Paper No. 237-4
Presentation Time: 8:55 AM
LATE QUATERNARY LANDSCAPE EVOLUTION AND ORIGIN OF THE ORIENTED-LAKES COASTAL PLAIN, TUKTOYAKTUK PENINSULA, WESTERN ARCTIC CANADA
Environmental conditions, geological processes and chronology associated with the initiation and development of oriented lakes over millennial timescales are little known but essential for understanding how these arctic lowlands evolve. We report field observations from the McKinley Bay Coastal Plain of western Arctic, Canada, to elucidate such landscape evolution. The region includes over 900 oriented lakes, most with deep central basins and shallow marginal shelves. Landscape evolution is reconstructed from preglacial to postglacial conditions, with oriented lakes developing in basins conditioned by fluvial and eolian processes. Initially, the region was occupied by a preglacial braidplain (ca. 73–27 ka) and, during late Wisconsinan glaciation, by an alluvial braided-channel network that extended beyond the glacial limit (ca. 18.6–14.3 ka). Most lakes with deep central basins are inherited from this fluvial channel network. Eolian processes were active during the late glacial and postglacial period (ca. 12.8–1.9 ka), reworking fluvial deposits except where glacial outwash mantled the surface north of the Toker Point Stade limit. Eolian erosion modified existing basins and created other shallow deflationary basins, as small barchanoid dunes migrated downwind under cold, dry paraglacial conditions between about 12.8 and 10.7 ka. At the onset of the Early Holocene climatic optimum, vegetation cover developed ca. 10.7 ka and parabolic dunes formed and continued to migrate between 9.6 and 4.6 ka. In the absence of much near-surface ground ice, lateral expansion of deep-basin lakes and shallow stabilized deflationary basins predominated during the Late Holocene through wind-induced wave and current processes. Lake deepening has progressed as taliks penetrate the underlying permafrost. Overall, this sequence of oriented-lake formation does not support a thaw lake cycle but, rather, small basin evolution of a periglacial landscape.