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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A Study of the Springs in the Upper Sulphur Creek Basin

Ludlow, Laurie 04 1900 (has links)
<p>Sulphur Creek, which occupies a basin to the north and west of Ancaster, Ontario, is fed by approximately 100 springs. This is the first detailed investigation of these springs. The results of this study are presented and a number of interesting conclusions have been drawn from them.Several directions for further research are also indicated.</p> <p> Physical analysis of the springs has revealed that they are on a planar, lacustrine blue clay aquiclude, which was formed as a result of meltwater ponding against an ice lobe, during the late Wisconsin glaciation. The meltwater lake covered most of the Sulphur Creek Basin, as indicated by the fact that blue clay was found all along the Creek's course. However, further research is required to determine the exact extent of this proglacial lake. </p> <p> A preliminary study of six springs was also undertaken in hope of determining the residence time of the groundwaters feeding the springs. It was found that there are significant short term trends in spring temperature, solute abundancies and 180 composition with season, suggesting that the residence times are surprisingly short. Also, the trends in the above variables suggest that groundwater residence time tends to vary from spring to spring. However, there are contradictions in trend when different variables are compared, which again suggests that further research is warranted. </p> / Thesis / Bachelor of Science (BSc)
2

Laurentide Ice Sheet Retreat during the Younger Dryas: Central Upper Peninsula of Michigan, USA

Walters, Kent A. 15 October 2013 (has links)
No description available.
3

Glacio-isostatic adjustment modelling of improved relative sea-level observations in southwestern British Columbia, Canada

Gowan, Evan James 06 December 2007 (has links)
In the late Pleistocene, most of British Columbia and northern Washington was covered by the Cordilleran ice sheet. The weight of the ice sheet caused up to several hundred metres of depression of the Earth’s crust. This caused relative sea level to be higher in southwestern British Columbia despite lower global eustatic sea level. After deglaciation, postglacial rebound of the crust caused sea level to quickly drop to below present levels. The rate of sea-level fall is used here to determine the rheology of the mantle in southwestern British Columbia. The first section of this study deals with determination of the postglacial sea-level history in the Victoria area. Constraints on sea-level position come from isolation basin cores collected in 2000 and 2001, as well as from previously published data from the past 45 years. The position of sea-level is well constrained at elevations greater than -4 m, and there are only loose constraints below that. The highstand position in the Victoria area is between 75-80 m. Sea level fell rapidly from the highstand position to below 0 m between 14.3 and 13.2 thousand calendar years before present (cal kyr BP). The magnitude of the lowstand position was between -11 and -40 m. Though there are few constraints on the lowstand position, analysis of the crustal response favours larger lowstand. Well constrained sea-level histories from Victoria, central Strait of Georgia and northern Strait of Georgia are used to model the rheology of the mantle in southwestern British Columbia. A new ice sheet model for the southwestern Cordillera was developed as older models systematically underpredicted the magnitude of sea level in late glacial times. Radiocarbon dates are compiled to provide constraints on ice sheet advance and retreat. The Cordillera ice sheet reached maximum extent between 17 and 15.4 cal kyr BP. After 15.4 cal kyr, the ice sheet retreated, and by 13.7 cal kyr BP Puget Sound, Juan de Fuca Strait and Strait of Georgia were ice free. By 10.7 cal kyr BP, ice was restricted to mountain glaciers at levels similar to present. With the new ice model, and using an Earth model with a 60 km lithosphere, asthenosphere with variable viscosity and thickness, and transitional and lower mantle viscosity based on the VM2 Earth model, predicted sea level matches the observed sea level constraints in southwestern British Columbia. Nearly identical predicted sea-level curves are found using asthenosphere thicknesses between 140-380 km with viscosity values between 3x10^18 and 4x10^19 Pa s. Predicted sea level is almost completely insensitive to the mantle below the asthenosphere. Modeled present day postglacial uplift rates are less than 0.5 mm yr^-1. Despite the tight fit of the predicted sea level to observed late-glacial sea level observations, the modelling was not able to fit the early Holocene rise of sea level to present levels in the central and northern Strait of Georgia.

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