Geology topics

Research about Canada

Source-linked reports with geographic coverage including Canada.

At least 145 records · Page 8Linked to original sources

USGS2014

Polychlorinated biphenyl concentrations of burbot Lota lota from Great Slave Lake are very low but vary by sex

Total polychlorinated biphenyl concentrations (ΣPCBs) in whole fish were determined for 18 ripe female burbot Lota lota and 14 ripe male burbot from Great Slave Lake, a lake with no known point sources of PCBs. In addition, ΣPCBs were determined both in the somatic tissue and in the gonads for a randomly selected subset of five females and five males. Mean ΣPCBs for females and males were 2.89 and 3.76 ng/g, respectively. Thus, males were 30 % greater in ΣPCB than females. Based on ΣPCB determinations for somatic tissue and gonads, ΣPCBs of females and males would be expected to decrease by 18 % and increase by 6 %, respectively, immediately after spawning due to release of gametes. Results from a previous study in eastern Lake Erie indicated that males were 28 and 71 % greater in ΣPCB than females from populations of younger (ages 6-13) and older (ages 14-17) burbot, respectively. Thus, although younger burbot from Lake Erie were about 50 times greater in ΣPCB than Great Slave Lake burbot, the relative difference in ΣPCBs between the sexes was remarkably similar across both populations. Our results supported the contention that the widening of the difference in ΣPCBs between the sexes in older burbot from Lake Erie was attributable to a “hot spot” effect operating on older burbot, as Lake Erie has received PCB point source loadings. Our results also supported the contention that male fish expend energy at a rate between 15 and 30 % greater than that of females. Eventually, these results will be useful in developing sex-specific bioenergetics models for fish.

Great Slave Lake;Northwest Territories↗

USGS2014

Males exceed females in PCB concentrations of cisco ( Coregonus artedi ) from Lake Superior

We determined whole-fish polychlorinated biphenyl (PCB) concentrations of 25 male and 25 female age-7 ciscoes ( Coregonus artedi ) captured from a spawning aggregation in Thunder Bay, Lake Superior, during November 2010. We also determined PCB concentrations in the ovaries and somatic tissue of five additional female ciscoes (ages 5–22). All 55 of these ciscoes were in ripe or nearly ripe condition. Bioenergetics modeling was used to determine the contribution of the growth dilution effect toward a difference in PCB concentrations between the sexes, as females grew substantially faster than males. Results showed that the PCB concentration of males (mean = 141 ng/g) was 43% greater than that of females (mean = 98 ng/g), and this difference was highly significant (P < 0.0001). Mean PCB concentrations in the ovaries and the somatic tissue of the five females were 135 and 100 ng/g, respectively. Based on these PCB determinations for the ovaries and somatic tissue, we concluded that release of eggs by females at previous spawnings was not a contributing factor to the observed difference in PCB concentrations between the sexes. Bioenergetics modeling results indicated that the growth dilution effect could explain males being higher than females in PCB concentration by only 3–7%. We concluded that the higher PCB concentration in males was most likely due to higher rate of energy expenditure, originating from greater activity and a higher resting metabolic rate. Mean PCB concentration in the cisco eggs was well below the U. S. Food and Drug Administration and Ontario Ministry of Environment guidelines of 2000 and 844 ng/g, respectively, and this finding may have implications for the cisco roe fishery currently operating in Lake Superior.

Lake Superior;Thunder Bay↗

USGS2014

Call broadcasting and automated recorders as tools for anuran surveys in a subarctic tundra landscape

