Northwestern British Columbia Research Articles

Dynamic auditory-acoustic properties differentiate word-final fricatives in Gitksan

Gitksan is an endangered, understudied Tsimshian language spoken in northwestern British Columbia. This study aims to provide an acoustic-phonetic description of Gitksan fricatives. Isolated words containing word-final fricatives were recorded with three Gitksan first-language speakers (2 male, 1 female; age 65 + ). Postvocalic fricative tokens ([s] = 159, [ɬ] = 123, [ç] = 180, [Xw] = 150, [χ] = 267) were analyzed. Dynamic, spectral measurements of peak frequency in equivalent rectangular bandwidths (peakERB; Reidy, 2016) were estimated from 17 20-ms windows centered at equidistant points between the onset and offset of the fricative. The resulting trajectories (windows 3–15) show that the peakERB decreases as the place of articulation shifts further back in the vocal tract (alveolar [s]∼25–31, palatal [ç]∼20–23, uvular [χ]∼17–19; exception: labiovelar [Xw]∼15–16, likely lowered by labialization). Also, the lateral alveolar [ɬ] shows a lower peakERB (∼22–24) than the central alveolar [s]. A random forest model (Breiman, 2001) was trained on 586 tokens in predicting the fricatives with peakERB measures of the 17 windows. The trained model was tested on 293 tokens; it identified [s] most accurately and [ɬ] least accurately. Additionally, the model's relative-importance ranking of the 17 peakERB predictors suggests that the middle third of the peakERB trajectory is robust in differentiating word-final fricatives in Gitksan.

Seismicity and seismic monitoring of Canada’s volcanic zones

Canada’s recently active volcanic zones (e.g., eruptions during the past 10 000 years) are all located along the tectonic plate boundary region of western Canada, extending for more than 2000 km from southern British Columbia to the Yukon/Alaska border. In this article, we describe the history of seismic monitoring in and near these volcanic zones and the past and current seismicity detection thresholds. The most recently active volcanoes in Canada are Tseax Cone (∼1700s) and Lava Fork (∼1800s), both in northwestern British Columbia. However, no eruptions have occurred in Canada since the deployment of the earliest seismographs in 1898 (Victoria, BC) and 1904 (Sitka, Alaska). Seismic detection levels have decreased from M∼7 in 1900 to M∼0–1 (in many regions) today, with more than 120 seismic stations currently operating in British Columbia and the Yukon, including ∼20 seismic stations within the volcanic zones. The most recent significant seismic activity attributed to volcanic zones in Canada is the 2007 Nazko Cone earthquake swarm when nearly 1000 tiny (M < 3) earthquakes occurred here over the span of about 2 months. These were all deep earthquakes (∼30 km) near the base of the crust and showed the patterns expected from an injection of magma deep into the crust. Prior to that, at the western end of the Anahim Volcanic Belt, more than 40 felt earthquakes occurred from 1940 to 1943. We provide a summary of these two swarms and other seismicity as well as some recent and ongoing studies into seismicity at some of Canada’s volcanic zones and new developments in seismic monitoring of volcanoes (including using distributed acoustic sensing).

Determination of the erosion level of a porphyry copper deposit using soil geochemistry

As exploration is time-consuming, costly, and risky, determination of the erosion surface of a metalliferous deposit before geophysical surveying and exploration drilling might be very helpful. Geochemical haloes can be used to determine whether the erosion surface is supra-ore or sub-ore and thus reduce the risk of exploration operations. The aim of this investigation is to determine the erosion surface of the North ROK porphyry deposit (NRPD) in northwestern British Columbia in Canada using linear productivity (LP), which is the content of an element defining the halo multiplied by the width of the halo. A total of 2045 soil samples from the B horizon were analysed using ICP-MS for 36 elements, including Cu, Mo, Pb, Zn, Au, As, Ag, Ni, Co, Fe, and Mn. The data-set was snalysed to obtain the statistical parameters and the elements Cu, Mo, Pb, and Zn were chosen to calculate the linear productivity and the total linear productivity. These four elements were modelled using probability plots to identify and separate subpopulations in terms of anomalous haloes and background, including the threshold values of each subpopulation. The results of the probability plot modelling and thresholds values were then used to map the distribution of each element in a GIS to calculate the linear productivity. The total linear productivity indicated that the erosion surface is supra-ore. Finally, a 3D orebody model of the Cu, Mo, Pb, and Zn distributions was constructed using borehole data and used to validate the results.

