Geological map of Canada

Wheeler, J O; Hoffman, PF; Card, K D; Davidson, Andrew; Sanford, B V; Okulitch, A V; Roest, W. R.

doi:10.4095/208175

Cited by 141 publications

(84 citation statements)

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“…Esker formation has been linked to variations in sediment supply (Aylsworth and Shilts, 1989) and substrate lithological controls (Clark and Walder, 1994), but we rule these out due to the relatively uniform lithology of the study area (Wheeler et al, 1996). It has also been shown that esker sediments are derived primarily from the local substrate (Bolduc, 1992), with no obvious variation in lithology in this region that might explain the observed increase in eskers during deglaciation and their absence beneath ice divides (Figs.…”

Section: Discussionmentioning

confidence: 96%

Increased channelization of subglacial drainage during deglaciation of the Laurentide Ice Sheet

Storrar

Stokes

Evans

2014

Geology

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The confi guration of subglacial meltwater is a critical control on ice sheet dynamics, and the presence of pressurized water distributed across the bed can induce dynamic instabilities. However, this process can be offset by effi cient evacuation of water within large subglacial channels, and drainage systems beneath alpine glaciers have been shown to become increasingly channelized throughout the melt season in response to the increased production of meltwater. This seasonal evolution has recently been inferred beneath outlet glaciers of the Greenland Ice Sheet, but the extent to which this process occurs across much larger spatial and temporal scales is largely unknown, introducing considerable uncertainty about the evolution of subglacial drainage networks at the ice sheet scale and associated ice sheet dynamics. This paper uses an unprecedented data set of over 20,000 eskers to reconstruct the evolution of channelized meltwater systems during the fi nal deglaciation of the Laurentide Ice Sheet (13-7 kyr B.P.). We demonstrate that eskers become more frequent during deglaciation and that this coincides with periods of increased rates of ice margin recession and climatic warming. Such behavior is reminiscent of the seasonal evolution of drainage systems observed in smaller glaciers and implies that channelized drainage became increasingly important during deglaciation. An important corollary is that the area of the bed subjected to a less effi cient pressurized drainage system decreased, which may have precluded dynamic instabilities, such as surging or ice streaming.

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Section: Discussionmentioning

confidence: 96%

Increased channelization of subglacial drainage during deglaciation of the Laurentide Ice Sheet

Storrar

Stokes

Evans

2014

Geology

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“…Rates are expressed in terms of total P (Supplement B 1 ). Background colours indicate surficial geology (Wheeler et al 1996). Inset maps provide more detail for areas indicated by the red boxes.…”

Section: Trophic Statusmentioning

confidence: 99%

“…For large lakes (namely Lakes Simcoe, Erie, Huron, and Ontario), bays were considered a separate location if they were distinct from the main basin. We also specified the surficial geology of each location (in the database table "GEOL"; Table A4) obtained from Natural Resources Canada's GeoGratis repository (Wheeler et al 1996). Second, we identified specific sites (each with a unique SITE_ID) within each lake, reservoir, or wetland.…”

Section: Literature Searchmentioning

confidence: 99%

Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis

Orihel

Baulch

Casson

et al. 2017

Can. J. Fish. Aquat. Sci.