Relatively little is known about population ecology of anurans in arctic and subarctic tundra regions, in part because it is difficult to survey anurans in these landscapes. Anuran survey protocols developed for temperate regions have limited applicability in arctic and subarctic tundra landscapes, which may lack roads and vehicle access, and experience variable and inclement weather during short anuran breeding seasons. To evaluate approaches to address some of the limitations of surveying anurans in tundra landscapes, we assessed the effectiveness of using breeding call broadcasts to increase detection of Boreal Chorus Frogs ( Pseudacris maculata ) and Wood Frogs ( Lithobates sylvaticus ) near Cape Churchill, Manitoba, Canada. We also evaluated how counts of anurans derived from automated audio recorders compared with those obtained simultaneously by observers. We detected on average 0.4 additional Wood Frogs per survey when we broadcasted calls ( x̄ = 0.82, SD = 1.38), an increase of > 40% compared to surveys without broadcasts ( x̄ = 1.24, SD = 1.51; Wilcoxon test; Z = 2.73, P = 0.006). In contrast, broadcasting Boreal Chorus Frog calls did not increase the number of chorus frog detections (Wilcoxon test; Z < 0.001, P > 0.90). Detections of Wood Frogs in a 100-m radius were lower via automated recorders ( x̄ = 0.60, SD = 0.87 SD) than by observers during simultaneous surveys ( x̄ = 0.96, SD = 1.27 Z = 2.07, P = 0.038), but those of Boreal Chorus Frogs were not different (x = 1.72, SD = 1.31; x̄ = 1.44, SD = 1.5; Z = 1.55, P > 0.121). Our results suggest that broadcasting calls can increase detection of Wood Frogs, and that automated recorders are useful in detecting both Wood Frogs and Boreal Chorus Fogs in arctic and subarctic tundra landscapes.

The Journal of North American Herpetology↗

USGS2013

Estimating transmission of avian influenza in wild birds from incomplete epizootic data: implications for surveillance and disease spreac

Estimating disease transmission in wildlife populations is critical to understand host–pathogen dynamics, predict disease risks and prioritize surveillance activities. However, obtaining reliable estimates for free-ranging populations is extremely challenging. In particular, disease surveillance programs may routinely miss the onset or end of epizootics and peak prevalence, limiting the ability to evaluate infectious processes. We used profile likelihood to estimate the force of infection (FOI) in a low pathogenic avian influenza virus (LPAIv) epizootic model from censored time series of LPAIv prevalence in hatch-year waterfowl (order Anseriformes) at postbreeding and migration sites in North America. We found a mean LPAIv FOI of 0·12 day −1 [95% CI, 0·00–0·39], corresponding to an incidence rate of 0·11 day −1 , with geographic heterogeneity (min–max: 0·02–0·23 day −1 ) among study sites. These high infection rates indicate that most hatch-year waterfowl are likely infected with LPAIv early in the fall migration. Comparison of model-predicted and observed immunity confirmed our assumption of naïve hatch-year waterfowl and suggested long-term immunity (>6 months) for adults. Using the mean LPAIv incidence rate, we predict a shorter and lower epizootic curve for highly pathogenic avian influenza virus (HPAIv; 5 weeks with peak prevalence of 28% and 30% mortality) than LPAIv (8 weeks with peak prevalence of 50%). These findings indicate it is harder to detect HPAIv than LPAIv with swabs from live birds, which are commonly used during disease surveillance. Synthesis and applications . Our study highlights the potential of integrating incomplete surveillance data with epizootic models to quantify disease transmission and immunity. This modelling approach provides an important tool to understand spatial and temporal epizootic dynamics and inform disease surveillance. Our findings suggest focusing highly pathogenic avian influenza virus (HPAIv) surveillance on postbreeding areas where mortality of immunologically naïve hatch-year birds is most likely to occur, and collecting serology to enhance HPAIv detection. Our modelling approach can integrate various types of disease data facilitating its use with data from other surveillance programs (as illustrated by the estimation of infection rate during an HPAIv outbreak in mute swans Cygnus olor in Europe).

