the pattern and timing of faunal exchange across the crossroads of the northern continents and the potential impact of past climatic events on differentiation. Mammals and associated parasite specimens have been collected and preserved from more than 200 field sites in eastern Russia, Alaska and northwestern Canada since 1999. Previously, fossils and taxonomic comparisons between Asia and North America mammals have shed light on these events. Molecular phylogenetics based on BCP specimens is now being used to trace the history of faunal exchange and diversification. We have found substantial phylogeographic structure in the Arctic and in Beringia in mustelid carnivores, arvicoline rodents, arctic hares and soricine shrews, including spatially concordant clades and contact zones across taxa that correspond to the edges of Beringia. Among the tapeworms of these mammalian hosts, new perspectives on diversity have also been developed. Arostrilepis horrida (Hymenolepididae) was considered to represent a single widespread and morphologically variable species occurring in a diversity of voles and lemmings in eastern and western Beringia and more broadly across the Holarctic region. The BCP has demonstrated a complex of at least 10 species that are poorly differentiated morphologically. The diversity of Paranoplocephala spp. and Anolocephaloides spp. (Anoplocephalidae) in Beringia included relatively few widespread and morphologically variable species in arvicolines. BCP collections have changed this perspective, allowing the recognition of a series of highly endemic species of Paranoplocephala that demonstrate very narrow host specificity, and additional species complexes among arvicolines. Thus, extensive, previously unrecognized, diversity for tapeworms of 2 major families characterizes the Beringian fauna. By elucidating evolutionary relationships and phylogeographic variation among populations, species and assemblages, refined views of the sequence and timing of biotic expansion, geographic colonization and impact of episodic climate change have been developed for Beringia. Ultimately, Beringia was a determining factor in the structure and biogeography of terrestrial faunas across the Nearctic and Neotropical regions during the Pliocene and Quaternary.

Berengia↗
USGS1951

Stratigraphy and structure of the southern foothills section between the Etivluk and Kiligwa Rivers

The part of the Southern Foothill section, Arctic foothills province, that lies beteween the Etivluk and Kiligwa Rivers was investigated by Navy Oil Unit party 6 during the 1950 field season, A belt about 16 miles wide and 60 miles long (approximately 800 square miles) was mapped in considerable detail (see index map, pl. 1). The mapped area is in the west-central part of the Arctic Foothills province, wholly within the boundaries of Naval Petroleum Reserve No. 4. Major drainage consists of the middle reaches of the Etivluk, Ipnavik, Kuna, and Kiligwa Rivers. Principal objectives of the party, using previous geologic studies in. the Okpikruak-Kiruktagiak Rivers area 1/ ao an initial working base, were stratigraphic and structural studies of the outcrops in the interstream areas. In view of the former interest in possible Lisburne limestone plays, the Lisburne Ridge west of the Etivluk River and the northward nosing of the Triassic complex between the Ipnavik and Kuna Rivers were designated as areas for particular emphasis. The party included six men: two geologists; two field assistants, a cook, and a weasel mechanic. Three weasels were available for transportation; two of which were maintained in operating condition for daily field use. As many exposures as were pertinent or accessible were examined. Vertical photographs were used for plotting data and for areal control; relative vertical control was established with altimeters, The effective working radius from base camp as increased from 8 miles to 20 miles by making frequent 2- or 3-day spike trips.

