Holocene patterns of sediment yield reconstructed from sediments in four lakes
are used to assess the geomorphic sensitivity of four alpine-subalpine basins in
Cathedral Provincial Park, British Columbia. A three stage process was used to
assess basin sensitivity.
Stage one involved appraisal of the potential generalisability over the
landscape of the results to be derived from the lake basins. The four lakes,
Quiniscoe , Glacier, Pyramid and Lake of the Woods lie at or just below treeline.
Glacier, Pyramid and Quiniscoe lakes lie in cirque basins. Slope frequency analyses
show that whilst slopes in these basins are representative of those in the cirques
of Cathedral park they differ significantly from the wider landscape.
Stage two of the process involved identification of Holocene variability in
the sediment yield record. Cores from each of the lakes were correlated using
magnetic susceptibility measurements and lithostratigraphy to define
chronostratigraphic units. The mass of allochthonous mineral sediment deposited
in each of these units was estimated using measured sediment density, carbonate
content, loss on ignition, and biogenic silica. Sediment yield to the lake for each
unit was calculated based on dating of zone boundaries, estimates of trap
efficiency, and the mineral mass estimate. In order to identify significant variations
in the record, a new method was developed for estimating error associated
sediment yield estimates derived from lake sediments. Sediment yield estimates
were compared with the published Holocene climate record to make an initial
assessment of sensitivity.
Stage three involved discriminating between true sensitivity to climate
change in the record and coincidental correlation. The approach was to identify
process linkages between the observed changes in sediment yield and the climate
change record. Two methods of inferring process were used. Firstly process
change was inferred directly from the sedimentology of the lake sediments.
Secondly magnetic and mineralogical characterisations of lake and catchment
sediments were used to identify changing sediment sources.
The results show considerable variability in the patterns of Holocene
sediment yield amongst the study basins. In particular, Glacier and Quiniscoe
Lakes show a marked increase in sediment yield under cooler conditions ca. 3390
BP, which is not apparent at Pyramid and Lake of the Woods. The increase is
driven by increased surface erosion in the two higher basins under cooler
conditions, and with retreating treeline. The results suggest that the sensitivity of alpine and subalpine basins is
both temporally and spatially contingent. The links between climate change,
process change and variation in sediment yield are not simple, rather they is
mediated by a series of 'resistances'. The variability in sediment yield was
compared with the variable nature of the catchments and four important controls
were identified: Sediment production, vegetation, relief, and the extent of fluvial
development in the catchment. Maximum sensitivity was observed in steep
ecotonal sites with a well developed fluvial system.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/6688 |
| Date | 11 1900 |
| Creators | Evans, Martin |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Relation | UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/] |
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