To see the other types of publications on this topic, follow the link: Laurentides region.
Journal articles on the topic 'Laurentides region'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Laurentides region.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Gauthier, Robert. "La répartition et l'habitat du Tomenthypnum falcifolium au Québec–Labrador." Canadian Journal of Botany 65, no. 2 (February 1, 1987): 286–98. http://dx.doi.org/10.1139/b87-040.
Full textAbstract:
The discovery of Tomenthypnum falcifolium (Ren. ex Nich.) Tuom. in Canada is rather recent. For a long time, it was considered as a variety of Tomenthypnum nitens. Some characters allowing the distinction of the two species are discussed and illustrated. Distribution maps of both species in the Québec–Labrador Peninsula are presented. Habitat conditions of Tomenthypnum falcifolium in the Laurentides Park are derived from a study of peatland vegetation. It grows mainly in extremely poor fens, the dominant peatland type of this region. It is a hummock-preferring species and never forms extensive colonies. Its ecological amplitude is then rather different from that of Tomenthypnum nitens which is more commonly found in rich fens.
2
Desponts, Mireille, André Desrochers, Louis Bélanger, and Jean Huot. "Structure de sapinières aménagées et anciennes du massif des Laurentides (Québec) et diversité des plantes invasculaires." Canadian Journal of Forest Research 32, no. 12 (December 1, 2002): 2077–93. http://dx.doi.org/10.1139/x02-127.
Full textAbstract:
This study was undertaken to determine the contribution of old-growth and senescent forest stands regenerated through clear-cutting to the biodiversity of wet boreal fir stands in eastern Quebec because overmature stands are becoming scarce in that region. The study area was located in the Laurentian Mountains north of the city of Québec. The structure and composition of nonvascular plant communities (mosses, hepatica, lichens, and saprophytic fungi) of old-growth forests were compared with those of mature or senescent fir stands harvested 60 years ago. Nonvascular plants have a more uniform structure and a lower diversity in mature than in senescent or old-growth forests. A variety of specialized soil- and wood-inhabiting species and many rare species not observed in mature stands regenerated through clear-cutting are found in the latter. Structural diversity of senescent second-growth fir stands becomes similar to that of old-growth stand because of mortality within the overstory. These structural characteristics favour the development of diversified nonvascular plant communities, especially wood-inhabiting species found on slightly decomposed woody debris and soil-inhabiting species that colonize disturbed soils.[Journal translation]
3
Wójcik, Katarzyna. "(Re)visions télévisuelles de la colonisation du Nord – série médiatique d’Un homme et son péché de Claude-Henri Grignon." Romanica Silesiana 18, no. 2 (December 28, 2020): 86–97. http://dx.doi.org/10.31261/rs.2020.18.07.
Full textAbstract:
Claude-Henri Grignon’s novel Un homme et son péché presents the life of French Canadian colonial settlers of the Laurentides region at the end of XIXth century. It depicts a realistic image of the colonisation period of Quebec history. The novel is at the origin of a media series that englobes a radio adaptation, three filmic adaptations, theater adaptations, a comic, and two television series. The aim of this article is to discuss the vision of colonisation by analysing two television series based on Un homme et son péché: Les Belles Histoires des pays d’en haut broadcast from 1956 to 1970 and Les Pays d’en haut broadcast from 2016 to 2019 on ICI Radio-Canada Télé 1. The analysis will try to trace modifications inherent to the process of adaptation on different levels (protagonists, representation of space, ideological discourse) and their influence on the vision of the colonisation period.
4
Hébert, Rémi, Claude Samson, and Jean Huot. "Factors Influencing the Abundance of Berry Plants for Black Bears, Ursus americanus, in Quebec." Canadian Field-Naturalist 122, no. 3 (July 1, 2008): 212. http://dx.doi.org/10.22621/cfn.v122i3.601.
Full textAbstract:
Berries generally represent the primary food source used by Black Bears (Ursus americanus) during summer and sometimes fall. Our study attempted to identify factors influencing the abundance of these critical resources for Black Bears in Quebec. We used data from the ecological inventories of the Ministère de l’Environnement du Québec. Three different study areas were selected, including the Papineau-Labelle Wildlife Reserve (326 sample plots; 24 species), the Laurentides Wildlife Reserve (679 sample plots; 16 species) and the Côte-Nord administrative region (1944 sample plots; 30 species). Each site represented a different bioclimatic domain. Characteristics of the dominant vegetation (density and height), soil texture, and drainage classes (vertical or oblique) were used as analysis factors. In general, height and density of the dominant vegetation had a significant effect on the abundance of berry plants. Berry plants were more abundant in plots where dominant vegetation height and density were low. Soil texture had little effect on the abundance of berry plants, and the influence of drainage varied depending on the region. This study allowed us to determine the optimal sites of berry resources for Black Bears.
5
Brigot, Guillaume, Marc Simard, Elise Colin-Koeniguer, and Alexandre Boulch. "Retrieval of Forest Vertical Structure from PolInSAR Data by Machine Learning Using LIDAR-Derived Features." Remote Sensing 11, no. 4 (February 13, 2019): 381. http://dx.doi.org/10.3390/rs11040381.
Full textAbstract:
This paper presents a machine learning based method to predict the forest structure parameters from L-band polarimetric and interferometric synthetic aperture radar (PolInSAR) data acquired by the airborne UAVSAR system over the Réserve Faunique des Laurentides in Québec, Canada. The main objective of this paper is to show that relevant parameters of the PolInSAR coherence region can be used to invert forest structure indicators computed from the airborne LIDAR sensor Laser Vegetation and Ice Sensor (LVIS). The method relies on the shape of the observed generalized PolInSAR coherence region that is related to the three-dimensional structure of the scene. In addition to parameters describing the coherence shape, we consider the impact of acquisition parameters such as the interferometric baseline, ground elevation and local surface slope. We use the parameters as input a multilayer perceptron model to infer canopy features as estimated from LIDAR waveform. The output features are canopy height, cover and vertical profile class. Canopy height and canopy cover are estimated with a normalized RMSE of 13%, 15% respectively. The vertical profile was divided into 3 distinct classes with 66% accuracy.
6
Gagnier, Marianne, Isabelle Laurion, and Anthony J. DeNicola. "Control and Surveillance Operations to Prevent Chronic Wasting Disease Establishment in Free-Ranging White-Tailed Deer in Québec, Canada." Animals 10, no. 2 (February 12, 2020): 283. http://dx.doi.org/10.3390/ani10020283.
Full textAbstract:
Chronic wasting disease (CWD), a degenerative and fatal prion disease affecting cervids, was detected for the first time in the province of Québec, Canada, in a red deer (Cervus elaphus) farm in the Laurentides region on 10 September 2018. To assess CWD prevalence and control the disease in the free-ranging white-tailed deer (Odocoileus virginianus) population, a response plan including enhanced surveillance, population control, regulatory measures, and public outreach was deployed by the Ministry of Forests, Wildlife, and Parks (MFFP). In the 401 km2 white-tailed deer control area, a total of 750 free-ranging white-tailed deer were culled over 70 days, from 22 September to 15 December 2018. Of the culled deer, 534 were tested for CWD. We also tested for CWD a total of 447 white-tailed deer hunted from the enhanced surveillance zone and 2584 free-ranging white-tailed deer harvested outside this zone. Regulations were applied to prevent the spread of the disease through movements of infected animals harvested by hunters. Although no case of CWD was detected in free-ranging cervids in Québec in 2018, this does not confirm the absence of the disease in these populations. However, the results suggest that if CWD is present, few free-ranging cervids are infected, making it possible to prevent its establishment in the province of Québec.
7
Patenaude, Marc, Paul Baudron, Laurence Labelle, and Janie Masse-Dufresne. "Evaluating Bank-Filtration Occurrence in the Province of Quebec (Canada) with a GIS Approach." Water 12, no. 3 (March 1, 2020): 662. http://dx.doi.org/10.3390/w12030662.
