ENHANCEMENT OF LITHOLOGICAL DATABASES NEEDED TO SUPPORT QUATERNARY SUBSURFACE MAPPING IN MINNESOTA

A key step in protecting and wisely utilizing the aquifers from which a majority of Minnesota residents obtain their drinking water is determining their geometry, their properties, and how they connect to the land surface and the activities that take place there. The Minnesota Geological Survey (MGS) County Geologic Atlas (CGA) Series provides this information to the extent achievable, at a county scale, to support planning and natural resource management while providing context for site-scale investigations in the form of comprehensive surficial, subsurface, and bedrock geologic mapping, and associated databases. CGA mapping is accelerating, as the essential role of regional 3D geologic mapping in protecting public health and economic development, through informed groundwater protection and management, is increasingly recognized. Quaternary 3D mapping for these Atlases utilizes field-based knowledge, well-construction records, geostatistics, closely-spaced cross-sections, and digital compilation of surfaces to map sand bodies, at the land surface and in subsurface glacial deposits. Delineation of these potential aquifers supports ground water modeling, monitoring, and other applications employed in managing water sustainably. To ensure that this 3D Quaternary geological mapping is optimized and completed efficiently, enhanced information resources and references are needed. A coordinated set of lithological databases, as well as associated documentation, therefore is being prepared to support current and future Quaternary subsurface mapping in Minnesota, including bathymetry, organic deposit extent and thickness, lacustrine sediment thickness, improved access to NRCS soil mapping, incremental compilation of detailed surficial geological mapping, and improved lithological categorization of water-well records.