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At least 91 records · Page 5Linked to original sources

USGS2010

An analysis of the carbon balance of the Arctic Basin from 1997 to 2006

This study used several model-based tools to analyse the dynamics of the Arctic Basin between 1997 and 2006 as a linked system of land-ocean-atmosphere C exchange. The analysis estimates that terrestrial areas of the Arctic Basin lost 62.9 Tg C yr -1 and that the Arctic Ocean gained 94.1 Tg C yr -1 . Arctic lands and oceans were a net CO 2 sink of 108.9 Tg C yr -1 , which is within the range of uncertainty in estimates from atmospheric inversions. Although both lands and oceans of the Arctic were estimated to be CO 2 sinks, the land sink diminished in strength because of increased fire disturbance compared to previous decades, while the ocean sink increased in strength because of increased biological pump activity associated with reduced sea ice cover. Terrestrial areas of the Arctic were a net source of 41.5 Tg CH 4 yr -1 that increased by 0.6 Tg CH 4 yr -1 during the decade of analysis, a magnitude that is comparable with an atmospheric inversion of CH 4 . Because the radiative forcing of the estimated CH 4 emissions is much greater than the CO 2 sink, the analysis suggests that the Arctic Basin is a substantial net source of green house gas forcing to the climate system.

Tellus, Series B: Chemical and Physical Meteorolog↗

USGS2013

Laurentian origin for the North Slope of Alaska: Implications for the tectonic evolution of the Arctic

The composite Arctic Alaska–Chukotka terrane plays a central role in tectonic reconstructions of the Arctic. An exotic, non-Laurentian origin of Arctic Alaska–Chukotka has been proposed based on paleobiogeographic faunal affinities and various geochronological constraints from the southwestern portions of the terrane. Here, we report early Paleozoic trilobite and conodont taxa that support a Laurentian origin for the North Slope subterrane of Arctic Alaska, as well as new Neoproterozoic–Cambrian detrital zircon geochronological data, which are both consistent with a Laurentian origin and profoundly different from those derived from similar-aged strata in the southwestern subterranes of Arctic Alaska–Chukotka. The North Slope subterrane is accordingly interpreted as allochthonous with respect to northwestern Laurentia, but it most likely originated farther east along the Canadian Arctic or Atlantic margins. These data demonstrate that construction of the composite Arctic Alaska–Chukotka terrane resulted from juxtaposition of the exotic southwestern fragments of the terrane against the northern margin of Laurentia during protracted Devonian(?)–Carboniferous tectonism.

Lithosphere↗

USGS2022

First juvenile Chum Salmon confirms successful reproduction for Pacific salmon in the North American Arctic

The distributional extent of Pacific salmon Oncorhynchus spp. in the North American Arctic is unresolved. While adult Pacific salmon have a recurring presence across the Alaskan North Slope and into the Canadian Arctic, it is uncertain if these fish are part of established Arctic populations, vagrants from outside sources reproducing unsuccessfully, or both. Here we present the first confirmed record of a juvenile Chum Salmon O. keta captured in the nearshore marine ecosystem in the North American Arctic. This provides the first scientific evidence of successful spawning and early marine survival of Pacific salmon in the North American Arctic. It was caught near Kaktovik, Alaska in August 2017 with a group of similarly sized age-0 Mackenzie River Arctic Cisco Coregonus autumnalis . Stable isotope and otolith microchemistry analyses are consistent with use of the nearshore estuarine corridor from the Mackenzie River west along the northern coast. This contributes critical information needed to identify, manage, and conserve biodiversity at the northern range edge, and will help to clarify the status of Pacific salmon as potentially emerging fisheries develop in the North American Arctic due to climate warming.