Full textAbstract:
Due to the abundance of surface water in the province of Quebec, Canada, it is suspected that many groundwater wells are pumping a mixture of groundwater and surface water via induced bank filtration (IBF). The regulatory framework in Quebec provides comprehensive guidelines for the development and monitoring of surface water and groundwater drinking water production systems. However, the regulations do not specifically address hybrid groundwater-surface water production systems such as IBF sites. More knowledge on the use of IBF in the province is needed to adjust the regulations with respect to the particularities of these systems. In order to provide a first evaluation of municipal wells potentially using IBF and the corresponding population served by these wells, a Geographic Information Science framework (GISc) was used to implement an IBF spatial database and calculate the distance from each well to the nearest surface water body. GISc is based on open source GIS programs and openly available data, to facilitate the reproducibility of the work. From this provincial scale approach, we show that nearly one million people are supplied by groundwater from municipal wells located <500 m from a surface water body, and half a million have a significant probability to be supplied by IBF wells. A more focused look at the watershed scale distribution of wells allows us to improve our interpretations by considering the aquifer type and other regional factors. This approach reveals strong spatial variability in the distribution of wells in proximity to surface water. Of the three selected regions, one has a high potential for IBF (Laurentides), one requires additional information do draw precise conclusions (Nicolet), and the third region (Vaudreuil-Soulanges) is unlikely to have widespread use of IBF. With this study, we demonstrate that extensive use of IBF is likely and that there is a need for improved understanding and management of these sites in order to properly protect the drinking water supply.
8
Bell, M., and E. P. Laine. "Erosion of the Laurentide Region of North America by Glacial and Glaciofluvial Processes." Quaternary Research 23, no. 2 (March 1985): 154–74. http://dx.doi.org/10.1016/0033-5894(85)90026-2.
Full textAbstract:
Collection of seismic reflection data from continental margins and ocean basins surrounding North America makes it possible to estimate the amount of material eroded from the area formerly covered by Laurentide ice sheets since major glaciation began in North America. A minimum estimate is made of 1.62 × 106 km3, or an average 120 m of rock physically eroded from the Laurentide region. This figure is an order of magnitude higher than earlier estimates based on the volume of glacial drift, Cenozoic marine sediments, and modern sediment loads of rivers. Most of the sediment produced during Laurentide glaciation has already been transported to the oceans. The importance of continental glaciation as a geomorphic agency in North America may have to be reevaluated. Evidence from sedimentation rates in ocean basins surrounding Greenland and Antarctica suggests that sediment production, sediment transport, and possibly denudation by permanent ice caps may be substantially lower than by periodic ice caps, such as the Laurentide. Low rates of sediment survival from the time of the Permo-Carboniferous and Precambrian glaciations suggest that predominance of marine deposition during some glacial epochs results in shorter lived sediment because of preferential tectonism and cycling of oceanic crust versus continental crust.
9
Bobrowsky, Peter, and Nathaniel W. Rutter. "The Quaternary Geologic History of the Canadian Rocky Mountains." Géographie physique et Quaternaire 46, no. 1 (November 23, 2007): 5–50. http://dx.doi.org/10.7202/032887ar.
Full textAbstract:
ABSTRACT The Canadian Rocky Mountains figured prominently during the glacial history of western Canada. First as a western limit or boundary to the Laurentide Ice Sheet, second as an eastern margin of the Cordilleran Ice Sheet, and finally as a centre of local Montane ice. Throughout the Quaternary, complex interactions of glacier ice from these three ice sources markedly changed the physical form of the Rocky Mountains, Trench and Foothills areas. Investigations into the Quaternary history of this region have been ongoing since the beginning of the last century. Since about 1950, the number of studies performed in this area have increased significantly. This paper briefly reviews the historical accomplishments of Quaternary work in the region up to the period of about 1950. From this time to the present, individual study efforts are examined in detail according to the three geographic regions: 1) the northern Rocky Mountains (from the Liard Plateau south to the McGregor Plateau), 2) the central Rocky Mountains (from the McGregor Plateau south to the Porcupine Hills) and 3) the southern Rocky Mountains (from the Porcupine Hills south to the international border). In the northern region, geologic data suggest a maximum of two Rocky Mountain glaciations and only one Laurentide glaciation and no ice coalescence. In the central region, three of four Rocky Mountain events, and at least two Laurentide events are known. Only in the central region is there good evidence for ice coalescence, but the timing of this event is not clearly established. In the south, at least three Rocky Mountain episodes and a variable number of Laurentide episodes are recognized. There is no evidence for ice coalescence. A number of facts support the proposal that Cordilleran ice crossed the Continental Divide and joined with local Montane ice at several locations. However, this expansion of western ice occurred before the Late Wisconsinan in all areas but Jasper. In general, the chronological data presented suggest that the Late Wisconsinan glaciation in the Rocky Mountains was a short-lived event which started around or after 20 ka years ago and ended before 12 ka ago.
10
Wolfe, Stephen A., David J. Huntley, and Jeff Ollerhead. "Relict Late Wisconsinan Dune Fields of the Northern Great Plains, Canada*." Paleoenvironments 58, no. 2-3 (July 18, 2006): 323–36. http://dx.doi.org/10.7202/013146ar.
Full textAbstract:
Abstract Late Wisconsinan dune activity is investigated within the present-day boreal forest and parkland regions of the northern Great Plains, Canada, to extend the understanding of the spatial and temporal eolian record. Optical ages from stabilized sand dunes document the timing of past activity. Eolian activity ranges from about 16 ka in west-central Alberta to 9 ka in northwestern Saskatchewan. Between about 16 and 13 ka, dune activity in central Alberta occurred in an ice-proximal tundra setting along the margins of the Laurentide and Cordilleran ice sheets. Predominant dune-forming winds were from the west and northwest. Dune activity continued in this area between about 13 and 11 ka within parkland and grassland settings as the Laurentide Ice Sheet retreated to the northeast. Winds continued to blow from the west and northwest, and the climate was likely influenced by an increasingly dominant Pacific air mass. Also beginning at about 13 ka, dune-forming winds along the margins of the retreating Laurentide Ice Sheet were influenced by anticyclonic winds from the southeast that were maintained until about 9 ka. As the Laurentide Ice Sheet retreated, these southeasterly anticyclonic winds were successively replaced by winds from the northwest associated with the Pacific air mass. Dune activity across the region terminated in a time-transgressive manner from the southwest, at about 11 ka, to the northeast, at about 9 ka, with the establishment of boreal forest vegetation and reduced wind strength.
11
Angelis, Hernán De, and Johan Kleman. "Palaeo-ice streams in the northern Keewatin sector of the Laurentide ice sheet." Annals of Glaciology 42 (2005): 135–44. http://dx.doi.org/10.3189/172756405781812925.
Full textAbstract:
AbstractEvidence for ice streams in the Laurentide ice sheet is widespread. In the region of northern Keewatin and the Boothia Peninsula, Nunavut, Canada, palaeo-ice streams have been recognized, but their location, size and potential role in ice-sheet dynamics are poorly constrained. Based on the interpretation of satellite imagery, we produce a palaeo-ice-stream map of this region. Glacial directional landforms, eskers and moraines were mapped and integrated into landform assemblages using a glacial geological inversion model. Palaeo-frozen bed areas were also identified. Relative age of the geomorphic swarms was assessed by cross-cutting relationships and radiocarbon ages where available. Using this information we obtained a glaciologically plausible picture of ice-stream evolution within the northernmost Laurentide ice sheet. On the M’Clintock Channel corridor, three generations of pure ice streams are found. On Baffin Island and the Gulf of Boothia, glaciation was dominated by frozen-bed zones located on high plateaus and ice streams running along the troughs, i.e. topographic ice streams. A massive convergent pattern at the head of Committee Bay drained ice from both the Keewatin and Foxe sectors and was probably one of the main deglaciation channels of the Laurentide ice sheet. Finally, our results indicate that streaming flow was present in the deep interior of the Laurentide ice sheet, as recently shown for the Greenland and Antarctic ice sheets.
12
Hofer, D., C. C. Raible, A. Dehnert, and J. Kuhlemann. "The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region." Climate of the Past 8, no. 3 (May 24, 2012): 935–49. http://dx.doi.org/10.5194/cp-8-935-2012.
Full textAbstract:
Abstract. Using a highly resolved atmospheric general circulation model, the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Six 30-yr time slice experiments of the Last Glacial Maximum at 21 thousand years before the present (ka BP) and of a less pronounced glacial state – the Middle Weichselian (65 ka BP) – are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing and in the prescribed time-varying sea surface temperature and sea ice, which are taken from a lower-resolved, but fully coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A high surface elevation of the Laurentide ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying sea surface temperatures and sea ice are of second order importance compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner compared with the topographic changes.
13
Stoker, Benjamin J., Martin Margold, John C. Gosse, Alan J. Hidy, Alistair J. Monteath, Joseph M. Young, Niall Gandy, Lauren J. Gregoire, Sophie L. Norris, and Duane Froese. "The collapse of the Cordilleran–Laurentide ice saddle and early opening of the Mackenzie Valley, Northwest Territories, Canada, constrained by 10Be exposure dating." Cryosphere 16, no. 12 (December 6, 2022): 4865–86. http://dx.doi.org/10.5194/tc-16-4865-2022.