Late-Stage Low-Temperature Hydrothermal Alteration Overprint at the East Zone in the Red Chris Porphyry Cu-Au Deposit, Northwestern British Columbia, Canada

Abstract High- and intermediate-temperature alteration assemblages at the East zone in the Red Chris porphyry Cu-Au deposit, northwestern British Columbia, Canada, are varyingly overprinted by a lower-temperature intermediate argillic alteration assemblage composed of illite-kaolinite-hematite-carbonate. The intermediate argillic assemblage extensively overprinted the upper 600 m of the porphyry deposit and is present discontinuously to depths of 1,500 m below the premining surface. Kaolinite is dominant in shallow levels and gradually diminishes with depth, replaced by illite as the dominant clay mineral. Hematite replaced hydrothermal and igneous magnetite, but the intensity diminishes with depth. Mixtures of ankerite, dolomite, siderite, and calcite replaced mafic silicates and formed veins. Oxygen and hydrogen isotopes confirm a magmatic fluid source for the potassic assemblages preserved at depth as well as for the overprinted phyllic assemblage in the upper part and flanks of the East zone. In contrast, the superposed intermediate argillic assemblages formed by a mixture of magmatic and meteoric fluids. Sulfide minerals and sulfur isotopes retain zonal patterns for porphyry Cu deposits and appear largely unaffected by the overprinted intermediate argillic assemblage. Carbon and oxygen isotopes in carbonate vary with depth that may reflect a thermal gradient as a rising fluid cooled. The intermediate argillic assemblage is spatially associated with and overprinted on as yet undated late monzodioritic dikes—the youngest phase in the host Late Triassic Red stock. The relative age relationships and stable isotopic geochemistry indicate the intermediate argillic alteration assemblage represents the flux of magmatic-derived hydrothermal fluid that mixed with external fluid and thus represents either the last fluid pulse in the porphyry Cu deposit or a younger, temporally distinct hydrothermal fluid.

Paleoenvironmental interpretation of the Late Triassic Norian – Rhaetian boundary interval in the Whitehorse Trough (Stikine Terrane, northern Canadian Cordillera)

The Norian – Rhaetian boundary (NRB) is associated with significant faunal turnover in a wide variety of groups. Following the relative stability of the Norian Stage, this boundary potentially marks the beginning of a protracted and continuous episode of elevated extinction rates, which culminated with the end-Triassic mass extinction. Despite the importance of the NRB to paleontological trends in the Late Triassic, much about this event remains enigmatic, including potential causal mechanisms as well as the characteristics of the resulting paleoenvironmental changes. Fossiliferous limestone of the Sinwa Formation occurs in extensive outcrops throughout northwestern British Columbia and provides an exceptional record of Upper Triassic stratigraphy that represents a paleogeographic region largely uninvestigated prior. The present study integrates lithostratigraphic, paleontological, and geochemical data to reconstruct the shallow marine paleoenvironments recorded by the Sinwa Formation in two sections on Mount Sinwa, south of Atlin, within the Stikine Terrane. The progression of lithological facies observed in these sections suggests a gradual base level rise throughout the late Norian. Following this steady facies progression is a prominent shift from coral reef boundstone to shale near the top of both sections. This facies change approximately coincides with the NRB interval as evidenced by the first occurrence of the latest Norian – Rhaetian conodont species Mockina mosheri morphotype B, as well as by Re – Os isochron ages of organic-rich limestone. Although the base level rise observed at the NRB interval could be due to regional tectonics, it could also potentially be recording eustatic sea level rise given the lack of consensus around sea level change at the NRB. Measurements of late Norian 87Sr/86Sr ratios on Mount Sinwa are consistent with those recorded in Tethyan studies, but the Panthalassan record overall does not replicate the same drop across the NRB observed in the Tethys. The lithological facies shift is also immediately preceded by a negative excursion in the δ13C values of carbonate, indicating that the NRB interval on Mount Sinwa is associated with coral reef collapse as well as the globally observed disruption of carbon cycling.

