STATUS: PRELIMINARY DEGLACIATION MAPS FOR NORTH AMERICA
DYKE, ARTHUR S.. Terrain Sciences Division, Geological Survey of Canada.
Moore, Andrew . Terrain Sciences Division, Geological Survey of Canada.
Robertson, Louis . Terrain Sciences Division, Geological Survey of Canada.
At the annual meeting of the Canadian Geophysical Union in May, 2001, a workshop decided that it was necessary to update the North American deglaciation map series in support of planned high-resolution uplift modelling. As a first step, we have updated the Dyke and Prest (1987) map series, incorporating the most significant changes known to us and added the 15, 16, and 17 ka time slices. The next steps are to increase the resolution of the map series to 500 year intervals in the radiocarbon time scale and then proceed to 500 year intervals in the calendar time scale.
Unlike the previous maps, the new maps are fully digital and all "accepted" radiocarbon dates constraining ice and glacial lake fronts are plotted from a database. Key varve dates are also included, converted to radiocarbon time. Currently, the database contains about 3700 accepted dates. Marine shell dates, a major component of the database, are adjusted by a set of regional reservoir corrections that range from 800 years in the Pacific Ocean and Champlain Sea to 450 years in the outer Gulf of St Lawrence (Dyke et al., in prep.). A parallel database of about 600 "retired" radiocarbon dates, many of which were used to constrain previous ice margins, is also available.
In comparison to the previous maps, deglaciation is delayed on average by about 1000 years.
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