Cenozoic history of the Bering land bridge
The seaway between the Pacific and Arctic basins has often been a land route between Siberia and Alaska.
Alaska, Siberia↗
SEARCH · Search USGS
Results for “Arctic”
Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Pleistocene marine microfauna in the Bootlegger Cove Clay, Anchorage, Alaska
Ostracods and Foraminifera, associated with mollusks, indicate a marine depositional environment for part of the Bootlegger Cove Clay. The definite Arctic and North Atlantic affinities of the microfauna suggest a possible migration through the Bering-Chukchi seaway during the late Pleistocene.
Alaska↗
Technical comment on “Global pattern of nest predation is disrupted by climate change in shorebirds”
Kubelka et al. (Report, 9 November 2018, p. 680-683) claim that climate change has disrupted patterns of nest predation in shorebirds. They report that predation rates have increased since the 1950s, especially in the Arctic. We describe methodological problems with their analyses and argue that there is no solid statistical support for their claims.
Science↗
The evolution of a tropical biodiversity hotspot
The role of the environment in the origin of new species has long been debated. Harvey et al. examined the evolutionary history and species diversity of suboscine birds in the tropics (see the Perspective by Morlon). Contrary to expectations that the tropics have higher rates of speciation, the authors observed that higher and more constant speciation rates occur in harsh environments relative to the tropics. Thus, for this group of birds, diversification in temperate to Arctic regions followed by the movement and retention of species in the tropics results in their higher local levels of species diversity.
Science↗
Phytosociological study of the dwarf shrub heath of Simeonof Wilderness, Shumagin Islands, Southwestern Alaska
The maritime dwarf shrub heath vegetation of the Northern Pacific, Simeonof Island, Shumagin Islands, Southwestern Alaska, was studied according to the Braun-Blanquet approach. Based on 30 releve??s of 16 m2 that include vascular plants, bryophytes, and lichens, two new associations could be described belonging to the class Loiseleurio-Vaccinietea (order Rhododendro-Vaccinietalia): Rubo-Empetretum nigri and Carici-Empetretum nigri. The wind-sheltered Rubo-Empetretum nigri (alliance Phyllodoco-Vaccinion) mainly occurs in the lowlands on level terrain or sloping sites at lower foot slopes of mountains on deeper, mesic soil; this association is the zonal vegetation of the lowlands. Boreal, widespread and amphi-Beringian species are prominent in the distribution-type spectrum of the vascular plants. Two variants of Rubo-Empetretum nigri are described. A Geranium erianthum variant occurs on south-facing slopes and is rich in vascular plants species. A Plagiothecium undulatum variant is restricted to northern exposures and is rich in bryophytes and lichens. A Carici-Empetretum nigri (alliance Loiseleurio-Diapension) occurs on shallow soil on wind exposed sites at higher elevations in the mountains. It is very rich in lichen species of arctic-alpine distribution. Canonical correspondence analysis (CCA) suggests that altitude, nutrient content of the soil and exposition are the most important differential ecological factors. Soil depth, total carbon and nitrogen content, plant available phosphorus and all other measured cation contents are higher in Rubo-Empetretum than in Carici-Empetretum. Literature comparisons confirm the occurrence of both associations in other areas on the Southwest Alaska Peninsula and Aleutian Islands. Presumably both associations have an amphi-Beringian distribution. The syntaxonomy of boreal-montane dwarf shrub heaths and synecological aspects are briefly discussed. ?? 2004 Gebru??der Borntraeger.