NEW RECORDS ABOUT THE DIVERSITY, DISTRIBUTION, AND SEASONAL ACTIVITY PATTERNS BY BATS IN YUKON AND NORTHWESTERN BRITISH COLUMBIA

The bat fauna of northwestern Canada remains poorly known, principally owing to a lack of dedicated surveys across this vast region. To better assess the diversity of bats in the region, we compiled records from several acoustic survey projects and capture sessions whose purpose was to inventory bats in Yukon and northwestern British Columbia (BC) from 2013 to 2018. During our surveys we obtained the 1st apparent acoustic records for Yuma Myotis (Myotis yumanensis), Californian Myotis (M. californicus), Long-eared Myotis (M. evotis), Silver-haired Bat (Lasionycteris noctivagans) and Eastern Red Bat (Lasiurus borealis) from this region. We also captured 2 Long-eared Myotis in northwestern BC. Additionally, our surveys provided range extensions of Northern Myotis (M. septentrionalis), Long-legged Myotis (M. volans), and Hoary Bat (Lasiurus cinereus). Finally, by deploying bat detectors in late autumn, and in some cases throughout the winter, we provide data about seasonal patterns for bat activity in some locations, revealing that bats in northwestern BC may be active as late as 29 October and emerge as early as 30 March, a pattern similar to that observed in southern BC. By combining data from several disparate surveys, conducted for different reasons by different researchers, we were able to provide a fuller picture of the bat fauna of this vast region. Our data provides further evidence that the bat fauna of northwestern Canada is richer than previously documented.

Selenium Distribution in the Gossan of a Porphyry Copper Deposit, Red Chris Mine, British Columbia, Canada

Abstract In 2015, the Red Chris mine in northwestern British Columbia began processing near-surface ores from the Red Chris copper-gold deposit and encountered higher leachable selenium concentrations in process water than had been anticipated from testing of deeper ores. Samples of gossan, near-surface rock, and deeper hypogene rock were submitted for analytical, mineralogical, and kinetic geochemical testing to investigate the origin of the leachable selenium, its mineralogical form, and the release mechanisms. This paper presents testing results and implications for understanding the selenium distribution in weathered rocks at sulfide mineral deposits. Shallow weathered rock, including the gossan, contained higher selenium concentrations and higher ratios of selenium to sulfur relative to the hypogene bedrock. Laboratory weathering and leaching tests indicated that selenium is released from source sulfides by oxidation and retained in a variety of secondary mineral forms. Mean selenium content in the solids was measured as follows: gossan and shallow bedrock >> deeper near-surface bedrock > hypogene bedrock. Water-leachable selenium varied but generally followed a similar trend, with samples of gossan containing the highest water-leachable selenium. Selenium was determined to be preferentially leached from the gossan samples at high pH values, indicating an adsorbed form. We propose that the weathering profile of the Red Chris deposit was previously capped with a well-developed thick gossan, which formed during the Paleogene and was eroded during the last period of glaciation. The current weathered rock reflects the residual base of the former oxidized profile.

Evaluating the use of hair as a non-invasive indicator of trace mineral status in woodland caribou (Rangifer tarandus caribou)

