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1
White, Adrienne. "Glacier Changes across Northern Ellesmere Island." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39102.
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This thesis investigates the causes and patterns of glacier and ice shelf changes across Northern Ellesmere Island, including rapid recent changes to marine-terminating glaciers and the mass balance of the Milne Ice Shelf along Ellesmere Island’s northern coastline.
The first part describes the change in the areal extent of 1773 glacier basins across northern Ellesmere Island between ~1999 and ~2015 that were measured from optical satellite imagery. The results show that the regional ice coverage decreased by 1705.3 km2 over the ~16-year period, a loss of ~5.9%. This indicates a marked acceleration compared to the 3.4% loss recorded by Sharp et al. (2014) between ~1960 and ~2000. Ice shelves had the greatest losses relative to their size, of ~42.4%. Glaciers feeding into ice shelves reduced in area by 4.7%, while tidewater glaciers reduced in area by 3.3%. Marine-terminating glaciers with floating ice tongues reduced in area by 4.9% and 19 of 27 ice tongues disintegrated, causing these glaciers to retreat to their grounding lines. Land-terminating glaciers lost 4.9% of their 1999 area, including the complete loss of three small ice caps (<1.5 km2). These changes indicate the high sensitivity of the ice cover of northern Ellesmere Island to recent climate warming, and that continued losses are likely to occur in the future. In particular, the ice masses most susceptible to further losses are marine-terminating glaciers with floating termini and small land-terminating ice caps at low elevations.
To further investigate the forcings leading to the recent losses of floating ice tongues, the second part focuses on marine-terminating glacier changes in the Yelverton Bay region of northern Ellesmere Island since 1959. From 1959-2017, the total ice tongue area decreased by 49.07 km2, with the majority of this loss occurring from 2005-2009 (34.68 km2). The loss of ice tongues since 2005 occurred when open water replaced multi-year landfast sea ice and first-year sea ice in the regions adjacent to the ice tongues. These changes were accompanied by an increase in mean annual mid-depth (i.e., 100 and 200 m) ocean temperatures from -0.29°C from 1999-2005 to 0.67°C from 2006-2012. Despite the recent return of ocean temperatures to below pre-2006 levels, atmospheric summer temperatures have continued to rise (+0.15°C decade-1 between 1948 and 2016), with open water continuing to occur. This suggests that loss of buttressing from sea ice appears to be the primary control on ice tongue losses, with air and ocean warming important in weakening the sea ice and ice tongues, together with offshore wind events in some years. Based on current climate it is unlikely that ice tongues will reform in the future.
To examine the stability of the remaining ice shelves, the Milne Ice Shelf was selected as a case study to analyse the processes and patterns of surface mass balance. In 2008 a mass balance network of eight stakes was established across the Milne Ice Shelf and over the past 10 years has revealed a mean annual surface mass balance of -0.33 ±0.04 m water equivalent yr-1. Comparison of this surface mass balance rate with past ice thickness change measurements made by Mortimer et al. (2012) indicate that recent thinning may be limited to the surface, and accelerating over time. Individual stake and snow measurements reveal a surface mass balance gradient, whereby ablation decreases with proximity to the seaward edge of the ice shelf. The ablation gradient is driven by the microclimatology recorded at three automatic weather stations installed along the ice shelf, which show that air temperature and solar radiation decreases towards the coastline, while snow accumulation increases. Climate analysis suggests that the entire Milne Ice Shelf is in a state of negative mass balance in years with >200 melting degree days (MDD), while the one net positive balance year (in 2013) occurred when MDD totals were 105 yr-1. Although the Milne Ice Shelf is the most stable remaining ice shelf along the northern coast of Ellesmere Island, the relationship between climate and mass balance, along with a recent increase in calving along its landward margins, indicate that it is out of equilibrium with current climate.
Overall, the ice coverage across northern Ellesmere Island is shrinking. The land-terminating ice that formed under cooler climatic conditions of the past, particularly low-lying small ice caps, are out of equilibrium with current climatological conditions. In addition, recent changes in the ice tongues and ice shelves demonstrate that the northern coastline of Ellesmere Island is approaching a future where the permanent floating ice cover can no longer be sustained.
2
Kitto, Stephen G. "The Environmental History of Te Waihora – Lake Ellesmere." Thesis, University of Canterbury. Geological Sciences, 2010. http://hdl.handle.net/10092/5028.
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Te Waihora – Lake Ellesmere is an expansive, shallow, turbid, brackish, hyper-eutrophic, lowland lake located on the east coast of New Zealand’s South Island. The catchment and lake are in a highly modified state, with much of the catchment used for intensive agriculture and the lake’s level artificially controlled by cutting a channel through the barrier separating the lake from the sea. Although it is known that Waihora is highly modified, it is difficult to determine the factors contributing to the current lake state and what constitutes a natural state for this lake. In order to plan management strategies, it is important to have this information. This study aims to provide insight into these matters using paleoecological techniques, in particular, analysis of sediment characteristics, palynology and diatom analysis, on cores obtained from the lake bed.
The results of these analyses show that Waihora has had a diverse history, beginning as a freshwater lake, low in nutrients, not long before c. 7500 years ago, following the fusion of Kaitorete ‘Spit’ with Bank Peninsula. This freshwater state was interrupted by the discharge of a large river into the basin, causing a permanent barrier opening and tidal, brackish conditions to prevail. A second brackish state formed after this, caused either by a shift in the discharge point through the barrier or, more likely, a second avulsion event of the Waimakariri River to a discharge point into Waihora. Upon the avulsion of this river to a discharge point north of Banks Peninsula, a freshwater, nutrient rich lake formed. Subsequently, human influenced lake changes became evident, with a hypereutrophic, shallow, brackish lake forming. This research provides evidence that modern lake management has led to decreased lake levels and increasing salinity within Waihora. Intensive agriculture, particularly since the 1970’s has led to an increase in nutrients within the lake and its current hypereutrophic state. A combination of lake level management and the ‘Wahine Storm’ (1968) has led to the lake’s current turbid, phytoplankton dominated state. Therefore, sediment characteristics, palynological and diatom data suggest that a natural condition for the lake is one with lower nutrient levels, lower salinity with greater depth and area than the current lake, with a large distribution of freshwater riparian vegetation and little halophytic vegetation.
If restoration of the lake is a target then (1) the lake should be opened to the sea less frequently, allowing a decrease in lake salinity and conditions conducive to the prevalence of freshwater riparian vegetation to prevail, and (2) a transition from a phytoplankton dominated state to a macrophyte dominated state should be targeted, by maintaining the lake at greater depths, the use of riparian planting practices and decreasing nutrient input. However, the latter will be costly and involve questionable trade-offs between lake values and stakeholders. Regardless of whether or not restoration of Waihora to something resembling a natural state is, or will be, a management aim, a decrease in nutrient input catchment wide and riparian planting in the area surrounding the lake should be a priority and may present a more realistic, short term management objective.
3
Atkinson, David E. (David Elmer) Carleton University Dissertation Geography. "Spectral reflectance survey on the Fosheim Peninsula, Ellesmere Island, N.W.T." Ottawa, 1992.
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4
Harding, Tommy. "Dispersion aérienne et distribution spatiale des microorganismes dans la cryosphère : biodiversité dans la neige et l'air du Haut-Arctique canadien." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27707/27707.pdf.
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5
Couture, Nicole J. "Sensitivity of permafrost terrain in a high Arctic polar desert : an evaluation of response to disturbance near Eureka, Ellesmere Island, Nunavut." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31213.
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A first approximation of ground ice volume for the area surrounding Eureka, Nunavut, indicates that it comprises 30.8% of the upper 5.9 m of permafrost. Volume depends on the type of ice examined, ranging from 1.8 to 69.0% in different regions of the study area. Excess ice makes up 17.7% of the total volume of frozen materials in the study area. Melt of ground ice in the past has produced thermokarst features which include ground subsidence of up to 3.2 m, formation of tundra ponds, degradation of ice wedges, thaw slumps greater than 50 m across, gullying, and numerous active layer detachment slides. With a doubling of atmospheric carbon dioxide, the rise in mean annual temperatures for the area is projected to be 4.9 to 6.6°C, which would lengthen the thaw season and increase thaw depths by up to 70 cm. The expected geomorphic changes to the landscape are discussed.
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Víquez, Ana M. "Isolation and characterization of alkane monooxygenase (alkB) genotypes from Arctic contaminated soils by culture-independent methods." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98510.
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Alkane monooxygenases (encoded by the alkB gene) are a group of microbial enzymes that catalyze the first reaction of alkane degradation. Studies to determine the diversity and prevalence of alkB genotypes in the environment have focused on culturable organisms. The goal of this research was to use culture-independent methods (DGGE, clone library) to identify and characterize alkB genes, and to determine their prevalence in Arctic contaminated soils. General alkB PCR degenerate primers (alkB-Mc) were designed using the conserved nucleotide sequences of the Histidine I Box and Histidine III Box. General alkB-Mc and alkM (Acinetobacter spp. alkane monooxygenase genes) primers were used to screen the soils for the presence of alkane monooxygenase genotypes. A predominance of the Rhodococcus spp. alkB genotypes and the absence of alkM genotypes in these soils was found. alkB PCR fragments amplified from the soils were analyzed by DGGE (Denaturing Gradient Gel Electrophoresis). BlastN and blastX results of the DGGE bands sequences showed that they were similar to Rhodococcus spp. alkB genotypes (~80-90% DNA identity and ~80-90% amino acid homology). An alkB clone library was built using the general alkB-Mc primer set, screened by RFLP (Restriction Fragment Length Polymorphism) and characterized by sequencing of alkB clones. BlastN and blastX results of the alkB clone sequences showed the presence of divergent alkB genotypes (≤ 70% DNA identity and ≤ 67% of amino acid homology to data base sequences). The alignment of the clone-derived amino acid sequences to confirm functional alkane monooxygenase sequences revealed the presence of Histidine Box II and the HYG motif in all of the deduced amino acid clone sequences. These results indicate that the alkB sequences from the clone library represent novel alkB sequences. Both alkB DGGE and clone library techniques were independently able to identify alkB genotypes from High G+C microorganisms as predominant in the 1A03 soil sample. Nevertheless, only the clone library approach identified putative novel alkB sequences. Mineralization of hexadecane and naphthalene was clearly observed at subzero temperatures (-5ºC) in Arctic contaminated soils, proving that the indigenous microbial communities could mineralize these representative hydrocarbons at subzero temperatures in an environment that is predominantly frozen for most of the year.
