Canadian Rocky Research Articles

Protection status, human disturbance, snow cover and trapping drive density of a declining wolverine population in the Canadian Rocky Mountains

Protected areas are important in species conservation, but high rates of human-caused mortality outside their borders and increasing popularity for recreation can negatively affect wildlife populations. We quantified wolverine (Gulo gulo) population trends from 2011 to 2020 in > 14,000 km2 protected and non-protected habitat in southwestern Canada. We conducted wolverine and multi-species surveys using non-invasive DNA and remote camera-based methods. We developed Bayesian integrated models combining spatial capture-recapture data of marked and unmarked individuals with occupancy data. Wolverine density and occupancy declined by 39%, with an annual population growth rate of 0.925. Density within protected areas was 3 times higher than outside and declined between 2011 (3.6 wolverines/1000 km2) and 2020 (2.1 wolverines/1000 km2). Wolverine density and detection probability increased with snow cover and decreased near development. Detection probability also decreased with human recreational activity. The annual harvest rate of ≥ 13% was above the maximum sustainable rate. We conclude that humans negatively affected the population through direct mortality, sub-lethal effects and habitat impacts. Our study exemplifies the need to monitor population trends for species at risk—within and between protected areas—as steep declines can occur unnoticed if key conservation concerns are not identified and addressed.

A before-after-control-impact study of wildlife fencing along a highway in the Canadian Rocky Mountains

Wildlife exclusion fencing has become a standard component of highway mitigation systems designed to reduce collisions with large mammals. Past work on the effectiveness of exclusion fencing has relied heavily on control–impact (i.e., space-for-time substitutions) and before–after study designs. These designs limit inference and may confound the effectiveness of mitigation with co-occurring process that also changes the rate of collisions. We used a replicated (n = 2 sites monitored for over 1000 km years combined) before-after-control-impact study design to assess fencing effectiveness along the Trans-Canada Highway in the Rocky Mountains of Canada. We found that collisions declined for common ungulates species (elk, mule deer, and white-tailed deer) by up to 96% but not for large carnivores. The weak response of carnivores is likely due to the combination of fence intrusions and low sample sizes. We calculated realized fencing effectiveness by applying the same change in collision rates observed at control (unfenced) sites as the expected change for adjacent fenced sections. Compared with the apparent fencing effectiveness (i.e., the difference in WVCs rates before and after fencing was installed), the realized estimates of fencing effectiveness declined by 6% at one site and increased by 10% at another site. When factoring in the cost of ungulate collisions to society, fencing provided a net economic gain within 1 year of construction. Over a 10-year period, fencing would provide a net economic gain of > $500,000 per km in reduced collisions. Our study highlights the benefits of long-term monitoring of road mitigation projects and provides evidence of fencing effectiveness for reducing wildlife–vehicle collisions involving large mammals.

Hydrological process controls on streamflow variability in a glacierized headwater basin

AbstractMountain glacierized headwaters are currently witnessing a transient shift in their hydrological and glaciological systems in response to rapid climate change. To characterize these changes, a robust understanding of the hydrological processes operating in the basin and their interactions is needed. Such an investigation was undertaken in the Peyto Glacier Research Basin, Canadian Rockies over 32 years (1988–2020). A distributed, physically based, uncalibrated glacier hydrology model was developed using the modular, object‐oriented Cold Region Hydrological Modelling Platform to simulate both on and off‐glacier high mountain processes and streamflow generation. The hydrological processes that generate streamflow from this alpine basin are characterized by substantial inter‐annual variability over the 32 years. Snowmelt runoff always provided the largest fraction of annual streamflow (44% to 89%), with smaller fractional contributions occurring in higher streamflow years. Ice melt runoff provided 10% to 45% of annual streamflow volume, with higher fractions associated with higher flow years. Both rainfall and firn melt runoff contributed less than 13% of annual streamflow. Years with high streamflow were on average 1.43°C warmer than low streamflow years, and higher streamflow years had lower seasonal snow accumulation, earlier snowmelt and higher summer rainfall than years with lower streamflow. Greater ice exposure in warmer, low snowfall (high rainfall) years led to greater streamflow generation. The understanding gained here provides insight into how future climate and increased meteorological variability may impact glacier meltwater contributions to streamflow and downstream water availability as alpine glaciers continue to retreat.