Trace mineral imbalances can have significant effects on animal health, reproductive success, and survival. Monitoring their status in wildlife populations is, therefore, important for management and conservation. Typically, livers and kidneys are sampled to measure mineral status, but biopsies and lethal-sampling are not always possible, particularly for Species at Risk. We aimed to: 1) determine baseline mineral levels in Northern Mountain caribou (Rangifer tarandus caribou; Gmelin, 1788) in northwestern British Columbia, Canada, and 2) determine if hair can be used as an effective indicator of caribou mineral status by evaluating associations between hair and organ mineral concentrations. Hair, liver, and kidney samples from adult male caribou (nHair = 31; nLiver, nKidney = 43) were collected by guide-outfitters in 2016–2018 hunting seasons. Trace minerals and heavy metals were quantified using inductively-coupled plasma mass spectrometry, and organ and hair concentrations of same individuals were compared. Some organ mineral concentrations differed from other caribou populations, though no clinical deficiency or toxicity symptoms were reported in our population. Significant correlations were found between liver and hair selenium (rho = 0.66, p<0.05), kidney and hair cobalt (rho = 0.51, p<0.05), and liver and hair molybdenum (rho = 0.37, p<0.10). These findings suggest that hair trace mineral assessment may be used as a non-invasive and easily-accessible way to monitor caribou selenium, cobalt, and molybdenum status, and may be a valuable tool to help assess overall caribou health.

150 Myr of Episodic Metamorphism Recorded in the Yukon-Tanana Terrane, Northern Canadian Cordillera: Evidence from Monazite and Xenotime Petrochronology

Abstract We used in situ laser-ablation split-stream petrochronology to target monazite and xenotime associated with specific metamorphic index minerals in the Florence Range metamorphic suite in the northern Canadian Cordillera. Based on this petrochronological approach, we reconstruct the polyphase metamorphic evolution of the Yukon-Tanana terrane in northwestern British Columbia. Our new data reveal a complex P–T–t path, requiring three metamorphic episodes and passing through the kyanite, sillimanite, and andalusite stability fields over 150 Myr from the Permian to the Early Cretaceous. The earliest preserved metamorphic event is cryptic, reaching the kyanite stability field (&amp;gt;600°C, &amp;gt;0.6 GPa) at ca. 270–240 Ma followed by retrograde metamorphism at ca. 240–215 Ma. Renewed garnet growth occurred during a second prograde metamorphic event at ca. 195–185 Ma. Garnet breakdown, possibly linked to decompression and/or cooling in the suprasolidus stability field of sillimanite and K-feldspar (&amp;gt;675°C, &amp;lt;0.8 GPa), is well-documented at ca. 185–170 Ma. Finally, a third metamorphic episode is characterized by the local growth of andalusite, then cordierite, and reached &amp;gt;600°C below 0.3–0.4 GPa after ca. 120 Ma. This study illustrates the importance of analyzing petrochronometers in their textural context, especially inclusions in porphyroblasts, and the complementary P–T–t information that can be extracted from monazite and xenotime. Our new data are compatible with two separate contractional events involving the Yukon-Tanana terrane during the Permian–Triassic and Late Triassic to Early Jurassic, followed by Cretaceous contact metamorphism.

The Jurassic Laberge Group in the Whitehorse Trough of the Canadian Cordillera: Using Detrital Mineral Geochronology and Thermochronology to Investigate Tectonic Evolution