Alaska↗
USGS2013

Tectonic map of the Circum-Pacific region, Pacific basin sheet

Circum-Pacific Map Project : The Circum-Pacific Map Project was a cooperative international effort designed to show the relationship of known energy and mineral resources to the major geologic features of the Pacific basin and surrounding continental areas. Available geologic, mineral, and energy-resource data are being complemented by new, project-developed data sets such as magnetic lineations, seafloor mineral deposits, and seafloor sediment. Earth scientists representing some 180 organizations from more than 40 Pacific-region countries are involved in this work. Six overlapping equal-area regional maps at a scale of 1:10,000,000 form the cartographic base for the project: the four Circum-Pacific Quadrants (Northwest, Southwest, Southeast, and Northeast), and the Antarctic and Arctic Sheets. There is also a Pacific Basin Sheet at a scale of 1:17,000,000. The Base Map Series and the Geographic Series (published from 1977 to 1990), the Plate-Tectonic Series (published in 1981 and 1982), the Geodynamic Series (published in 1984 and 1985), and the Geologic Series (published from 1984 to 1989) all include six map sheets. Other thematic map series in preparation include Mineral-Resources, Energy-Resources and Tectonic Maps. Altogether, more than 50 map sheets are planned. The maps were prepared cooperatively by the Circum-Pacific Council for Energy and Mineral Resources and the U.S. Geological Survey and are available from the Branch of Distribution, U. S. Geological Survey, Box 25286, Federal Center, Denver, Colorado 80225, U.S.A. The Circum-Pacific Map Project is organized under six panels of geoscientists representing national earth-science organizations, universities, and natural-resource companies. The six panels correspond to the basic map areas. Current panel chairmen are Tomoyuki Moritani (Northwest Quadrant), R. Wally Johnson (Southwest Quadrant), Ian W.D. Dalziel (Antarctic Region), vacant. (Southeast Quadrant), Kenneth J. Drummond (Northeast Quadrant), and George W. Moore (Arctic Region). Project coordination and final cartography was being carried out through the cooperation of the Office of the Chief Geologist of the U.S. Geological Survey, under the direction of General Chairman, George Gryc of Menlo Park, California. Project headquarters were located at 345 Middlefield Road, MS 952, Menlo Park, California 94025, U.S.A. The framework for the Circum-Pacific Map Project was developed in 1973 by a specially convened group of 12 North American geoscientists meeting in California. The project was officially launched at the First Circum-Pacific Conference on Energy and Mineral Resources, which met in Honolulu, Hawaii, in August 1974. Sponsors of the conference were the AAPG, Pacific Science Association (PSA), and the Coordinating Committee for Offshore Prospecting for Mineral Resources in Offshore Asian Areas (CCOP). The Circum-Pacific Map Project operates as an activity of the Circum-Pacific Council for Energy and Mineral Resources, a nonprofit organization that promotes cooperation among Circum-Pacific countries in the study of energy and mineral resources of the Pacific basin. Founded by Michel T. Halbouty in 1972, the Council also sponsors conferences, topical symposia, workshops and the Earth Science Series books. Tectonic Map Series : The tectonic maps distinguish areas of oceanic and continental crust. Symbols in red mark active plate boundaries, and colored patterns show tectonic units (volcanic or magmatic arcs, arc-trench gaps, and interarc basins) associated with active plate margins. Well-documented inactive plate boundaries are shown by symbols in black. The tectonic development of oceanic crust is shown by episodes of seafloor spreading. These correlate with the rift and drift sequences at passive continental margins and episodes of tectonic activity at active plate margins. The recognized episodes of seafloor spreading seem to reflect major changes in plate kinematics. Oceanic plateaus and other prominences of greater than normal oceanic crustal thickness such as hotspot traces are also shown. Colored areas on the continents show the ages of deformation and metamorphism of basement rocks and the emplacement of igneous rocks. Transitional tectonic (molassic) and reactivation basins are shown by a colored boundary, and if they are deformed, a colored horizontal line pattern indicates the age of deformation. Colored bands along basin boundaries indicate age of inception, and isopachs indicate thickness of platform strata on continental crust and cover on oceanic crust. Colored patterns at separated continental margins show the age of inception of rift and drift (breakup) sequences. Symbols mark folds and faults, and special symbols show volcanoes and other structural features. Affiliations are as of compilation of the data. This map was created in quadrants and then compiled together. They are the Northwest land, Northwest Marine (different compilers), Northeast, Southwest and Southeast, and parts in plate-boundary sections.

Circum-Pacific Map↗