Physical indicators of ice-jam-induced flooding and the history of flood frequency in cores taken from lakes within the Peace-Athabasca Delta, northern Alberta, Canada.

摘要

Ice jam induced flooding of the Peace-Athabasca Delta (PAD) in northern Alberta, Canada is thought to be the primary mechanism for the recharging of hydrologically isolated basins within the delta. Core analyses from lakes selected on the basis of sensitivity to flooding indicate that dark-colored laminations within the cores are coarser, have higher magnetic susceptibilities, lower moisture content, plus higher quartz, feldspar and carbonate content than lighter laminations. These dark-colored laminations reflect non-flood deposition, whereas the finer-grained, lighter-colored laminations signify flood deposition. Sequences from highly flood sensitive lakes display well-defined laminations and bedding features that contain clear evidence of changing energy conditions, exhibit the highest rates of deposition, and record the highest lamination counts. In basins that likely experience less frequent flooding, laminations and bedding features become less well-defined, there is less variability in grain size and organic content, deposition rates decline, laminae frequency decreases, and the average thickness of individual laminations increases. Variability of laminae frequency and thickness within the sequences clearly illustrates the role of climate change in the delta. Variations in texture and mineralogy not only demonstrate the role of climate change within the delta, but also suggest changes in the conditions of individual lakes indicating that the regulation of Peace River water flow by the W. A. C. Bennett Dam may have accelerated the effects of climate change within some portions the PAD.