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Lévesque, Esther. "Plant distribution and colonization in extreme polar deserts, Ellesmere Island, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0021/NQ27680.pdf.
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Favero, Pauline. "Active layer detachment morphology, sedimentology, and mechanisms, Fosheim Peninsula, Ellesmere Island." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28180.
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Active layer detachments on the Fosheim Peninsula have been assumed to develop over periods of minutes to a few hours. This assumption played an integral role in the understanding of relationships between active layer detachment deposit morphology, morphometry and sedimentology and active layer detachment dynamics. Field observations of two failures at 'Big Slide Creek' on the Fosheim Peninsula in August 2005 showed that while one failure conformed to the pre-existing assumption of near-instantaneous formation, movement and cessation of movement, the other failure did not and exhibited progressive expansion over several days. Several active layer detachments known to have initiated in 2005 were visited in 2006 to assess whether active layer detachments known to have failed via a prolonged mode display surficial and internal morphological characteristics that are unique from active layer detachments known to have failed via a near-instantaneous mode and to evaluate the ability of the infinite slope model to adequately predict slope stability.
Results have indicated that active layer detachments known to have failed via a prolonged mode display a number of surficial and internal morphological characteristics that differ from those at active layer detachments known to have failed via a near-instantaneous mode. Based on Factor of Safety calculations, peak effective stress stability analysis indicates that Fosheim Peninsula slopes should be stable if pore-water pressures are not artesian, whereas residual effective stress stability analysis indicates that slopes greater than 6° on the Fosheim Peninsula are unstable even if pore water pressures are not artesian. Sensitivity analyses indicates that under peak conditions, Factors of Safety on Fosheim Peninsula slopes are most sensitive to changes in cohesion while under residual conditions, slope instability is related to increases in both slope angle and head of water above the slip plane.
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Barry, Peter. "Ground ice characteristics in permafrost on the Fosheim Peninsula, Ellesmere Island, N.W.T. : a study utilizing ground probing radar and geomorphological techniques." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56907.
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This thesis investigates the nature and distribution of ground ice occurrences on the central Fosheim Peninsula, Ellesmere Island, and assesses the potential for thermokarst in light of possible climatic warming.Field observations conducted in 1990 and 1991 involved geomorphological and cryostratigraphic examinations of twenty-eight ground ice sections exposed in retrogressive thaw slumps and ground probing radar surveys of two of the thaw slumps. Samples were taken of ground ice and sediments exposed in thaw slump headwalls for laboratory analysis.
Samples were analyzed for moisture content, grain size distribution, and Atterberg limits. Gravimetric ice contents were calculated and an average ice content profile was constructed for the study area.
Ground ice was found to be an important component of permafrost on the Fosheim Peninsula and was widely observed in Holocene marine sediments. The ice occurred in two stratigraphic settings at depths of one to five meters in silt and clay, and at ten meters or deeper beneath massive clay. Ice contents were generally found to increase rapidly with depth down to three meters, below which ice content was stabilized.
Ground probing radar was found to be a useful tool for permafrost research, given its ability to discriminate between ice and soil, as well as between frozen and unfrozen water.
10
Whissell, Gavin. "Merging metagenomic and microarray technologies to explore bacterial catabolic potential of Arctic soils." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98518.
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A novel approach for screening metagenomic libraries by merging both metagenomic and microarray platforms was developed and optimized. This high-throughput screening strategy termed "metagenomic microarrays" involved the construction of two Arctic soil large-insert libraries and the high density arraying of the clone plasmid DNA (~50 kb) onto glass slides. A standard alkaline lysis technique used for the purification of plasmid DNA was adapted and optimized to function efficiently in a 96-well format, providing an economically viable means of producing sufficient high-quality plasmid DNA for direct printing onto microarrays. The amounts of printed material and probe, required for maximal clone detection, were optimized. To examine catabolic clone detection libraries were first screened by PCR for catabolic genes of interest. Two PCR-positive clones were printed onto microarrays, and detection of these specific clones in the printed libraries was achieved using labeled probes produced from PCR fragments of known sequence. Also, hybridizations were performed using labeled PCR fragments derived from the amplification of a catabolic gene from the total community DNA. The ability of selected probes to specifically target clones of interest was demonstrated. This merger of metagenomics and microarray technologies has shown great promise as a tool for screening the natural microbial community for catabolic potential and could also be used to profile microbial diversity in different environments.
11
Wood, Hannah. "The benthic ecology and food web dynamics of Te Waihora (Lake Ellesmere)." Thesis, University of Canterbury. School of Biological Sciences, 2008. http://hdl.handle.net/10092/2274.
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Coastal and shallow lakes are often subjected to eutrophication due to nutrients from catchment farming activities. Lake Ellesmere (Te Waihora) is a hyper-eutrophic lake which has gained recent attention because of concerns over its ecological health and fishery status. This study investigated the benthic ecology of the lake by extensive spatial and temporal sampling. Eight littoral sites were sampled on a single occasion, and 20 benthic sites were sampled once per season for one year. Water chemistry conditions, substrate and invertebrate communities varied significantly around the lake. Salinity, pH, DO and seston were primarily affected by freshwater inputs from inflow streams and salt water intrusion due to the lake opening to the sea. On these occasions, salinity reached 32 ‰ at the lake outlet. The lake invertebrate community was depauperate, comprising of only two species of invertebrate predators restricted to the littoral zone and eight benthic invertebrate taxa, dominated by oligochaetes, amphipods and chironomids. Benthic invertebrate abundances also reflect the dominant local substrate, where oligochaetes and chironomids preferred areas of silt substrate, whereas Potamopyrgus preferred harder substrate. Stable isotope and gut analysis determined that the primary food sources within the lake were phytoplankton and algae. Macrophytes provided a minimal contribution to the food web, possibly relating to the change in status from a clear water, macrophyte dominated lake to a turbid, phytoplankton dominated condition since the Wahine Storm in 1968. Isotope analysis also showed that the lake food web was markedly different in its carbon values from food webs of its inflow streams and nearby marine source. However the lake food web did show a marine-derived carbon signature. A mesocosm experiment testing the effect of common lentic predators on the abundance of the lake chironomid Chironomus zealandicus, showed that if invertebrate predators were present in the lake they could markedly reduce the abundance of the pest prey species. This study highlights that the frequent re-suspension of bottom sediments, lake level fluctuation resulting in wetting and drying of littoral zones, and the management of the lake opening to the sea all have an effect on the benthic ecology of Te Waihora.
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Triglav, Katherine. "The under-ice dynamics of High Arctic lakes : the importance of physicochemical interactions with phytoplankton and bacterial communities in Stuckberry Valley, Ellesmere Island." Master's thesis, Université Laval, 2021. http://hdl.handle.net/20.500.11794/70382.