The Laberge Group is an Early to Middle Jurassic sequence of mostly siliciclastic sedimentary rocks that were deposited in a marginal marine environment in the northern Canadian Cordillera. It forms a long narrow belt with a total thickness of 3–4 km extending for more than 600 km across southern Yukon and northwestern British Columbia. These sedimentary rocks overlap the Yukon-Tanana, Stikinia and Cache Creek terranes that form the main components of the Intermontane superterrane. The Laberge Group contains a record of the erosion of some of these terranes, and also offers some constraints on the timing of their amalgamation and accretion to the Laurentian margin. The Laberge Group was deposited with local unconformity on the Late Triassic Stuhini Group (in British Columbia) and correlative Lewes River Group (in Yukon), both of which are volcanic-rich, and assigned to the Stikinia terrane. The Laberge Group is in turn overlain by Middle Jurassic to Cretaceous clastic rocks, including the Bowser Lake Group in BC and the Tantalus Formation in Yukon. Clast compositions and detrital zircon populations within the Laberge Group and between it and these bounding units indicate major shifts in depositional environment, basin extent and detrital sources from Late Triassic to Late Jurassic. During the Early Jurassic clast compositions in the Laberge Group shifted from sediment- and volcanic-dominated to plutonic-dominated, and detrital zircon populations are dominated by grains that yield ages that approach or overlap their inferred depositional ages. This pattern is consistent with progressive dissection and unroofing of (an) active arc(s) to eventually expose Triassic to Jurassic plutonic suites. Detrital rutile and muscovite data from the Laberge Group indicate rapid cooling and then exhumation of adjoining metamorphic rocks during the Early Jurassic, allowing these to contribute detritus on a more local scale. The most likely source for such metamorphic detritus is within the Yukon-Tanana terrane, and its presence in the Laberge Group may constrain the timing of amalgamation and accretion of the Yukon-Tanana and Stikinia terranes. Thermochronological data also provide new insights into the evolution of the Laberge Group basin. Results from the U–Th/(He) method on detrital apatite suggest that most areas experienced post-depositional heating to 60°C or more, whereas U–Th/(He) results from detrital zircon show that heating to more than 200°C occurred on a more local scale. In detail, Laberge Group cooling and exhumation was at least in part structurally controlled, with more strongly heated areas situated in the footwall of an important regional fault system. The thermochronological data are preliminary, but they suggest potential to eventually constrain the kinematics and timing of inversion across the Laberge Group basin and may also have implications for its energy prospectivity. In summary, the Laberge Group is a complex package of sedimentary rocks developed in an active, evolving tectonic realm, and many questions remain about the details of its sources and evolution. Nevertheless, the available information demonstrates the potential of combined geochronological and thermochronological methods applied to detrital minerals to unravel links between regional tectonics, basin development and clastic sedimentation.

Latest Triassic–Early Jurassic Stikine–Yukon-Tanana terrane collision and the onset of accretion in the Canadian Cordillera: Insights from Hazelton Group detrital zircon provenance and arc–back-arc configuration

AbstractThe Hazelton Group is a Rhaetian–Bajocian (uppermost Triassic–Middle Jurassic) volcano-sedimentary sequence that represents both the last pre-accretionary arc volcanic cycle of Stikinia and its early synaccretionary aftermath. Hazelton magmatism of central Stikinia succeeded the Late Triassic (mainly Carnian–Norian) Stuhini arc, which ceased activity as a result of end-on collision with the pericratonic Yukon-Tanana terrane. The Hazelton volcanic belt lies to the south along strike with the coeval Whitehorse trough, the synorogenic clastic basin that developed on top of the Stikinia–Yukon-Tanana collision zone. Whereas the sources of voluminous clastic sediments in the Whitehorse trough were its rapidly exhuming shoulders, the thin clastic intervals in the Hazelton Group in northwestern British Columbia were derived from local to subregional block uplifts that supplied mainly ca. 230–215 Ma zircons eroded from the plutonic roots of the Stuhini arc. Lesser components include late Paleozoic (ca. 350–330 Ma) zircons from Stikinia's basement and penecontemporaneous (ca. 205–172 Ma) zircons from Hazelton volcanic/subvolcanic sources. Reexamination of the four main volcanic fields that make up the lower Hazelton Group suggests that the main Hazelton volcanic belt formed a southward-convex magmatic arc from eastern Stikinia across the Skeena arch, including the Toodoggone and Telkwa belts, with the Spatsizi and Stewart-Iskut regions of northwestern British Columbia in its back-arc. The Whitehorse trough and Hazelton belt represent a collision zone to active arc pair. Southward advance of the arc and counterclockwise rotation of the Stikinia microplate contributed to closure against the Quesnellia arc and assembly of the inner Canadian Cordilleran terrane collage.

