Harford County Geology

The map below is the 1968 Geologic Map of Harford County, Maryland, published by the Maryland Geological Survey. It serves as the primary mapping reference for the Harford County Geology Reference Project. Because geological terminology, age determinations, and tectonic interpretations have changed since the map was published, the project compares the original mapped units with information from later Maryland Geological Survey and U.S. Geological Survey publications. The map is presented for educational purposes and should not be used for navigation or to identify collecting locations.

Harford County Geology Reference Project

The Harford County Geology Reference Project is an educational effort to organize and interpret published geologic information for Harford County, Maryland. The project uses the 1968 Geologic Map of Harford County as its primary mapping reference and compares the original map units and symbols with later Maryland Geological Survey and U.S. Geological Survey research. The goal is to provide a clearer, more accessible summary of the county’s Piedmont and Coastal Plain geology, including unit names, ages, modern correlations, and tectonic or orogenic associations. The project is intended as a public reference and learning resource, not as a replacement for official geologic mapping.

** You will need the Harford County Geologic Framework file to work with the two spreadsheets. The definition of the data attributes is in the key.