Application of lidar data to mapping glacial landform/sediment associations, Champaign County, Illinois

The recently-compiled LiDAR image of Champaign County, Illinois provides new understanding of landform/sediment relationships in this low-relief, glaciated terrain. Conventional 7.5' topographic maps with a 1.5m contour interval provide evidence of the major landforms, but more subtle and important geomorphic features stand out on the LiDAR image. A quick glance at the prominent end moraines on the image confirms that north-northeastward-trending moraines of a lobate, late Wisconsin Episode ( approximately 20,000 cal yr BP) ice front were partially overridden by two distinctive southwestward advances and retreats, all from the Lake Michigan Lobe. The subtle textures of the terrain on the ground moraine deposited during each of these events are distinctly different, but the processes that created these textures, whether glacial or periglacial, are not obvious at this writing. Some of the geomorphic features that are particularly well-displayed or recognized for the first time are: 1, A lateral fault-like offset in the Pesotum Moraine, with an apparent dump moraine connecting the offset moraine fragments. 2, Palimpsest traces of older moraines draped by till of later readvances north of Champaign. 3, Remnants of ice-walled lakes in terrain immediately in front of the Pesotum Moraine. 4, Southwest-trending, anastamosing, esker-like ridges on terrain up-ice from the Champaign Moraine in northwest Champaign County. 5, Tunnel-valley-like linear depressions on the terrain up-ice from the Newton (youngest readvance) Moraine in northeast Champaign County. Most of these features were not previously known or described, despite the intense study of glacial features in the county over the past century. LiDAR adds an order of magnitude more detail to the surface textures on this low-relief glacial landscape and will prove to be a valuable tool in mapping surficial geology and understanding glacial and periglacial processes in similar landscapes.