Journal of Applied Ecology↗

USGS2013

U–Pb, Rb–Sr, and U-series isotope geochemistry of rocks and fracture minerals from the Chalk River Laboratories site, Grenville Province, Ontario, Canada

As part of the Geologic Waste Management Facility feasibility study, Atomic Energy of Canada Ltd. (AECL) is evaluating the suitability of the Chalk River Laboratories (CRL) site in Ontario, situated in crystalline rock of the southwestern Grenville Province, for the possible development of an underground repository for low- and intermediate-level nuclear waste. This paper presents petrographic and trace element analyses, U–Pb zircon dating results, and Rb–Sr, U–Pb and U-series isotopic analyses of gneissic drill core samples from the deep CRG-series characterization boreholes at the CRL site. The main rock types intersected in the boreholes include hornblende–biotite (±pyroxene) gneisses of granitic to granodioritic composition, leucocratic granitic gneisses with sparse mafic minerals, and garnet-bearing gneisses with variable amounts of biotite and/or hornblende. The trace element data for whole-rock samples plot in the fields of within-plate, syn-collision, and volcanic arc-type granites in discrimination diagrams used for the tectonic interpretation of granitic rocks. Zircons separated from biotite gneiss and metagranite samples yielded SHRIMP-RG U–Pb ages of 1472 ± 14 (2 σ ) and 1045 ± 6 Ma, respectively, in very good agreement with widespread Early Mesoproterozoic plutonic ages and Ottawan orogeny ages in the Central Gneiss Belt. The Rb–Sr, U–Pb, and Pb–Pb whole-rock errorchron apparent ages of most of the CRL gneiss samples are consistent with zircon U–Pb age and do not indicate substantial large-scale preferential element mobility during superimposed metamorphic and water/rock interaction processes. This may confirm the integrity of the rock mass, which is a positive attribute for a potential nuclear waste repository. Most 234 U/ 238 U activity ratios (AR) in whole rock samples are within errors of the secular equilibrium value of one, indicating that the rocks have not experienced any appreciable U loss or gain within the past 1 Ma. However, 234 U/ 238 U AR in fracture mineral samples collected down to borehole lengths of about 740 m deviate from the secular equilibrium value and 234 U/ 238 U model ages calculated for fracture mineral samples showing excess 234 U range from 593 to 1415 ka, thus providing evidence of fracture flow in the associated bedrock during the past 1.5 Ma. Rare earth element patterns are variable in fracture-filling calcites and Fe oxides/hydroxides but are similar to those observed in associated whole-rock samples. The observed Ce anomalies are very small ( Ce N / Ce N ∗ ≈ 1 "> CeN/CeN∗≈1 ), do not vary with depth, and, therefore, do not contain evidence that the studied fracture minerals precipitated from oxidizing waters at the conceptual depth of a repository.

Ontario↗

USGS2013

Assessment of undiscovered conventional oil and gas resources of the Western Canada Sedimentary Basin, Canada, 2012

The U.S. Geological Survey recently completed a geoscience-based assessment of undiscovered oil and gas resources of provinces within the Western Canada Sedimentary Basin. The Western Canada Sedimentary Basin primarily comprises the (1) Alberta Basin Province of Alberta, eastern British Columbia, and the southwestern Northwest Territories; (2) the Williston Basin Province of Saskatchewan, southeastern Alberta, and southern Manitoba; and (3) the Rocky Mountain Deformed Belt Province of western Alberta and eastern British Columbia. This report is part of the U.S. Geological Survey World Petroleum Resources Project assessment of priority geologic provinces of the world. The assessment was based on geoscience elements that define a total petroleum system (TPS) and associated assessment unit(s). These elements include petroleum source rocks (geochemical properties and petroleum generation, migration, and accumulation), reservoir description (reservoir presence, type, and quality), and petroleum traps (trap and seal types, and timing of trap and seal formation relative to petroleum migration). Using this framework, the Elk Point-Woodbend Composite TPS, Exshaw-Fernie-Mannville Composite TPS, and Middle through Upper Cretaceous Composite TPS were defined, and four conventional assessment units within the total petroleum systems were quantitatively assessed for undiscovered resources in the Western Canada Sedimentary Basin.

