MULTI-FACETED ANALYSIS OF THE UPSTREAM PORTION OF SELECTED LAURENTIDE ICE SHEET PALEO-ICE STREAMS; INSIGHTS INTO THEIR LONG-TERM BEHAVIOR

The geomorphological approach has been particularly effective for mapping paleo-ice streams and to recognize major ice stream configuration shifts; however, additional methods are necessary to better establish the full upstream extension of paleo-ice streams, as well as their long-term behavior. Till stratigraphic and compositional data, Quaternary geology maps, remote sensing and subsurface data document the evidence for ice streaming beyond the clear geomorphic imprint of several Laurentide Ice Sheet paleo-ice streams from published inventories. Some upstream portions may lack certain geomorphological characteristics, such as well-defined lateral shear margin moraines, but have long dispersal trains aligned with the main paleo-ice stream trunk of the downstream portion. Others have ice stream bed features partly overprinted by younger landforms or even buried under younger sediments. The analysis also shows that while upstream lateral margins are more often diffuse than sharp, some appear to coincide with long bedrock structures suggesting a potential role for these upstream geological structures on ice streaming. An integrated approach that includes geomorphological, geological, and geophysical information not only can help map paleo-ice streams, it can also improve our understanding of their dynamic and transient behavior through time.