Alaska↗

USGS1973

Probable rift origin of the Canada basin, Arctic Ocean

Formation of the Canada basin by post-Triassic rifting seems the most workable and logical hypothesis with information available. Speculated counterclockwise rotation of the Alaska-Chukchi continental edge best rationalizes the complex geology of northern Alaska, whereas a single continental block before the Jurassic makes the best palinspastic fit for Arctic America. The Arctic Ocean is the focus of present-day spreading and probably was the focus of earlier stages of spreading in which spread of the Canada basin would be an initial stage. If the Atlantic formed by seafloor spreading, spread of the Canada basin is probable because analogies between the Arctic and Atlantic edges indicate a common origin for the ocean basins. Late Cretaceous and younger deflections of the Cordillera in the Arctic and diabasic emplacements in the northern Arctic Islands may reflect later stages of spreading. Pre-Mesozoic plate tectonism may be represented by the widespread Proterozoic diabasic emplacements in the Canadian Arctic and by the Franklinian-Innuitian tract where the volcanogenic rocks and deformation resulted not from a classical eugeosyncline-miogeosyncline couple but from the junction of a mid-Paleozoic continental edge and another plate on closure of a pre-Arctic Ocean.

Open-File Report↗

USGS2018

Mineral phase-element associations based on sequential leaching of ferromanganese crusts, Amerasia Basin Arctic Ocean

Ferromanganese (FeMn) crusts from Mendeleev Ridge, Chukchi Borderland, and Alpha Ridge, in the Amerasia Basin, Arctic Ocean, are similar based on morphology and chemical composition. The crusts are characterized by a two- to four-layered stratigraphy. The chemical composition of the Arctic crusts differs significantly from hydrogenetic crusts from elsewhere of global ocean by high mean Fe/Mn ratios, high As, Li, V, Sc, and Th concentrations, and high detrital contents. Here, we present element distributions through crust stratigraphic sections and element phase association using several complementary techniques such as SEM-EDS, LA-ICP-MS, and sequential leaching, a widely employed method of element phase association that dissolves mineral phases of different stability step-by-step: Exchangeable cations and Ca carbonates, Mn-oxides, Fe-hydroxides, and residual fraction. Sequential leaching shows that the Arctic crusts have higher contents of most elements characteristic of the aluminosilicate phase than do Pacific crusts. Elements have similar distributions between the hydrogenetic Mn and Fe phases in all the Arctic and Pacific crusts. The main host phases for the elements enriched in the Arctic crusts over Pacific crusts (Li, As, Th, and V) are the Mn-phase for Li and Fe-phase for As, Th, and V; those elements also have higher contents in the residual aluminosilicate phase. Thus, higher concentrations of Li, As, Th, and V likely occur in the dissolved and particulate phases in bottom waters where the Arctic crusts grow, which has been shown to be true for Sc, also highly enriched in the crusts. The phase distributions of elements within the crust layers is mostly consistent among the Arctic crusts, being somewhat different in element concentrations in the residual phase.

Minerals↗

USGS2011

U.S. Geological Survey circum-arctic resource appraisal

Among the greatest uncertainties in future energy supply is the amount of oil and gas yet to be found in the Arctic. Using a probabilistic geology-based methodology, the U.S. Geological Survey has assessed the area north of the Arctic Circle. The Circum-Arctic Resource Appraisal (CARA) consists of three parts: (1) Mapping the sedimentary sequences of the Arctic (Grantz and others 2009), (2) Geologically based estimation of undiscovered technically recoverable petroleum (Gautier and others 2009, discussed in this presentation) and (3) Economic appraisal of the cost of delivering the undiscovered resources to major markets (also reported at this conference by White and others). We estimate that about 30% of the world's undiscovered gas and about 13% of the world's undiscovered oil may be present in the Arctic, mostly offshore under less than 500m of water. Billion BOE-plus accumulations of gas and oil are predicted at a 50% probability in the Kara Sea, Barents Sea, offshore East and West Greenland, Canada, and Alaska. On a BOE basis, undiscovered natural gas is three times more abundant than oil in the Arctic and is concentrated in Russian territory. Oil resources, while critically important to the interests of Arctic countries, are probably not sufficient to significantly shift the current geographic patterns of world oil production. Copyright 2011, Offshore Technology Conference.

