Landscape Evolution at Wanuskewin Heritage Park, Saskatoon Saskatchewan.
Date
1997
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Degree Level
Masters
Abstract
Regional deglaciation of the study site (520 13' N, 1060 35' W) 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, such as the Opimihaw Creek valley, to be incised through surficial sediments and
underlying till formations. Large stream discharges associated with a cool, moist postglacial
climate contributed to the erosion of the landscape.
The following physiographic elements were observed in the study area: the till
plain; alluvial terraces; mass movement landforms; the modem stream channel. The
alluvial terraces located in the valley bottom are the focus of this study.
Prior to ca. 4.6 ka BP, a combination of a rise in base level and gradual climate
change 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 vegetation cover,
combined with variable precipitation and stream discharge, led to initial rapid channel
aggradation. Sedimentation rates gradually declined as the environment became
increasingly moist leading to a more constant stream discharge, a denser vegetation cover
and reduced slope wash.
Excavations at several valley bottom alluvial terraces reveal five sedimentary
facies: facies 1, vertical accretion sediments; facies 2, proximal channel sediments; facies
3, alluvium and/or colluvium; facies 4, fluvial sands; facies 5, channel gravels. The
generally fining upwards sequence from coarse-grain fluvial channel deposits (facies 3 -
5) to finer-grained proximal channel and vertical accretion sediments (facies 1 and 2)
records the migration of the stream channel across its floodplain throughout the
aggradation phase. Repeated pedogenesis and human occupation indicate periodic
subaerial exposure of the floodplain. Downstream sites are generally dominated by finergrained
facies and are characterised by more rapid sedimentation rates than upstream
sites.
Within the last ca O. 1 to 0.2 ka BP, a geomorphic threshold was crossed and the
stream incised its floodplain. The proximity of the South Saskatchewan river to alluvial
terraces at the mouth of the creek indicates the creek was likely responding to a drop in
base level. Currently, there is very little flow in the creek, due in part to several beaver
dams along its length.
Description
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Citation
Degree
Master of Science (M.Sc.)
Department
Geography and Planning
Program
Geography and Planning