Baltimore Gabbro Complex

Hypersthene gabbro with subordinate amounts of olivine gabbro, norite, anorthositic gabbro, and pyroxenite; igneous minerals and textures well preserved in some rocks, other rocks exhibit varying degrees of alteration and recrystallization with a new metamorphic mineral assemblage.
State Maryland
Name Baltimore Gabbro Complex
Geologic age Late Precambrian (?) - Early Paleozoic
Lithologic constituents
Igneous > Plutonic > Gabbroic > Gabbro
Igneous > Plutonic > Ultramafic > Pyroxenite
Igneous > Plutonic > Gabbroic > Gabbro > Norite

Cleaves, E.T., Edwards, J., Jr., and Glaser, J.D., 1968, Geologic Map of Maryland: Maryland Geological Survey, Baltimore, Maryland, scale 1:250,000.

In 1995 the Water Resources Division of the U.S. Geological Survey digitized the geologic map of Maryland from the 1968 paper map (Reference MD001). Information about products from the Maryland Geological Survey can be found at

NGMDB product
Counties Anne Arundel - Baltimore - Cecil - Harford - Howard - Prince George's - Baltimore