Conference Paper↗

USGS1973

Probable rift origin of Canada Basin, Arctic Ocean

Formation of the Canada basin by post-Triassic rifting seems the most workable and logical hypothesis on the basis of available information. Speculated counterclockwise rotation of the Alaska-Chukchi continental edge best rationalizes the complex geology of northern Alaska, whereas the assumption that a single continental block was present before the Jurassic makes the best palinspastic fit for Arctic America. The Arctic Ocean is the focus of present-day spreading and probably was the focus of earlier stages of spreading in which spread of the Canada basin would have been an initial stage. Spread of the Canada basin is probable if the Atlantic formed by sea-floor spreading, because analogies between the Arctic and Atlantic edges indicate a common origin for the ocean basins. Late Cretaceous and younger deflections of the Cordillera in the Arctic and diabasic emplacements in the northern Arctic Islands may reflect later stages of spreading. Pre-Mesozoic plate tectonism may be represented by the widespread Proterozoic diabasic emplacements in the Canadian Arctic and by the Franklinian-lnnuitian tract, where the volcanogenic rocks and deformation resulted not from a classical eugeosyncline-miogeosyncline couple, but from the junction of a mid-Paleozoic continental edge and another plate on closure of a pre-Arctic Ocean.

Book chapter↗

USGS2002

The central arctic caribou herd

From the mid-1970s through the mid-1980s, use of calving and summer habitats by Central Arctic herd caribou ( Rangifer tarandus granti ) declined near petroleum development infrastructure on Alaska's arctic coastal plain (Cameron et al. 1979; Cameron and Whitten 1980, Smith and Cameron 1983. Whitten and Cameron 1983a, 1985: Dau and Cameron 1986). With surface development continuing to expand westward from the Prudhoe Bay petroleum development area (Fig. 4.1), concerns arose that the resultant cumulative losses of habitat would eventually reduce productivity of the caribou herd. Specifically, reduced access of adult females to preferred foraging areas might adversely affect growth and fattening (Elison et al. 1986. Clough et al. 1987), in turn depressing calf production (Dauphiné 1976, Thomas 1982, Reimers 1983, White 1983, Eloranta and Nieminen 1986. Lenvik et al. 1988, Thomas and Kiliaan 1991) and survival (Haukioja and Salovaara 1978, Rognmo et al. 1983, Skogland 1984, Eloranta and Nieminen 1986, Adamczewski et al. 1987). Those concerns, though justified in theory, lacked empirical support. With industrial development in arctic Alaska virtually unprecedented, there was little basis for predicting the extent and duration of habitat loss, much less the secondary short- and long-term effects on the well-being of a particular caribou herd. Furthermore, despite a general acceptance that body condition and fecundity of the females are functionally related for reindeer and caribou, it seemed unlikely that any single model would apply to all subspecies of Rangifer , and perhaps not even within a subspecies in different geographic regions. We therefore lacked a complete understanding of the behavioral responses of arctic caribou to industrial development, the manner in which access to habitats might be affected, and how changes in habitat use might translate into measurable effects on fecundity and herd growth rate. Our study addressed the following objectives: 1) estimate variation in the size and productivity of the Central Arctic herd; 2) estimate changes in the distribution and movements of Central Arctic herd caribou in relation to the oil field development; 3) estimate the relationships between body condition and reproductive performance of female Central Arctic herd caribou, and 4) compare the body condition, reproductive success, and offspring survival of females under disturbance-free conditions (i.e., east of the Sagavanirktok River) with the status of those exposed to petroleum-related development (i.e., west of the Sagavanirktok River).