Phytocoenologia↗
Comparative phytosociological investigation of subalpine alder thickets in southwestern Alaska and the North Pacific
We present the first vegetation analysis of subalpine alder (Alnus viridis) thickets in southwestern Alaska. The data are primarily from mesic, hilly and mountainous sites ranging from the westernmost tip of the Alaska Peninsula to the northern Kenai Peninsula, spanning 1,000 km on an E–W gradient and 700 km on a N–S gradient. 127 relevés from 18 sites represent the range of structural and compositional variation in the matrix of vegetation and landform diversity. Data were analyzed by multivariate and traditional Braun-Blanquet methods. One association is distinguished, Sambuco racemosi-Alnetum viridis ass. nov. with three new subassociations, oplopanacetosum horridi, typicum, and rubetosum spectabilis with the latter subdivided into four variants. These phytocoena are well-differentiated, although they form a syntaxonomical continuum. The composition and structure of these communities are described and interpreted in relation to complex environmental factors; these are analyzed using Jancey's ranking on F-values. Community composition is primarily related to elevation, longitude, soil moisture, and latitude. Phytogeographic comparison of southwestern Alaska alder communities with those elsewhere in the North Pacific suggests a close floristic relationship to those of southcentral, southeastern Alaska and coastal British Columbia, Canada. All these communities belong to the same association, while those of the eastern and southern parts of the Kamchatka Peninsula, Russia belong to a different association. Syntaxonomy of the 4 major communities is discussed. Within the Northern Hemisphere, vascular plant species of southwestern Alaska alder thickets primarily occur in East Asia and North America, 36 %; while 26 % are circumpolar, and 22 % are restricted to North America. From a latitudinal perspective, the distribution of vascular plant species within these alder thickets peaks in the high-subarctic, low-subarctic, and temperate latitudinal zones, with low representation of arctic species.
Alaska↗
Cooling perspectives on the risk of pathogenic viruses from thawing permafrost
Climate change is inducing wide-scale permafrost thaw in the Arctic and subarctic, triggering concerns that long-dormant pathogens could reemerge from the thawing ground and initiate epidemics or pandemics. Viruses, as opposed to bacterial pathogens, garner particular interest because outbreaks cannot be controlled with antibiotics, though the effects can be mitigated by vaccines and newer antiviral drugs. To evaluate the potential hazards posed by viral pathogens emerging from thawing permafrost, we review information from a diverse range of disciplines. This includes efforts to recover infectious virus from human remains, studies on disease occurrence in polar animal populations, investigations into viral persistence and infectivity in permafrost, and assessments of human exposure to the enormous viral diversity present in the environment. Based on currently available knowledge, we conclude that the risk posed by viruses from thawing permafrost is no greater than viruses in other environments such as temperate soils and aquatic systems.
mSystems↗
Lithostratigraphic, conodont, and other faunal links between lower Paleozoic strata in northern and central Alaska and northeastern Russia
Lower Paleozoic platform carbonate strata in northern Alaska (parts of the Arctic Alaska, York, and Seward terranes; herein called the North Alaska carbonate platform) and central Alaska (Farewell terrane) share distinctive lithologic and faunal features, and may have formed on a single continental fragment situated between Siberia and Laurentia. Sedimentary successions in northern and central Alaska overlie Late Proterozoic metamorphosed basement; contain Late Proterozoic ooid-rich dolostones, Middle Cambrian outer shelf deposits, and Ordovician, Silurian, and Devonian shallow-water platform facies, and include fossils of both Siberian and Laurentian biotic provinces. The presence in the Alaskan terranes of Siberian forms not seen in wellstudied cratonal margin sequences of western Laurentia implies that the Alaskan rocks were not attached to Laurentia during the early Paleozoic. The Siberian cratonal succession includes Archean basement, Ordovician shallow-water siliciclastic rocks, and Upper Silurian–Devonian evaporites, none of which have counterparts in the Alaskan successions, and contains only a few of the Laurentian conodonts that occur in Alaska. Thus we conclude that the lower Paleozoic platform successions of northern and central Alaska were not part of the Siberian craton during their deposition, but may have formed on a crustal fragment rifted away from Siberia during the Late Proterozoic. The Alaskan strata have more similarities to coeval rocks in some peri-Siberian terranes of northeastern Russia (Kotelny, Chukotka, and Omulevka). Lithologic ties between northern Alaska, the Farewell terrane, and the peri-Siberian terranes diminish after the Middle Devonian, but Siberian afµnities in northern and central Alaskan biotas persist into the late Paleozoic.
Alaska↗
Thermal effects of the ocean on permafrost
In high latitudes the large difference between the mean annual temperature at the ground surface and in the unfrozen sediments beneath bodies of water can affect ground temperatures to depths of several hundred feet. The effect is of particular interest near the edge of the ocean where it depends upon the magnitude of the temperature difference between the land surface and ocean bottom, the thermal properties of the ground materials, and past changes in climate and/or shore-line configuration. Theoretical considerations suggest that, except where there are transgressing shore lines, permafrost to depths greater than about 100 feet beneath the ocean bottom is not to be expected at points farther than a few thousand feet offshore. Similar considerations indicate that geothermal installations along the Arctic coast can give information regarding post-Pleistocene shore-line changes. The geothermal effects of bodies of water offer an explanation for the anomalously large outward earth-heat flow recently reported by A. D. Misener for Resolute Bay, Cornwallis Island, N. W. T., Canada.
