The National Geologic Map Database is migrating to a new infrastructure. We apologize for any service disruptions during this process.

U.S. Geological Survey Home AASG Logo USGS HOME CONTACT USGS SEARCH USGS
National Geologic Map Database
Map showing publication footprint
  • Usage in publication:
    • Ellicott City granite
  • Modifications:
    • Named
  • Dominant lithology:
    • Granite
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Knopf, E.B., and Jonas, A.I., 1929, Baltimore County report [Maryland]: Maryland Geological Survey County Report, 420 p.


Summary:

Named the Ellicott City granite for Ellicott City, Baltimore Co., northeastern MD. Unit is a narrow outcrop of massive biotite-quartz monzonite that is very similar in appearance to the Woodstock granite. Intrudes the Wissahickon formation. Age may be as late as late Paleozoic.

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Ellicott City Granodiorite
  • Modifications:
    • Age modified
    • Geochronologic dating
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Higgins, M.W., 1973, Superimposition of folding in the northeastern Maryland Piedmont and its bearing on the history and tectonics of the central Appalachians, IN Glover, Lynn, III, and Ribbe, P.H., eds., The Byron N. Cooper volume: American Journal of Science, v. 273-A, p. 150-195.


Summary:

Isotopic dating (Rb-Sr) of the Ellicott City Granodiorite indicates the unit is of Silurian age (425 Ma).

Source: GNU records (USGS DDS-6; Reston GNULEX).


Map showing publication footprint
  • Usage in publication:
    • Ellicott City Granodiorite*
  • Modifications:
    • Age modified
  • AAPG geologic province:
    • Piedmont-Blue Ridge province
Publication:

Drake, A.A., Jr., 1998, Geologic map of the Kensington quadrangle, Montgomery County, Maryland: U.S. Geological Survey Geologic Quadrangle Map, GQ-1774, scale 1:24,000


Summary:

The Ellicott City Granodiorite is considered of Ordovician age based on its relationship to the Guilford Granite and Woodstock Granite. Unit appears on generalized geologic map of MD Piedmont.

Source: GNU records (USGS DDS-6; Reston GNULEX).


Search archives

For more information, please contact Nancy Stamm, Geologic Names Committee Secretary.

Asterisk (*) indicates published by U.S. Geological Survey authors.

"No current usage" (†) implies that a name has been abandoned or has fallen into disuse. Former usage and, if known, replacement name given in parentheses ( ).

Slash (/) indicates name conflicts with nomenclatural guidelines (CSN, 1933; ACSN, 1961, 1970; NACSN, 1983, 2005, 2021). May be explained within brackets ([ ]).

Accessibility FOIA Privacy Policies and Notices

USA Gov U.S. Department of the Interior | U.S. Geological Survey
Supported by the National Cooperative Geologic Mapping Program
Page Contact Information: Personnel
Page Last Modified: Thu 21 May 2026 05:02:34 PM MDT