Alaska, Northwest Territories, Yukon Territory↗

USGS2019

The benthic foraminifera cassidulina from the Arctic Ocean: Application to paleoceanography and biostratigraphy

We investigated the morphology, biostratigraphy, shell stable isotope composition and paleogeography of the common Arctic benthic foraminifera, Cassidulina teretis (Tappan 1951) (sometimes assigned to Islandiella (NÃ¸rvang 1958), for application to Quaternary paleoceanography. Cassidulina teretis, which has been studied by several generations of Arctic foraminiferal specialists, is used in Arctic Ocean paleoceanographic reconstructions based on foraminiferal assemblages and, increasingly, isotope shell chemistry. Here we review its modern and fossil distribution including discussions of its taxonomy, ecology, biostratigraphy and shell chemistry. Cassidulina teretis Tappan 1951, originally described from the Gubik Formation, northern Alaska coastal plain, has variability in test size, apertural morphology and development of an umbilical boss representing intra- and inter-population differences across the Arctic and subarctic in modern, Quaternary and Pliocene assemblages. Nonetheless, our studies and those previously published lead us to conclude that populations from the Arctic Ocean represent a single species proposed by Tappan as Cassidulina teretis. Its modern distribution is mainly 200 to 1000 m water depth, often living within the core of the relatively warm Atlantic Layer. However, shallower occurrences suggest other factors, such as food supply, are also critical to its ecology. The Holocene distribution of Cassidulina teretis in the Beaufort Sea boundary indicate millennial-scale changes in relative abundance related to changing Atlantic Layer influence, sea-ice cover, surface productivity and food availability. There are extremely large changes in its abundance during the last deglacial interval on the Yermak Plateau, Barents Sea slope and the Laptev Sea reflecting rapid ocean changes during the BÃ¸lling-AllerÃ¸d, Younger Dryas, and Preboreal. Similarly, C. teretis abundance changes during the last 300,000 years allow us to use it, at least regionally, as a useful biostratigraphic marker. The stable isotopic composition of Cassidulina teretis tests holds promise for establishing an isotope stratigraphy across the Arctic Ocean and perhaps also in the Nordic Seas, off Iceland and in the northern North Atlantic Ocean, once disequilibrium values and offsets from other Arctic benthic species are more firmly established.

Micropaleontology↗

USGS1997

Soluble trace elements and total mercury in Arctic Alaskan snow

Ultraclean field and laboratory procedures were used to examine trace element concentrations in northern Alaskan snow. Sixteen soluble trace elements and total mercury were determined in snow core samples representing the annual snowfall deposited during the 1993-94 season at two sites in the Prudhoe Bay oil field and nine sites in the Arctic National Wildlife Refuge (Arctic NWR). Results indicate there were two distinct point sources for trace elements in the Prudhoe Bay oil field- a source associated with oil and gas production and a source associated with municipal solid-waste incineration. Soluble trace element concentrations measured in snow from the Arctic NWR resembled concentrations of trace elements measured elsewhere in the Arctic using clean sample-collection and processing techniques and were consistent with deposition resulting from widespread arctic atmospheric contamination. With the exception of elements associated with sea salts, there were no orographic or east-west trends observed in the Arctic NWR data, nor were there any detectable influences from the Prudhoe Bay oil field, probably because of the predominant easterly and northeasterly winds on the North Slope of Alaska. However, regression analysis on latitude suggested significant south-to-north increases in selected trace element concentrations, many of which appear unrelated to the sea salt contribution.

Alaska↗

USGS2005

Correlated declines in Pacific arctic snow and sea ice cover

Simulations of future climate suggest that global warming will reduce Arctic snow and ice cover, resulting in decreased surface albedo (reflectivity). Lowering of the surface albedo leads to further warming by increasing solar absorption at the surface. This phenomenon is referred to as “temperature–albedo feedback.” Anticipation of such a feedback is one reason why scientists look to the Arctic for early indications of global warming. Much of the Arctic has warmed significantly. Northern Hemisphere snow cover has decreased, and sea ice has diminished in area and thickness. As reported in the Arctic Climate Impact Assessment in 2004, the trends are considered to be outside the range of natural variability, implicating global warming as an underlying cause. Changing climatic conditions in the high northern latitudes have influenced biogeochemical cycles on a broad scale. Warming has already affected the sea ice, the tundra, the plants, the animals, and the indigenous populations that depend on them. Changing annual cycles of snow and sea ice also affect sources and sinks of important greenhouse gases (such as carbon dioxide and methane), further complicating feedbacks involving the global budgets of these important constituents. For instance, thawing permafrost increases the extent of tundra wetlands and lakes, releasing greater amounts of methane into the atmosphere. Variable sea ice cover may affect the hemispheric carbon budget by altering the ocean–atmosphere exchange of carbon dioxide. There is growing concern that amplification of global warming in the Arctic will have far-reaching effects on lower latitude climate through these feedback mechanisms. Despite the diverse and convincing observational evidence that the Arctic environment is changing, it remains unclear whether these changes are anthropogenically forced or result from natural variations of the climate system. A better understanding of what controls the seasonal distributions of snow and ice is fundamental to the problem.

