Relay Quartz Diorite

Intensely foliated, fine-grained, light colored; ranges from quartz diorite to albite granite; age 550 +/- 50 m.y. * by radiogenic dating.
State Maryland
Name Relay Quartz Diorite
Geologic age Early Paleozoic - Late Precambrian (?)
Lithologic constituents
Igneous > Plutonic > Granitic > Alkali-feldspar-granite
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 Anne Arundel - Baltimore - Howard - Baltimore