GSA Bulletin↗
Radial outflow and unsteady retreat of late Wisconsin to early Holocene icecap in the northern Long Range upland, Newfoundland
A swampy very low-relief drift terrain along the medial zone of the northern Long Range Mountains passes outward into fresh glacially eroded bed rock of low to moderate relief. Striations, crescentic gouges, lunate fractures, streamlined stoss-and-ice surfaces, erratics, and other evidence in the upland abundantly reveal radial outflow from a late-glacial icecap that was centered over the Long Range and discharged through peripheral fjord-like valleys to coastal lowlands. A discontinuous belt of moraines and concentrated boulders delineates a still-stand or readvance after the icecap had retreated entirely to the upland and was about 50 km broad. Relatively thick till and an abundance of boulders in the medial low-relief zone suggest that after further contraction to 10 to 15 km wide, the icecap contracted rather slowly. These upland moraines may correlate with cool intervals 11,000 to 9,000 yr ago in the oxygen-isotope record of the ice core from Camp Century, Greenland, or with glacier advances 9,000 to 8,000 yr ago in Greenland and the Canadian Arctic.
Geological Society of America Bulletin↗
Glaciotectonic origin of the Massachusetts coastal end moraines and a fluctuating late Wisconsinan ice margin
Late Wisconsinan end moraines on Cape Cod and islands south and west of Cape Cod are believed to be glaciotectonic features formed by advancing ice fronts. Evidence of a glaciotectonic origin includes the stratified drift composition of the moraines, dislocated preglacial and glaciolacustrine deposits, tilted preglacial and glacial beds, folding and thrust faulting, and morphologic similarity to ancient and modern glaciotectonic moraines. Evidence for major ice readvances during over-all general recession includes the moraines themselves, till atop stratified drift, and the numerous basal tills that are inferred to exist beneath Cape Cod Bay. The Thompson Glacier end moraine in the Canadian Arctic Archipelago is considered to be a modern example of how late Wisconsinan end moraines on Cape Cod and the islands were formed. The Thompson Glacier is overriding its outwash plain, displacing outwash deposits forward and upward beyond the ice front. New sheets are added to the base of the moraine, and till is deposited atop the moraine as the ice overrides it. Evidence from Cape Cod and the nearby islands indicates that over-all recession of late Wisconsinan ice was characterized by alternating episodes of ice-front retreat, during which the outwash plains were formed, and of ice-front advance, during which the moraines were built. Retreat of the ice from Cape Cod and the islands may have been similar to the retreat of the Lake Michigan lobe, deposits of which contain evidence of at least 12 moraine-building episodes caused by readvancing ice during the over-all retreat of the late Wisconsinan ice sheet.
Geological Society of America Bulletin↗
Paleobiogeographic affinities of emsian (late early devonian) gastropods from farewell terrane (west-central Alaska)
The vast majority of Emsian gastropods from Limestone Mountain, Medfra B-4 quadrangle, west-central Alaska (Farewell terrane) belong to species with lecithotrophic larval strategy. The present data show that there is no significant difference in the paleobiogeo-graphic distribution of Emsian gastropod genera with lecithotrophic and planktotrophic larval strategies. Numerical analysis of the faunal affinities of the Emsian gastropod fauna from the Farewell terrane reveals that this terrane has much stronger faunal connections to regions like Variscan Europe, eastern Australia, and the Alexander terrane of southeast Alaska than to cratonic North America (Laurentia). The Canadian Arctic Islands is the only region of cratonic North America (Laurentia) that shows significant faunal affinities to the Emsian gastropod faunas of the Farewell terrane. The analysis also indicates a close faunal link between the Farewell and Alexander terranes. Published paleontological and geological data suggest that the Farewell and Alexander terranes represents tectonic entities that have been rifted away from the Siberia, Baltica, or the paleo-Pacific margin of Australia. The results of the present numerical analysis are not in conflict with any of these possibilities. However, the principle of spatial continuity of the wandering path prefers Siberia as the most probable "parental" paleocontinent for the derivation of both the Farewell and Alexander terranes. ?? 2008 The Geological Society of America.