Quantifying relative contributions of source waters from a subalpine wetland to downstream water bodies

AbstractSubalpine regions of the Canadian Rocky Mountains are expected to experience continued changes in hydrometeorological processes due to anthropogenically mediated climate warming. As a result, fresh water supplies are at risk as snowmelt periods occur earlier in the year, and glaciers contribute less annual meltwater, resulting in longer growing seasons and greater reliance on rainfall to generate runoff. In such environments, wetlands are potentially important components that control runoff processes, but due to their location and harsh climates their hydrology is not well studied. We used stable water isotopes of hydrogen and oxygen (δ2H and δ18O), coupled with MixSIAR, a Bayesian mixing model, to understand relative source water contributions and mixing within Burstall Wetland, a subalpine wetland (1900 m a.s.l.), and the larger Burstall Valley. These results were combined with climate data from the Burstall Valley to understand hydrometeorological controls on Burstall Wetland source water dynamics over spatiotemporal timescales. Our results show that the seasonal isotopic patterns within Burstall Wetland reflect greater reliance on snowmelt in spring and rainfall in the peak and post‐growing season periods. We found a substantial degree of mixing between precipitation (rain and snow) and stored waters in the landscape, especially during the pre‐growing season. These findings suggest that longer growing seasons in subalpine snow‐dominated landscapes put wetlands at risk of significant water loss and increased evaporation rates potentially leading to periods of reduced runoff during the peak‐ growing season and in extreme cases, wetland dry out.

Using ground-based thermal imagery to estimate debris thickness over glacial ice: fieldwork considerations to improve the effectiveness

AbstractDebris-covered glaciers are an important component of the mountain cryosphere and influence the hydrological contribution of glacierized basins to downstream rivers. This study examines the potential to make estimates of debris thickness, a critical variable to calculate the sub-debris melt, using ground-based thermal infrared radiometry (TIR) images. Over four days in August 2019, a ground-based, time-lapse TIR digital imaging radiometer recorded sequential thermal imagery of a debris-covered region of Peyto Glacier, Canadian Rockies, in conjunction with 44 manual excavations of debris thickness ranging from 10 to 110 cm, and concurrent meteorological observations. Inferring the correlation between measured debris thickness and TIR surface temperature as a base, the effectiveness of linear and exponential regression models for debris thickness estimation from surface temperature was explored. Optimal model performance (R2 of 0.7, RMSE of 10.3 cm) was obtained with a linear model applied to measurements taken on clear nights just before sunrise, but strong model performances were also obtained under complete cloud cover during daytime or nighttime with an exponential model. This work presents insights into the use of surface temperature and TIR observations to estimate debris thickness and gain knowledge of the state of debris-covered glacial ice and its potential hydrological contribution.

Radiocarbon dates and late Quaternary vertebrates from cave deposits in the central Canadian Rocky Mountains

New radiocarbon dates on biological remains from cave deposits in the Canadian Rocky Mountains range in age from infinite to modern but are largely restricted to the Holocene (9560±40 years B.P. to modern). The consistency in radiocarbon ages is interpreted as resulting from geologic processes associated with deglaciation and may reflect timeframes when cave conditions in some areas of the Canadian Rocky Mountains became suitable for deposition and preservation of biological remains. When considered at taxonomic levels permitted by morphological identification, recovered vertebrate remains from cave deposits are consistent with the modern biota of the region, suggesting early post-Late Glacial Maximum establishment of the modern biota and relative stability of mammal assemblages through the Holocene. Preliminary evaluation of recovered plant remains highlights a potentially underevaluated source of palaeoecological data for higher elevations.