Arctic Research of the United States↗

USGS2021

Dynamic selection for forage quality and quantity in response to phenology and insects in an Arctic ungulate

Spatiotemporal variation in forage is a primary driver of ungulate behavior, yet little is known about the nutritional components they select, and how selection varies across the growing season with changes in forage quality and quantity. We addressed these uncertainties in barren-ground caribou ( Rangifer tarandus ), which experience their most important foraging opportunities during the short Arctic summer. Recent declines in Arctic caribou populations have raised concerns about the influence of climate change on summer foraging opportunities, given shifting vegetation conditions and insect harassment, and their potential effects on caribou body condition and demography. We examined Arctic caribou selection of summer forage by pairing locations from females in the Central Arctic Herd of Alaska with spatiotemporal predictions of biomass, digestible nitrogen (DN), and digestible energy (DE). We then assessed selection for these nutritional components across the growing season at landscape and patch scales, and determined whether foraging opportunities were constrained by insect harassment. During early summer, at the landscape scale, caribou selected for intermediate biomass and high DN and DE, following expectations of the forage maturation hypothesis. At the patch scale, however, caribou selected for high values of all forage components, particularly DN, suggesting that protein may be limiting. During late summer, after DN declined below the threshold for protein gain, caribou exhibited a switch at both spatial scales, selecting for higher biomass, likely enabling mass and fat deposition. Mosquito activity strongly altered caribou selection of forage and increased their movement rates, while oestrid fly activity had little influence. Our results demonstrate that early and late summer periods afford Arctic caribou distinct foraging opportunities, as they prioritize quality earlier in the summer and quantity later. Climate change may further constrain caribou access to DN as earlier, warmer Arctic summers may be associated with reduced DN and increased mosquito harassment.

Alaska↗

USGS2022

Attraction, entrance, and passage efficiency of Arctic Grayling, trout, and suckers at Denil fishways in the Big Hole River basin, Montana

The Big Hole River basin in southwestern Montana supports the only indigenous, self‐sustaining fluvial population of Arctic Grayling Thymallus arcticus in the conterminous United States, but the basin is fragmented by numerous low‐head irrigation diversion dams. Denil fishways at 63 diversion dams provide Arctic Grayling and other fishes opportunities for year‐round access to critical habitats; however, their efficiency has not been evaluated. We quantified attraction, entrance, and passage for hatchery‐reared Arctic Grayling, wild trout (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta ), and wild suckers (White Sucker Catostomus commersonii and Longnose Sucker C. catostomus ) during 14 field trials conducted at six Denil fishways over a representative range of fishway slopes and hydraulic conditions using passive integrated transponder telemetry. Attraction (60.4–84.3%) and entrance (44.3–78.6%) efficiencies were variable across test conditions and reduced overall fishway efficiencies (19.1–55.8%). In contrast, upon entry, passage efficiencies were high (96.2–97.0%) for all taxa across all test conditions. Attraction of hatchery‐reared Arctic Grayling increased with upstream depth (a surrogate for fishway discharge) and attraction flow, but attraction of wild fish was less affected by these conditions. Entrance of Arctic Grayling, Brook Trout, and Brown Trout decreased with upstream depth and fishway slope, especially when plunging entrance conditions associated with shallow downstream depths were present. However, entrance of Arctic Grayling and both trout species increased with downstream depth, and submerged fishway entrances demonstrated promise for increasing entrance efficiency at fishways with high discharges and steep slopes. We demonstrate that comprehensive evaluations of fishway efficiency components can identify specific solutions that improve fishway efficiency; application of these engineering solutions at individual fishways (as needed) could improve their efficiency and further enhance aquatic connectivity for fishes in the Big Hole River basin and elsewhere.

