Norbeck Quartz Diorite

Ranges from weakly foliated quartz diorite to strongly gneissic and schistose rock with recrystallized textures; more massive rocks have igneous textures; age 510 +/- 10 m.y. * by radiogenic dating.
State Maryland
Name Norbeck Quartz Diorite
Geologic age Cambrian
Lithologic constituents
Igneous > Plutonic > Dioritic > Quartz-diorite
Comments Radiogenic date from Wetherill et al., 1966 (ref. MD003)

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

Wetherill, G.W., Tilton, G.R., Davis, G.L., Hart, S.R., and Hopson, C.A., 1966, Age measurements in the Maryland Piedmont: Journal of Geophysical Research, v. 71, p. 2139-2155.

NGMDB product
Counties Montgomery