Multi-decadal basal slip enhancement at Saskatchewan Glacier, Canadian Rocky Mountains

AbstractGlacier motion responds dynamically to changing meltwater inputs, but the multi-decadal response of basal sliding to climate remains poorly constrained due to its sensitivity across multiple timescales. Observational records of glacier motion provide critical benchmarks to decode processes influencing glacier dynamics, but multi-decadal records that precede satellite observation and modern warming are rare. Here we present a record of motion in the ablation zone of Saskatchewan Glacier that spans seven decades. We combine in situ and remote-sensing observations to inform a first-order glacier flow model used to estimate the relative contributions of sliding and internal deformation on dynamics. We find a significant increase in basal sliding rates between melt-seasons in the 1950s and those in the 1990s and 2010s and explore three process-based explanations for this anomalous behavior: (i) the glacier surface steepened over seven decades, maintaining flow-driving stresses despite sustained thinning; (ii) the formation of a proglacial lake after 1955 may support elevated basal water pressures; and (iii) subglacial topography may cause dynamic responses specific to Saskatchewan Glacier. Although further constraints are necessary to ascertain which processes are of greatest importance for Saskatchewan Glacier's dynamic evolution, this record provides a benchmark for studies of multi-decadal glacier dynamics.

Burn Severity in Canada's Mountain National Parks: Patterns, Drivers, and Predictions

AbstractFine‐scale estimation of burn severity in the Canadian Rocky Mountain region with mixed‐severity fires is of substantial implications but still lacking. We investigated satellite‐derived burn severity from 1985 to 2015 at 30‐m resolution in three mountain national parks in Canada: Banff, Kootenay, and Yoho National Parks. Results show that fuel type had the most significant influence on burn severity, whereas the three groups of continuous variables (topography, vegetation, and climate) contributed equally to the model, indicating the complex mechanism of environmental controls on fire behavior in this heterogeneous mountain region. The predicted burn severity potentials of the whole parks in 2002 and 2012 showed overall consistent spatial patterns, and lightning‐caused fires produced more high‐severity burn areas than prescribed fires. Generally, local communities in the intensive fire management zone were predicted to have relatively low burn severity, reflecting the fire management effectiveness.

OPINION: The resilience myth: is it just in our heads?

We recently finished weeks of service in different intensive care units (ICUs) on opposite sides of the Canadian Rockies. Neither of us had the most crushing of weeks, but we both experienced sadness and exhaustion in ways that come from long hours coupled with tragedy for many, and the end of life for some. For too long, we had avoided frank discussions about our work environment and what drives us to work in the place we do and in the way we do.

Large-area high spatial resolution albedo retrievals from remote sensing for use in assessing the impact of wildfire soot deposition on high mountain snow and ice melt

Soot deposition from wildfires decreases snow and ice albedo and increases the absorption of shortwave radiation, which advances and accelerates melt. Soot deposition also induces algal growth, which further decreases snow and ice albedo. In recent years, increasingly severe and widespread wildfire activity has occurred in western Canada in association with climate change. In the summers of 2017 and 2018, westerly winds transported smoke from extensive record-breaking wildfires in British Columbia eastward to the Canadian Rockies, where substantial amounts of soot were deposited on high mountain glaciers, snowfields, and icefields. Several studies have addressed the problem of soot deposition on snow and ice, but the spatiotemporal resolution applied has not been compatible with studying mountain icefields that are extensive but contain substantial internal variability and have dynamical albedos. This study evaluates spatial patterns in the albedo decrease and net shortwave radiation (K*) increase caused by soot from intense wildfires in Western Canada deposited on the Columbia Icefield (151 km2), Canadian Rockies, during 2017 and 2018. Twelve Sentinel-2 images were used to generate high spatial resolution albedo retrievals during four summers (2017 to 2020) using a MODIS bidirectional reflectance distribution function (BRDF) model, which was employed to model the snow and ice reflectance anisotropy. Remote sensing estimates were evaluated using site-measured albedo on the icefield's Athabasca Glacier tongue, resulting in a R2, mean bias, and root mean square error (RMSE) of 0.68, 0.019, and 0.026, respectively. The biggest inter-annual spatially averaged soot-induced albedo declines were of 0.148 and 0.050 (2018 to 2020) for southeast-facing glaciers and the snow plateau, respectively. The highest inter-annual spatially-averaged soot-induced shortwave radiative forcing was 203 W/m2 for southeast-facing glaciers (2018 to 2020) and 106 W/m2 for the snow plateau (2017 to 2020). These findings indicate that snow albedo responded rapidly to and recovered rapidly from soot deposition. However, ice albedo remained low the year after fire, and this was likely related to a bio-albedo feedback involving microorganisms. Snow and ice K* were highest during low albedo years, especially for south-facing glaciers. These large-scale effects accelerated melt of the Columbia Icefield. The findings highlight the importance of using large-area high spatial resolution albedo estimates to analyze the effect of wildfire soot deposition on snow and ice albedo and K* on icefields, which is not possible using other approaches.