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Même les écosystèmes les plus nord du monde ont été affectés par le réchauffement climatique et les lacs de l'Extrême-Arctique ne font pas exception. L'île d'Ellesmere est à la limite nord du Canada et des changements de régime vers des taxons associés à des saisons de croissance plus longues ont déjà été documentés dans les lacs de cette région. La côte nord de l'île d'Ellesmere est dans une région pour laquelle on prévoit le plus grand réchauffement annuel au cours des 80 prochaines années. Il est donc impératif de comprendre le fonctionnement des lacs côtiers sensibles avant que d'autres changements ne se produisent. J'ai étudié une série de quatre lacs de la vallée de Stuckberry (82º54 N, 66º58 W) pour donner un aperçu de leur dynamique phytoplanctonique sous la glace. Mes objectifs étaient 1) identifier et quantifier les communautés photosynthétiques dans les lacs de la vallée de Stuckberry, 2) déterminer les variables physico-chimiques qui ont exercé le contrôle le plus fort sur la variation de la communauté au sein des lacs et entre les lacs, et 3) élargir la compréhension des écosystèmes d'eau douce sous la glace de l'Extrême-Arctique et leur fonction. Les intensités lumineuses et l'oxygène dissous exerçaient un contrôle primordial sur la distribution et l'abondance des organismes photosynthétiques et la conductivité spécifique et l'azote jouaient aussi des rôles importants. Ces variables distinguaient clairement deux lacs oxiques profonds des deux lacs anoxiques peu profonds. Les différences des types de communautés photosynthétiques entre les lacs et les profondeurs étaient liées aux concentrations d'oxygène dissous : la lignée des algues rouges dominait dans les eaux oxiques, tandis que les bactéries sulfureuses pourpres dominaient dans les eaux anoxiques. Les pigments indiquaient aussi que les dinoflagellés, les cryptophytes et les haptophytes étaient abondants partout dans les quatre lacs, alors que les chrysophytes et les chlorophytes étaient présentes en plus faibles concentrations. Ma thèse représente l'une des très rares études de communautés photosynthétiques sous la glace de l'Extrême-Arctique, et elle fait progresser considérablement notre compréhension des processus écologiques dans cette région hautement sensible.Even the world’s most northern ecosystems have been affected by climate warming and High Arctic lakes are no exception. Ellesmere Island is at the northernmost limit of Canada, and regime shifts have already been documented in its lakes towards taxa associated with longer growing seasons. It has been projected that the northern coast of Ellesmere Island is within a region that will experience the greatest annual warming in the Arctic over the next 80 years, and so understanding the functioning of its sensitive coastal lakes is critical before further changes occur. I studied a series of four lakes in Stuckberry Valley (82º54 N, 66º58 W) to give insight into their under-ice phytoplankton dynamics. My objectives were 1) identify and quantify the photosynthetic communities found in the Stuckberry Valley lakes, 2) determine the physicochemical variables that exerted the strongest control over within- and between-lake community variation, and 3) expand the understanding of under-ice High Arctic freshwater ecosystems and their function. Light intensities and DO concentrations exerted primary control over the distribution and abundance of photosynthetic organisms, in addition to important roles played by specific conductivity and nitrogen. These variables clearly distinguished two deep, oxic lakes from two shallow, anoxic lakes. Differences in photosynthetic community types between lakes and depths was strongly linked to DO concentrations: the red pigment algal line dominated in oxic waters, while purple sulfur bacteria (PSB) were found in anoxic zones. Pigments indicated that dinoflagellates, cryptophytes, and haptophytes were abundant throughout all four lakes, with lower concentrations of chrysophyte and chlorophyte pigments. My thesis represents one of the very few studies of High Arctic under-ice photosynthetic communities, and it significantly advances our understanding of ecological processes in this highly sensitive region.
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Grom, Jackie. "Retrogressive thaw slump process and morphology, Eureka Sound Lowlands, Ellesmere Island, Nunavut, Canada." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22043.
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Climate change is expected to have a significant impact on arctic regions, most notably in ice-rich permafrost regions. Retrogressive thaw slumps, backwasting resulting from the exposure of ice-rich permafrost, are a prominent thermokarst feature throughout the arctic and are projected to increase in frequency and extent under warming climate scenarios. However, there is limited information on retrogressive thaw slump activity and field observations are complicated by dynamic interactions between morphology and climate. This work attempts to further define these controls to increase understanding of retrogressive thaw slump processes. Spatial variations in headwall retreat indicate energy input and morphological influence on the landform. Morphologic factors such as ice face angles and the nature of ground ice are observed and analyzed for a relation to ice ablation and headwall retreat. Additionally, spatial microclimates are investigated to define the specific energy conditions at the ablating ice face. Analysis indicates that air temperatures in the vicinity of the ice face vary from exterior temperatures in response to solar radiation and wind speed and direction. Periods of high solar radiation and winds originating from upslope of the headwall potentially create a feedback process for headwall retreat.Les changements climatiques auront des impacts significatifs sur les regions arctiques, particulièrement les régions de pergélisol. Les glissements régressif dû au dégel (retrogressive thaw slumps), sont le résultat de l'exposition du pergélisol riche en glace. Ces glissements sont des formes de terrain (thermokarst) communes aux régions arctiques, et leur fréquence et distribution risquent d'augmenter due aux scénarios de changements climatiques. Toutefois, nous avons des connaissances limitées sur l'activité des glissements régressif dû au dégel et les observations de terrain sont compliquées dues aux interactions dynamiques entre la morphologie et le climat. La présente étude tente de définir les facteurs de contrôle afin d'améliorer notre compréhension du processus des glissement régressif dû au dégel. Les variations spatiales du retrait du mur frontal (headwall) indiquent un intrant d'énergie et une influence morphologique de la forme de terrain. Les facteurs morphologiques, tels l'angle du front de glace et la nature de la glace souterraine ont été observées et analysées en relation avec le taux d'ablation de la glace et le retrait du front (headwall). De plus, les patrons spatiaux de micro-climat ont été étudiés afin de définir les conditions spécifiques d'énergie au front d'ablation de la glace. Les analyses ont indiqué que la température de l'air à proximité de la paroi de glace varie comparativement à la température extérieure, en réponse à la radiation solaire et la vitesse et direction du vent. Les périodes de haute radiation solaire et les vents qui proviennent du haut du mur frontal ont le potentiel de créer un processus de retrait du mur frontal.
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Collins, Karen Elizabeth. "Reconstruction of late quaternary ice-flow directions, east central Ellesmere Island, Northwest Territory." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6718.
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This study identifies Late Quaternary glacial ice-flow direction in east-central Ellesmere Island, N.W.T., by the study of its composition and its relation to bedrock sources. The spatial distribution of five till types suggests a hypothesis which attempts to reconcile the Innuitian Ice Sheet model of Blake with the Franklin Ice Complex model of England. Glaciers draining from ice sheets in northern Ellesmere Island and Greenland filled Kane Basin and flowed southward toward Smith Sound. When this southward-flowing ice reached the bottleneck at Smith Sound (40 km wide), it overrode the adjacent landmasses of Pim Island and Cape Herschel and forced Buchanan Bay ice southward through the channel that is now occupied by Rice Strait. Southward-flowing ice continued to drain towards Baffin Bay, overriding the coastal areas of Nares Strait at Wade Point and Cape Isabella. The results presented here partially support the Innuitian ice sheet hypothesis, but do not negate the Franklin Ice Complex model. (Abstract shortened by UMI.)
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Morin, Jean. "Facies analysis of Lower Permian cyclic carbonates, west-central Ellesmere Island, Canadian Arctic." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7553.
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At least 36 decametre-scale, largely symmetric high-frequency cycles spanning approximately 15 Ma make up the carbonate-dominated succession of Lower Permian sequence 3 of the Sverdrup Basin in Fosheim and Hamilton peninsulas. These cycles record a rift pulse caracterized by the uplift, passive subsidence, collapse and passive subsidence of the Fosheim-Hamilton subbasin and show that during the rifting phase of the Sverdrup Basin deposition of conformity-bounded sequences was tectonically rather than eustatically controlled. The active rifting-phase of the Sverdrup Basin comprises four unconformity-bounded sequences that range in age from Visean to Kungurian. The third-sequence in Fosheim and Hamilton peninsulas area, west central Ellesmere Island comprises six formations. The Canyon Fiord Formation is composed of lithofacies ranging from basin margin fluvial to marine siliciclastics. The Belcher Channel, Antoinette, Tanquary and Nansen formations are made up of inner- to midshelf carbonates that encompass the Mount Bayley Formation, a thick evaporite succession deposited within the Fosheim-Hamilton subbasin. Petrographic analysis of the carbonate-dominated facies in sequence 3 has delimited nineteen platformal facies representing lagoonal, barrier and shoal, reefal and non-reefal mid-shelf depositional environments. These facies are organized into high-frequency depositional cycles that record the interplay between eustasy, tectonism and sediment supply. In order to facilitate their regional analysis, cycles were grouped into five idealized cycles. From proximal to distal, these cycles include: Sandstone-Grainstone; Grainstone-Palaeoaplysinid; Packstone-Phylloid; Wackestone; and Anhydrite cycles. These high-frequency cycles are grouped into a Pre-, Syn- and Post-evaporite cyclic assemblages, each of which possess an unique stacking pattern. The Pre-evaporite Assemblage comprises 9 cycles characterized by relatively similar thickness and composition. High-frequency cyclicity within this assemblage was controlled by glacio-eustatic oscillations with only local tectonic influence. (Abstract shortened by UMI.)
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Spiegelman, Dan. "Exploring the fusion of metagenomic library and DNA microarray technologies." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98805.
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We explored the combination of metagenomic library and DNA microarray technologies into a single platform as a novel way to rapidly screen metagenomic libraries for genetic targets. In the "metagenomic microarray" system, metagenomic library clone DNA is printed on a microarray surface, and clones of interest are detected by hybridization to single-gene probes. This study represents the initial steps in the development of this technology. We constructed two 5,000-clone large-insert metagenomic libraries from two diesel-contaminated Arctic soil samples. We developed and optimized an automated fosmid purification protocol to rapidly-extract clone DNA in a high-throughput 96-well format. We then created a series of small prototype arrays to optimize various parameters of microarray printing and hybridization, to identify and resolve technical challenges, and to provide proof-of-principle of this novel application. Our results suggest that this method shows promise, but more experimentation must be done to establish the feasibility of this approach.
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Pouliot, Jérémie. "Biodiversité microbienne des écosystèmes extrêmes : analyse moléculaire de la diversité des Archaea dans deux lacs méromictiques arctiques." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25756/25756.pdf.
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Robertson, Scott M. "Holocene deglacial and sea level history of Dobbin Bay, eastern Ellesmere Island, Arctic Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40101.pdf.
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Thériault, Pierre. "Synrift sedimentation in the Upper Carboniferous Canyon Fiord Formation, SW Ellesmere Island, Canadian Arctic." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7631.
