CGRG Bibliography of Canadian Geomorphology
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Author : Grubb, M.C.; Menounos, B.; and Gilbert, R.
Date : 2009.
Title : Late Holocene sedimentation change in Kitsumkalum Lake, northwestern British Columbia.
Publication : CANQUA–CGRG Biennial Meeting. May 3-8, 2009. Simon Fraser University, Burnaby Campus, Burnaby, British Columbia.
Issue : Programme and Abstracts Volume
Page(s) : 82.
Abstract
Annually laminated (varved) lake sediments record interactions between hydroclimatologic and geomorphologic processes. They enable researchers to constrain the timing of changes in sediment delivery and deposition. We analyzed inorganic varved sediments in 13 percussion and vibracores recovered from Kitsumkalum Lake to document historic changes in sedimentation. The sedimentation rate above the facies change ranges from 0.5 cm in the present day to 1.5 cm at 4 m depth. An abrupt facies change in three distal sediment cores is interpreted from the bulk physical properties of sediments present at 3 – 4 m depth. This facies change delineates a dramatic shift from massive sands and sandy laminations to silt and clay couplets. Hemlock (Tsuga heterophylla) needles at the facies boundary were radiocarbon dated to 325 ± 15 14C yr BP (381 ± 25 cal yr BP). The radiocarbon date complies with a varve count of 415 yrs BP, furthering the evidence for varved sediments in Kitsumkalum Lake. A Chirp sub-bottom acoustic survey of the lake shows an acoustically opaque surface at an equal depth as the facies change in the distal sediment cores. We attribute the cause of the abrupt change in sediment size in Kistumkalum Lake to channel avulsion and progradation of the Nelson River delta. Inactive channels present on the delta surface provide evidence for this hypothesis. However, the cause of the avulsion remains uncertain.
Bibliography of Canadian Geomorphology