Quality Control Impacts on Total Precipitation Gauge Records for Montane Valley and Ridge Sites in SW Alberta, Canada

This paper presents adjustment routines for Geonor totalizing precipitation gauge data collected from the headwaters of the Oldman River, within the southwestern Alberta Canadian Rockies. The gauges are situated at mountain valley and alpine ridge locations with varying degrees of canopy cover. These data are prone to sensor noise and environment-induced measurement errors requiring an ordered set of quality control (QC) corrections using nearby weather station data. Sensor noise at valley sites with single-vibrating wire gauges accounted for the removal of 5% to 8% (49–76 mm) of annual precipitation. This was compensated for by an increase of 6% to 8% (50–76 mm) from under-catch. A three-wire ridge gauge did not experience significant sensor noise; however, the under-catch of snow resulted in 42% to 52% (784–1342 mm) increased precipitation. When all QC corrections were applied, the annual cumulative precipitation at the ridge demonstrated increases of 39% to 49% (731–1269 mm), while the valley gauge adjustments were −4% to 1% (−39 mm to 13 mm). Public sector totalizing precipitation gauge records often undergo minimal QC. Care must be exercised to check the corrections applied to such records when used to estimate watershed water balance or precipitation orographic enhancement. Systematic errors at open high-elevation sites may exceed nearby valley or forest sites.

LOWER CAMBRIANRUSOPHYCUSFROM ELLESMERE ISLAND, ARCTIC CANADA: ICHNOFOSSIL OF A PREDATORY, NON-TRILOBITE ARTHROPOD

ABSTRACTCruziana and Rusophycus are commonly assumed to be trilobite trace fossils, although associated exoskeletons are almost invariably absent from host strata. In the lower Cambrian Dallas Bugt Formation of Ellesmere Island, Arctic Canada, high-energy, cross-laminated sandstones locally with dense populations of large Skolithos are overlain by thin-bedded, bioturbated, argillaceous, medium-grained glauconitic sandstones of lagoonal aspect, yielding Rusophycus along with an assortment of other “worm” burrows. Some specimens of Rusophycus are located over small Skolithos shafts and the bottoms of Arenicolites, suggesting a predator-prey relationship. Many preserve the impression of a strongly vaulted carapace with a broad, triangular dorsal outline between 1 cm and 7 cm across. A blunt anterior “prow” projects slightly forward and arches dorsally, forming a keyhole-shaped notch. The arthropod dug into the sediment up to 5 cm deep with an antero-posterior angle of up to ∼ 45° from the sea floor; in some cases it dug obliquely laterally and rarely sideways. Retroverse scratches—preserved in hyporelief as sharp-crested ridges—suggest about 20 pairs of endopodites tipped by a pair of small claws typically dug in unison, the anterior ones starting with a V-angle of 140° and decreasing posteriorly to 90°, in rare cases more tightly. Limb length increased posteriorly, although none extended beyond the carapace. Leg muscles were strong enough to rake through the muddy sand and pull inwards either straight or in a slightly forward-curving arc, but were also slightly flexible to wiggle around obstacles. Some specimens show subsequent re-burrowing which produced cross-cutting and opposed scratches. No evidence for exopodite brushings is present. Successive carapace imprints and scratches organized in transverse rugae in some specimens suggest repeatedly plunging and digging as the arthropod pulled backward in the sediment. This was likely aided by a stout trunk and a fan-shaped uropod-like structure flanking the telson which increased grip and leverage. A pair of eye stalks may have projected from the anterior notch, and these could have been retracted during digging, but there is no evidence for antennae. The tracemaker was not a trilobite but an unrelated crustacean-like arthropod, although there is no known late early Cambrian body fossil to which it can be ascribed. The specimens are classified as Rusophycus jenningsi (Fenton and Fenton, 1937) and a neotype is selected for this ichnospecies from the Gog Group near where it was first collected. Its range extends from the southern Canadian Rocky Mountains north along depositional strike to Victoria Island and northwest to Ellesmere Island and northern Greenland. Two new ichnofamilies are established: Rusophycidae and Cruzianidae.