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The Upper Carboniferous Canyon Fiord Formation is genetically related to continental rifting during the early history of Sverdrup Basin. The basal part of the formation, on southwestern Ellesmere Island, has been subdivided into five distinct facies assemblages: (i) a lower sandstone assemblage, deposited in the floodplain environment of high sinuosity streams, and locally in lacustrine and paludal environments; (ii) a conglomerate assemblage, deposited in the alluvial fan to proximal braided stream environment; (iii) an upper sandstone assemblage, deposited in braided stream and coastal plain environments; (iv) an evaporite assemblage, deposited in a local coastal playa and hypersaline lagoon; and (v) a limestone assemblage, deposited in restricted to relatively open, shallow marine environments. These assemblages are exposed within two N-S-oriented outcrop belts, informally called the Trold Fiord belt and the Blind Fiord belt. The outcrop belts are separated by a N-S oblique strike-slip fault of Tertiary age, and are associated with two distinct, Late Carboniferous half-grabens of opposite polarity: (i) the Trold Fiord Depression, situated in the northeastern part of the study area; and (ii) the Blind Fiord Depression, situated in the southwestern part of the study area. The characteristics of the Trold Fiord and Blind Fiord basin-fill successions indicate that sedimentation was controlled by at least two tectono-sedimentary episodes (TSE-1 and TSE-2). (Abstract shortened by UMI.)
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Veillette, Julie. "Stucture et dynamique d'écosystèmes aquatiques côtiers du haut Arctique comme sentinelles de changements environnementaux." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27290/27290.pdf.
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Sherry, Colleen Theresa. "An upper Carboniferous shelf-to-basin transect: Nansen and Hare Fiord Formations, NW Ellesmere Island." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/9814.
Full textAbstract:
An ancient transition from shallow marine platform to deep basin is preserved in the Upper Carboniferous strata of the Sverdrup Basin on northwestern Ellesmere Island. The shelf break is delineated by an approximately 200 km long discontinuous reef tract extending from Audhild Bay to the head of Hare Fiord within the Nansen Formation. The reef tract is marked by a series of massive, coalesced shelf edge buildups which developed during a major second order regression within the Sverdrup Basin. The shelf edge buildups are largely composed of phylloid alga-rich boundstones with abundant early marine synsedimentary cement. Fenestellid bryozoans, however, dominate buildups that grew in deeper slope settings. Shoreward of the reef tract lie cyclic, shallowing-upward carbonate shelf deposits, also of the Nansen Formation. The outer shelf deposits include bedded oolitic and foraminiferal grainstones representing a shallow water sand apron located immediately behind the reef tract. Basinward of the shelf edge reef tract lie correlative slope-to-basin rhythmic mixed deposits of the Hare Fiord Formation. The upper slope deposits are dominated by fine grained calcisiltites while the lower slope/basin facies comprise calcisiltites, siltstones and shales interbedded with abundant turbidities and debrites. The massive prograding shelf edge buildups reach stratigraphic thicknesses up to 1 km. The Nansen reef tract appears to be a reef complex in which the reefal rim remained relatively deeply submerged, but still within the photic zone, through much of its growth. The carbonate buildups on the shelf, shelf edge and slope all represent potential petroleum-bearing stratigraphic traps within the Sverdrup Basin. If these occur in the subsurface they would be likely exploration targets but unfortunately within the study area little porosity remains. Where the buildups are extensively dolomitized, higher porosity and permeability create excellent potential hydrocarbon reservoirs. (Abstract shortened by UMI.)
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Smith, Iain Roderick. "Late Quaternary glacial histories and Holocene paleoenvironmental records from northeast and southwest Ellesmere Island, Nunavut, Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0025/NQ34836.pdf.
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Hilmo, Maidie. "Images, icons, and texts, illustrated English literary works from the Ruthwell Cross to the Ellesmere Chaucer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ62517.pdf.
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Lee, Carmen C. "Geology of the Palaeogene, Ellesmere Island, Arctic Canada : sedimentology and stratigraphy of the Eureka Sound Group." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409042.
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Riediger, Cynthia Louise. "Sedimentology and tectonic history of the Eureka Sound and Beaufort formations, southern Ellesmere Island, Arctic, Canada." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24904.
Full textAbstract:
The Eureka Sound Formation in the eastern Canadian Arctic Archipelago is an Upper Cretaceous to Paleogene pre- and syn-tectonic deposit that records the uplift and segmentation of the Early Carboniferous to Tertiary Sverdrup Basin.
Scattered outliers of the Eureka Sound Formation on southern
Ellesmere Island rest unconformably on or are faulted against Devonian strata. In the vicinity of Vendom, Stenkul, Baumann and Sor Fiords, the Eureka Sound Formation attains a maximum thickness of 480 m and comprises a sequence of nonmarine and brackish water deposits that ranges in age from mid-Paleocene to Late Eocene.
Eureka Sound strata which crop out along the shores of Stenkul Fiord are divided into four lithofacies assemblages. The stratigraphic section is composed mainly of two nonmarine assemblages
which alternate throughout the sequence. Lithofacies Assemblage I consists of fining-upward sandstones which attain thicknesses of 20 m and are interpreted as fluvial deposits. Lithofacies Assemblage II comprises interbedded mudstones and coal in seams up to 8 m thick, and are interpreted as floodbasin deposits of an alluvial plain.
Two marine lithofacies assemblages (III, IV) are recognized locally and constitute a minor part of the stratigraphic succession.
Lithofacies Assemblage III comprises the basal strata in the study area and consists of approximately 90 m of buff-weathering
mudstones and interbedded thin coals which were deposit ed in brackish lagoonal, estuarine and salt marsh environments. Lithofacies Assemblage IV occurs locally in the middle of the stratigraphic section and consists of up to 10m of white, well sorted quartz arenites and minor mudstones, which are interpreted
as deposits of a barrier island system.
To the northeast of Stenkul Fiord at Makinson Inlet, outliers
of the Eureka Sound Formation rest unconformably on Paleozoic strata, and are in turn overlain with angular unconformity
by as much as 120 m of Early Miocene fanglomerates of the Beaufort Formation. The ages of these sediments, in conjunction
with ages reported from the Eureka Sound and Beaufort Formations in other parts of Ellesmere and Axel Heiberg Islands, bracket the timing of the orogenic phase of the Eurekan orogeny in the eastern Arctic as Late Eocene to Miocene.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Wilks, Taryn. "Response of benthic invertebrate fauna to fluctuating lake levels and salinity concentrations in Lake Ellesmere/Te Waihora." Thesis, University of Canterbury. Biological Sciences, 2010. http://hdl.handle.net/10092/5008.
Full textAbstract:
Lake Ellesmere/Te Waihora is one of New Zealand’s largest coastal, brackish water lakes. It has nationally significant wetland bird populations and is regionally important for iwi. The lake regularly experiences fluctuations in water level, resulting in a continually expanding and contracting littoral zone. This study investigated the impacts of these water level changes on the ecology of the lake. Water chemistry results collected over 12 months, confirm the lake is hypertrophic, due to high nutrient (nitrogen and phosphorus) concentrations resulting in high chlorophyll a levels and low water clarity. Water chemistry conditions were collected at five locations around the lake and showed marked spatial variation, with the eastern most end (Kaituna Lagoon) having generally the best water quality and lowest salinity (mean 4.9 ppt). Mean concentrations of total nitrogen ranged from 1.63 to 2.4 mg/L, chlorophyll a from 50 to 148 ug/L and total suspended solids from 151 – 248 mg/L. Seasonally, highest nutrient concentrations (mean, total nitrogen = 2.625 mg/L, dissolved reactive phosphorus = 0.059 mg/L and total phosphorus = 0.365 mg/L) occurred in late summer months (February – March), slightly decreasing but remaining high throughout winter.
The benthic invertebrate community was surprisingly diverse, Crustacea (Paracorophium excavatum), Oligochaeta, Mollusca (Potamopyrgus antipodarum) and Chironomidae (Chironomus zealandicus) were dominant community members in the littoral zone, although 24 other taxa were collected. At high water levels, taxonomic richness increased in the eulittoral zone, while decreasing in the mid-littoral and lower littoral zones. In contrast, density decreased with higher water level in the eulittoral and mid-littoral zones, while increasing in the lower littoral zone. Benthic invertebrate communities appeared to be adapted to periods of intermittent dewatering, and even sustained dewatering under cooler temperatures. Despite the relatively high diversity of benthic invertebrates, invertebrate predators are generally absent from the lake. My results suggest multiple factors and interactions from predation pressure, salinity and lack of macrophytes are likely responsible for the absence of predatory invertebrates such as damselfly (Xanthocnemis zealandica) and dragonfly (Procordulia grayi) larvae.
The lack of significant relationships between water quality variables and water level, and the positive relationship between chlorophyll a and salinity, suggests that current lake opening events do not have a positive effective on either water quality or phytoplankton biomass in Lake Ellesmere/Te Waihora. However, the current lake opening regime seems to be favourable to benthic invertebrate survival in the littoral zone, as the lake is predominantly open over winter when temperatures are lower, reducing the risk of desiccation. Anthropogenic activities which modify hydrodynamic and water quality conditions can potentially have a large negative impact on the structure and diversity of the littoral invertebrate community as well as flow on effects through the lake food web. Based on results from this study, I suggest a minimum lake level at Taumutu of 0.6 m during the months from November – April in order to protect benthic invertebrate communities in the eulittoral zone from extensive loss of habitat, extreme temperature and reduced risk of desiccation. Having a minimum set at ~0.6 m would provide sufficient littoral zone habitat for the lakes extensive bird life and fish populations. In addition, immediate efforts are needed into reducing nutrient loads into the lake, through improved farm management (nutrient and stocking budgets) and riparian fencing. Furthermore, physical and chemical water quality properties would benefit from an increased water level over summer months, by reducing water temperatures, diluting readily available nutrient concentrations and potentially reducing phytoplankton (and potentially toxic cyanobacterial) blooms.