Full textAbstract:
Abstract. Deglaciation of the northwestern Laurentide Ice Sheet in the central Mackenzie Valley opened the northern portion of the deglacial Ice-Free Corridor between the Laurentide and Cordilleran ice sheets and a drainage route to the Arctic Ocean. In addition, ice sheet saddle collapse in this section of the Laurentide Ice Sheet has been implicated as a mechanism for delivering substantial freshwater influx into the Arctic Ocean on centennial timescales. However, there is little empirical data to constrain the deglaciation chronology in the central Mackenzie Valley where the northern slopes of the ice saddle were located. Here, we present 30 new 10Be cosmogenic nuclide exposure dates across six sites, including two elevation transects, which constrain the timing and rate of thinning and retreat of the Laurentide Ice Sheet in the area. Our new 10Be dates indicate that the initial deglaciation of the eastern summits of the central Mackenzie Mountains began at ∼15.8 ka (17.1–14.6 ka), ∼1000 years earlier than in previous reconstructions. The main phase of ice saddle collapse occurred between ∼14.9 and 13.6 ka, consistent with numerical modelling simulations, placing this event within the Bølling–Allerød interval (14.6–12.9 ka). Our new dates require a revision of ice margin retreat dynamics, with ice retreating more easterly rather than southward along the Mackenzie Valley. In addition, we quantify a total sea level rise contribution from the Cordilleran–Laurentide ice saddle region of ∼11.2 m between 16 and 13 ka.
14
Vujanovic, Vladimir, Marc St-Arnaud, Peterjürgen Neumann, and J. André Fortin. "Diarimella laurentidae anam.: sp.nov. from Quebec." Canadian Journal of Botany 76, no. 12 (December 1, 1998): 2037–41. http://dx.doi.org/10.1139/b98-234.
Full textAbstract:
Diarimella laurentidae, a new species occurring on dead bark and decorticated twigs of American beech (Fagus grandifolia Ehrh.), is reported from the Muir's Wood ecological reserve, located in the centre of the Haut-Saint-Laurent region in the province of Quebec. Diarimella laurentidae is characterized by stromatic, pulvinate, black, setose fructifications composed of a basal stroma of textura angularis, a brown peripheral wall of textura porrecta, conidiomatal setae of two types, and unicellular multisetulate conidia. Its relationships with described Diarimella species is discussed. This is the first report of a species of Diarimella from North America.Key words: Diarimella laurentidae, new fungus species, coelomycete, Fagus grandifolia.
15
Kassab, Christine M., Samantha L. Brickles, Kathy J. Licht, and G. William Monaghan. "Exploring the use of zircon geochronology as an indicator of Laurentide Ice Sheet till provenance, Indiana, USA." Quaternary Research 88, no. 3 (September 20, 2017): 525–36. http://dx.doi.org/10.1017/qua.2017.71.
Full textAbstract:
AbstractA pilot study was designed to evaluate the potential of zircon geochronology as a provenance indicator of till from the Lake Michigan, Saginaw, and Huron-Erie Lobes of the Laurentide Ice Sheet. Based on existing ice flow-path models, we hypothesized that till from each lobe would have different zircon age population distributions because the lobes originated from regions of the Canadian Shield with different bedrock ages. After correcting for zircon fertility, the majority of grains in all till samples are 1600–950 Ma, with ~30 % of ages >2500 Ma. This similarity means that till from the three lobes cannot be clearly differentiated based on their zircon populations. The dominant ages found and the homogeneity of distributions in the till indicates a non-Shield source and, instead, reflect an origin from some combination of underlying till and sedimentary bedrock in the Great Lakes region. Even though the datasets are small, the tills have similarities to zircon distributions in Michigan Basin rocks. This implies that a substantial fraction of zircon in till was not transported long distances from the Canadian Shield. Although zircon ages are not distinct between tills, the method provides a novel application to understand Laurentide Ice Sheet glacial erosion and transport.
16
Kaplan, Michael R., W. Tad Pfeffer, Christophe Sassolas, and Gifford H. Miller. "Numerical modelling of the Laurentide Ice Sheet in the Baffin Island region: the role of a Cumberland Sound ice stream." Canadian Journal of Earth Sciences 36, no. 8 (August 21, 1999): 1315–26. http://dx.doi.org/10.1139/e99-027.
Full textAbstract:
A numerical model reconstruction was made of the northeastern Laurentide Ice Sheet in the Baffin Island - Foxe Basin region using geophysical, terrestrial, and marine geologic evidence for initial and boundary conditions. The simulated ice sheet consists of a Foxe Dome with additional smaller Hall and Amadjuak domes and a Penny Ice Divide. A specific objective was to determine boundary conditions that would allow advance of a marine-based low surface slope ice stream into and out of Cumberland Sound, a major marine embayment in the uplifted rim of the eastern Canadian Arctic (up to 1200 m deep), while maintaining ice free or nonsliding (e.g., cold-based) thin ice on adjacent plateaus of Cumberland Peninsula; this scenario accommodates interpretations based on terrestrial and marine studies in this region. After an initial ice-sheet configuration is placed on the eastern Arctic terrain, basal sliding is allowed in specified regions. Basal sliding below sea level and between the Foxe Dome and Cumberland Sound and a reasonable but critical initial ice sheet volume and dome surface elevation are needed to obtain advance along and out of Cumberland Sound. Rapid flow into Hudson Strait and along Cumberland Sound causes drawdown and a change in ice-sheet configuration. Although more Foxe Dome ice flows into western Hudson Strait than Cumberland Sound in the simulations, the latter may still have been an important conduit connecting the interior of the northeastern Laurentide Ice Sheet to the Labrador Sea, thereby affecting regional ice sheet dynamics, specifically ice surface elevations and flow paths.
17
Pickler, C., H. Beltrami, and J. C. Mareschal. "Laurentide Ice Sheet basal temperatures during the last glacial cycle as inferred from borehole data." Climate of the Past 12, no. 1 (January 22, 2016): 115–27. http://dx.doi.org/10.5194/cp-12-115-2016.
Full textAbstract:
Abstract. Thirteen temperature–depth profiles ( ≥ 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region that was covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.
18
Roy, Gilles. "Une épidémie d’insectes, facteur de déboisement dans le Québec." Cahiers de géographie du Québec 2, no. 4 (April 12, 2005): 233–40. http://dx.doi.org/10.7202/020090ar.
Full textAbstract:
Spruce budworm bas invaded the forest of Québec since 1939, especially the pines of the coniferous area. There are jour major infested regions : three are located on the North shore of the St. Lawrence river : in the Gatineau river bassin, in the Laurentians between the Lachute Area and lake St. John, and in the North Shore region behind Baie Comeau Sept-Iles. The fourth region starts behind Rimouski and spreads eastward, covering the whole Gaspé peninsula. In this last the authorities are quite concerned about this plague, which is becoming a serious menace to the forest industries. Various air-spays have been used during the past jour years in order to circumscribe the dammages, and more than 4,000,000 acres have been treated with DDT, first step toward the rehabilitation of the forest.
19
Morin, Hubert, and Danielle Laprise. "Histoire récente des épidémies de la Tordeuse des bourgeons de l'épinette au nord du lac Saint-Jean (Québec): une analyse dendrochronologique." Canadian Journal of Forest Research 20, no. 1 (January 1, 1990): 1–8. http://dx.doi.org/10.1139/x90-001.
Full textAbstract:
The chronology of spruce budworm (Choristoneurafumiferana (Clem.)) oubreaks for the past 200 years has been reconstructed by dendrochronological analysis of balsam fir (Abiesbalsamea (L.) Mill.) and white spruce (Piceaglauca (Moench) Voss) samples from virgin forests, unaffected by insecticide spraying programs and recently protected against fires in the north and northwest of Lac Saint-Jean. Outbreaks began around 1974, 1944, 1909, and possibly, 1832. They are closely linked with those described in the Laurentide wildlife reserve. The frequency, duration and severity of growth rings suppression associated with outbreaks are similar to those registered during outbreaks in the southern forests, except for the 1974 outbreak, which was shorter and less severe. Other outbreaks registered in southern regions, where the proportion of balsam fir is higher, have reached this region where balsam fir populations are marginal. These results underline the importance of these ecological disturbances in the population dynamics of the host trees of the region.