Special Paper of the Geological Society of America↗
Neoproterozoic–early Paleozoic provenance evolution of sedimentary rocks in and adjacent to the Farewell terrane (interior Alaska)
New detrital zircon U-Pb data from the Farewell terrane of interior Alaska illuminate its early provenance evolution and connections with other Alaskan terranes. Five samples come from Neoproterozoic units in the central Farewell terrane. Basal “ferruginous beds” and the overlying Windy Fork Formation have prominent detrital zircon age populations between 2000 and 1800 Ma, with the Windy Fork Formation also having major age peaks between 700 and 600 Ma. Younger (Lone Formation) samples yield grains mainly between 750 and 550 Ma, with fewer older Proterozoic grains. Eleven samples come from deep-water early Paleozoic rocks (southeastern Farewell terrane). Ordovician sandstone (Post River Formation) has a major age population at ca. 490 Ma and subordinate 785–550 Ma populations that overlap age peaks in the Lone Formation. Turbidites in the overlying Terra Cotta Mountains Sandstone (Silurian) yield distinctly different spectra, with major ca. 450–420 Ma age populations and numerous grains between 2000 and 900 Ma. Devonian Barren Ridge Limestone samples have spectra like those of the Terra Cotta Mountains Sandstone, plus some Early Devonian grains. The Silurian shift in detrital zircon age spectra coincides with a major influx of siliciclastic sediment suggestive of a tectonic (collisional?) event involving the Farewell terrane. Neoproterozoic through Devonian successions in the Arctic Alaska–Chukotka and Alexander terranes show a similar up-section shift in detrital zircon spectra, supporting links between these terranes and the Farewell terrane during the early Paleozoic. Detrital zircon ages from the White Mountains and Livengood terranes, adjacent to the northern Farewell terrane, include major early Paleozoic populations that overlap those seen in partly coeval Farewell strata.
Alaska↗
The Lower Cretaceous sequence of western Alaska – demise of the Koyukuk terrane?
Lower Cretaceous marine sedimentary rocks, deposited in shallow shelf and basin settings and unconformity-bound, are well exposed in southwest Alaska. Collections of Early Cretaceous fossils from across western Alaska show that similar and coeval Lower Cretaceous clastic rocks are widely distributed though only locally exposed. Volcanic rocks become an important part of the Lower Cretaceous sequence in the Yukon-Koyukuk basin where they have been interpreted to represent a mobile intra-oceanic island arc, the Koyukuk terrane, that collided with Arctic Alaska to form the Brooks Range orogen. The volcanic rocks are chemically unlike Aleutian arc rocks but share compositional characteristics with spatially related, mid-Cretaceous alkaline intrusive rocks. The volcanic-bearing sequence was also deposited on an angular unconformity, includes both shallow shelf and basin depositional settings, and is unconformably overlain by mid-Cretaceous clastic rocks. The volcanic rocks are therefore considered part of the Lower Cretaceous sequence now identified across western Alaska. In this interpretation, the Lower Cretaceous volcanic rocks are an initial expression of the mid-Cretaceous tectonic regime that included extensional exhumation and subsidence, crustal and upper mantle melting, and high temperature metamorphism in the hinterland of the Brooks Range orogen. The Cretaceous heating that led to hinterland crust and upper mantle change may have been caused by deep mantle disturbances in a post-subduction setting. This interpretation has implications for the timing of contractional orogenesis, the location and nature of the related continental borderland, and the tectonic setting for development of the Anguyucham and related oceanic terranes.
Alaska↗
Using thermal limits to assess establishment of fish dispersing to high-latitude and high-elevation watersheds
Distributional shifts of biota to higher latitudes and elevations are presumably influenced by species-specific physiological tolerances related to warming temperatures. However, it is establishment rather than dispersal that may be limiting colonizations in these cold frontier areas. In freshwater ecosystems, perennial groundwater springs provide critical winter thermal refugia in these extreme environments. By reconciling the thermal characteristics of these refugia with the minimum thermal tolerances of life stages critical for establishment, we develop a strategy to focus broad projections of northward and upward range shifts to the specific habitats that are likely for establishments. We evaluate this strategy using chum salmon ( Oncorhynchus keta ) and pink salmon ( Oncorhynchus gorbuscha ) that seem poised to colonize Arctic watersheds. Stream habitats with a minimum temperature of 4 °C during spawning and temperatures above 2 °C during egg incubation were most vulnerable to establishments by chum and pink salmon. This strategy will improve modelling forecasts of range shifts for cold freshwater habitats and focus proactive efforts to conserve both newly emerging fisheries and native species at northern and upper distributional extremes.