Fact Sheet↗

USGS2013

Estimating abundance of the Southern Hudson Bay polar bear subpopulation using aerial surveys, 2011 and 2012

The Southern Hudson Bay (SH) polar bear subpopulation occurs at the southern extent of the species’ range. Although capture-recapture studies indicate that abundance remained stable between 1986 and 2005, declines in body condition and survival were documented during the period, possibly foreshadowing a future decrease in abundance. To obtain a current estimate of abundance, we conducted a comprehensive line transect aerial survey of SH during 2011–2012. We stratified the study site by anticipated densities and flew coastal contour transects and systematically spaced inland transects in Ontario and on Akimiski Island and large offshore islands in 2011. Data were collected with double observer and distance sampling protocols. We also surveyed small islands in Hudson Bay and James Bay and flew a comprehensive transect along the Québec coastline in 2012. We observed 667 bears in Ontario and on Akimiski Island and nearby islands in 2011, and we sighted 80 bears on offshore islands during 2012. Mark-recapture distance sampling and sightresight models yielded a model-averaged estimate of 868 (SE: 177) for the 2011 study area. Our estimate of abundance for the entire SH subpopulation (951; SE: 177) suggests that abundance has remained unchanged. However, this result should be interpreted cautiously because of the methodological differences between historical studies (physical capture) and this survey. A conservative management approach is warranted given the previous increases in the duration of the ice-free season, which are predicted to continue in the future, and previously documented declines in body condition and vital rates.

Hudson Bay↗

USGS2012

The seismic velocity structure of the Newfoundland Appalachian orogen

The deep structure of the Newfoundland Appalachian orogen is investigated by analyses of three intersecting seismic refraction/wide-angle reflection profiles which traverse the Gander and Dunnage zones or central mobile belt of Newfoundland. A simultaneous travel time inversion for velocity and interface was applied to the in-line seismic refraction/wide-angle reflection data and constrained by synthetic amplitude models. The results of the modeling procedure show a subhorizontally layered crust with upper crustal velocities ranging from 5.4 to 6.2 km/s, a midcrustal velocity of 6.25–6.35 km/s, and a lower crustal velocity of 6.7±0.2 km/s. The top of the lower crust is marked by a series of prominent reflections between 18 and 23 km depth which suggest a complex layered velocity interface. Strong laterally coherent Moho reflections indicate a sharp crust-mantle transition at 35 ± 3 km. The uppermost mantle has a velocity of 8.0±0.2 km/s, and a reflecting horizon at 55 km depth suggests an increase to velocities approaching 8.5 km/s. Normal moveout corrections applied to fan profiles provide constraining evidence for the reflecting horizon at the top of the lower crust and laterally continuous Moho reflections at 11–12 s two-way travel time. Comparisons with a coincident deep seismic reflection profile show that the refraction and reflection Mohos match to better than 2–3 km. Bulk Poisson's ratios of 0.23–0.24 for the whole crust calculated from P m P / S m S travel times suggest a crust dominated by quartzofeldspathic lithologies and a notable absence of voluminous mafic additions to the lower crust. The absence of a deep crustal root, coupled with the bulk intermediate composition inferred for the lower crust from the seismic refraction/wide-angle data, implies that the crust beneath central Newfoundland has undergone multiple periods of reactivation and equilibration following successive orogenic episodes.

Newfoundland and Labrador↗

USGS2012

Tholeiitic‐alkalic transition at subglacial volcanoes, Tuya region, British Columbia, Canada