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Hill, Stewart Adams. "A new member of the zygopteridales from the lower Upper Devonian (Frasnian) of Ellesmere, N.W.T., Arctic Canada." Thesis, Virginia Tech, 1992. http://hdl.handle.net/10919/45029.
Full textAbstract:
A newly discovered fern-like fossil plant is described from the Lower
Upper Devonian of southern Ellesmere. This plant occurs as an element of an
Archaeopteris dominated flora preserved in sediments of the Nordstrand
Point Formation (mid-late Frasnian) at Bird Fiord. The plant demonstrates a
pinnate vegetative system with three orders of branch and laminate pinnules,
of a general sphenopteroid type. Primary pinnae usually diverge from the
main axis in distichous pairs (Le., in a quadriseriate manner), but rarely depart
singly (i.e., in a biseriate manner). Each primary pinna bears an aphlebia in
the catadromic position. Laminate pinnules are broadly lobed with a
proximally overtopped vein system. Anatomically, this plant is characterized
by an elongate, mesarch, bipolar protostele that is ribbon to clepsydroid in
shape. Proximal to each primary pinna node, an initially crescent-shaped,
bipolar pinna trace diverges from the main axis stele. This trace appears to
become four-ribbed before dividing to yield a pair of bipolar primary pinna
traces. A pair of circular, centrarch aphlebia traces depart from the catadromic
ribs of a primary pinna trace in its four-ribbed stage. Protoxylem is helically
thickened, with metaxylem pitting ranging from scalariform to circular.
Secondary xylem is unknown. Both the morphology and anatomy of this
plant are non-gymnospermous and suggest affinity instead with zygopterid
ferns. Within the Zygopteridales, this plant seems to align most closely with
the Rhacopytaceae. The Frasnian dating of this plant suggests that laminated
foliage had been achieved by some zygopterid ferns long before previously
recognized. The presence of Sphenopteris-like pinnules in this Frasnian plant
also shows that one should be careful in attributing such foliage to early
gymnosperms.
Master of Science
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Clarke, Shawne. "An experimental study on the influence of climatic fluctuations on solifluction, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0032/MQ38739.pdf.
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Hill, Stewart Adams. "A new member of the zygopteridales from the lower Upper Devonian (Frasnian) of Ellesmere, N.W.T., Artic Canada /." This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10062009-020228/.
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Malone, Shawn Joseph. "Tectonic evolution of northern Ellesmere Island: insights from the Pearya Terrane, Ellesmerian Clastic Wedge And Sverdrup Basin." Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3496.
Full textAbstract:
The tectonic evolution of northern Ellesmere Island is dominated by the accretion of the Pearya Terrane and the progressive reworking of materials from the Pearya Terrane and the northern Caledonides. Geochronology from a suite of seven Succession I orthogneiss samples defines a range of earliest Neoproterozoic ages from 962 ± 6 Ma to 974 ± 8 Ma. Geochemistry of both zircon and whole rock samples reveal a complex magmatic history tapping multiple sources. The rocks include both I and S type granitoids, with silica contents ranging from 62% to 73%. Trace element geochemistry reveals LILE enrichment decoupled from low to depleted HFSE values, suggestive of an origin above a subduction zone. Isotope geochemistry supports input from juvenile and evolved materials, with εNd(i) values between -1 and -4.6, and a similar range for εHf from zircon. The northern elements of the Caledonian Orogen preserve a record of magmatism in the c. 985 Ma to 920 Ma range. These ages are also observed in orthogneiss units of the south central Brooks Range and Farewell terrane, Alaska. The Pearya Terrane orthogneiss units and those currently dispersed in Alaska are interpreted to have originated near or on the eastern margin of Greenland and record post-Rodinia assembly subduction outboard of the supercontinent.
Succession II (Trettin, 1987) of the Pearya Terrane represents variably metamorphosed metasedimentary rocks of Proterozoic to early Paleozoic age. These units are structurally juxtaposed with Succession I orthogneiss and Paleozoic sedimentary units of the Pearya Terrane. Detrital zircon age spectra from seven samples of Neoproterozoic meta-sedimentary rocks reveal three groups defined by observed dominant age peaks and youngest observed age populations. Group I includes three quartzite samples and contains numerous c. 1100 Ma to 1800 Ma peaks, with the youngest population at c. 1050 Ma. Two samples of immature meta-sandstone form Group II, defined by a dominant c. 970 Ma age peak. Two samples from the diamictite unit below the Deutchers Glacier thrusts form Group III, with a similar pattern of c. 1000 Ma to 1800 Ma age peaks to Group I; however, this group includes a small population of c. 600 Ma to 700 Ma grains as well. The ubiquitous Mesoproterozoic ages reflect a Grenvillian-Sveconorwegian provenance. These data are consistent with detrital zircon datasets from other North Atlantic-Arctic Caledonide terranes, reinforcing stratigraphic links between the Pearya Terrane and the northern Caledonides. The utility of the Pearya Terrane dataset is multiplied by probable links to Circum-Arctic and Cordilleran terranes, many of which contain similar populations of Mesoproterozic-aged detrital zircon.
U/Pb ages and Hf isotopic data from detrital zircon suites sampled from Ordovician to Carboniferous sedimentary rock of the Pearya Terrane and northern Ellesmere Island record define the background for terranes translating along the northeastern Laurentian margin in the Paleozoic. Ordovician to Silurian clastic sediments deposited on the Pearya Terrane record pre terrane accretion provenance dominated by recycling of the metaigneous and metasedimentary Proterozoic basement as well as an Ordovician arc source. The provenance of Late Devonian sediments deposited during the Ellesmerian Orogen is dominated by similar recycled materials, with new sources derived from Paleoproterozoic domains of the Canadian-Greenland shield and documented late Devonian granitoids emplaced the Canadian Arctic Islands and Arctic Alaska. The basal Sverdrup Basin records increasing proportions of Paleoprtoerozoic and Archean aged grains relative to Mesoproterozoic ages, suggestive of increased contributions from the Laurentian craton and no little detritus exotic to Laurentia. Detrital zircon age spectra from Devonian to Carboniferous sediments in the northern Cordilleran clastic wedge and western Canadian Arctic Islands contain abundant exotic zircon likely derived from the Caledonian and Timanian Orogens. This variance of sediment provenance indicates that the eastern Canadian Arctic Island were isolated from non-Laurentian or Caledonian detritus, and that sources of the exotic Timanian zircon reconstruct farther west along the margin.
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Clarke, Shawne Arianne. "An experimental study on the influence of climatic fluctuations on solifluction, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4538.
Full textAbstract:
A field experiment, involving direct manipulation of surface microclimate, was undertaken in the continuous permafrost zone to examine the influence of climatic fluctuations on solifluction rates and movements throughout the active layer. Movements and soil temperature were measured continuously from 1993-1997 using five electro-mechanical meters and thermocouple cables on an 8$\sp\circ$ colluvial slope in Hot Weather Creek valley, Ellesmere Island. Natural variation of movement among the years and the meters was measured until summer of 1996 when surface climatic treatments (surface warming, wetting, a combination of these two, and cooling) were performed. The longer-term effects of the treatments were monitored until August 1997. Near-surface measurements alone do not provide an accurate picture of solifluction in areas with two-sided freezing ("cold" permafrost) because there can be substantial variation in movement rates at depth. In addition, multi-year average rates potentially hide a considerable range of annual variability and do not allow for the examination of a relationship between climatic fluctuations and annual movement. (Abstract shortened by UMI.)
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Kells, Melanie P. "Sequence stratigraphy and depositional history of the Artinskian to Kungurian sequence, Otto Fiord area, northwestern Ellesmere Island." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10139.
Full textAbstract:
The Artinskian to Kungurian Sequence of the Otto Fiord area is dominated by the Great Bear Cape, Raanes and Trappers Cove formations in addition to the upper portions of the Nansen and Hare Fiord formations. The Great Bear Cape Formation (10-300 m), in the Otto Fiord area, is a yellowish-weathering, cliff-forming, packstone to grainstone dominated by echinoderms, bryozoans, and brachiopods. The Raanes Formation (10-225 m) is greenish-weathering, recessive to resistant, shaly to silty, variably cherty wackestone to packstone dominated by bryozoans, brachiopods, crinoids, and sponge spicules in addition to resistant, massive, very fine-grained, bryozoan-lime mud wackestone forming bioherms. The Trappers Cove Formation (55-1000 m) is black to dark gray spiculitic chert that is interfingered with thinly-bedded, black, recessive shales and siltstones. (Abstract shortened by UMI.)
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Julien, Jean-Rémi. "Écologie alimentaire et dynamique de populations du labbe à longue queue (Stercorarius longicaudus) à Alert, Île d'Ellesmere, Nunavut." Thesis, Université Laval, 2012. http://www.theses.ulaval.ca/2012/28451/28451.pdf.
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Atkinson, Nigel. "The last glaciation and relative sea level history of central Baumann Fiord, southwest Ellesmere Island, Canadian High Arctic." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ40025.pdf.
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Caswell, Brandon Christopher. "⁴⁰AR/³⁹AR geochronology of biotite from ductile shear zones of the Ellesmere-Devon crystalline terrane, Nunavut, Canadian Arctic." Thesis, University of Iowa, 2018. https://ir.uiowa.edu/etd/6070.
