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Master of Science (M.S.)
Year Degree Awarded
Month Degree Awarded
varves, climate change, geochemistry, tephrochronology, lake sediments, XRF
Sediments in Lake C3, Ellesmere Island, Canada, contain annual laminations, providing a record of sediment accumulation for 1900+ years. Marine sediments are also present at base of cores, recording lake isolation following isostatic rebound of the Taconite Inlet region in the mid-Holocene. Beyond weak correlations with snowfall and summer temperature and precipitation, varve thickness comparisons with instrumental data were largely unsuccessful, likely due to turbidite-induced erosion. However, summer climate conditions are of key importance in varve thicknesses at many Arctic sites and we expect this to be true at Lake C3. Trends in the thickness record also correspond in approximate timing and response to large-scale climate events including the Little Ice Age (thin laminations) and the Medieval Warm Period (thick laminations). Long term trends and variability in the thickness record are also likely influenced by the weakening flow of the Taconite River following deglaciation as well as localized geomorphic events.
Elemental profiles combined with varve thickness features identify anoxic periods resulting from ice-cover- or marine incursion- induced stratification. Through synthetic aperature radar imagery we verify the strong link between air temperature and ice-cover conditions during the summer. Modification to tephra isolation methods resulted in the successful extraction of cryptotephra. Shards are currently undergoing microprobe identification to identify volcanic source and eruption timing. Sediments at Lake C3 provide a high-resolution record of local and regional environmental change and add to the high-latitude network of reconstructions with the objective of placing current changes in a long-term context.
Raymond S. Bradley