A lake sediment-based proxy of floods in the Rocky Mountain Front Ranges,Canada |
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Authors: | Erik Schiefer Robert Gilbert Marwan A Hassan |
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Institution: | (1) Department of Geography, Planning and Recreation, Northern Arizona University, Box 15016, Flagstaff, AZ 86011, USA;(2) Department of Geography, Queen’s University, Kingston, ON, K7L3N6, Canada;(3) Department of Geography, University of British Columbia, 1984 West Mall, Vancouver, BC, V6T1Z2, Canada |
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Abstract: | We analyzed lake sediment deposits and local hydrometric records to assess the potential for developing a high-resolution
record of sediment delivery from the Rock Lake catchment, situated in the non-glacierized Front Ranges of the Rocky Mountains,
Canada. Rhythmic couplets of silt–clay characterized the clastic sediments recovered from the deep central basin of the lake.
Contemporary sediment yield to Rock Lake (10.7 ± 1.8 Mg km−2 year−1) is comparable to other studied Canadian Cordillera lakes that have sedimentary lithologies and absence of glacier cover,
but distinct rhythmic deposition is relatively unique to this basin. Spatial patterns of deposition within the lake were assessed
by correlating rhythmites between multiple sediment cores and by sub-bottom, acoustic profiling. Bracketed dates for a spatially
continuous sequence of eight thick rhythmites were established by correlating laminations between core samples collected more
than 30 years apart. We identified a consistent pattern between the rhythmite and hydrometric data series between 1975 and
2006 and determined that specific flooding events caused by summer rainstorms are associated with each of the eight thick
rhythmites. We observed a good relationship between rhythmite thickness and total flood volume that exceeded a threshold discharge.
Acoustic profiling showed that the lake could be a good candidate for longer-term proxy development. We discuss how some of
the methods used in this study could benefit ongoing paleoenvironmental assessments based on lacustrine rhythmite series. |
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