20
Pickler, C., H. Beltrami, and J. C. Mareschal. "Laurentide Ice Sheet basal temperatures at the Last Glacial Cycle as inferred from borehole data." Climate of the Past Discussions 11, no. 4 (August 27, 2015): 3937–71. http://dx.doi.org/10.5194/cpd-11-3937-2015.
Full textAbstract:
Abstract. Thirteen temperature-depth profiles (&geq; 1500 m) measured in boreholes in eastern and central Canada were inverted to determine the ground surface temperature histories during and after the last glacial cycle. The sites are located in the southern part of the region covered by the Laurentide Ice Sheet. The inversions yield ground surface temperatures ranging from −1.4 to 3.0 °C throughout the last glacial cycle. These temperatures, near the pressure melting point of ice, allowed basal flow and fast flowing ice streams at the base of the Laurentide Ice Sheet. Despite such conditions, which have been inferred from geomorphological data, the ice sheet persisted throughout the last glacial cycle. Our results suggest some regional trends in basal temperatures with possible control by internal heat flow.
21
Duk-Rodkin, A., R. W. Barendregt, C. Tarnocai, and F. M. Phillips. "Late Tertiary to late Quaternary record in the Mackenzie Mountains, Northwest Territories, Canada: stratigraphy, paleosols, paleomagnetism, and chlorine - 36." Canadian Journal of Earth Sciences 33, no. 6 (June 1, 1996): 875–95. http://dx.doi.org/10.1139/e96-066.
Full textAbstract:
A stratigraphic sequence of unconsolidated sediments ranging in age from Late Pliocene to Late Pleistocene is recorded in the Canyon Ranges of the Mackenzie Mountains. Three of the sections (Katherine Creek, Little Bear River, and Inlin Brook) expose bedrock and Tertiary gravel overlain by colluvium and a multiple till sequence of montane origin, separated by paleosols and capped by a till of Laurentide origin. The sections are correlated on the basis of lithology, paleosol development, paleomagnetism, and chlorine dating of surface boulder erratics. A formal stratigraphic nomenclature is proposed for the deposits of this region. The sequence of glacial tills separated by paleosols reflects a long record of glacial–interglacial cycles. Soil properties from the oldest paleosol to modern soil show a general decrease in the degree of soil development, suggesting a progressive deterioration of interglacial climatic conditions. A normal–reverse–normal sequence of remanent magnetization was determined within the stratigraphic succession and assigned to the Gauss–Matuyama–Brunhes chrons, respectively. A Gauss age was assigned to the basal colluvium, an early Matuyama age (including Olduvai) to the first two tills, and a Brunhes age to the last three tills. Laurentide deposits are of Late Wisconsinan age and are restricted to the uppermost part of the stratigraphic succession. Chlorine dates for surface boulders place the all-time limit of the Laurentide Ice Sheet at about 30 ka. The Late Wisconsinan Laurentide Ice Sheet was the only continental ice to reach the Mackenzie and Richardson mountains of the northern Cordillera.
22
Bednarski, Jan M., and I. Rod Smith. "Laurentide and montane glaciation along the Rocky Mountain Foothills of northeastern British Columbia." Canadian Journal of Earth Sciences 44, no. 4 (April 1, 2007): 445–57. http://dx.doi.org/10.1139/e06-095.
Full textAbstract:
Mapping the surficial geology of the Trutch map area (NTS 94G) provides new data on the timing of continental and montane glaciations along the Foothills of northeastern British Columbia. Striated surfaces on mountain crests were dated to the Late Wisconsinan substage by cosmogenic dating. The striations were produced by eastward-flowing ice emanating from the region of the Continental Divide. This ice was thick enough to cross the main ranges and overtop the Rocky Mountain Foothill summits at 2000 m above sea level (asl). It is argued here that such a flow, unhindered by topography, could only have been produced by the Cordilleran Ice Sheet and not by local cirque glaciation. During this time, the Cordilleran Ice Sheet dispersed limestone and schist erratics of western provenance onto the plains beyond the mountain front. Conversely, the Laurentide Ice Sheet did not reach its western limit in the Foothills until after Cordilleran ice retreated from the area. During its maximum, the Laurentide ice penetrated the mountain valleys up to 17 km west of the mountain front, and deposited crystalline erratics from the Canadian Shield as high as 1588 m asl along the Foothills. In some valleys a smaller montane advance followed the retreat of the Laurentide Ice Sheet.
23
Liverman, David G. E., N. R. Catto, and N. W. Rutter. "Laurentide glaciation in west-central Alberta: a single (Late Wisconsinan) event." Canadian Journal of Earth Sciences 26, no. 2 (February 1, 1989): 266–74. http://dx.doi.org/10.1139/e89-022.
Full textAbstract:
The Grande Prairie region in west-central Alberta shows evidence of Late Wisconsinan Laurentide glaciation in the form of a widespread till, containing abundant erratic clasts derived from the Canadian Shield. Two sections, located on the Smoky River at Watino and on the Simonette River 80 km to the southwest, expose sediment lying stratigraphically below the till. A similar sequence is exposed in both localities: 5–10 m of coarse quartzite gravel overlain by a thick sequence of sand and silt. The gravel contains no Laurentide erratics and is thus preglacial. The contact between the basal gravel and the overlying sand and silt is sharp and conformable. 14C dates from the base of the Simonette section and throughout the Watino section suggest a Middle Wisconsinan age. Thus, the sediment exposed is interpreted as a conformable Middle Wisconsinan sequence. The sedimentary sequences were deposited in a moderate- to low-energy braided stream system flowing towards the north. The general fining-up trend in the sections was produced as a result of channel abandonment, rather than by a change in regional base level. The sand and gravel units contain no material derived from the Canadian Shield. Consequently, the surface till is Late Wisconsinan, and represents the only Laurentide glaciation in this area of Alberta.
24
Villeneuve, Normand, Miroslav M. Grandtner, and J. André Fortin. "The coenological organization of ectomycorrhizal macrofungi in the Laurentide Mountains of Quebec." Canadian Journal of Botany 69, no. 10 (October 1, 1991): 2215–24. http://dx.doi.org/10.1139/b91-278.
Full textAbstract:
Ectomycorrhizal macrofungus communities were classified across a sequence of four forest associations in the Laurentide Mountains. Cluster analysis was used to delimit two types of coenological units: grouping and sociological group. Three macrofungal groupings and two subgroupings, which vary with physiognomic and floristic–edaphic parameters of the forest sites, were delimited. Each of these grouping units is characterized by one of the six delimited sociological groups of fungi that are consecutively replaced following changes in latitude and altitude. When considering the similarity of species composition, Laurentide groupings appear to be isolated from other macrofungal assemblages in North American temperate forests and mainly affected by geographic partitioning of sites and by the physiognomy and type of forest vegetation within a given phytoclimatic region. As seen by the respective richness at the family level, Eurasian and Laurentide communities show similar patterns of zonal distribution, mainly owing to the role of climatic factors. A numerical analysis supported the hypothesis that the edaphic environment, as well as the vascular vegetation, might exert a significant influence on the delimitation and distribution of ectomycorrhizal communities. The interdependence of ectomycorrhizal communities and phytocoenoses at the ecosystem level is discussed. Key words: cluster analysis, community, ectomycorrhiza, macrofungus, macromycete, mycocoenology.
25
Swezey, Christopher S., Bradley A. Fitzwater, G. Richard Whittecar, Shannon A. Mahan, Christopher P. Garrity, Wilma B. Alemán Gonzalez, and Kerby M. Dobbs. "The Carolina Sandhills: Quaternary eolian sand sheets and dunes along the updip margin of the Atlantic Coastal Plain province, southeastern United States." Quaternary Research 86, no. 3 (November 2016): 271–86. http://dx.doi.org/10.1016/j.yqres.2016.08.007.
Full textAbstract:
AbstractThe Carolina Sandhills is a physiographic region of the Atlantic Coastal Plain province in the southeastern United States. In Chesterfield County (South Carolina), the surficial sand of this region is the Pinehurst Formation, which is interpreted as eolian sand derived from the underlying Cretaceous Middendorf Formation. This sand has yielded three clusters of optically stimulated luminescence ages: (1) 75 to 37 thousand years ago (ka), coincident with growth of the Laurentide Ice Sheet; (2) 28 to 18 ka, coincident with the last glacial maximum (LGM); and (3) 12 to 6 ka, mostly coincident with the Younger Dryas through final collapse of the Laurentide Ice Sheet. Relict dune morphologies are consistent with winds from the west or northwest, coincident with modern and inferred LGM January wind directions. Sand sheets are more common than dunes because of effects of coarse grain size (mean range: 0.35-0.59 mm) and vegetation. The coarse grain size would have required LGM wind velocities of at least 4-6 m/sec, accounting for effects of colder air temperatures on eolian sand transport. The eolian interpretation of the Carolina Sandhills is consistent with other evidence for eolian activity in the southeastern United States during the last glaciation.