Efficacy of Visual Encounter Surveys for Coastal Tailed Frog Detection

AbstractCoastal tailed frogs Ascaphus truei inhabit montane streams and forested habitats in the Coast and Cascade mountains from northern California to the Skeena River watershed in northwestern British Columbia. Terrestrial adults and juveniles of this cryptic biphasic species are difficult to survey as they are small, do not vocalize, and may be associated with woody ground structures or subsurface refugia at considerable distances from natal streams. We performed a comparative analysis of the detection rate of postmetamorphic coastal tailed frogs and ecological factors hypothesized to influence detection when conducting visual encounter and pitfall trap surveys. We conducted concurrent surveys in northwestern British Columbia at six sites over similar time periods using both techniques. The average detection rate of visual encounter surveys (mean = 0.249, SD = 0.702) was greater than that of pitfall sampling (mean = 0.138, SD = 0.773) when cool temperatures and high humidity favor aboveground movement during the daytime. Light-touch ground searches of refuge habitats likely enhanced detection during visual surveys. Although the average detection rate was less, pitfall traps provided 24-h sampling and were less affected by the experience of the surveyor and the occurrence of ground cover. In general, variation in seasonal behavior influenced detection regardless of method. The relatively higher cost and fixed nature of pitfall traps should be weighed against the ability to apply more cost-effective visual encounter surveys to a greater number of sites.

POLES, POTLATCHING, AND PUBLIC AFFAIRS

In the summer of 1987 the Tsimshians of the village of Kitsumkalum in northwestern British Columbia raised three totem poles, a massive undertaking that enabled them to demonstrate the strength of their community and the political potency of their leaders to mobilize support for their goals. Today, aboriginal culture is being used as a resource to devise creative strategies for asserting or negotiating a social and political status quo. The pole raising was a means for these Tsimshians to restructure their mode of political expression and important aspects of their social organization along tradition lines. This paper examines how aboriginal culture was used to contextualize and negotiate policy issues critical to the community: land claims, self-government, and economic development.

Development of a laser ablation ICP-MS method for the analysis of fluid inclusions associated with volcanogenic massive sulfide deposits

There is increasing acceptance of the presence of variable magmatic contributions to the mineralizing fluids in the formation of volcanogenic massive sulfide (VMS) deposits. The world-class Windy Craggy Cu-Co-Au deposit (&gt;300 MT @ 2.12 wt% Cu) in northwestern British Columbia is of interest because, unlike most VMS deposits, fluid inclusions in quartz from within the deposit range from relatively low to intermediate salinity (most 6–16 wt% equivalent). In this study we used an excimer (193 nm) laser ablation system interfaced to a quadrupole inductively coupled plasma mass spectrometer to quantify key metals and metalloids that are considered by many to be indicative of magmatic contributions to hydrothermal ore deposits. Although LA-ICP-MS signals from these low-salinity inclusions are highly transient, we were able to quantify Na, Mg, K, Ca, Mn, Fe, Co, Cu, Zn, Sr, Sn, Ba, Ce, Pb and Bi consistently – of the 34 elements that were monitored. Furthermore, Cl, Sb, Cd, Mo, Rb, Br and As were also measured in a significant number of inclusions. Comparison of the fluid inclusion chemistry with unaltered and altered mafic volcanic and sedimentary rocks and mineralized samples from the deposit indicate that enrichment in the main ore metals (Cu, Zn, Fe, Pb) in the inclusions reflects that of the altered rocks and sulfides. Metals and metalloids that may indicate a magmatic contribution typically show much greater enrichments in the fluid inclusions over the host rocks at the same Cu concentration; in particular Bi, Sn and Sb are significantly elevated when compared to the host rock samples. These data are consistent with the ore-forming fluids at Windy Craggy having a strong magmatic contribution.Supplementary material: fluid inclusion data for temperature of homogenization and salinity, and full analytical results for laser ablation ICP-MS analyses of individual inclusions for the two analytical sessions are available at https://doi.org/10.6084/m9.figshare.c.5443094

Study of the Influence of Non-Deposit Locations in Data-Driven Mineral Prospectivity Mapping: A Case Study on the Iskut Project in Northwestern British Columbia, Canada

