LOBATE INTERACTIONS AND GLACIAL LANDSYSTEM HETEROGENEITY ALONG THE SOUTHERN MARGIN OF THE LAURENTIDE ICE SHEET, NORTHEASTERN MINNESOTA

Throughout much of the late Pleistocene, northeastern Minnesota was occupied by varyingly thick glacial ice that issued from the Quebec-Labrador dispersal center and associated Hudson Bay saddle of the Laurentide Ice Sheet (LIS). Subglacial processes operating at the interface between this ice and its bed, in conjunction with an evolving subglacial topography, englacial sediment load, and meltwater drainage regime, contributed to the development of a diverse and well-preserved glacial landform archive in this area. Ongoing county-scale mapping, aided by enhanced access to high-resolution LiDAR-derived digital elevation datasets within the past decade, has engendered new conceptual frameworks that better relate regional glacial stratigraphic and geomorphological approaches. Such linkages have helped to refine knowledge concerning the pattern and style of retreat of the LIS southern margin in an area with poor geochronological constraint. In particular, recent efforts have led to the discovery of palimpsest surfaces (e.g., buried eskers, overprinted ice-marginal deltas, and relict meltwater channels), interlobate assemblages, and cross-cutting landforms (e.g., streamlined glacial lineaments) that detail polyphase interactions of the late Wisconsinan Rainy, Brainerd and Superior lobes along the eastern trajectory of the Mesabi Iron Range, and the western margin of the Lake Superior basin. Documented along-strike heterogeneity in the morphology and sedimentologic composition of the Vermilion moraine complex, and newly recognized De Geer moraine assemblages within the proto-glacial Lake Agassiz basin, are here viewed as elements of contrasting glacial landsystems generated by spatially and temporally disparate submerged grounding zone and subaerial terminus environments during the last recession of the LIS. Continuing work, including new OSL dating of key landsystem components, will seek to better unify absolute and relative chronologies throughout the region.