CGRG Bibliography of Canadian Geomorphology
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Author : Anderson, T.W.; Prévost, C.; and Garneau, M
Date : 1995
Title : Historical lake sediment, pollen and diatom records indicative of land-use changes in the Oak Ridges Moraine, Southern Ontario, Canada
Publication : Abstracts of the 28th Annual Meeting of the American Association of Stratigraphic Palynologists, Ottawa 1995
Issue :
Page(s) :
Abstract
Surface cores from kettle lakes in the Oak Ridges Moraine document the history of land-use change in a major agricultural/recreational resource area of southern Ontario. Certain cores intersected a unit (up to 1 m in thickness) of sticky, grey clay commonly overlain by a thin unit of soft organic (FeS-rich) mud and underlain by organic lake sediment (gyttja), marl or peat. In North Thompson Lake, the clay deposit extends throughout the entire lake basin where it unconformably overlies peat (nearshore) and lake sediment (offshore). The clay deposit is rich in plant detritus and thus represents a period of accelerated soil erosion, slope-wash, and siltation in the lake as a result of deforestation at the time of European settlement (commencing about 145 years ago). The clay deposit is clear evidence that the early settlers had exploited the Oak Ridges Moraine with little regard for land-use management at the time. Their only goal was to remove the trees and clear the land as rapidly as possible for cultivation. Close to 2.5-, 5- and 50-fold increases in upland herb pollen deposition (grains/cm-2/yr-1), dry bulk density (g/cc) and rates of sedimentation (g/m-2/yr-1), respectively, across the organic/inorganic contact (settlement horizon) at North Thompson Lake attest to the magnitude of this exploitation. Absence of diatoms in the clay deposit confirms siltation was a major factor in the lake as a result of deforestation and soil erosion/deposition. Deforestation also had an adverse effect on the hydrological component of the Oak Ridges Moraine. These and other settlement and post-settlement land-use changes such as the effects of suburbanization in the mid-1900's will be discussed.
Bibliography of Canadian Geomorphology