Canadian Journal of Fisheries and Aquatic Sciences↗
At the forefront: evidence of the applicability of using environmental DNA to quantify the abundance of fish populations in natural lentic waters with additional sampling considerations
Environmental DNA (eDNA) sampling has proven to be a valuable tool for detecting species in aquatic ecosystems. Within this rapidly evolving field, a promising application is the ability to obtain quantitative estimates of relative species abundance based on eDNA concentration rather than traditionally labor-intensive methods. We investigated the relationship between eDNA concentration and Arctic char ( Salvelinus alpinus ) abundance in five well-studied natural lakes; additionally, we examined the effects of different temporal (e.g., season) and spatial (e.g., depth) scales on eDNA concentration. Concentrations of eDNA were linearly correlated with char population estimates ( = 0.78) and exponentially correlated with char densities ( = 0.96 by area; 0.82 by volume). Across lakes, eDNA concentrations were greater and more homogeneous in the water column during mixis; however, when stratified, eDNA concentrations were greater in the hypolimnion. Overall, our findings demonstrate that eDNA techniques can produce effective estimates of relative fish abundance in natural lakes. These findings can guide future studies to improve and expand eDNA methods while informing research and management using rapid and minimally invasive sampling.
Canadian Journal of Fisheries and Aquatic Sciences↗
Relationship of otolith strontium-to-calcium ratios and salinity: Experimental validation for juvenile salmonids
Analysis of otolith strontium (Sr) or strontium-to-calcium (Sr:Ca) ratios provides a powerful tool to reconstruct the chronology of migration among salinity environments for diadromous salmonids. Although use of this method has been validated by examination of known individuals and translocation experiments, it has never been validated under controlled experimental conditions. In this study, incorporation of otolith Sr was tested across a range of salinities and resulting levels of ambient Sr and Ca concentrations in juvenile chinook salmon ( Oncorhynchus tshawytscha ), coho salmon ( Oncorhynchus kisutch ), sockeye salmon ( Oncorhynchus nerka ), rainbow trout ( Oncorhynchus rnykiss ), and Arctic char ( Salvelinus alpinus ). Experimental water was mixed, using stream water and seawater as end members, to create experimental salinities of 0.1, 6.3, 12.7, 18.6, 25.5, and 33.0 psu. Otolith Sr and Sr:Ca ratios were significantly related to salinity for all species (r2 range: 0.80-0.91) but provide only enough predictive resolution to discriminate among fresh water, brackish water, and saltwater residency. These results validate the use of otolith Sr:Ca ratios to broadly discriminate salinity histories encountered by salmonids but highlight the need for further research concerning the influence of osmoregulation and physiological changes associated with smoking on otolith microchemistry.
Canadian Journal of Fisheries and Aquatic Sciences↗
Limnology and fish ecology of sockeye salmon nursery lakes of the world
Many important, recently glaciated oligotrophic lakes that lie in coastal regions around the northern rim of the Pacific Ocean produce anadromous populations of sockeye salmon, Oncorhynchus nerka. This paper describes the limnology and fish ecology of two such lakes in British Columbia, five in Alaska, and one in Kamchatka. Then we discuss the following general topics: the biogenic eutrophication of nursery lakes from the nutrients released from salmon carcasses wherein during years of highest numbers of spawners, lake phosphate balances in Lakes Babine, Iliamna, and Dalnee are significantly affected; the use of nursery lakes by young sockeye that reveals five patterns related to size and configuration of lake basins and the distribution of spawning areas; the interactions between various life history stages of sockeye salmon and such resident predators, competitors, and prey as Arctic char, lake trout, Dolly Varden, cutthroat trout, lake whitefish, pygmy whitefish, pond smelt, sticklebacks, and sculpins; the self-regulation of sockeye salmon abundance in these nursery lakes as controlled by density-dependent processes; the interrelations between young sockeye salmon biomass and growth rates, and zooplankton abundance in Babine Lake; and finally, the diel, vertical, pelagial migratory behavior of young sockeye in Babine Lake and the new hypothesis dealing with bioenergetic conservation.
Journal of the Fisheries Research Board of Canada↗