Critical Minerals Collection

The Critical Mineral Occurrence Potential Map of Maryland shows areas within the State of Maryland that may have the potential to contain one or more of the 35 mineral resources identified by the U.S. Department of Interior as critical to the economic and national security of the United States (Fortier et al., 2018). Production of the map was funded jointly by the Maryland Geological Survey (MGS) and the United States Geological Survey (USGS) Earth Mineral Resources Initiative (Earth MRI) and National Geological and Geophysical Data Preservation Program (NGGDPP). To produce the map, a variety of publicly available geologic data were analyzed to identify areas within the state of Maryland where geologic conditions favor the occurrence of deposits formed by one or more of the mineral systems included in Open-File Report 2020-1042, “Systems-Deposits-Commodities-Critical Minerals Table for the Earth Mapping Resources Initiative'' (Hofstra and Kreiner, 2020). Within the boundaries of the State of Maryland we have identified 14 areas that each correspond to one or more geologic units or physiographic regions or features within which one or more of the 35 critical minerals has the potential to occur. For areas that correspond to formal geologic units, area outlines correspond to geologic map unit contacts extracted from various map sources, including recently completed geologic quadrangle maps published by the MGS. For areas that correspond to physiographic regions or features, area outlines either were drawn by hand based on descriptions in references, or correspond to geologic map unit contacts extracted from map sources.

As part of the NGGDPP FY 2020 the MGS produced maps to support critical mineral resource identification in Maryland by compiling and digitizing some of the aforementioned data. The GIS maps and associated geodatabases were developed in the GeMS standard.

Approximate Elevation of pre-Cretaceous Basement Rock Beneath Coastal Plain Deposits in Maryland

This map represents select borehole data chiefly derived from the Maryland Geological Survey Maryland Coastal Plain Aquifer Information System (Andreasen et al., 2013), with additional lithologic data from Maryland Geological Survey Report of Investigations No. 44 (Hansen and Edwards, 1986). Borehole data has been reorganized into a format compatible with GeMS (Geologic Map Schema), as established by the U.S. Geological Survey National Cooperative Geologic Mapping Program (2020).

A contoured raster surface was generated using a natural neighbor interpolation of points of known elevation located along the Fall Line (the approximate location of the eastern edge of the outcrop of pre-Cretaceous basement rock) and of depth-to-bedrock data obtained from boreholes that were drilled through coastal plain sediments and penetrated pre-Cretaceous basement rock.

A geodatabase associated with the digital map houses borehole data including latitude, longitude, elevation, approximate depth to bedrock, total depth, bedrock lithology where available, and data used to estimate depth to bedrock (e.g. depth to bedrock, depth to saprolite, geophysical well data, presence of rock chips) is available below.

Select Well Locations and Associated Well Data

This map represents boreholes that have been cataloged as part of three separate efforts undertaken by the Maryland Geological Survey (MGS). The first group of boreholes is cataloged in the MGS Basic Data Report No. 5 (BDR 5), “Deep Wells of Maryland” (Edwards, 1970). This report contains a catalog of 349 wells drilled in Maryland prior to 1970, including every oil and gas well in the state, every water well deeper than 1000 feet, shallower water wells that provided important stratigraphic information, and the deepest well in each county. The second group of boreholes is cataloged in MGS Basic Data Report No. 11 (BDR 11), “Garrett County water-well records, chemical-quality data, ground-water use, coal test-hole data, and surface-water data, with a section on gas-well records” (Nutter et al., 1980). The third group of boreholes includes those boreholes that so far have been inventoried in the MGS Drill Cuttings Collection and Land-Based Core Collection, which together include all MGS-owned cuttings and cores from boreholes throughout Maryland.

A contoured raster surface was generated using a natural neighbor interpolation of points of known elevation located along the Fall Line (the approximate location of the eastern edge of the outcrop of pre-Cretaceous basement rock) and of depth-to-bedrock data obtained from boreholes that were drilled through coastal plain sediments and penetrated pre-Cretaceous basement rock.

A geodatabase associated with the digital map houses borehole data including latitude, longitude, date drilled, total depth, formation/unit names and depths, formations encountered, and depth of formations encountered is available below.