Ash Mountain, South Tuya, and Tuya Butte are three small basaltic volcanoes in the Stikine volcanic belt of northern British Columbia. The volcanoes rise 700, 500, and 400 m above their bases and are about 3.2, 1.6, and 2.6 km 3 in volume, respectively. They began eruptive activity under several hundred meters of overlying glacial ice, or water in an ice‐impounded lake, and undegassed pillow lava was erupted and forms the bases of all three. Later, as the vents grew into shallow water, explosive phreatomagmatic activity erupted partly degassed glassy tuffs. Finally, when the volcano emerged through the surface of the ice or water (or the water was drained), degassed subaerial lava flows were erupted and were converted to assemblages of foreset‐bedded pillow breccia and pillow lava when subaerial flows crossed a shoreline and flowed into meltwater lakes. The undegassed subglacial pillow base of Ash Mountain is overlain by partly degassed pillows and hyaloclastite tuff cut by dikes; at South Tuya the pillow base is overlain by hyaloclastite tuffs and lenses of pillow lava; at Tuya Butte the pillow base is overlain by foreset‐bedded pillow lava, pillow breccias, and hyaloclastite tuffs, which in turn are overlain by subaerial lava flows composing a small shield volcano. The undegassed basal subglacial pillow lava of the three volcanoes contain 0.10 ± 0.01 wt % sulfur and ∼0.5 wt % H 2 O. The overlying partly degassed assemblages contain 0.06 ± 0.02% sulfur and ∼0.2% H 2 O at Ash Mountain, 0.07±0.01% sulfur at South Tuya, and 0.03±0.01% sulfur at Tuya Butte. The differences in the degree of degassing can be related to the nature of eruption and quenching and the distance of flow of the subaerial lava. When the volcanoes switched from subglacial to shallow water or subaerial eruptions, as shown by change to more explosive activity and then to subaerial lava flows (and by a marked reduction of sulfur in volcanic glass), the magma shifted from tholeiitic to alkalic composition. This transition occurs at each of the three volcanoes. The tholeiitic and alkalic magmas cannot be related by shallow crystal fractionation and apparently originated by differing degrees of deep melting at a mantle source. Prior to eruption the tholeiitic melts overlay alkalic melts in shallow chambers underlying each of the volcanoes because of their lower density and were, therefore, the first to erupt under subglacial conditions. As the volcano grew through the ice (or ice‐impounded water), the volcanic conduit vented to the atmosphere, producing a partial depressurization of the conduit and the subsurface chamber. This sudden reduction in confining pressure caused enhanced vesiculation of volatile saturated melts, particularly of the more volatile‐rich alkalic melts, causing them to rise to the top of the chamber and erupt.

British Columbia↗

USGS2012

Magnetic properties of the Bay of Islands ophiolite suite and implications for the magnetization of oceanic crust

Rock magnetic properties, opaque mineralogy, and degree of metamorphism were determined for 101 unoriented samples from the North Arm and Blow-Me-Down massifs of the Bay of Islands ophiolite complex, Newfoundland. The weathered and metamorphosed extrusive basalt samples have a weak, secondary magnetization arising from oxidation and exsolution of ilmenite of unknown origin. The initial magnetization of the underlying sheeted dike complex appears to have been destroyed by hydrothermal alteration soon after formation. The magnetic intensity of the gabbroic samples increases as the degree of alteration increases, with the highly altered upper metagabbros having an average intensity of 3×10 −3 emu/c 3 . Because magnetization of the metagabbro samples is related to nonpervasive, variable alteration, these crustal units are unlikely to make a significant contribution to lineated magnetic anomalies. A compilation of our results and other studies suggests a model in which oceanic crust magnetization results from an upper extrusive basalt source layer, roughly 600 m thick, with no contribution from a deeper source layer recognizable from these Bay of Islands data.

Newfoundland↗

USGS2012

Gray Wolf (Canis lupus) movements and behavior around a kill site and implications for GPS collar studies

Global Positioning System (GPS) radio-collars are increasingly used to estimate Gray Wolf ( Canis lupus ) kill rates. In interpreting results from this technology, researchers make various assumptions about wolf behavior around kills, yet no detailed description of this behavior has been published. This article describes the behavior of six wolves in an area of constant daylight during 30 hours, from when the pack killed a Muskox ( Ovibos moschatus ) calf and yearling on Ellesmere Island, Nunavut, Canada, to when they abandoned the kill remains. Although this is only a single incident, it demonstrates one possible scenario of pack behavior around a kill. Combined with the literature, this observation supports placing a radio-collar on the breeding male to maximize finding kills via GPS collars and qualifying results depending on whatever other information is available about the collared wolf’s pack.

