Late quaternary glacier fluctuations, Itsi Range, Yukon Territory

Understanding past glacier fluctuations is critical for understanding Holocene paleoclimate, yet glacier chronologies in the northeastern Canadian Cordillera remain sparse and are frequently obscured by the occurrence of geologic scatter. This thesis reconstructs late Pleistocene and Holocene glacier changes in the Itsi Range, Yukon Territory, and examines processes driving regionally consistent scatter in moraine ages. Using terrestrial in situ 10Be surface exposure dating, I identify two Little Ice Age advances at the Itsi Glacier among the Itsi Range: 0.96 ka ± 0.36 (outer moraine) and 0.20 ka ± 0.05 (inner moraine). Erratics dated to 11.61 ka ± 0.54 indicate Cordilleran Ice Sheet retreat concurrent with the Younger Dryas termination. To contextualize the Itsi Glacier chronology with other regional advances, I compiled 10Be dated moraine records across western North America moraines organized by moraine morphostratigraphic position as denoted by end groups 1 – 3. The Itsi Glacier inner moraine aligns closely with end group 1 (0.13 ka ± 0.10), while outer moraine ages reflect significant scatter, mirroring the poorly constrained end group 2 record (0.46 ka ± 0.35). Distinctions among end group 1 and 2 moraine ages across latitudes suggest that northeastern Canadian Cordillera glaciers emplaced their moraines centuries earlier than those in the southwest. I assess the western North America moraine record with relevant multicentennialscale climate proxy records to deduce what factors influence glacier growth and retreat. Late Holocene advances were driven by orbital forcing, with additional contributions from temperature, precipitation, greenhouse gas emissions, and solar irradiance anomalies coherent with end group 1 culminations. End group 2 moraine scatter complicates its climatic interpretation. A parsimonious explanation for the inconsistencies among end group 2 moraine ages point to the result of amalgamated moraines, heterogeneous mixtures of previously exposed and reincorporated moraine boulders, deposited between 3.54 – 2.50 ka during the TiedemannPeyto Advance. Further research must be carried out to quantify geomorphic uncertainties inherent to techniques of cosmogenic nuclide dating.