26
Hofer, D., C. C. Raible, A. Dehnert, and J. Kuhlemann. "The impact of different glacial boundary conditions on atmospheric dynamics and precipitation in the North Atlantic region." Climate of the Past Discussions 8, no. 1 (January 4, 2012): 63–101. http://dx.doi.org/10.5194/cpd-8-63-2012.
Full textAbstract:
Abstract. Using a highly resolved atmospheric general circulation model the impact of different glacial boundary conditions on precipitation and atmospheric dynamics in the North Atlantic region is investigated. Seven 30-yr time slice experiments of the Last Glacial Maximum (21 ka ago) and of a less pronounced glacial state – the Middle Weichselian (65 ka ago) – are compared to analyse the sensitivity to changes in the ice sheet distribution, in the radiative forcing, and in the prescribed time-varying lower boundary conditions, which are taken from a lower-resolved but fully-coupled atmosphere-ocean general circulation model. The strongest differences are found for simulations with different heights of the Laurentide ice sheet. A large altitude of this ice sheet leads to a southward displacement of the jet stream and the storm track in the North Atlantic region. These changes in the atmospheric dynamics generate a band of increased precipitation in the mid-latitudes across the Atlantic to southern Europe in winter, while the precipitation pattern in summer is only marginally affected. The impact of the radiative forcing differences between the two glacial periods and of the prescribed time-varying lower boundary conditions – evaluated using two simulations of the Last Glacial Maximum with a global mean temperature difference of 1.1 °C – are of second order compared to the one of the Laurentide ice sheet. They affect the atmospheric dynamics and precipitation in a similar but less pronounced manner as the topographic changes.
27
Pronk, A. G., P. T. Bobrowsky, and M. A. Parkhill. "An Interpretation of Late Quaternary Glacial Flow Indicators in the Baie des Chaleurs Region, Northern New Brunswick." Géographie physique et Quaternaire 43, no. 2 (December 18, 2007): 179–90. http://dx.doi.org/10.7202/032768ar.
Full textAbstract:
ABSTRACT A sequence of late Quaternary geologic events in northern New Brunswick is determined from striation analysis derived from published data, open file reports, and field research conducted by the authors since 1985. These data are integrated with clast provenance and clast fabric trend analysis, as well as information from other studies in the surrounding area. South of the Baie des Chaleurs, a complicated Late Wisconsinan glacial history is preserved in the form of erosive features including nailhead striae, miniature crag-and-tails, and various scars, striations, and fractures. The rarity of sedimentary deposits and datable materials precludes simple stratigraphie interpretation. Based on over 1,000 striation sites, we conclude four major phases of glacial flow affected the area during the Late Wisconsinan: 1) an early flow to the southeast which reflects local Appalachian ice; 2) a second phase of glacial flow to the east indicating a Laurentide ice influence in western New Brunswick; 3) a third phase of glacial flow to the north-northeast, which may represent ice response to drawdown in the Baie des Chaleurs; and 4) a final multidirectional flow indicating localized ice response during the last stages of Late Wisconsinan glaciation. The absence of Canadian Shield erratics in northern New Brunswick is explained in terms of ice streaming along the St. Lawrence channel beneath a southward-flowing Laurentide Ice Sheet. Basal ice debris (including Shield erratics) was apparently truncated and removed by the obliquely flowing ice stream, leaving relatively clean ice in the Ice Sheet as it entered Gaspésie and ultimately New Brunswick.
28
Markewich, Helaine W., Ronald J. Litwin, Milan J. Pavich, and George A. Brook. "Late Pleistocene eolian features in southeastern Maryland and Chesapeake Bay region indicate strong WNW–NW winds accompanied growth of the Laurentide Ice Sheet." Quaternary Research 71, no. 3 (May 2009): 409–25. http://dx.doi.org/10.1016/j.yqres.2009.02.001.
Full textAbstract:
AbstractInactive parabolic dunes are present in southeastern Maryland, USA, along the east bank of the Potomac River. More elongate and finer-grained eolian deposits and paha-like ridges characterize the Potomac River–Patuxent River upland and the west side of Chesapeake Bay. These ridges are streamlined erosional features, veneered with eolian sediment and interspersed with dunes in the low-relief headwaters of Potomac- and Patuxent-river tributaries. Axis data for the dunes and ridges indicate formation by WNW–NW winds. Optically stimulated luminescence and radiocarbon age data suggest dune formation from ∼ 33–15 ka, agreeing with the 30–13 ka ages Denny, C.S., Owens, J.P., Sirkin, L., Rubin, M., 1979. The Parsonburg Sand in the central Delmarva Peninsula, Maryland and Delaware. U.S. Geol. Surv. Prof. Pap. 1067-B, 16 pp. suggested for eolian deposits east of Chesapeake Bay. Age range and paleowind direction(s) for eolian features in the Bay region approximate those for late Wisconsin loess in the North American midcontinent. Formation of midcontinent loess and Bay-region eolian features was coeval with rapid growth of the Laurentide Ice Sheet and strong cooling episodes (δ18O minima) evident in Greenland ice cores. Age and paleowind-direction coincidence, for eolian features in the midcontinent and Bay region, indicates strong mid-latitude WNW–NW winds for several hundred kilometers south of the Laurentide glacial terminus that were oblique to previously simulated anticyclonic winds for the last glacial maximum.
29
Liakka, Johan, and Marcus Lofverstrom. "Arctic warming induced by the Laurentide Ice Sheet topography." Climate of the Past 14, no. 6 (June 22, 2018): 887–900. http://dx.doi.org/10.5194/cp-14-887-2018.
Full textAbstract:
Abstract. It is well known that ice sheet–climate feedbacks are essential for realistically simulating the spatiotemporal evolution of continental ice sheets over glacial–interglacial cycles. However, many of these feedbacks are dependent on the ice sheet thickness, which is poorly constrained by proxy data records. For example, height estimates of the Laurentide Ice Sheet (LIS) topography at the Last Glacial Maximum (LGM; ∼ 21 000 years ago) vary by more than 1 km among different ice sheet reconstructions. In order to better constrain the LIS elevation it is therefore important to understand how the mean climate is influenced by elevation discrepancies of this magnitude. Here we use an atmospheric circulation model coupled to a slab-ocean model to analyze the LGM surface temperature response to a broad range of LIS elevations (from 0 to over 4 km). We find that raising the LIS topography induces a widespread surface warming in the Arctic region, amounting to approximately 1.5 ∘C per km of elevation increase, or about 6.5 ∘C for the highest LIS. The warming is attributed to an increased poleward energy flux by atmospheric stationary waves, amplified by surface albedo and water vapor feedbacks, which account for about two-thirds of the total temperature response. These results suggest a strong feedback between continental-scale ice sheets and the Arctic temperatures that may help constrain LIS elevation estimates for the LGM and explain differences in ice distribution between the LGM and earlier glacial periods.
30
Koo, Hyo-Jin, Young-Keun Jin, and Hyen-Goo Cho. "Change in Sediment Provenance on the Inner Slope of the Chukchi Rise and Their Paleoenvironmental Implications." Applied Sciences 11, no. 14 (July 14, 2021): 6491. http://dx.doi.org/10.3390/app11146491.
Full textAbstract:
The Arctic Ocean is one of the world’s most remarkable regions with respect to global climate change. The core ARA09C-St03 was analyzed for mineral composition and Nd isotope to determine the sediment provenance and reconstruct the paleoenvironment in the inner slope of the Chukchi Rise. Core ARA09C-St03 represents overall cycles of brown and gray color with three distinct dark brown layers and two pinkish-white layers and is divided into eight sedimentary units based on the lithological feature. The core has a continuous record of the late marine isotope stage (MIS) 5 to the Holocene and in particular provides a particularly high-resolution record from the Last Glacial Maximum (LGM). Sediment is derived mainly from the adjacent East Siberian Sea and the North American region, and changes in sediment provenance are controlled by climate-dependent particle size. During the glacial/stadial periods, sediments in Units 3, 5, and 8 were supplied by the East Siberian Sea via meltwater-derived suspension. The major ice-rafted debris (IRD) events in Units 2, 4, and 7, characterized by abundant dolomite and K/C ratio, were sourced from North America. The North America-derived materials reflect the initiation and disintegration of the Laurentide Ice Sheet and icebergs transported them across the open Arctic Ocean. The differences in provenance within these periods may be related to the scale of the Laurentide Ice Sheet. Interglacial sediments, including those from Units 1 and 6, are of mixed origin from Eurasia and the Canadian Archipelago and may have been transported by oceanic current and seasonal sea ice. These periods are likely associated with the negative Arctic Oscillation (AO) intensifying the Beaufort Gyre.