Ellesmere Island, Nunavut↗

USGS2012

Varying sediment sources (Hudson Strait, Cumberland Sound, Baffin Bay) to the NW Labrador Sea slope between and during Heinrich events 0 to 4

Core HU97048-007PC was recovered from the continental Labrador Sea slope at a water depth of 945 m, 250 km seaward from the mouth of Cumberland Sound, and 400 km north of Hudson Strait. Cumberland Sound is a structural trough partly floored by Cretaceous mudstones and Paleozoic carbonates. The record extends from ∼10 to 58 ka. On-board logging revealed a complex series of lithofacies, including buff-colored detrital carbonate-rich sediments [Heinrich (H)-events] frequently bracketed by black facies. We investigate the provenance of these facies using quantitative X-ray diffraction on drill-core samples from Paleozoic and Cretaceous bedrock from the SE Baffin Island Shelf, and on the < 2-mm sediment fraction in a transect of five cores from Cumberland Sound to the NW Labrador Sea. A sediment unmixing program was used to discriminate between sediment sources, which included dolomite-rich sediments from Baffin Bay, calcite-rich sediments from Hudson Strait and discrete sources from Cumberland Sound. Results indicated that the bulk of the sediment was derived from Cumberland Sound, but Baffin Bay contributed to sediments coeval with H-0 (Younger Dryas), whereas Hudson Strait was the source during H-events 1–4. Contributions from the Cretaceous outcrops within Cumberland Sound bracket H-events, thus both leading and lagging Hudson Strait-sourced H-events.

Hudson Strait;Cumberland Sound;Baffin Bay↗

USGS2012

Laboratory toxicity and benthic invertebrate field colonization of Upper Columbia River sediments: Finding adverse effects using multiple lines of evidence

From 1930 to 1995, the Upper Columbia River (UCR) of northeast Washington State received approximately 12 million metric tons of smelter slag and associated effluents from a large smelter facility located in Trail, British Columbia, approximately 10 km north of the United States–Canadian border. Studies conducted during the past two decades have demonstrated the presence of toxic concentrations of heavy metals in slag-based sandy sediments, including cadmium, copper, zinc, and lead in the UCR area as well as the downstream reservoir portion of Lake Roosevelt. We conducted standardized whole-sediment toxicity tests with the amphipod Hyalella azteca (28-day) and the midge Chironomus dilutus (10-day) on 11 samples, including both UCR and study-specific reference sediments. Metal concentrations in sediments were modeled for potential toxicity using three approaches: (1) probable effects quotients (PEQs) based on total recoverable metals (TRMs) and simultaneously extracted metals (SEMs); (2) SEMs corrected for acid-volatile sulfides (AVS; i.e., ∑SEM − AVS); and (3) ∑SEM − AVS normalized to the fractional organic carbon (f oc ) (i.e., ∑SEM − AVS/f oc ). The most highly metal-contaminated sample (∑PEQ TRM = 132; ∑PEQ SEM = 54; ∑SEM − AVS = 323; and ∑SEM − AVS/ foc = 64,600 umol/g) from the UCR was dominated by weathered slag sediment particles and resulted in 80% mortality and 94% decrease in biomass of amphipods; in addition, this sample significantly decreased growth of midge by 10%. The traditional ∑AVS – SEM, uncorrected for organic carbon, was the most accurate approach for estimating the effects of metals in the UCR. Treatment of the toxic slag sediment with 20% Resinex SIR-300 metal-chelating resin significantly decreased the toxicity of the sample. Samples ∑SEM − AVS > 244 was not toxic to amphipods or midge in laboratory testing, indicating that this value may be an approximate threshold for effects in the UCR. In situ benthic invertebrate colonization studies in an experimental pond (8-week duration) indicated that two of the most metal-contaminated UCR sediments (dominated by high levels of sand-sized slag particles) exhibited decreased invertebrate colonization compared with sand-based reference sediments. Field-exposed SIR-300 resin samples also exhibited decreased invertebrate colonization numbers compared with reference materials, which may indicate behavioral avoidance of this material under field conditions. Multiple lines of evidence (analytical chemistry, laboratory toxicity, and field colonization results), along with findings from previous studies, indicate that high metal concentrations associated with slag-enriched sediments in the UCR are likely to adversely impact the growth and survival of native benthic invertebrate communities. Additional laboratory toxicity testing, refinement of the applications of sediment benchmarks for metal toxicity, and in situ benthic invertebrate studies will assist in better defining the spatial extent, temporal variations, and ecological impacts of metal-contaminated sediments in the UCR system.