Montana↗

USGS2025

Energetic value of Arctic forage-sized fish with implications for a nearshore seabird predator

Arctic cod ( Boreogadus saida , also called polar cod) are considered the single most important Arctic forage fish due to their high abundance and nutritional quality. Because Arctic cod are strongly ice associated and prefer colder waters, their frequency in coastal waters has declined with warming, decreasing availability to nearshore predators. To consider the nutritional quality of alternative prey, we measured energy density and estimated whole-body energy of forage-size (39–200 mm) fishes collected during summers 2021–2023 ( n = 274). The fishes sampled included 16 potential prey species from Foggy Island Bay (70.3°N, 147.5°W, near Prudhoe Bay) and Lion Bay (70.2°N, 146.4°W, near Flaxman Island), northern Alaska. Dry weight energy densities ranged from 16.2 to 27.5 kJ g -1 (mean ± SD = 22.0 ± 1.73 kJ g -1 , n = 274) across individuals. Of common species, Arctic cod had the highest mean energy density (24.3 ± 1.1 kJ g -1 , n = 25) and fourhorn sculpin ( Myoxocephalus quadricornis ) had the lowest (19.7 ± 0.8 kJ g -1 , n = 20). To account for size differences among prey species, whole-body energy of typical fish sizes available to predators were modeled using whole-body energy to length relationships and length distributions. Juvenile salmonids (e.g., ciscoes and whitefishes) provided the most energy per individual and were four-fold greater than smaller-bodied Arctic cod. Predators that consume juvenile ciscoes and whitefishes may be more resilient to declines in Arctic cod availability than predators with smaller gapes.

Alaska↗

USGS2014

Phenological adjustment in arctic bird species: relative importance of snow melt and ecological factors

Previous studies have documented advancement in clutch initiation dates (CIDs) in response to climate change, most notably for temperate-breeding passerines. Despite accelerated climate change in the Arctic, few studies have examined nest phenology shifts in arctic breeding species. We investigated whether CIDs have advanced for the most abundant breeding shorebird and passerine species at a long-term monitoring site in arctic Alaska. We pooled data from three additional nearby sites to determine the explanatory power of snow melt and ecological variables (predator abundance, green-up) on changes in breeding phenology. As predicted, all species (semipalmated sandpiper, Calidris pusilla , pectoral sandpiper, Calidris melanotos , red-necked phalarope, Phalaropus lobatus , red phalarope, Phalaropus fulicarius , Lapland longspur, Calcarius lapponicus ) exhibited advanced CIDs ranging from 0.40 to 0.80 days/year over 9 years. Timing of snow melt was the most important variable in explaining clutch initiation advancement (“climate/snow hypothesis”) for four of the five species, while green-up was a much less important explanatory factor. We found no evidence that high predator abundances led to earlier laying dates (“predator/re-nest hypothesis”). Our results support previous arctic studies in that climate change in the cryosphere will have a strong impact on nesting phenology although factors explaining changes in nest phenology are not necessarily uniform across the entire Arctic. Our results suggest some arctic-breeding shorebird and passerine species are altering their breeding phenology to initiate nesting earlier enabling them to, at least temporarily, avoid the negative consequences of a trophic mismatch.

