A CARTOGRAPHIC ODE TO CHAPMAN: A REVISED REGIONAL DEPICTION OF POSTGLACIAL LANDSCAPE EVOLUTION IN THE CHAMPLAIN VALLEY

In the years following Donald Chapman’s seminal 1937 publication on the postglacial history of the Champlain Valley, numerous authors have developed improved age constraints and described new techniques for estimating the spatial extent of Glacial Lake Vermont and the Champlain Sea. However Chapman’s maps still represent the most comprehensive and regional depiction of postglacial lake levels throughout the the Champlain Valley. Existing maps lack the necessary detail to provide useful constraints on the relationship between postglacial landscape evolution and modern land use activities in the Champlain Valley.

Newly available lidar data is used to refine elevations of deltas and other shoreline features identified by earlier workers and to identify new features. These are used to develop revised shoreline projections for the Coveville, upper Fort Ann, and lower Fort Ann levels of Lake Vermont and the upper marine limit of the Champlain Sea.

Inspired by work depicting the extent of Pleistocene lakes in the Western Great Basin, we offer a post-Chapman cartographic synthesis of almost 80 years of research within the Champlain Valley. We include reconstructions of glacial ice margins constrained by surficial landforms, locations of lacustrine and deltaic sediments, wave-cut terraces, and lidar-derived shorelines. Our results suggest further refinement is needed within smaller arms of each lake level depicted extending into modern stream valleys and tributaries that now drain into Lake Champlain. A combination of new lidar products and up-valley interpolation of fluvial-deltaic sandplains may provide further constraints on these preliminary shorelines.