The late Holocene paleohydrology of Pine Lake, Alberta: a multiproxy investigation |
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| Authors: | ID Campbell William M Last Celina Campbell Stephen Clare John H McAndrews |
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| Institution: | (1) Canadian Forest Service, 5320-122 St. Edmonton, AB, Canada, T6H 3S5;(2) Department of Geological Sciences, University of Manitoba, Winnipeg, MB, Canada, R3T 2N2;(3) Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2H4;(4) Alberta Environmental Protection, 10th Floor, Oxbridge Place, 9820-106 St. Edmonton, AB, Canada, T5K 2J6;(5) Departments of Botany and Geology, University of Toronto, Canada;(6) Department of Botany, Royal Ontario Museum, 100 Queen's Park Crescent, Toronto, ON, Canada, M5S 2C6 |
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| Abstract: | This paper reports on a high-resolution, multi-proxy, late-Holocene study from a lake in the Aspen Parkland of southern Alberta, Canada. A sediment core spanning the last 4000+ yrs from Pine Lake was analyzed for charcoal, granulometry, grain roundness, tephra content, geochemistry, mineralogy and pollen. This multi-proxy record indicates: (1) increasing anoxia causing a shift in S deposition from gypsum to pyrite due to increasing moisture availability in the late Holocene; (2) a decrease in Mg flux into the lake due to the development of the aspen forest, which reduced water flow through the Mg-rich shallow sand aquifer; the aspen forest expansion was in turn induced by the extirpation of plains bison prior to settlement; and (3) a change in the upland fire regime from frequent low-biomass grass fires to less frequent but higher biomass under-story fires, also as a result of the expansion of the aspen forest. Not only are the different proxies sensitive to different rates and magnitudes of change, they also show different sensitivities to different types of hydrological change: the mineralogy and geochemistry are sensitive to changes in water level and redox potential, and to changes in the relative strengths of the aquifers feeding the lake, while the granulometry is sensitive to total hydrological balance. Thus, apparently contradictory proxy results should be viewed as complementary. |
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| Keywords: | late-Holocene water chemistry bison aspen fire regime pollen mineralogy granulometry hydrology Great Plains |
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