Full textAbstract:
This thesis presents a 40Ar/39Ar geochronological analyses of biotite from thin ductile shear zones in Paleoproterozoic granulite-facies gneisses from the Ellesmere-Devon crystalline terrane, Nunavut, Canada. The gneisses are part of the Paleoproterozoic Thelon tectonic zone. U-Pb dates of zircon show that the gneisses have magmatic protolith ages ranging from 2007–1958 Ma. The quartzofeldspathic gneisses in southeast Ellesmere Island display centimeter-scale E- to NE-striking sinistral and dextral mylonite zones offsetting pegmatitic dikes that are the last stage of ductile deformation of the basement rocks. Samples were taken from nearshore outcrops at Hayes Fiord, Pim Island, NE of the Leffert Glacier and NW of Cape Isabella. Biotite clusters replace orthopyroxene as the result of post-granulite facies metamorphism in the gneisses. Biotite in mylonitic and ultramylonitic fabrics is found as flattened clusters and also as individual crystals defining shear bands related to mylonitization. Eight samples were dated, including biotite from five mylonites, one deformed pegmatite, one tonalite and muscovite from a pegmatite. Major element X-ray maps demonstrate that the biotite is chemically homogenous. Backscattered electron images and electron dispersive spectroscopy via scanning electron microscopy confirm that biotite lacks intercrystalline layering with other K phases. Step-heating analysis of mica at the University of Vermont yielded Paleoproterozoic 40Ar/39Ar ages. The apparent age spectra form plateau ages in all but one mylonite sample. Biotite from a protomylonite was 2051 ± 26 Ma, older than the protolith ages obtained from U-Pb zircon geochronology, and most likely indicates excess Ar. Pegmatitic muscovite was 1977 ± 35 Ma. Biotite dates range from 1874 ± 13 Ma to 1838 ± 14 Ma for the five mylonites without excess Ar. Biotite dated from ductile shear zones signals the latest deformation in the basement, which was active as early as 1887 Ma.
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Dalton, Abigail. "Iceberg Production and Characteristics at the Termini of Tidewater Glaciers around the Prince of Wales Icefield, Ellesmere Island." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36992.
Full textAbstract:
Since the 1960s, warming air and sea surface temperatures have led to decreasing sea ice extent and longer periods of open water in the Canadian Arctic Archipelago (CAA). Recent and rapid changes have also been observed in the ice discharge patterns of glaciers in this region. For example, Trinity and Wykeham glaciers on the Prince of Wales Icefield (POW), SE Ellesmere Island, contributed ~62% of total ice discharge to the ocean from the Canadian Arctic Archipelago in 2016, compared to ~22% in 2000. Given these changes, an important question is whether there is a relationship between changing sea ice conditions (e.g., extent, freeze up dates, break up dates) and iceberg production from these glaciers.
This study used synthetic aperture radar (Radarsat-1, 2 and ALOS PALSAR) and optical (Landsat-7 and 8) imagery to identify iceberg plume events and sea ice break-up/freeze-up dates between 1997 and 2015 for 40 tidewater glaciers around the POW. Results show a clear relationship between the presence of sea ice and the production of icebergs from glaciers, with most events occurring during the open water season and fewer when sea ice was present. While there have not been clear increasing trends of icebergs produced from all glaciers in the POW, Trinity and Wykeham glaciers show that increases in detected iceberg plumes coincide with increases in previously measured glacier velocity and significant terminus retreat. Comparison to ocean temperature, surface air temperature from NCEP/NCAR reanalysis and tidal data showed no clear relationship with increased calving events, however further research into all factors is recommended. It is likely that there are several factors contributing to the spatial and temporal variability of iceberg production from the POW.
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Smith, Denis. "Corporate power, risk assessment and the control of major hazards : A study of Canvey Island and Ellesmere Port." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234229.
Full textAbstract:
This thesis examines the role of corporate power in the decision making and regulatory processes for major hazard sites in the UK. In particular, emphasis is placed on the role of risk analytical techniques and the associated use of technical expertise in the public inquiry process by focusing on two areas, Canvey Island (Essex) and Ellesmere Port (Cheshire), over a twenty year period. Evidence shows that the ability of public groups to intervene effectively in the decision making process varies both .spatially and temporally. In order to set this data within a theoretical framework the analysis of public inquiries in these areas takes place in the context of three competing perspectives on power, namely pluralist, elitist and Marxist. Through the use of a number of mediating concepts the three theoretical persectives on power are married to the empirical data derived for the two areas. The research shows that each of the perspectives fails to provide an adequate explanation for events. Against this background some of the models of scientific expertise within decision making are evaluated and it is suggested that such models need to be set in a wider economic and social framework than had previously been allowed for by some authors. It is argued that risk analysis can be used to support the interests of powerful groups and as a consequence its validity as an input into decision making needs to be subjected to more critical scrutiny than has previously been the case. The thesis concludes by making a number of recommendations for the various bodies involved in making judgements about major hazards.
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Samad, Shameer Sheik. "An analysis of the impact of sea level rise on Lake Ellesmere - Te Waihora and the L2 drainage network, New Zealand." Thesis, University of Canterbury. Civil Engineering, 2007. http://hdl.handle.net/10092/1186.
Full textAbstract:
The potential impact of sea level rise on Lake Ellesmere - Te Wiahora and the subsequent effect on the efficiency and performance of the L2 Drainage network was investigated in relation to the operation of the L2 Drainage scheme. Lake Ellesmere is currently manually opened for drainage to the sea when the lake levels reach 1.05 m above mean sea level (asl) in summer and 1.13 m asl in winter. With a rise in sea level, the lake opening levels for both summer and winter would have to increase in order to maintain the current hydraulic gradient. Higher lake levels would impact drainage schemes such as the L2 drainage network. An integral research approach was used to study this potential impact, including fieldwork, analysis of data, hydrologic and hydraulic modelling. Both the hydrologic and hydraulic response of the L2 catchment and river were reproduced with reasonable accuracy by the use of computational models. Simulations of 2, 10 and 20 year annual recurrence intervals (ARI) rainstorm events coupled with higher lake levels show increase flooding along the length of the river. An increase in the lake opening levels, coupled with south-easterly wind was shown to have increased the degree of flooding on adjacent farmlands, but only a 3.50 per cent increase of water level (for all conditions simulated) 3.5 km upstream of the L2 River. The study clearly shows that weed growth within the L2 River plays an important part in controlling the water level within the channel. Results show it was responsible for an observed water level rise of 0.30 m from the winter to summer season. The combined use of hydraulic and hydrological models provides an effective tool to study future impacts on the drainage efficiency and performance of the L2 drainage scheme and other similar systems. The potential for both models to be used as a predictive tool for improving the operation of the L2 scheme and Lake Ellesmere was only limited by the difficulty in estimating model parameters especially for the hydrologic model.
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Van, Hove Patrick. "Limnologie du Nord de l'Île d'Ellesmere." Doctoral thesis, Université Laval, 2005. http://hdl.handle.net/20.500.11794/19428.
Full textAbstract:
Les lacs et les fjords du nord de l’Île d’Ellesmere, au Nunavut, renferment des écosystèmes uniques qui dépendent de la glace pour le maintien de leur structure. Certains de ces « cryo-écosystèmes » sont stratifiés en permanence, formés d’une couche d’eau douce flottant sur une couche d’eau de mer. Ces stratifications sont entre autres dues à la limitation du brassage par le vent en raison de la présence d’un couvert de glace permanent. Les travaux présentés ici ont comme objectif principal d’évaluer la diversité limnologique et biologique des lacs côtiers du nord de l’Île d’Ellesmere afin de mieux comprendre leur réponse aux changements environnementaux et climatiques à deux échelles temporelles : leurs variations à long terme à l’échelle de l’Holocène et leur réponse récente au climat dans le cours des dernières décennies. D’abord, les différents environnements sont présentés comme faisant partie d’une chronoséquence limnologique d’évolution du paysage à l’échelle de l’Holocène, à partir d’un fjord stratifié jusqu’à un lac d’eau douce en passant par un lac méromictique stratifié en permanence. Les facteurs de changements des environnements sont ensuite explorés en observant leur réponse aux changements climatiques récents. Puis, une étude de l’écologie microbienne de ces lacs et de ces fjords est présentée, insistant sur la dominance des picocyanobactéries dans leurs eaux de surface, en contraste avec les eaux de l’Océan Arctique, d’où sont issus ces milieux aquatiques. Une analyse moléculaire de la diversité génétique des cyanobactéries a été également effectuée et celle-ci met en valeur les grandes tolérances des cyanobactéries. Enfin, les communautés de zooplancton présentes dans ces environnements sont étudiées, afin d’élargir le portrait de ces environnements, et d’établir un point de base pour les études futures des transformations causées par les changements climatiques. Cette région du globe est très sensible aux changements climatiques, et les propriétés de ces écosystèmes tels que décrits ici sont un point de départ pour l’évaluation des changements futurs.The lakes and fjords of northern Ellesmere Island, Nunavut, harbor unique ice-dependant ecosystems. Some of these “cryo-ecosystems” are permanently stratified, with a freshwater layer overlying sea water. This extreme stratification is due in part to the limitation of wind-derived mixing because of the presence of a perennial ice-cover. The main objective of the work presented here was to evaluate the limnological and biological diversity of coastal lakes of northern Ellesmere Island in order to better understand their response to environmental change at two timescales: their long term variations over the Holocene and their recent responses to climate over the last few decades. The environments were shown to form a limnological chronosequence that reflected landscape evolution at the Holocene timescale, from stratified fjords to freshwater lakes, via phases in which the water bodies were stratified, meromictic lakes with different degrees of wind-induced mixing depending on the duration of ice cover, from perennial to seasonally open water conditions under warmer climates. Each of these phases is represented today in northern Nunavut. The sensitivity of these stratified ecosystems to environmental change at shorter timescales was then explored, by observing the limnological impacts of current climate change in the Ellesmere Island region. As a first step towards addressing the question of biodiversity and microbial community structure in these ecosystems, a molecular ecology analysis of the lake and fjord biota was made, and underscored the dominance of picocyanobacteria in their surface waters, in contrast with the low abundance of these microbes in the Arctic Ocean, from which those aquatic environments originate. The DNA analysis of the picocyanobacteria implied broad tolerances among these organisms, with the same genetic groups found in a great variety of environments, both on a local and a planetary scale. Finally, a study was undertaken of the zooplankton communities in a lake and fjord of northern Ellesmere Island to develop a broader portrait of these unique ecosystems, and to establish a baseline for future studies of the ongoing impacts of climate changes. This region of the globe is highly sensitive to climate change, and the properties of these ecosystems as discovered and described here are likely to undergo great transformations in the years to come.
