CGRG Bibliography of Canadian Geomorphology
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Author : Burt, A.K.; Aitken, A.E.; and Walker, E.G
Date : 1998
Title : Landscape Evolution at Wanuskewin Heritage Park, Saskatoon, Saskatchewan.
Publication : 1998 Annual Meeting, Geological Society of America, Toronto, October 26-29. Abstracts with Program.
Issue :
Page(s) :
Abstract
The Opimihaw Creek valley (52o 13' N, 106o 35' W), located within Wanuskewin Heritage Park, Saskatoon, Saskatchewan is a microcosm of the development of post-glacial landscapes and human culture of Canada's Prairie heartland. The current study focuses on the interpretation of the evolving Opimihaw Creek landscape from deglaciation to the present day. Physiographic elements that were investigated include an upland till plain, colluvium on the hillslopes and alluvial terraces on the valley bottom. Regional deglaciation and drainage of glacial Lake Saskatchewan occurred by ca. 10.5 ka BP. Channelisation of flow into the South Saskatchewan River and a gradual drop in base level caused small tributary stream valleys to be incised through surficial sediments and underlying till formations. Large stream discharges associated with a cool, moist post-glacial climate contributed to the erosion of the landscape. Prior to ca. 4.6 ka BP, a combination of a rise in base level and gradual climate shift to warmer, drier conditions led to the crossing of a geomorphic threshold, shifting the stream from an incising to an aggrading system. Slope wash resulting from a reduction in vegetative cover, combined with variable precipitation and stream discharge, led to initial rapid channel aggradation. Excavations in several valley bottom alluvial terraces reveal a generally fining upwards sequence from coarse-grained fluvial channel deposits to finer-grained overbank deposits. These sediments record the migration of the stream channel across its floodplain throughout the aggradation phase. Downstream sites are generally dominated by finer-grained facies and are characterised by more rapid sedimentation rates than upstream sites. Overbank deposits record repeated pedogenesis associated with human occupation. As the environment became increasingly moist in the late Holocene, sedimentation rates gradually declined due to a denser vegetative cover and reduced slopewash. Within the last ca. 0.1 to 0.2 ka BP, a second geomorphic threshold was crossed and the Opimihaw Creek incised its floodplain in response to a drop in base level.
Bibliography of Canadian Geomorphology