PILOT PROJECT TO SUPPORT A QUATERNARY GEOLOGY MAP OF MINNESOTA AT 1:500,000

To optimize and facilitate county-scale geologic mapping in Minnesota, there is a need to augment supporting databases, to better resolve stratigraphic issues, and to improve understanding of regional Quaternary geological material, process, and history. To address these topics, the Great Lakes Geologic Mapping Coalition has supported work on statewide lithologic databases, stratigraphic naming, and regional cross-sections. Logically following this work, at what from several perspectives is just the right time, the next step is to enhance all Quaternary geologic work in the state through completion of a new 1:500,000 state Quaternary geology map, as a step forward from the previous map (Hobbs and Goebel, 1982). Users of County Geologic Atlases in Minnesota desire consistency in naming, definition, and characterization of strata, while multi-county analyses increasingly call for harmonized multi-county hydrostratigraphic syntheses. A new state Quaternary map constructed for the first time on a lithostratigraphic basis will improve and accelerate Atlas production by clarifying context and by further resolving stratigraphic issues. The map will be drawn as a generalization of previous county-scale mapping, and as an enhancement of previous 1:500,000 mapping, with reference to lidar, soil mapping, and lithologic databases. The current pilot project has initiated mapping with a focus on determining the best practices for joining existing maps and maps of different scales while creating content suitable for a regional map. The outcome of the pilot is 1:500,000-resolution mapping of a 1:250,000 map area, in the manner intended for the statewide map. Procedures for completion of the full map are being developed, as are metrics for calculating resources needed. The intended 1:500,000 Quaternary geologic map of Minnesota will clarify definition, nomenclature, correlation, and characterization of Quaternary stratigraphy statewide, thus further ensuring consistency, clarity, optimization, and efficiency in future county-scale mapping. As with the current state bedrock map, from which Mesozoic and Paleozoic strata may be removed to reveal underlying Precambrian geology, the new surficial geology map will be layered, at least with water and peat strata overlying fully mapped uppermost mineral sediments.