The accuracy of data-driven predictive mineral prospectivity models relies heavily on the training datasets used. These models are usually trained using data for “known” deposit locations as well as “non-deposit” locations that are based on randomly generated point patterns. In this study, data related to the Seabridge Gold Inc Iskut project, an epithermal Au deposit in northwestern British Columbia (BC), Canada, are used to test the utility of data-driven mineral prospectivity modeling. The input spatial dataset is comprised mostly of publicly available data. Data for 18 vein and epithermal Au known mineral occurrences (KMO) are obtained from the BC Geological Survey’s MINFILE repository and selected as training deposit locations. A total of eleven sets of non-deposit locations (NDL) were also created, including one set of selected non-prospective KMO for Au deposits from the MINFILE and ten sets of random point patterns. Given the scale of this study, most of the KMO recorded on the property are of the epithermal deposit type. Hence, they could not be used as a selection criterion. Data-driven mineral potential models are generated using the random forest (RF) algorithm and trained on multiple data sets. The comparison of RF models demonstrated that using non-prospective KMO generates more accurate predictions than the random point pattern. The produced mineral prospectivity maps delineated multiple areas with higher discovery potential, which matched viable targets for the Au-Cu epithermal-porphyry system identified through previous Seabridge Gold Inc. (Toronto, ON, Canada) field reconnaissance and drilling programs.

Preliminary observations of nivation processes, Cathedral Massif, Northwestern British Columbia, Canada

ABSTRACT Nivation, the suite of weathering and transportation processes attributed to late-lying snowpatches, is linked to the formation of cryoplanation terraces (CTs). CTs resemble giant staircases arranged in repeating sequences of low-gradient treads and steep scarps that extend over hundreds of meters. The nivation hypothesis of CT development has been supported in recent literature examining weathering and erosion trends, but the mechanisms involved in transporting sediment across CT treads remain underinvestigated. Sorted stripes, a type of patterned ground encountered on CT treads, have been linked to efficient snow meltwater flow across low gradients, indicating that these features could be an important component of CT formation. In this study, we use short-term soil thermal and moisture records, particle-size analysis, and apparent thermal diffusivity calculations to examine periglacial processes operating on two incipient CTs. Initial results indicate that: (1) the coarse (boulder and cobble size) portions of sorted stripes function as subsurface channels for sediment transportation across gently sloping CT treads (generally < 12°) by flowing water; (2) hillslope hydrology is an important component of the erosion processes sculpting upland periglacial environments; and (3) late-lying snowbank environments are highly dynamic during warm weather, with large amounts of sediment transported over short periods.

Gridded bias correction of modeled PM2.5 for exposure assessment, and estimation of background concentrations over a coastal valley region of northwestern British Columbia, Canada

ABSTRACT Chemical transport models (CTM) can have large biases and errors when simulating pollutant concentrations. To improve the characterization of fine particulate matter (PM2.5) over complex terrain for exposure assessments, three mathematical formulae that utilized the relationship between modeled and observed quantile concentrations at a monitor location were developed. These were then applied to 1 year of CMAQ model output of PM2.5 over the Terrace–Kitimat Valley of northwestern British Columbia, Canada. The final products enhanced the representation of ambient levels at existing monitoring stations when evaluated with conventional statistical measures. Better agreement of corrected outputs with observed compliance metrics was also found. On average, the absolute errors of amended outputs were 11% and 10% for the annual mean PM2.5 and 98th percentiles of daily concentrations, respectively, compared to 45% and 61%, respectively, in the original outputs. These improvements provided greater confidence to use the amended outputs to estimate concentrations at locations without monitors. The predominance of pristine conditions in the modeling domain was exploited to derive annual background PM2.5 concentrations over the valley, which was estimated to be 2.0–2.3 μg m−3. To our knowledge, this is the first study to calculate background PM2.5 concentrations over northern BC coastlands using bias-corrected outputs from an air quality model. Implications: Bias correction of CMAQ model output was necessary for assessing regulatory compliance for ambient PM2.5. The implications are notable. First, for low to moderate spatial heterogeneity in monitoring data, the use of regression equations that relates quantile mean concentrations of model outputs to those of observational data enhances the estimation of PM2.5 at unmonitored locations. Second, by providing spatial pollutant distribution ahead of planned industrial development in Terrace–Kitimat Valley (TKV), corrected model output offers a baseline for tracking progress in airshed management. Third, correction improved pollutant exposure classification, for which the risk was predominantly low. Finally, 2.0–2.3 μg m−3 should be considered as PM2.5 concentrations that are irreducible when setting voluntary targets for ambient levels in the area.

