An update of geologic mapping in Massachusetts

Despite the state's relatively high population density and decades of detailed study of the bedrock geology, only about half of the 7.5' quadrangles in Massachusetts have been published as GQ series geologic maps. As the state's population continues to grow, the availability of basic geologic data becomes increasingly crucial for informed land-use and water-management decision making. Much of the published 1:24000 scale geologic mapping predates recent advances in the understanding of regional tectonics, and needs to be updated. The Office of the State Geologist has begun a geologic mapping program in Massachusetts to address these needs. Two mapping projects were conducted through the STATEMAP component of the National Cooperative Geologic Mapping program in 2003. These projects focused on 7.5' quadrangles along the I-495 corridor, which is experiencing extensive population growth and development. The first project involved conversion of published 1:24,000-scale surficial geology to digital form for 10 quadrangles in southeastern Massachusetts. A semi-automated process was developed for this project that easily converts published paper geologic maps into vectorized, georeferenced datalayers. The second project involved 1:24000-scale geologic mapping of the Marlborough quadrangle in east-central Massachusetts. Products include traditional maps of bedrock and surficial geology as well as two new prototype products: a fracture characterization map and a surficial materials map. These projects mark the first time in Massachusetts' history that quadrangle-scale geologic data will be available in digital form to consultants and stakeholders, thus greatly expediting and improving the use and analysis of all geologic data. In addition, the inclusion of fracture characterization and surficial materials maps adds substantially to the value of traditional geologic map products. The new maps provide supplemental data on the hydrologic characteristics of the bedrock and the vertical stacking of surficial deposits that previously was unavailable. STATEMAP projects in 2004 will continue to focus along the I-495 corridor, and will involve revision and new mapping in the Wilmington, Reading, South Groveland, Lawrence, Hudson, and Oxford quadrangles.