31
Clark, Peter U. "Unstable Behavior of the Laurentide Ice Sheet over Deforming Sediment and Its Implications for Climate Change." Quaternary Research 41, no. 1 (January 1994): 19–25. http://dx.doi.org/10.1006/qres.1994.1002.
Full textAbstract:
AbstractGeologic records of fluctuations of the Laurentide ice sheet margin following the most recent glacial maximum (ca. 20,000 14C yr B.P.) identify fundamental differences in ice-sheet behavior depending on subglacial bed conditions. Rapid and irregular icemargin fluctuations occurred only over areas of deforming sediment, indicating nonclimatic forcing controlled by the inherent instability of coupled ice sheet-deforming sediment dynamics. In contrast, largely uninterrupted ice-margin retreat with no evidence of significant readvance occurred over rigid-bed areas, indicating stable behavior. Unstable ice-sheet behavior was most pronounced from 15,000 until 10,000 14C yr B.P., by which time most of the ice margin had retreated onto a rigid bed. Unstable ice-sheet behavior would have been an integral component in controlling variable fluxes of icebergs and meltwater, as well as meltwater routing, to the North Atlantic, thus affecting thermohaline circulation. The abrupt climate oscillations in the North Atlantic region that ended at 10,000 14C yr B.P. may thus have their origin in the inherently unstable behavior of the Laurentide ice sheet overriding deforming sediment.
32
Young, R. R., J. A. Burns, R. B. Rains, and D. B. Schowalter. "Late Pleistocene glacial geomorphology and environment of the Hand Hills region and southern Alberta, related to Middle Wisconsin fossil prairie dog sites." Canadian Journal of Earth Sciences 36, no. 9 (September 1, 1999): 1567–81. http://dx.doi.org/10.1139/e99-044.
Full textAbstract:
Ichnofossils (burrow casts) and fossils from an extinct form of prairie dog, Cynomys niobrarius churcherii, in the Hand Hills of south-central Alberta, have provided an important Late Pleistocene stratigraphic marker. The marker fossils provide relative and chronostratigraphic (radiocarbon) ages for nonglacial, periglacial, glacial, and glaciotectonic events and environments in the region. The high-elevation, hilltop position of the fossil sites (~200 m above the surrounding plains) permits reliable extrapolations of glacial environments to the surrounding region. The burrow casts were preserved by infilling from surrounding and overlying sediments through processes of inwashing and animal activity. Three thousand bones, primarily of the extinct prairie dog Cynomys niobrarius churcherii, were recovered from one site, and several hundred more from other locations. Accelerator radiocarbon dates (AMS) on bone collagen show that the prairie dogs lived in the area from at least 33 000 BP to around 22 000 BP. Prairie dog burrow casts crosscut well-developed periglacial structures and stratigraphically underlie all glacial sediments, indicating that harsh periglacial environments preceded their colonization and that the region was later submerged by Laurentide ice. Deformed sediments, 0.5 to 1.5 m thick, were found throughout the upland. The products of deformation overlie, truncate, and (or) incorporate burrow casts, indicating that only limited erosion and glacial deformation occurred during glaciation. Reconstructed ice sheet profiles show a northwest-southeast flow that could only have been achieved by coalescent Laurentide and Cordilleran ice sheets. This demonstrates that a theoretical "ice-free corridor" that some think persisted between the ice sheets during the Late Wisconsin "maximum," did not exist.
33
Dyke, Arthur S., Lynda A. Dredge, and Jean-Serge Vincent. "Configuration and Dynamics of the Laurentide Ice Sheet During the Late Wisconsin Maximum." Géographie physique et Quaternaire 36, no. 1-2 (November 29, 2007): 5–14. http://dx.doi.org/10.7202/032467ar.
Full textAbstract:
ABSTRACT Prior to 1943 the Laurentide Ice Sheet was considered to have three major domes centered in Keewatin, Labrador, and Patricia (TYRRELL, 1898 a, b; 1913). FLINT (1943) argued that these centres were of only local and temporary importance and favoured a single-domed ice sheet. Despite the lack of supporting geological evidence, and despite the proposition of a Foxe Dome in the interim (IVES and ANDREWS, 1963), the single-dome concept was not seriously challenged until the late 1970's and, in fact, is still strenuously supported (HUGHES era/., 1977 ; DENTON and HUGHES, 1981). This paper extends and modifies recent conclusions that the Laurentide Ice Sheet had more than one dome at the Late Wisconsin maximum. We propose a model incorporating five domes (M'Clintock, Foxe, Labrador, Hudson, and (?) Caribou) based on the position of ice divides, ice flow patterns, drift composition, late-glacial features, postglacial isostatic recovery and free-air gravity anomalies. Our Labrador and Hudson domes closely correspond to Tyrrell's Labradorean and Patrician ice sheets; our Caribou and M'Clintock domes together with the Franklin Ice Complex over the Queen Elizabeth Islands north of the Laurentide Ice Sheet, correspond to Tyrrell's original Keewatin Ice Sheet. The style of glaciation of the Foxe Basin region was not known to Tyrrell, but our reconstruction of the Foxe Dome is in close agreement with the original proposal of Ives and Andrews. Like Tyrrell, our reconstruction is based on field evidence obtained through extensive mapping; the single dome model continues to be unsupported by geological data.
34
Dredge, Lynda A., and L. Harvey Thorleifson. "The Middle Wisconsinan History of the Laurentide Ice Sheet." Géographie physique et Quaternaire 41, no. 2 (January 15, 2008): 215–35. http://dx.doi.org/10.7202/032680ar.
Full textAbstract:
ABSTRACT Evidence for Middle Wisconsinan ice limits and climates comes from sites scattered around the periphery of the Laurentide Ice domain and from the Hudson Bay Lowlands. Interpretations are based on dated wood, peat, shell and sediment; biological climate indicators (chiefly cool-climate indicators); and stratigraphie sequences of both glacial and nonglacial units. The best evidence comes from the prairie provinces and the Great Lakes areas, both of which indicate substantial ice retreat from earlier southern glacial limits, and cool, boreal-tundra climates. The western arctic may have experienced an early warm period but both the western arctic — northwestern plains and eastern maritime areas may later have become ice accumulation areas. Three maps portray various possible ice limits. The first shows substantial ice cover in the arctic, but reduced ice cover in the prairies and Great Lakes, and expanded maritime ice caps (rather than Laurentide Ice) in the southeast and on Baffin Island. This ice mass distribution may reflect Middle Wisconsinan shifts in air masses and ocean currents. Ice volumes generated by this model are in accord with the marine oxygen isotope record and perceived global sea level changes. A modification to this model, which resolves some of the controversy in the Hudson Bay Lowlands, shows a calving bay penetrating into the heart of the ice sheet, induced by dynamic instability of the marine-based ice mass in Hudson Bay during relatively high glacial isostatic and eustatic seas. A third reconstruction portrays extensive climatically induced déglaciation and retains Laurentide ice only in parts of the northwest and Labrador-Ungava, with local ice in the Appalachian-Atlantic region. This model is based on alternative genetic interpretations of lithologic units and reassessment of age assignments.
35
Castillo, Pablo, Ebrahim Pourjam, Juan E. Palomares-Rius, Mohammad Reza Atighi, Carolina Cantalapiedra-Navarrete, and Majid Pedram. "Molecular and morphological characterisations of two new species of Rotylenchus (Nematoda: Hoplolaimidae) from Iran." Nematology 13, no. 8 (2011): 951–64. http://dx.doi.org/10.1163/138855411x571795.