Trail↗

USGS2012

Compression map, functional groups and fossilization: A chemometric approach (Pennsylvanian neuropteroid foliage, Canada)

Nearly all of the spectrochemical studies involving Carboniferous foliage of seed-ferns are based on a limited number of pinnules, mainly compressions. In contrast, in this paper we illustrate working with a larger pinnate segment, i.e., a 22-cm long neuropteroid specimen, compression-preserved with cuticle, the compression map. The objective is to study preservation variability on a larger scale, where observation of transparency/opacity of constituent pinnules is used as a first approximation for assessing the degree of pinnule coalification/fossilization. Spectrochemical methods by Fourier transform infrared spectrometry furnish semi-quantitative data for principal component analysis. The compression map shows a high degree of preservation variability, which ranges from comparatively more coalified pinnules to less coalified pinnules that resemble fossilized-cuticles, noting that the pinnule midveins are preserved more like fossilized-cuticles. A general overall trend of coalified pinnules towards fossilized-cuticles, i.e., variable chemistry, is inferred from the semi-quantitative FTIR data as higher contents of aromatic compounds occur in the visually more opaque upper location of the compression map. The latter also shows a higher condensation of the aromatic nuclei along with some variation in both ring size and degree of aromatic substitution. From principal component analysis we infer correspondence between transparency/opacity observation and chemical information which correlate with varying degree to fossilization/coalification among pinnules.

Nova Scotia↗

USGS2012

Stable isotope evidence for glacial lake drainage through the St. Lawrence Estuary, eastern Canada, ~13.1-12.9 ka

Postglacial varved and rhythmically-laminated clays deposited during the transition from glacial Lake Vermont (LV) to the Champlain Sea (CS) record hydrological changes in the Champlain-St. Lawrence Valley (CSLV) at the onset of the Younger Dryas ∼13.1–12.9 ka linked to glacial lake drainage events. Oxygen isotope (δ18O) records of three species of benthic foraminifera (Cassidulina reniforme, Haynesina orbiculare, Islandiella helenae) from six sediment cores and the freshwater ostracode Candona from one core were studied. Results show six large isotope excursions (∼0.5 to >2‰) in C. reniforme δ18O values, five excursions in H. orbiculare (<0.5 to ∼1.8‰), and five smaller changes in I. helenae (<0.5‰). δ18O values in Candona show a 1.5–2‰ increase in the same interval. These isotopic excursions in co-occurring marine and freshwater species in varve-like sediments indicate complex hydrological changes in the earliest Champlain Sea, including brief (sub-annual) periods of complete freshening. One hypothesis to explain these results is that multiple abrupt freshwater influx events caused surface-to-bottom freshening of the Champlain Sea over days to weeks. The most likely source of freshwater would have been drainage of the Morehead Phase of glacial Lake Agassiz, perhaps in a series of floods, ultimately draining out the St. Lawrence Estuary.

St. Lawrence Estuary↗

USGS2012

Source rock contributions to the Lower Cretaceous heavy oil accumulations in Alberta: a basin modeling study

The origin of the immense oil sand deposits in Lower Cretaceous reservoirs of the Western Canada sedimentary basin is still a matter of debate, specifically with respect to the original in-place volumes and contributing source rocks. In this study, the contributions from the main source rocks were addressed using a three-dimensional petroleum system model calibrated to well data. A sensitivity analysis of source rock definition was performed in the case of the two main contributors, which are the Lower Jurassic Gordondale Member of the Fernie Group and the Upper Devonian–Lower Mississippian Exshaw Formation. This sensitivity analysis included variations of assigned total organic carbon and hydrogen index for both source intervals, and in the case of the Exshaw Formation, variations of thickness in areas beneath the Rocky Mountains were also considered. All of the modeled source rocks reached the early or main oil generation stages by 60 Ma, before the onset of the Laramide orogeny. Reconstructed oil accumulations were initially modest because of limited trapping efficiency. This was improved by defining lateral stratigraphic seals within the carrier system. An additional sealing effect by biodegraded oil may have hindered the migration of petroleum in the northern areas, but not to the east of Athabasca. In the latter case, the main trapping controls are dominantly stratigraphic and structural. Our model, based on available data, identifies the Gordondale source rock as the contributor of more than 54% of the oil in the Athabasca and Peace River accumulations, followed by minor amounts from Exshaw (15%) and other Devonian to Lower Jurassic source rocks. The proposed strong contribution of petroleum from the Exshaw Formation source rock to the Athabasca oil sands is only reproduced by assuming 25 m (82 ft) of mature Exshaw in the kitchen areas, with original total organic carbon of 9% or more.