193

133

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Many physical, chemical, and biological processes in freshwater ecosystems mobilize the nutrient phosphorus (P) from sediments, which in turn may contribute to the formation of harmful algal blooms. Here, we critically reviewed internal P loading in Canadian fresh waters to understand the geographic patterns and environmental drivers of this important process. From 43 publications, we consolidated 618 estimates of internal P loading from Canadian freshwater ponds, lakes, reservoirs, and coastal wetlands (n = 70). Expressed in terms of total P, short-term gross rates in sediment samples (L gross ) ranged from −27 to 54 mg·m −2 ·day −1 (n = 461), while long-term net rates in whole ecosystems (L net ) ranged from −1694 to 10 640 mg·m −2 ·year −1 (n = 157). The main environmental drivers of this variation were oxygen, pH, geology, and trophic state. Internal P loading tended to be higher during the open-water season and most prominent in small prairie lakes. Priorities for future research on internal P loading should include resolving methodological problems, assessing the relative importance of different mechanisms, examining the influence of anthropogenic activities, and quantifying rates in understudied ecosystems. Résumé :De nombreux processus physiques, chimiques et biologiques dans les écosystèmes d'eau douce mobilisent le phosphore (P), un élément nutritif, des sédiments, ce qui peut favoriser la formation de fleurs d'eau néfastes. Nous avons effectué un examen critique de l'apport interne de P dans les plans d'eau douce canadiens afin de comprendre les motifs de répartition géographique et les facteurs environnementaux qui influent sur cet important processus. À la lumière de 43 publications, nous avons colligé 618 estimations de l'apport interne de P d'étangs, de lacs, de réservoirs et de milieux humides littoraux d'eau douce canadiens (n = 70). Exprimés en termes de P total, les taux d'apport de P à court terme pour les échantillons de sédiments (L gross ) vont de −27 à 54 mg·m -2 ·jour -1 (n = 461), alors que les taux nets à long terme à l'échelle de l'écosystème (L net ) vont de −1694 à 10 640 mg·m -2 ·an -1 (n = 157). Les principaux facteurs environnementaux influant sur ces variations sont l'oxygène, le pH, la géologie et l'état trophique. L'apport interne de P tend à être plus élevé durant la période d'eau libre et le plus marqué dans les petits lacs de prairie. La priorité des travaux futurs sur l'apport interne de P devrait porter sur la résolution de problèmes méthodologiques, l'évaluation de l'importance relative de différents mécanismes, l'examen de l'influence des activités humaines et la quantification des taux dans les écosystèmes sous-étudiés. [Traduit par la Rédaction]

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“…Since digital bedrock maps are available at reasonably high resolution (1:5,000,000) for this basin (Wheeler et al, 1997), the true average bedrock age of the Fraser basin is well constrained at 260 ± 39 Ma . Using only the eight modeled tributaries in Eq.…”

Section: Fraser River Dissolved Fluxes In Global Contextmentioning

confidence: 99%

Spatial and temporal dynamics of biogeochemical processes in the Fraser River, Canada : a coupled organic-inorganic perspective

Voß¹

2014

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The great geologic and climatic diversity of the Fraser River basin in southwestern Canada render it an excellent location for understanding biogeochemical cycling of sediments and terrigenous organic carbon in a relatively pristine, large, temperate watershed. Sediments delivered by all tributaries have the potential to reach the ocean due to a lack of main stem lakes or impoundments, a unique feature for a river of its size. This study documents the concentrations of a suite of dissolved and particulate organic and inorganic constituents, which elucidate spatial and temporal variations in chemical weathering (including carbonate weathering in certain areas) as well as organic carbon mobilization, export, and biogeochemical transformation. Radiogenic strontium isotopes are employed as a tracer of sediment provenance based on the wide variation in bedrock age and lithology in the Fraser basin. The influence of sediments derived from the headwaters is detectable at the river mouth, however more downstream sediment sources predominate, particularly during high discharge conditions. Bulk radiocarbon analyses are used to quantify terrestrial storage timescales of organic carbon and distinguish between petrogenic and biospheric organic carbon, which is critical to assessing the role of rivers in long-term atmospheric CO 2 consumption. The estimated terrestrial residence time of biospheric organic carbon in the Fraser basin is 650 years, which is relatively short compared to other larger rivers (Amazon, Ganges-Brahmaputra) in which this assessment has been performed, and is likely related to the limited floodplain storage capacity and non-steadystate post-glacial erosion state of the Fraser River. A large portion of the dissolved inorganic carbon load of the Fraser River (>80%) is estimated to derive from remineralization of dissolved organic carbon, particularly during the annual spring freshet when organic carbon concentrations increase rapidly. This thesis establishes a baseline for carbon cycling in a largely unperturbed modern mid-latitude river system and establishes a framework for future process studies on the mechanisms of organic carbon turnover and organic matter-mineral associations in river systems.

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Geological map of Canada

Cited by 141 publications

References 0 publications

Increased channelization of subglacial drainage during deglaciation of the Laurentide Ice Sheet

Increased channelization of subglacial drainage during deglaciation of the Laurentide Ice Sheet

Internal phosphorus loading in Canadian fresh waters: a critical review and data analysis

Spatial and temporal dynamics of biogeochemical processes in the Fraser River, Canada : a coupled organic-inorganic perspective

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