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Mortimer, Colleen Adel. "Quantification of Changes for the Milne Ice Shelf, Nunavut, Canada, 1950 - 2009." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19773.
Full textAbstract:
This study presents a comprehensive overview of the current state of the Milne Ice Shelf and how it has changed over the last 59 years. The 205 ±1 km2 ice shelf experienced a 28% (82 ±0.8 km2) reduction in area between 1950 – 2009, and a 20% (2.5 ±0.9km3 water equivalent (w.e.)) reduction in volume between 1981 – 2008/2009, suggesting a long-term state of negative mass balance. Comparison of mean annual specific mass balances (up to -0.34 m w.e. yr-1) with surface mass balance measurements for the nearby Ward Hunt Ice Shelf suggest that basal melt is a key contributor to total ice shelf thinning. The development and expansion of new and existing surface cracks, as well as ice-marginal and epishelf lake development, indicate significant ice shelf weakening. Over the next few decades it is likely that the Milne Ice Shelf will continue to deteriorate.
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White, Adrienne. "Dynamics and Historical Changes of the Petersen Ice Shelf and Epishelf Lake, Nunavut, Canada, since 1959." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23574.
Full textAbstract:
This study presents the first comprehensive assessment of the Petersen Ice Shelf and the Petersen Bay epishelf lake, and examines their current characteristics and changes to their structure between 1959 and 2012. The surface of the Petersen Ice Shelf is characterized by a rolling topography of ridges and troughs, which is balanced by a rolling basal topography, with thicker ice under the surface ridges and thinner ice under the surface troughs. Based on thickness measurements collected in 2011 and area measurements from August 2012, the Petersen Ice Shelf has a surface area of 19.32 km2 and a mean thickness of 29 m, with the greatest thicknesses (>100 m) occurring at the fronts of tributary glaciers feeding into the ice shelf. The tributary glaciers along the northern coast of Petersen Bay contributed an estimated area-averaged 7.89 to 13.55 cm yr-1 of ice to the ice shelf between 2011 and 2012. This input is counteracted by a mean surface ablation of 1.30 m yr-1 between 2011 and 2012, suggesting strongly negative current mass balance conditions on the ice shelf.
The Petersen Ice Shelf remained relatively stable until 2005 when the first break-up in recent history occurred, removing >8 km2 of ice shelf surface area. This break-up led to the drainage of the epishelf lake once the ice shelf separated from the southern coast, providing a conduit through which the freshwater from the lake escaped. More break-ups occurred in summers 2008, 2011 and 2012, which resulted in a >31.2 km2 loss in surface area (~63% of June 2005 area). While ephemeral regions of freshwater have occurred along the southern coast of Petersen Bay since 2005 (with areas ranging from 0.32-0.53 km2), open water events and a channel along the southern coast have prevented the epishelf lake from reforming. Based on these past and present observations it is unlikely that Petersen Ice Shelf will continue to persist long into the future.
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Mitchell, Hannah Laugesen. "A comparative study of riparian drain management and its effects on phosphate and sediment inputs to Te Waihora/Lake Ellesmere." Thesis, University of Canterbury. The Waterways Centre for Freshwater Management, 2012. http://hdl.handle.net/10092/9441.
Full textAbstract:
Issues affecting water quality are seen as one of the most important and pressing global problems of our era. In New Zealand, water bodies with the poorest water quality and ecological condition tend to be surrounded by pastoral land use. Lake Ellesmere/Te Waihora in Canterbury, New Zealand, is a typical example of the issues that nutrient and sediment run-off from pastoral land can create.
The aim of this study was to determine the relationship between sediment concentrations, phosphate concentrations, ecological state and the degree of riparian restoration on drains that flowed into Lake Ellesmere/Te Waihora, and to calculate the load of phosphorus and sediment delivered by each of the drains to Te Waihora over the year, comparing this to the loads carried by larger, natural streams and rivers. Little research has been done on these small artificial tributaries of the Lake Ellesmere/Te Waihora catchment. Data collection was carried out on 10 drains with variable degrees of riparian planting, monthly in summer and autumn, and fortnightly in winter and spring, due to higher variability in drain flows during this time.
Sites 1, 2 had low dissolved oxygen (DO) and high total phosphorus (TP), lack of flow and extremely high conductivity, and (with) Site 5, higher suspended particulate matter (SPM) concentrations. All these factors are consistent with the lack of ecology occurring in these drains. All drains failed to meet the Australian and New Zealand Environment and Conservation Council (ANZECC) guidelines for TP concentrations. All water chemistry parameters showed significant differences between seasons except conductivity. Mean water temperatures and pH were higher in summer and lower in winter, while mean DO levels were higher in winter (and spring) and lower in summer (and autumn). Macroinvertebrate analyses indicated moderate to severe pollution in all the drains, despite the amount of riparian planting present and the presence of macroinvertebrate community structure was related mainly to substrate size.
The degree and type of riparian planting present on the drains studied did not appear to affect TP, SPM, macroinvertebrates or general water quality. This is likely to be due to the fact that little of the riparian planting had been specifically planted for restoration purposes. The highest loads of TP and SPM occurred in winter and spring, and in the larger (wider and deeper) drains. As flow increased in the drain, so did the load of phosphorus and sediment carried. Comparison with Environment Canterbury monitoring data for the river tributaries of the lake indicated that more TP and SPM is carried to the lake by natural rivers and streams, than by the drains, but the latter do make a significant contribution. The percentage of TP that is in dissolved form was higher than had previously been assumed, in both the drains and the larger, natural rivers and streams.
It is recommended that future restoration work aim to reduce the amount of phosphorus and sediment entering the larger drains in winter and spring. More adequate riparian planting needs to occur on these drains, and it needs to be managed in a way that a reduction in dissolved phosphorus levels is also achieved.
43
Poey, Jean-Luc. "Stratigraphy and depositional environments of an Upper Ordovician to Lower Devonian shelf-to-basin transition, Svendsen Peninsula, Ellesmere Island, N.W.T." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5354.
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Drinkard, Sally Lyn, and Sally Lyn Drinkard. "Glacio-isostatic rebound rates from in-situ cosmogenic chlorine-36 dating of raised marine beaches in Makinson inlet, eastern Ellesmere island." Thesis, The University of Arizona, 1999. http://hdl.handle.net/10150/626778.
Full textAbstract:
Ellesmere Island, in the Canadian Arctic, and adjacent sea were covered by ice
during the Last Glacial Maximum (LGM, 20-10 ky ago). Postglacial rebound rates, indic
ative of ice sheet configuration, glacial and deglacial chronologies, and rheologic proper
ties of the underlying mantle, were determined for Makinson Inlet using a new approach
based on in-situ accumulation of cosmogenic 36Cl.
Surface and subsurface gravel samples were collected from fourteen paleobeaches
at elevations between the sea level and the Holocene marine limit at ca. 105 m a.s.l.
Apparent 36Cl ages range from ca. 4 to 13 ky and corrected 36Cl ages (in calendar years)
range from 10 ky to recent. Corrected 36Cl ages agree with 14C ages of organic material
from the same paleobeach sequence. Instantaneous uplift rates decrease from the high of
42 m ky- 1 at the beginning of emergence 10 ky ago, to less than I m ky- 1 today.
These results show the applicability of the cosmogenic 36CI exposure dating
method in studies of postglacial emergence. The ability to date inorganic surficial materi
als has two main advantages: (1) the approach may be used on any material, such as rocks
and sediments, that has been exposed at the surface due to isostatic rebound; and (2) an
arbitrarily large number of samples can be collected at the same location, thereby provid
ing the means of constructing a high-resolution record of exposure and isostatic emer
gence.
45
Kokelj, Steve. "The effect of detachment sliding on surface wash erosion in the continuous permafrost zone, Hot Weather Creek, Fosheim Peninsula, Ellesmere Island, N.W.T." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0003/MQ36709.pdf.
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de, Freitas Tim A. "Stratigraphy, mud buildups, and carbonate platform development of the Upper Ordovician to Lower Devonian sequence, Ellesmere, Hans, and Devon Islands, Arctic Canada." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7937.