Recent hydrological response of glaciers in the Canadian Rockies to changing climate and glacier configuration

Abstract. Mountain snow and ice greatly influence the hydrological cycle of alpine regions by regulating both the quantity of and seasonal variations in water availability downstream. This study considers the combined impacts of climate and glacier changes due to recession on the hydrology and water balance of two high-elevation basins in the Canadian Rockies. A distributed, physically based, uncalibrated glacier hydrology model developed in the Cold Regions Hydrological Modelling platform (CRHM) was used to simulate the glacier mass balance and basin hydrology of the Peyto and Athabasca glacier basins in Alberta, Canada. Bias-corrected reanalysis data were used to drive the model. The model calculates the water balance of glacierized basins, influenced by the surface energy and mass balance, and considers the redistribution of snow by wind and avalanches. It was set up using hydrological response units based on elevation bands, surface slope, and aspect, as well as changing land cover. Aerial photos, satellite images and digital elevation models (DEMs) were assimilated to represent the changing configurations of glacier area and the exposure of ice and firn. Observations of glacier mass balance, snow, and glacier ice surface elevation changes at glacier and alpine tundra meteorological stations and streamflow discharge at the glacier outlets were used to evaluate the model performance. Basin hydrology was simulated over two periods, 1965–1975 and 2008–2018, using the observed glacier configurations for those time periods. Both basins have undergone continuous glacier loss over the last 3 to 5 decades, leading to a 6 %–31 % reduction in glacierized area, a 78 %–109 % increase in ice exposure, and changes to the elevation and slope of the glacier surfaces. Air temperatures are increasing, mainly due to increasing winter maximum and summer minimum daily temperatures. Annual precipitation has increased by less than 11 %, but rainfall ratios have increased by 29 %–44 %. The results show that changes in both climate and glacier configuration have influenced the melt rates and runoff and a shift of peak flows in the Peyto Glacier basin from August to July. Glacier melt contributions increased/decreased from 27 %–61 % to 43 %–59 % of the annual discharges. Recent discharges were 3 %–19 % higher than in the 1960s and 1970s. The results suggest that increased exposure of glacier ice and lower surface elevation due to glacier thinning were less influential than climate warming in increasing streamflow. Streamflow from these glaciers continues to increase.

Ragnar Kjartansson and the Art of Pleasure

Ragnar Kjartansson and the Art of Pleasure

Leisure Constraints and Negotiation among Canadian and South Korean Mountain Hikers: An Extension of Motivations with the Constraints-Effect-Mitigation Model

This study examined mountain hikers’ negotiation of leisure constraints and the role that motivations played in this process. This investigation included a comparison between Canadian and South Korean hikers. Data were collected from a sample of 399 mountain hikers visiting the Canadian Rocky Mountains and mountains in South Korea. Results revealed that hiking constraints had a significant negative effect on constraints negotiation for both Canadians and South Koreans. Motivation had a strong positive effect on negotiation for both Canadians and South Koreans, but a non-significant effect on hiking participation. One main difference between the groups was observed: the South Korean sample displayed a significant negative relationship between constraints and hiking participation, and the Canadian sample revealed a significant positive relationship between constraint negotiation and hiking participation – suggesting Canadians negotiate their hiking constraints more readily than South Koreans.

Fire and Ice: The Impact of Wildfire‐Affected Albedo and Irradiance on Glacier Melt

AbstractWildfire occurrence and severity is predicted to increase in the upcoming decades with severe negative impacts on human societies. The impacts of upwind wildfire activity on glacier melt, a critical source of freshwater for downstream environments, were investigated through analysis of field and remote sensing observations and modeling experiments for the 2015–2020 melt seasons at the well‐instrumented Athabasca Glacier in the Canadian Rockies. Upwind wildfire activity influenced surface glacier melt through both a decrease in the surface albedo from deposition of soot on the glacier and through the impact of smoke on atmospheric conditions above the glacier. Athabasca Glacier on‐ice weather station observations show days with dense smoke were warmer than clear, non‐smoky days, and sustained a reduction in surface shortwave irradiance of 103 W m−2 during peak shortwave irradiance and an increase in longwave irradiance of 10 W m−2, producing an average 15 W m−2 decrease in net radiation. Albedo observed on‐ice gradually decreased after the wildfires started, from a summer average of 0.29 in 2015 before the wildfires to as low as 0.16 in 2018 after extensive wildfires and remained low for two more melt seasons without substantial upwind wildfires. Reduced all‐wave irradiance partly compensated for the increase in melt due to lowered albedo in those seasons when smoke was detected above Athabasca Glacier. In melt seasons without smoke, the suppressed albedo increased melt by slightly more than 10% compared to the simulations without fire‐impacted albedo, increasing melt by 0.42 m. w.e. in 2019 and 0.37 m. w.e. in 2020.