Alberta↗

USGS2011

Movements of wolves at the northern extreme of the species' range, including during four months of darkness

Information about wolf ( Canis lupus ) movements anywhere near the northern extreme of the species' range in the High Arctic (>75°N latitude) are lacking. There, wolves prey primarily on muskoxen ( Ovibos moschatus ) and must survive 4 months of 24 hr/day winter darkness and temperatures reaching -53 C. The extent to which wolves remain active and prey on muskoxen during the dark period are unknown, for the closest area where information is available about winter wolf movements is >2,250 km south. We studied a pack of ≥20 wolves on Ellesmere Island, Nunavut, Canada (80°N latitude) from July 2009 through mid-April 2010 by collaring a lead wolf with a Global Positioning System (GPS)/Argos radio collar. The collar recorded the wolf's precise locations at 6:00 a.m. and 6:00 p.m. daily and transmitted the locations by satellite to our email. Straight-line distances between consecutive 12-hr locations varied between 0 and 76 km. Mean (SE) linear distance between consecutive locations (n = 554) was 11 (0.5) km. Total minimum distance traveled was 5,979 km, and total area covered was 6,640 km 2 , the largest wolf range reported. The wolf and presumably his pack once made a 263-km (straight-line distance) foray to the southeast during 19–28 January 2010, returning 29 January to 1 February at an average of 41 km/day straight-line distances between 12-hr locations. This study produced the first detailed movement information about any large mammal in the High Arctic, and the average movements during the dark period did not differ from those afterwards. Wolf movements during the dark period in the highest latitudes match those of the other seasons and generally those of wolves in lower latitudes, and, at least with the gross movements measurable by our methods, the 4-month period without direct sunlight produced little change in movements.

Ellesmere Island;Nunavut↗

USGS2011

Seasonal habitat use and selection by grizzly bears in Northern British Columbia

We defined patterns of habitat use and selection by female grizzly bears (Ursus arctos) in the Besa-Prophet watershed of northern British Columbia. We fitted 13 adult females with Geographic Positioning System (GPS) radio-collars and monitored them between 2001 and 2004. We examined patterns of habitat selection by grizzly bears relative to topographical attributes and 3 potential surrogates of food availability: land-cover class, vegetation biomass or quality (as measured by the Normalized Difference Vegetation Index), and selection value for prey species themselves (moose [Alces alces], elk [Cervus elaphus], woodland caribou [Rangifer tarandus]. Stone's sheep [Ovis dalli stonei]). Although vegetation biomass and quality, and selection values for prey were important in seasonal selection by some individual bears, land-cover class, elevation, aspect, and vegetation diversity most influenced patterns of habitat selection across grizzly bears, which rely on availability of plant foods and encounters with ungulate prey. Grizzly bears as a group avoided conifer stands and areas of low vegetation diversity, and selected for burned land-cover classes and high vegetation diversity across seasons. They also selected mid elevations from what was available within seasonal ranges. Quantifying relative use of different attributes helped place selection patterns within the context of the landscape. Grizzly bears used higher elevations (1,595 ± 31 m SE) in spring and lower elevations (1,436 ± 27 m) in fall; the range of average elevations used among individuals was highest (500 m) during the summer. During all seasons, grizzly bears most frequented aspects with high solar gain. Use was distributed across 10 land-cover classes and depended on season. Management and conservation actions must maintain a diverse habitat matrix distributed across a large elevational gradient to ensure persistence of grizzly bears as levels of human access increase in the northern Rocky Mountains.

Northern British Columbia↗