Full textAbstract:
The Upper Ordovician to Lower Devonian platform in the Canadian Arctic twice evolved from a ramp to a rimmed shelf profile. Platform backstepping occurred in the fastigatus, acuminatus, cyphus?, sakmaricus (in North Greenland only) and linearis graptolite zones. Two major phases of pinnacle reef development followed platform backstepping, the first beginning in the lower Llandovery (cyphus Zone) and the second in the Ludlow (linearis Zone). Pinnacles of the first phase are uncommon, occur in the vicinity of Baumann Fiord, and show a vertical succession of lime mudstone, poorly exposed microbial carbonate, and coralgal biolithite, representing upward shallowing. The last named lithofacies is newly interpreted as representing a high-energy, wave-stressed environment that excluded stromatoporoid growth but favoured a sparse skeletal metazoan fauna, thickly encrusted by microbes. Paleo-surface area of these structures was apparently important for the accumulation of extensive ooids, which are associated with the upper parts of some pinnacle reefs. Three large mud buildups on central Ellesmere Island were established on the shelf margin subsequent to Upper Ordovician (fastigatus Zone) platform drowning. These structures show a vertical lithofacies succession: bioturbated lime mudstone is overlain by microbial carbonate then by mudstone-rich stromatoporoid floatstone and bindstone. The succession records overall upward shallowing. The olive green shale unit, well exposed in the vicinity of Trold Fiord, is an areally extensive and mappable middle Ludlow unit of the Cape Phillips Formation that postdates diachronous, middle Ludlow platform backstepping in the vicinity of Baumann Fiord. After backstepping, condensed sequences occurred over paleotopographic highs and expanded sections over lows, and a subsequent second major phase of platform rimming occurred. Stratigraphy known in the southern Arctic Islands is generally applicable to northeastern Ellesmere Island, but local lithological variations occur. The upper part of the Allen Bay Formation at Darling Peninsula, in particular, is unusually thick, and subtidal, perhaps resulting from greater subsidence, related to lithospheric flexure and deep marine clastic sedimentation that drowned the contiguous platform on North Greenland. Other formations recognized in this area include the Cape Storm, Douro, and Goose Fiord formations, although these, too, show minor lithological differences from type sequences. A thick grey siltstone unit in the vicinity of Bay and Vesle fiords is suggested to be a distal facies of the Red Canyon River Formation. This sequence is a progradational clastic wedge that likely represents the first, largest phase of the tripartite Caledonian Inglefield Uplift which profoundly affected carbonate deposition in the areas of southern and central Ellesmere Island during the late Silurian and early Devonian time. The base of this unit is diachronous and likely late Silurian in age. (Abstract shortened by UMI.)
47
Kokelj, Steven V. "The effect of detachment sliding on surface wash erosion in the continuous permafrost zone, Hot Weather Creek, Fosheim Peninsula, Ellesmere Island, Northwest Territories." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4070.
Full textAbstract:
An experimental design was developed to evaluate the effect of active-layer detachment sliding on surface wash erosion. Specifically, the aim was to examine to what extent the disturbance of vegetation cover, changes in hydrological conditions due to topographic modification by detachment sliding and the formation of a fresh active layer affect rates of surface wash erosion. Detachment slides generally accumulated more snow than adjacent slopes and yielded greater amounts of surface runoff than vegetated slopes with similar snow covers. Surface drainage was inhibited on well-vegetated hummocky slopes where lags between radiation inputs and discharge responses were greater than at the rilled detachment slide plots. During rainfall events following snowmelt, plot response was affected by antecedent moisture conditions and the vegetation cover: surface flow was generated only in detachment slide scars and at the mixed plots but not on vegetated undisturbed slopes or on the bare undisturbed slope. Suspended sediment concentrations at the fresh detachment slide scars are two orders of magnitude greater than on vegetated slopes. Greater amounts of surface runoff production at fresh scars and the removal of vegetation result in high rates of surface erosion and high sediment yields (1560 g/m$\sp2)$ at fresh detachment slide scars. (Abstract shortened by UMI.)
48
Woods, Kirstin Roseanne G. "Rangatiratanga in the context of Lake Ellesmere/Te Waihora : identifying the conditions necessary for the exercise and expression of tribal authority over tribal resources." Thesis, University of Canterbury. Department of Resource Management, 1989. http://hdl.handle.net/10092/2512.
Full textAbstract:
In a climate of administrative reform, the Government is attempting to address the Treaty of Waitangi and to give practical significance to its guarantees. This study assumes that without an understanding of terms used in the Treaty, attempts at its implementation face misunderstanding and confusion. Thus, the study begins by defining "rangatiratanga" as guaranteed in the Maori text of the Treaty. It proposes that rangatiratanga, within the framework of Maori tradition, is a process through which leadership is defined and decisions made. Fundamental to this process is a view of the world which recognises the interrelatedness} of all elements in nature. Findings from a study of Lake Ellesmere/Te Waihora and Ngai Tahu rangatiratanga suggest that Ngai Tahu face the task of reassessing their tribal structure after many years of European domination. Guarantees given in the Treaty suggest that the 'Government should actively support Ngai Tahu in this process but that the imposition of a uniform "tribal model" is inappropriate. In addition, if rangatiratanga is to be expressed in the context of Lake Ellesmere/Te Waihora, the interlocking nature of resource use within the lake's catchment points to the need for a partnership between all agencies involved in its management.- This can only occur where there is a convergence in attitude to environmental management on the part of both "partners".
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Sweet, Natalie L. "Paleoecology and sedimentology of late Silurian biogenic structures in the Duoro and Devon Island Formations on western Devon and southwestern Ellesmere Islands, Arctic Canada." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10385.
Full textAbstract:
Carbonate buildups of late-Ludlow-Pridoli age occur within an extensive Silurian reef 'belt' in the Canadian Arctic Islands. Two phases of mound development were documented. The buildups include mudmounds in the uppermost Douro Formation on western Devon Island, and skeletal mounds in the Devon Island Formation on southwestern Ellesmere, North Kent, and Seal islands and Colin Archer Peninsula on Devon Island. The mudmounds average 50m in diameter and 15m in height, and are composed predominantly of sparsely fossiliferous lime mudstone containing sponge spicules and micrite fabrics of probable microbial tabulate origin. In a few small ($\sim$3m diameter x 0.5m high) mudmounds, abundant, well-preserved lithistid sponges and distinct microbial fabrics represent an intimate association of encrusting, binding, baffling and sediment-producing constructors. Coral skeletal mounds, averaging 100m in diameter and 35m in height, have stromatactoid-rich mudstone cores and grade upwards from mudstone into fasciculate coral-floatstone and crinoidal wackestone. In contrast, in a skeletal mound core on North Kent Island, a floatstone facies characterized by fasciculate rugose and tabulate corals, and large tabular stromatoporoids, is overlain by a mudstone core facies. Although the skeletal mounds have been completely altered to a fine-grained dolomite, relict fabrics are preserved and suggest a diagenetic sequence similar to that for the mudmounds. The mudmounds grew during a period of substantial platform drowning, apparently related to tectonic movement on the Boothia Uplift. Farther north, growth of the skeletal mounds began on favourable highs of the drowned carbonate ramp, and continued as basinal siliciclastic muds accumulated. The event represented by the hardground and associated physical features can be correlated with related features in buildups farther south where the Douro ramp instead evolved into a carbonate shelf, represented by the Barlow Inlet Formation. (Abstract shortened by UMI.)
50
Johnstone, Jill F. "Responses of Cassiope tetragona, a high Arctic evergreen dwarf shrub, to variations in growing season temperature and growing season length at Alexandra Fiord, Ellesmere Island." Thesis, 1995. http://hdl.handle.net/2429/3845.
Full textAbstract:
The short-term responses of Cassiope tetragona, a high arctic evergreen shrub, to
variations in growing season climate were examined using experimental manipulations of
temperature and growing season length at Alexandra Fiord, Ellesmere Island. Surface
temperatures in the field were increased an average of 1-2 °C in two communities using open-top
greenhouses. Growing season length was altered in a snowbed community by using
manual snow manipulations to change the date of snowmelt. Growth and reproductive
responses of Cassiope tetragona to these manipulations were observed over two field seasons
following treatment establishment. Natural variations in vegetative and reproductive
characteristics of Cassiope tetragona were also monitored in unmanipulated communities
selected to represent a range of environmental conditions at the study site. Retrospective
analysis of past Cassiope growth and reproduction was used to provide a record of variations
in productivity spanning 25-35 years which could be related to climate records from
Ellesmere Island. For the retrospective analysis, patterns of internode lengths were used to
delimit sections of annual growth and chronologies of annual stem elongation, leaf number
and flower number were then analyzed using methods similar to those applied to tree-ring
studies.
In general, the reproductive parameters of Cassiope tetragona were observed to be
highly responsive to short-term variations in growing season climate, while vegetative
production exhibited a much more conservative response. Flower production and rates of
reproductive development were significantly stimulated by experimental warming.
Retrospective analysis of flower production support field observations indicating that flower
production is highly sensitive to annual variations in growing season temperatures. In
contrast, shoot growth showed moderate responses to experimental warming. Records of
past growth indicate that although vegetative production appears to be sensitive to annual
variations in summer temperatures, the degree of responsiveness is much lower than for reproductive parameters. Net growth and reproduction were not stronly affected by natural
or experimental variations in snowmelt timing, although phenology timing was
significantly altered.
The conservative growth response of Cassiope tetragona to short-term variations in
climate is suggested to be related to constraints on plant phenology which may restrict
flexibility in the period utilized by plants for aboveground growth. Preferential allocation
of within-plant resources to reproductive structures during periods of ameliorated growing
season climate may account for the observed strong reproductive responses to climate
variations. Trade-offs betweeen growth and reproduction have important implications for
predicting the long-term response of Cassiope tetragona to climate change. An
understanding of within-plant allocation strategies is also important to the interpretation of
past variations in growth and reproduction. Retrospective analysis of past Cassiope
production is likely to be a very useful tool for investigating ecological relationships and
past climate change.