Preservation and diagenesis of soft-bodied fossils and the occurrence of phosphate-associated rare earth elements in the Cambrian (Wuliuan) Spence Shale Lagerstätte

The Spence Shale Lagerstätte is a middle Cambrian (Miaolingian Series; Wuliuan Stage) fossil deposit in northern Utah and southern Idaho, USA. At present, it is known to preserve 89 species, from at least 10 phyla, of biomineralizing and soft-bodied taxa, and represents the only major Lagerstätte of Wuliuan age in Laurentia outside the Canadian Rockies. In addition to taxonomic diversity, the Spence Shale exposures represent a variety of depositional environments along a continental shelf, which have been affected by several diagenetic events, making it a compelling setting to improve our understanding of taphonomic and diagenetic pathways as they affect the broader Burgess Shale-type (BST) preservation. We present analyses of 28 specimens from six localities using scanning electron microscopy (SEM) and integrated energy dispersive X-ray spectrometry (EDS), together with comparisons of published data. Taxa are predominantly preserved as a combination of carbonaceous compressions, iron oxide and pyrite replacement, but eldoniids of the genus Eldonia consistently show enrichment in rare earth elements (REE). The REE, predominantly lanthanum and cerium, are enriched in the phosphate mineral monazite, which occurs in the inner coil of Eldonia ludwigi . This pattern, seen in all sampled Eldonia , differs from previous reports of REE association in BST preservation in being limited to one tissue type within a specific identifiable taxon. REE enrichment of tissues can occur during the lifetime of an individual or during fossilization, and we present both possible pathways along with an outline of taphonomic processes leading to the preservation of soft-bodied fossils from the Spence Shale. • Main preservation modes are carbonaceous compressions and iron oxides/pyrite. • Phosphatized Eldonia ludwigi have unique REE associations. • Preservation of tissue types is biased, as is found in other Paleozoic Lagerstätten.

Evidence for pre-Cenozoic extension in the eastern Main Ranges of the southern Canadian Rockies

Abstract The eastern Main Ranges of the southern Canadian Rocky Mountain thrust-and-fold belt include a network of normal faults (the result of apparent extensional episodes) that occur within a contractional orogen. The origin, timing, and nature of these normal faults remain unresolved. A widely accepted explanation proposes that the normal faults developed as a consequence of postcontractional transtension that occurred west of the Rocky Mountain Trench during the Paleogene Period. Detailed field mapping of deformation in the vicinity of several normal faults has provided evidence that the normal fault surfaces and adjacent strata underwent deformation during a contractional episode after the normal faults had formed. Within the study area, located in the upper Kicking Horse region of Yoho National Park, British Columbia, Canada, and within the larger region of the Rocky Mountain belt, the network of normal faults is proposed to have developed as a consequence of rifting that separated pericratonic terranes from North America and produced the Slide Mountain Ocean during the Carboniferous and Permian Periods. Overprinting from more recent tectonic episodes has obscured most of these inferred extensional faults throughout the North American Cordillera. Within the study area, however, the Cretaceous to Paleogene contraction carried the normal faults to their present location over unattenuated continental crust, without significant overprinting. This preservation of the network of normal faults allows for investigation of the relationships among the fault surfaces and the strata adjacent to each fault.