Full textAbstract:
AbstractTwo new amphimictic species, Rotylenchus iranicus n. sp. and R. conicaudatus n. sp., are described. Rotylenchus iranicus n. sp. is characterised mainly by an offset hemispherical lip region with 5-6, rarely 7, annuli, stylet 39-44 μm long, vulva located at 53-65% and rounded tail with 4-9 annuli and typical smooth tip. Morphologically this species is related to R. montanus, R. provincialis and R. aqualamus. Rotylenchus conicaudatus n. sp. is characterised mainly by a slightly offset conoid-rounded lip region with four or five, rarely six annuli, stylet 27-32 μm long, vulva located at 52-63% and conoid-rounded tail with 10-16 annuli and a typical annulated tip. Morphologically this species is related to R. pumilus, R. abnormecaudatus, R. acuspicaudatus and R. provincialis. The results of the phylogenetic analysis based on sequences of the D2-D3 expansion regions of 28S and ITS1-rRNA genes confirmed the species differentiation. Phylogenetic relationships with other species were difficult to assign using D2-D3 expansion regions of 28S. However, using ITS1-rRNA, R. conicaudatus n. sp. presented a close relationship with R. unisexus, whilst R. iranicus n. sp. was closely related to R. conicaudatus n. sp., R. unisexus, R. incultus and R. laurentinus.
36
Andriashek, Laurence D., and René W. Barendregt. "Evidence for Early Pleistocene glaciation from borecore stratigraphy in north-central Alberta, Canada." Canadian Journal of Earth Sciences 54, no. 4 (April 2017): 445–60. http://dx.doi.org/10.1139/cjes-2016-0175.
Full textAbstract:
Pleistocene sediments collected in north-central Alberta, Canada, were subsampled and studied for paleomagnetic remanence characteristics. A magnetostratigraphy has been established for sediments previously assumed to represent multiple continental (Laurentide) glaciations but for which no geochronology was available. Based on the Quaternary record elsewhere in Alberta and Saskatchewan, it was thought that some of these sediments were deposited during pre-late Wisconsinan glaciations. The Quaternary sedimentary successions of north-central Alberta have a thickness up to 300 m within buried valleys and are composed of diamicts interbedded with glaciolacustrine and outwash sediments. Most of the sampled units are not accessible from outcrop, and their sedimentology and stratigraphy is derived from core data only. In 4 of 16 borecores sampled to date, diamict that correlates with the Bronson Lake Formation till is reversely magnetized, indicating an Early Pleistocene age. This formation is underlain by either Empress Formation sediments or Colorado Group shale, and is overlain by one or more normally magnetized glacigenic sedimentary units of the Bonnyville, Marie Creek, and Grand Centre formations, respectively. This new record of Early Pleistocene glaciation in north-central Alberta places the westernmost extent of earliest Laurentide ice at least 300 km farther west than its previously established limit in the Saskatoon and Regina regions of the Canadian Interior Plains, but still to the east of the maximum extent of the Late Wisconsinan (Late Pleistocene) Laurentide Ice Sheet, which extended into the foothills of the Alberta and Montana Rocky Mountains.
37
Biström, Olof. "Uvarus laurentius sp. n. and Africodytes maximus sp. n. and new faunistic records of other Bidessini (Coleoptera, Dytiscidae) from the Ethiopian region." Entomologica Fennica 6, no. 1 (January 1, 1995): 43–46. http://dx.doi.org/10.33338/ef.83836.
Full textAbstract:
Two new Bidessini species from the Ethiopian region are described, viz. Uvarus laurentius sp. n. from Madagascar and Africodytes maximus sp. n. from Cameroon. The following new faunistic records are given: Uvarus nubilus (Régimbart) and Bidessus complicatus Sharp, recorded for the first time from Senegal; and Yola cuspis Bilardo & Pederzani and Africodytes rubromaculatus Biström recorded for the first time from Liberia.
38
Löfverström, Marcus, Johan Liakka, and Johan Kleman. "The North American Cordillera—An Impediment to Growing the Continent-Wide Laurentide Ice Sheet." Journal of Climate 28, no. 23 (December 1, 2015): 9433–50. http://dx.doi.org/10.1175/jcli-d-15-0044.1.
Full textAbstract:
Abstract This study examines the evolution of a continental-scale ice sheet on a triangular representation of North America, with and without the influence of the Cordilleran region. Simulations are conducted using a comprehensive atmospheric general circulation model asynchronously coupled to a three-dimensional thermomechanical ice-sheet model. The atmospheric state is updated for every 2 × 106 km3 increase in ice volume, and the coupled model is integrated to steady state. In the first experiment a flat continent with no background topography is used. The ice sheet evolves fairly zonally symmetric, and the equilibrium state is continent-wide and has the highest point in the center of the continent. This equilibrium ice sheet forces an anticyclonic circulation that results in relatively warmer (cooler) summer surface temperatures in the northwest (southeast), owing to warm (cold) air advection and radiative heating due to reduced cloudiness. The second experiment includes a simplified representation of the Cordilleran region. The ice sheet’s equilibrium state is here structurally different from the flat continent case; the center of mass is strongly shifted to the east and the interior of the continent remains ice free—an outline broadly resembling the geologically determined ice margin in Marine Isotope Stage 4. The limited glaciation in the continental interior is the result of warm summer surface temperatures primarily due to stationary waves and radiative feedbacks.
39
Braun, Alexander, Chung-Yen Kuo, C. K. Shum, Patrick Wu, Wouter van der Wal, and Georgia Fotopoulos. "Glacial isostatic adjustment at the Laurentide ice sheet margin: Models and observations in the Great Lakes region." Journal of Geodynamics 46, no. 3-5 (October 2008): 165–73. http://dx.doi.org/10.1016/j.jog.2008.03.005.
Full text
40
Lowell, Thomas V., Dale A. Becker, and Parker E. Calkin. "Quaternary Stratigraphy in Northwestern Maine: A Progress Report." Géographie physique et Quaternaire 40, no. 1 (December 4, 2007): 71–84. http://dx.doi.org/10.7202/032624ar.
Full textAbstract:
ABSTRACT A preliminary Quaternary stratigraphy for northwestern Maine can be assembled from interpretation of ice-flow indicators (dispersal and erosional), exposed sections, and drill-hole logs. Evidence from the ice-flow indicators delineates at least four regions each with different ice-flow histories. The distribution of these regions may result from an eastward invasion of Laurentide source ice during the early portion of the late Wisconsinan and subsequent development of a local ice dome during the closing portion of the Late Wisconsinan substage. Exposed sections contribute the following probable sequence of events to the stratigraphy: 1) deposition of alluvial fans, 2) deposition of a gray compact till beneath eastward flowing (Laurentide) ice, 3) deposition of a brown till beneath northward flowing local ice, 4) deglaciation by a southward retreating ice margin. These events appear continuous and have all been provisionally assigned a Late Wisconsinan age. Drill-hole logs confirm the sequence derived from the exposed sections and allow extension of the Quaternary stratigraphy. The drill-log data show three associated groups of sediments that may in turn result from at least three separate ice margin advances and recessions. The uppermost group of sediments is correlated with those found in exposed sections. The position of the drill-hole logs in an over-deepened basin suggest erosion by at least one even earlier glaciation.
41
Dredge, L. A. "Drift carbonate on the Canadian Shield. II: Carbonate dispersal and ice-flow patterns in northern Manitoba." Canadian Journal of Earth Sciences 25, no. 5 (May 1, 1988): 783–87. http://dx.doi.org/10.1139/e88-073.
Full textAbstract:
In northern Manitoba, carbonates were glacially dispersed westwards for distances up to 260 km beyond the limit of carbonate bedrock. The dispersal pattern in the surface till reflects the interaction of Keewatin and Hudson – Labrador ice in the region during the Wisconsin glaciation and suggests the presence of ice streams within the Laurentide Ice Sheet. Pre-Wisconsinan tills show different dispersal and ice-flow patterns. In unfrozen terrain, carbonate till sheets on the Shield buffer the effects of natural lake acidification and acid rain; however, their ability to buffer appears to be severely limited in permafrost terrain.
42
Kaplan, Michael R., and Alexander P. Wolfe. "Spatial and temporal variability of Holocene temperature in the North Atlantic region." Quaternary Research 65, no. 02 (January 30, 2006): 223–31. http://dx.doi.org/10.1016/j.yqres.2005.08.020.