Alaska↗

USGS2015

Biological response to climate change in the Arctic Ocean: The view from the past

The Arctic Ocean is undergoing rapid climatic changes including higher ocean temperatures, reduced sea ice, glacier and Greenland Ice Sheet melting, greater marine productivity, and altered carbon cycling. Until recently, the relationship between climate and Arctic biological systems was poorly known, but this has changed substantially as advances in paleoclimatology, micropaleontology, vertebrate paleontology, and molecular genetics show that Arctic ecosystem history reflects global and regional climatic changes over all timescales and climate states (10 3 –10 7 years). Arctic climatic extremes include 25°C hyperthermal periods during the Paleocene-Eocene (56–46 million years ago, Ma), Quaternary glacial periods when thick ice shelves and sea ice cover rendered the Arctic Ocean nearly uninhabitable, seasonally sea-ice-free interglacials and abrupt climate reversals. Climate-driven biological impacts included large changes in species diversity, primary productivity, species’ geographic range shifts into and out of the Arctic, community restructuring, and possible hybridization, but evidence is not sufficient to determine whether or when major episodes of extinction occurred.

arktos↗

USGS1995

Biostratigraphic and paleoclimatic significance of a new Pliocene foraminiferal fauna from the central Arctic Ocean

A Pliocene benthic foraminiferal fauna containing a previously unknown species association was found in the basal section of a piston core collected from the crest of Northwind Ridge (NWR) in the central Arctic Ocean. The fauna is dominated by Epistominella exigua, Cassidulina reniforme, Eponides tumidulus, Cibicides scaldisiensis, Lagena spp., Cassidulina teretis, Eponides weddellensis, Bolivina arctica , and Patellina corrugata . The presence of Cibicides scaldisiensis in the assemblage and the occurrence of Cibicides grossus higher in the core are indicative of an early Pliocene age. The morphologically distinctive species Cibicidoides sp. 795 of McNeil (in press) which occurs in the NWR core sample was previously known only from Oligocene through Miocene deposits in the Beaufort-Mackenzie Basin of Arctic Canada. Ehrenbergina sp. A and Cibicidoides aff. C . sp. 795, also present in the core, are new and endemic to the Arctic late Miocene and early Pliocene. These species, and possibly others, are survivors of the late Miocene (Messinian) sea-level crisis, which caused a significant faunal turnover in the Arctic Ocean. The predominantly calcareous assemblage indicates deposition above the calcium carbonate compensation depth in an upper bathyal environment. Paleogeographic affinities for the bulk of the assemblage indicate probable connections between the Arctic and the North Atlantic Oceans, but the endemic species identify environmental differences or partial isolation of the western Arctic Ocean. The species association suggests a cold but milder paleoclimate than that which existed during Pleistocene glacial intervals.

Marine Micropaleontology↗

USGS2019

Evolution of the Arctic Alaska Sedimentary Basin

The Arctic Alaska basin occupies the eastern part of the Arctic Alaska – Chukotka microplate, which rifted from the Canadian Arctic margin during opening of the Canada Basin. Stratigraphy comprises four tectonostratigraphic sequences. (1) The Devonian and older Franklinian sequence consists of sedimentary and metasedimentary rocks deposited on the Arctic passive margin of Laurentia and in a Devonian foreland basin, and deformed during Caledonian, Romanzof, and Ellesmerian tectonism. (2) The Mississippian – Triassic Ellesmerian sequence was deposited on the Arctic rifted passive margin of Laurentia during and after opening of the Angayucham Ocean basin. Predominant sediment routing was southward in present coordinates. (3) The Jurassic – Lower Cretaceous Beaufortian sequence was deposited during rift-opening of the Canada Basin, and includes graben fill on the rift shoulder and a southward offlapping clastic wedge beneath the Alaska North Slope. (4) The Lower Cretaceous – Cenozoic Brookian sequence was deposited in the Colville foreland basin and on the Beaufort rifted margin during Brooks Range – Chukotkan tectonism. Predominant sediment routing was eastward (longitudinal) in the underfilled foreland basin, and progressively became northward in the overfilled foreland basin and on the rifted margin. The Arctic Alaska basin is a prolific petroleum province from which more than 17 billion barrels of oil have been produced since 1977. The basin hosts the Prudhoe Bay oil field, the largest in North America.

Alaska↗