Structural geometry and kinematic history of the southern Kicking Horse Rim Cambrian carbonate platform: out-of-sequence thrust faulting in the southern Canadian Rocky Mountains

Abstract The structure of the southern Kicking Horse Rim Cambrian carbonate platform is spectacularly exposed in the Rocky Mountains southwest of Calgary, Alberta, Canada. Episodic uplift along the approximately 100 km long, north-northwest-trending Kicking Horse Rim during the middle and upper Cambrian controlled the position of the Cambrian carbonate platform to basin facies change. Extensive hydrothermal alteration, with local magnesite and/or Pb-Zn mineralization occurred along the west margin of the Rim. Spectacular slump scars, escarpments, megaconglomerates and slide masses locally mark the edge of the southern Kicking Horse Rim platform. Megaconglomerates form a unique and indisputable stratigraphic tie between the basin and platform and show that there is no stratigraphic gap or suture along this boundary. The change from carbonate- to shale-dominated lithologies resulted in a major change in structural style and the boundary between the Eastern and Western Main Ranges structural subprovinces. Serial and regional cross-sections across the area document the southward plunge of Kicking Horse Rim strata and the Eastern Main Ranges structural subprovince and show that this is due to underlying structure, and not stratigraphic thinning of the Cambrian carbonate platform. Prospective horizons for mineralization extend southward in the subsurface beyond their current southern limit of exposure. Kicking Horse Rim and associated Cambrian strata were carried northeastward along the Fatigue Thrust - blind thrust fault system. Because of a prominent hanging wall ramp through the entire Cambrian succession along the east side of the Kicking Horse Rim, the southern Kicking Horse Rim and Cambrian platform formed an asymmetric, east-facing anticline with a long gently-dipping west limb as they were uplifted and carried northeastward. In the northern part of the study area, displacement was along the Fatigue Thrust and the fault climbed through the Paleozoic section. In the south, most displacement on this fault system went into a blind detachment fault near the base of the thick basinal lower Ordovician section and overlying faulted detachment folds. The Simpson Pass Thrust truncated and overrode in its footwall the east-facing anticline and other structures developed in the hanging wall of the Fatigue Thrust. The Simpson Pass Thrust is out-of-sequence relative to the Fatigue Thrust and is one of the few larger displacement, out-of-sequence thrust faults recognized in the southern Canadian Rocky Mountains. Deformation of the Western Main Ranges and thrust faults near the Cambrian facies change occurred prior to the main motion along the Fatigue Thrust - blind thrust system. Motion on this thrust system, and the formation of faulted detachment folds that extend southward into the eastern part of the Porcupine Creek fan structure, occurred prior to motion on the Simpson Pass Thrust. Deformation of all these structures occurred during Jurassic–Early Cretaceous deformation most likely sometime prior to 125 Ma.

Glacial Melt in the Canadian Rockies and Potential Effects on Groundwater in the Plains Region

The prevailing concern in the Western Canadian Plains is that glaciers from the eastern Canadian Rocky Mountains (CRM) are losing mass, thus affecting groundwater recharge in the Plains. The generally accepted hypothesis is that those glaciers are the geological source of groundwater for aquifers located in the Plains. The aquifers located in this region, close to the eastern part of the Rockies, represent a major source of water for the local population. It is believed that aquifer recharge originates as infiltration from snowmelt and ice in the Front Ranges of the eastern Rockies. A growing concern relates to the significant glacier melt estimated from glacier mass balances, which indicate that glaciers and ice fields have experienced considerable mass losses over the last 15 years, between 1 and 5 km3 per year, thus reducing recharge. However, deep groundwater flow under melting glacier conditions in mountainous regions is poorly understood. In this study, three 2D numerical hydrogeological models are built in order to simulate the groundwater flow under the glaciers from the Main and Front Ranges of the CRM and the Plains in the province of Alberta, Canada. Numerical results and a sensitivity analysis indicate that up to three different regional groundwater-flow systems are present in the region. These systems reveal the time- and space-scales associated with the combination of a mountainous region, foothills, Plains, and deep geological conditions. Based on the current knowledge of the hydrogeology of the study area and numerical modelling results, it is highly unlikely that the melting of glaciers affects groundwater in the Plains in the immediate future. The contribution of glacier water in the eastern part of the Rockies is time-dependent with delayed groundwater flows of 1000s of years in the Front ranges, 1000s to 100,000s of years in the foothills and Foreland; and 100,000s to millions of years to the Plains, at the regional scale.