Comparative Gene Expression Analysis Reveals Mechanism of Pinus contorta Response to the Fungal Pathogen Dothistroma septosporum.

Many conifers have distributions that span wide ranges in both biotic and abiotic conditions, but the basis of response to biotic stress has received much less attention than response to abiotic stress. In this study, we investigated the gene expression response of lodgepole pine (Pinus contorta) to attack by the fungal pathogen Dothistroma septosporum, which causes Dothistroma needle blight, a disease that has caused severe climate-related outbreaks in northwestern British Columbia. We inoculated tolerant and susceptible pines with two D. septosporum isolates and analyzed the differentially expressed genes (DEGs), differential exon usage, and coexpressed gene modules using RNA-sequencing data. We found a rapid and strong transcriptomic response in tolerant lodgepole pine samples inoculated with one D. septosporum isolate, and a late and weak response in susceptible samples inoculated with another isolate. We mapped 43 of the DEG- or gene module-identified genes to the reference plant-pathogen interaction pathway deposited in the Kyoto Encyclopedia of Genes and Genomes database. These genes are present in PAMP-triggered and effector-triggered immunity pathways. Genes comprising pathways and gene modules had signatures of strong selective constraint, while the highly expressed genes in tolerant samples appear to have been favored by selection to counterattack the pathogen. We identified candidate resistance genes that may respond to D. septosporum effectors. Taken together, our results show that gene expression response to D. septosporum infection in lodgepole pine varies both among tree genotypes and pathogen strains and involves both known candidate genes and a number of genes with previously unknown functions.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Long-term nivation rates, Cathedral Massif, northwestern British Columbia

Cryoplanation terraces (CTs) are large (3000–800 000 m2) erosional landforms found in upland periglacial environments. Two hypotheses for the formation of CTs are supported in contemporary literature: (1) CT formation is controlled primarily by geologic structure; and (2) CTs are climatically controlled through nivation, a suite of erosional processes associated with late-lying snowbanks. A persistent question in periglacial geomorphology is whether nivation can produce CT-scale landforms. This paper examines the unusual deglaciation history of “Frost Ridge” on the Cathedral Massif, northwestern British Columbia, to estimate long-term denudation attributable to nivation processes active since the last glacial maximum. Frost Ridge forms one flank of an east–west-oriented glacial valley. During deglaciation, marginal drainage created V-shaped erosional notches on both valley walls. Minimization of solar radiation on the steep north-facing wall (Frost Ridge) allowed snowbanks to accumulate and persist in the marginal drainage features and nivation processes to erode the slope. Today, several large nivation hollows (incipient CTs) are present near the summit of Frost Ridge, while the V-shaped marginal drainage features are preserved at lower elevations and on the opposite, south-facing valley wall. A high-resolution survey using an unmanned aerial vehicle (UAV) allowed volumes of marginal drainage and incipient terrace features to be compared. Based on this volumetric comparison, denudation rates are estimated to range from 4.2 to 125.8 mm/kyr, which are comparable with relatively short-term nivation rates reported from Antarctica and mid-latitude alpine periglacial areas.

The age of the Tseax volcanic eruption, British Columbia, Canada

A recent volcanic eruption occurred at Tseax volcano that formed a series of tephra cones in northwestern British Columbia, Canada. The explosive to effusive eruption also formed a 32 km long sequence of Fe-rich Mg-poor basanite–trachybasalt lavas covering ∼40 km2. Oral histories of the Nisg_a’a Nation report that the eruption may have caused as many as 2000 fatalities. The actual eruption date and question of whether there was one or multiple eruptive episodes in the 14th and 18th centuries are, as of yet, unresolved. New radiocarbon dating of wood charcoal from immediately beneath vent-proximal tephra deposits and complementary age information suggest an eruption in 1675–1778 CE (95.4% probability) was responsible for the formation of the tephra cone. New paleomagnetic and geochemical data from the tephra cone and lava flows suggest there is, in fact, no statistically significant difference in time between the explosive and effusive deposits and that they formed during a single eruptive episode.