Status of geologic mapping in Massachusetts:

Geologic map coverage for the Commonwealth of Massachusetts is far from complete. Prior to 2004, published bedrock geologic maps only exist for approximately 30% of the state, and published surficial geologic maps only exist for 51% of the state. Very few of these maps exist in digital form. Many older bedrock geologic maps also do not contain all the information that is most useful for today's needs, or predate major advances in geology (such as Plate Tectonics), and therefore should be re-mapped.  The OMSG is rapidly changing these statistics.

In 2003, The Office of the Massachusetts State Geologist rejuvinated geologic mapping in Massachusetts and is now publishing several maps as both digital and paper products.

Our mapping philosophy:

A geologic map is an interpretation by a geologist, based on limited data, of how the underlying geology presently intersects the Earth's surface. These interpretations change over time as new outcrops are created by development, geochronologic and geochemical analyses are performed, and advances are made in the science of geology. In this sense, a geologic map is a status report of the current understanding of the geology underlying an area. Many geologists often produce several maps of an area throughout their careers. Geologists working for the OMSG attempt to produce the best maps possible given the resources available at the time. Maps are subjected to strict editorial standards, scientific review by 2-3 peers, and an editorial review before publication as Geologic Maps.

We strongly recommend taking a moment to read "Reading Maps with a Critical Eye: Becoming an Informed Map Reader" by the Maine Geological Survey, to get the most out of a geologic map. It is an excellent and concise guide to the different kinds of geologic maps and how to use them.



Types of Geologic Maps Available from the OMSG:

  • Geologic map - A geologic map that is the result of at least 2-3 years of fieldwork and detailed study. This map has undergone critical peer and editorial review. Some geologic problems may still exist that require additional detailed fieldwork and/or analyses to resolve.
  • Draft or Preliminary geologic map (Open File Map) - A reconnaisance level geologic map produced after 1 year and 3-4 months in the field. This map is a progress report of mapping that is currently underway. Lithologic contacts are generally approximately located and structural measurements are few. This map has not undergone peer review and is published as an Open File Map
  • Fracture characterization map - A new type of geologic map, developed by the OMSG intended for hydrogeologic applications. This map consists of 4-5 sheets that reclassify bedrock based on its physical and hydrogeologic properties, in addition to displaying the trends of major families of bedrock fractures in an area. It's a very useful map! It usually accompanies a bedrock geologic map.
  • GIS Well Database - An Arcview GIS database and project file containing information on water and geotechnical wells drilled in the quadrangle. Data collected from well completion reports submitted to MassDEP, MHD, and other state agencies. These accompany the fracture characterization maps.
  • Digitized USGS Surficial Geologic Maps - These are interim products that are used by the OMSG and USGS in preparing digital compilations (see below) of the surficial geology for large areas of the state.  These interim products take the form of scanned images of the original published USGS map, and ESRI export (E00) files of the digitized, generalizes geology.
  • Digital Map Compilations - These are digitized versions of geologic maps that have been previously published by the USGS, or were maps close to publication.  These are often available as GIS files and PDF files.


All of our bedrock geologic maps, and fracture characterization maps are available in traditional print form as 1:24,000-scale 7.5' quadrangles. These paper maps are digitally available as Adobe PDF documents, and require the free Adobe Reader to view and print.

Each bedrock map also is available digitally in GIS form as a series of ESRI shapefiles and export files denoting lithologic polygons, faults, structural measurements, and other accompanying data. Please see the metadata accompanying each map for more details.

GIS products accompanying fracture characterization maps consist of an ESRI shapefile containing the raw fracture data measured in the quadrangle.

Each well-database consists of an ESRI Arcview Project (mxt) file that references a series of shapefiles and scanned well-log images, if available.

All bedrock geologic maps produced by the OMSG and their accompanying GIS data are projected using NAD 1983, Zone 19, and are in the Massachusetts State Plane Mainland (FIPS 2001) coordinate system.

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webpage last updated 1/2007