Full textAbstract:
AbstractThe early Holocene climate of the North Atlantic region was influenced by two boundary conditions that were fundamentally different from the present: the presence of the decaying Laurentide Ice Sheet (LIS) and higher than present summer solar insolation. In order to assess spatial and temporal patterns of Holocene climate evolution across this region, we collated quantitative paleotemperature records at sub-millennial resolution and synthesized their temporal variability using principal components analysis (PCA). The analysis reveals considerable spatial variability, most notably in the time-transgressive expression of the Holocene thermal maximum (HTM). Most of the region, but especially areas peripheral to the Labrador Sea and hence closest to the locus of LIS disintegration, experienced maximum Holocene temperatures that lagged peak summer insolation by 1000–3000 years. Many sites from the northeastern North Atlantic sector, including the Nordic Seas and Scandinavia, either warmed in phase with maximum summer insolation (11,000–9000 years ago) or were less strongly lagged than the Baffin Bay–Labrador Sea region. These spatially complex patterns of Holocene climate development, which are defined by the PCA, resulted from the interplay between final decay of the LIS and solar insolation forcing.
43
Schannwell, Clemens, Uwe Mikolajewicz, Florian Ziemen, and Marie-Luise Kapsch. "Sensitivity of Heinrich-type ice-sheet surge characteristics to boundary forcing perturbations." Climate of the Past 19, no. 1 (January 23, 2023): 179–98. http://dx.doi.org/10.5194/cp-19-179-2023.
Full textAbstract:
Abstract. Heinrich-type ice-sheet surges are one of the prominent signals of glacial climate variability. They are characterised as abrupt, quasi-periodic episodes of ice-sheet instabilities during which large numbers of icebergs are released from the Laurentide ice sheet. The mechanisms controlling the timing and occurrence of Heinrich-type ice-sheet surges remain poorly constrained to this day. Here, we use a coupled ice sheet–solid Earth model to identify and quantify the importance of boundary forcing for the surge cycle length of Heinrich-type ice-sheet surges for two prominent ice streams of the Laurentide ice sheet – the land-terminating Mackenzie ice stream and the marine-terminating Hudson ice stream. Both ice streams show responses of similar magnitude to surface mass balance and geothermal heat flux perturbations, but Mackenzie ice stream is more sensitive to ice surface temperature perturbations, a fact likely caused by the warmer climate in this region. Ocean and sea-level forcing as well as different frequencies of the same forcing have a negligible effect on the surge cycle length. The simulations also highlight the fact that only a certain parameter space exists under which ice-sheet oscillations can be maintained. Transitioning from an oscillatory state to a persistent ice streaming state can result in an ice volume loss of up to 30 % for the respective ice stream drainage basin under otherwise constant climate conditions. We show that Mackenzie ice stream is susceptible to undergoing such a transition in response to all tested positive climate perturbations. This underlines the potential of the Mackenzie region to have contributed to prominent abrupt climate change events of the last deglaciation.
44
Grant, D. R. "Glacial style and ice limits, the Quaternary stratigraphic record, and changes of land and ocean level in the Atlantic Provinces, Canada." Dynamique et paléogéographie de l’inlandsis laurentidien 31, no. 3-4 (January 17, 2011): 247–60. http://dx.doi.org/10.7202/1000276ar.
Full textAbstract:
Evidence from scattered stratigraphie sections, from the relationship of a sequence of ice flow indicators to a raised interglacial marine platform, together with the limits of freshly glaciated terrain against weathered bedrock areas, indicates that late Wisconsinan glaciers spread weakly toward, and in many areas not beyond, the present coast. These were fed by a complex of small ice caps located on broad lowlands and uplands. The limiting factor was the deep submarine channels that transect the region. Thus, Laurentide ice was limited to northern Gulf of St. Lawrence. With this pattern of centripetal flow toward the Gulf, large areas remained unglacierized. There is now better geological corroboration of Fer-nald's hypothesis of nunatak botanic réfugia, though there was, perhaps during early Wisconsinan time, grounded ice in the Gulf and an outlet glacier in Laurentian Channel. Raised postglacial shorelines fit the model, with a general tilt toward the main shield ice sheet, but with two broad domes reflecting the ice complexes over New Brunswick and Newfoundland. Older emerged and submerged shorelines beyond the glacial limit complicate the pattern. At present northern regions are still rebounding while a zone of subsidence is migrating inland from the continental margin.
45
Gauthier, Michelle S., Tyler J. Hodder, Martin Ross, Samuel E. Kelley, Andrew Rochester, and Phil McCausland. "The subglacial mosaic of the Laurentide Ice Sheet; a study of the interior region of southwestern Hudson Bay." Quaternary Science Reviews 214 (June 2019): 1–27. http://dx.doi.org/10.1016/j.quascirev.2019.04.015.
Full text
46
CATTO, N., D. LIVERMAN, P. BOBROWSKY, and N. RUTTER. "Laurentide, cordilleran, and montane glaciation in the western Peace River ? Grande Prairie region, Alberta and British Columbia, Canada." Quaternary International 32 (1996): 21–32. http://dx.doi.org/10.1016/s1040-6182(96)90012-9.
Full text
47
Catto, Norm, David G. E. Liverman, Peter T. Bobrowsky, and Nat Rutter. "Laurentide, cordilleran, and montane glaciation in the western Peace River — Grande Prairie region, Alberta and British Columbia, Canada." Quaternary International 32 (January 1996): 21–32. http://dx.doi.org/10.1016/1040-6182(95)00061-5.
Full text
48
Cummings, Don, and Serge Occhietti. "Late Wisconsinan Sedimentation in the Québec City Region: Evidence for Energetic Subaqueous Fan Deposition During Initial Deglaciation." Géographie physique et Quaternaire 55, no. 3 (October 15, 2003): 257–73. http://dx.doi.org/10.7202/006854ar.
Full textAbstract:
Abstract In the St. Lawrence Valley just west of Québec City, initial deglaciation was accompanied by an energetic northward discharge of meltwater into a body of water, possibly subglacial, that was present in the axis of the valley. At Pointe Saint-Nicolas, a thick (> 35 m) ice-proximal sandy subaqueous fan was deposited during this event. The subaqueous fan is composed primarily of northwest-dipping turbidite sheets, with minor hyperconcentrated underflow channel fills and gravel-outwash deposits. By 11 200 14C BP, subaqueous fan sedimentation had stopped, and massive to rhythmically interbedded glaciomarine muds were being deposited. Introduction of muds into the basin promoted subaqueous slope failure and debris flowing locally. Between 10 950 and 10 800 14C BP, the Laurentide Ice Sheet readvanced southward onto the south shore, and deposited the subglacial St. Nicolas Till. With continued isostatic rebound and associated forced regression, tidal currents began to rework emergent coastal zones, and fluvial systems started to incise their valleys.
49
Murton, Julian B., Manfred Frechen, and Darrel Maddy. "Luminescence dating of mid- to Late Wisconsinan aeolian sand as a constraint on the last advance of the Laurentide Ice Sheet across the Tuktoyaktuk Coastlands, western Arctic Canada." Canadian Journal of Earth Sciences 44, no. 6 (June 29, 2007): 857–69. http://dx.doi.org/10.1139/e07-015.
Full textAbstract:
Luminescence dating of pre-glacial sand in the Tuktoyaktuk Coastlands, Northwest Territories, discounts an Early Wisconsinan age for the last Laurentide glaciation to cross the Arctic Coastal Plain and supports a Late Wisconsinan age. Aeolian dune sand from the Kittigazuit Formation near Cliff Point, on the southern shore of Liverpool Bay, predates till deposited during the Toker Point Stade. Potassium-rich feldspar from three stratigraphic sections ~35 km up-ice from the Toker Point glacial limit provides thermoluminescence age estimates that range from 18.7 ± 2.0 to 9.1 ± 1.0 ka and infrared stimulated luminescence age estimates of 23.8 ± 5.1 to 11.0 ± 2.1 ka. Quartz from four of the same samples provides optically stimulated luminescence age estimates of 16.5 ± 1.0 to 13.7 ± 0.9 ka. Collectively, these estimates reject the Early Wisconsinan age for the Toker Point Stade glaciation inferred hitherto from radiocarbon dating. A review of pre-glacial and post-glacial age estimates from the region indicates that during the Toker Point Stade ice advanced across the Tuktoyaktuk Coastlands no earlier than ~30 ka, and probably not before ~22 ka. Deglaciation had certainly commenced by 14.3 ka, and probably by ~16 ka. The Toker Point glaciation, therefore, dates approximately to the last glacial maximum, reinforcing the interpretation of the late rebuild up of the Laurentide Ice Sheet that characterized many parts of its margin.
50
Trommelen, Michelle, and Vic Levson. "Quaternary stratigraphy of the Prophet River, northeastern British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers." Canadian Journal of Earth Sciences 45, no. 5 (May 2008): 565–75. http://dx.doi.org/10.1139/e07-072.
Full textAbstract:
Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.